Chemical Changes During Processing and Storage of Foods: Implications for Food Quality and Human Health

By Delia B. Rodriguez-Amaya

Chemical Changes During Processing and Storage of Foods: Implications for Food Quality and Human Health presents a comprehensive and updated discussion of the major chemical changes occurring in foods during processing and storage, the mechanisms and influencing factors involved, and their effects on food quality, shelf-life, food safety, and health. Food components undergo chemical reactions and interactions that produce both positive and negative consequences. This book brings together classical and recent knowledge to deliver a deeper understanding of this topic so that desirable alterations can be enhanced and undesirable changes avoided or reduced.

Chemical Changes During Processing and Storage of Foods provides researchers in the fields of food science, nutrition, public health, medical sciences, food security, biochemistry, pharmacy, chemistry, chemical engineering, and agronomy with a strong knowledge to support their endeavors to improve the food we consume. It will also benefit undergraduate and graduate students working on a variety of disciplines in food chemistry

• Offers a comprehensive overview of the major chemical changes that occur in foods at the molecular level and discusses the positive and negative effects on food quality and human health
• Describes the mechanisms of these chemical changes and the factors that impede or accelerate their occurrence
• Helps to solve daily industry problems such as loss of color and nutritional quality, alteration of texture, flavor deterioration or development of off-flavor, loss of nutrients and bioactive compounds or lowering of their bioefficacy, and possible formation of toxic compounds

• Language: English
• Publisher: Academic Press
• Release date: Nov 25, 2020
• ISBN: 9780128173817

Book preview

Chemical Changes During Processing and Storage of Foods

Implications for Food Quality and Human Health

Edited by

Delia B. Rodriguez-Amaya

School of Food Engineering, University of Campinas, Campinas, SP, Brazil

Jaime Amaya-Farfan

Food and Nutrition Program, School of Food Engineering, University of Campinas, Campinas, Brazil

Table of Contents

Cover image

Title page

Copyright

List of Contributors

Chapter 1. Societal role of food processing: envisaging the future

Abstract

Contents

1.1 Introduction

1.2 Addressing food security

1.3 Meeting other societal needs and demands

1.4 Present and future challenges

References

Chapter 2. Denaturation of proteins, generation of bioactive peptides, and alterations of amino acids

Abstract

Contents

2.1 Introduction—proteins as multifunctional food components

2.2 The unique features of amino acids and the structuring of proteins

2.3 Protein denaturation

2.4 Bioactive peptides

2.5 Alterations of food proteins and amino acids caused by classical processing

2.6 Impact of nonconventional processes on protein and nonprotein amino acids

2.7 Concluding observations

Acknowledgments

References

Chapter 3. Oxidation of proteins

Abstract

Contents

3.1 Introduction

3.2 Mechanisms/pathways of protein oxidation

3.3 Analysis of protein oxidation products

3.4 Milk and dairy products

3.5 Meat and muscle foods

3.6 Plant-based food

3.7 Consequences of food protein oxidation on food quality, food safety, and human health

References

Chapter 4. Oxidation of lipids

Abstract

Contents

4.1 Introduction

4.2 Chemical alterations of lipids during processing and storage

4.3 Factors affecting lipid oxidation

4.4 Minimizing lipid oxidation

4.5 Implications for food quality

4.6 Implications for human health

References

Chapter 5. Alterations of polysaccharides, starch gelatinization, and retrogradation

Abstract

Contents

5.1 Introduction

5.2 Polysaccharides structure

5.3 Alterations of polysaccharides

5.4 Starch gelatinization

5.5 Starch retrogradation

5.6 Applications for food quality

5.7 Applications for human health

5.8 Conclusions

References

Chapter 6. The Maillard reactions

Abstract

Contents

6.1 Introduction

6.2 Stages of the Maillard reactions

6.3 Flavor and off-flavor compounds generated by the Maillard reaction

6.4 Structure and properties of melanoidins

6.5 Advanced glycation endproducts

6.6 Influencing factors

6.7 Impact on food quality

6.8 Impact on human health

6.9 Comparison with caramelization

6.10 Controlling the Maillard reaction

6.11 Final considerations

References

Chapter 7. Alterations of natural pigments

Abstract

Contents

7.1 Introduction

7.2 Anthocyanins

7.3 Betalains

7.4 Carotenoids

7.5 Chlorophylls

References

Chapter 8. Degradation of vitamins

Abstract

Contents

8.1 Introduction

8.2 Overview of vitamin losses in the food chain

8.3 Degradation of lipid-soluble vitamins

8.4 Degradation of water-soluble vitamins

References

Chapter 9. Generation of process-derived flavors and off-flavors

Abstract

Contents

9.1 Introduction

9.2 Coffee flavor

9.3 Chocolate flavor

9.4 Fruit and vegetable flavor

9.5 Meat flavor

9.6 Milk and dairy flavor

9.7 Wine flavor

References

Chapter 10. Generation of process-induced toxicants

Abstract

Contents

10.1 Introduction

10.2 Acrylamide

10.3 Benzene

10.4 Biogenic amines

10.5 Ethyl carbamate

10.6 Furan and methylfurans

10.7 Heterocyclic aromatic amines

10.8 3–MCPD and 3–MCPD esters

10.9 Nitrosamine

References

Chapter 11. Generation and alterations of bioactive organosulfur and phenolic compounds

Abstract

Contents

11.1 Introduction

11.2 Organosulfur compounds

11.3 Phenolic compounds

11.4 Concluding remarks

References

Chapter 12. Reactions and interactions of some food additives

Abstract

Contents

12.1 Introduction

12.2 Regulation of food additives

12.3 Antioxidants

12.4 Color additives

12.5 Flavoring agents

12.6 Preservatives

References

Chapter 13. Measuring chemical deterioration of foods

Abstract

Contents

13.1 Introduction

13.2 Types of chemical deterioration in food

13.3 Methods for measuring chemical deterioration in food

13.4 Conclusions and future trends

References

Index

Copyright

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List of Contributors

Jaime Amaya-Farfan

School of Food Engineering, University of Campinas, Campinas, SP, Brazil

Food & Nutrition Program, School of Food Engineering, University of Campinas, Campinas, SP, Brazil

Ângela Giovana Batista,     Department of Food and Nutrition, Universidade Federal de Santa Maria, Palmeira das Missões, Brazil

Juliano L. Bicas,     School of Food Engineering, University of Campinas, Campinas, SP, Brazil

Reinhold Carle

Institute of Food Science and Biotechnology, Hohenheim University, Stuttgart, Germany

King Abdulaziz University, Faculty of Science, Biological Department, Jeddah, Saudi Arabia

Chen Chao

State Key Laboratory of Food Nutrition and Safety, Tianjin University of Science & Technology, Tianjin, China

School of Food Science and Engineering, Tianjin University of Science & Technology, Tianjin, China

Per Ertbjerg,     Department of Food and Nutrition, University of Helsinki, Helsinki, Finland

Maria Beatriz Abreu Gloria,     Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil and Universidade Federal Rural de Pernambuco, Recife, Brasil

Helena Teixeira Godoy,     School of Food Engineering, University of Campinas, Campinas, SP, Brazil

Göker Gürbüz,     Department of Food and Nutrition, University of Helsinki, Helsinki, Finland

Marina Heinonen,     Department of Food and Nutrition, University of Helsinki, Helsinki, Finland

Fanbin Kong,     Department of Food Science and Technology, University of Georgia, USA

Lingling Liu,     Department of Agricultural and Biosystems Engineering, Iowa State University, USA

Xia Liu

State Key Laboratory of Food Nutrition and Safety, Tianjin University of Science & Technology, Tianjin, China

School of Food Science and Engineering, Tianjin University of Science & Technology, Tianjin, China

Daryl B. Lund,     University of Wisconsin-Madison, Cottage Grove, WI, United States

Lilia Masson,     Departamento de Ciencia de Alimentos y Tecnologia Química, Universidad de Chile, Santiago, Chile

Donald G. Mercer,     Food Science Department, University of Guelph, Guelph, Ontario, Canada

Fei Ren

State Key Laboratory of Food Nutrition and Safety, Tianjin University of Science & Technology, Tianjin, China

School of Food Science and Engineering, Tianjin University of Science & Technology, Tianjin, China

Delia B. Rodriguez-Amaya,     School of Food Engineering, University of Campinas, Campinas, SP, Brazil

Fereidoon Shahidi,     Department of Biochemistry, Memorial University of Newfoundland, St. John’s, NL, Canada

Juliana Kelly da Silva-Maia,     Departament of Nutrition, Universidade Federal do Rio Grande do Norte, Natal, Brazil

Shujun Wang

State Key Laboratory of Food Nutrition and Safety, Tianjin University of Science & Technology, Tianjin, China

School of Food Science and Engineering, Tianjin University of Science & Technology, Tianjin, China

Chapter 1

Societal role of food processing: envisaging the future

Delia B. Rodriguez-Amaya¹, Jaime Amaya-Farfan¹ and Daryl B. Lund²,    ¹1School of Food Engineering, University of Campinas, Campinas, SP, Brazil,    ²2University of Wisconsin-Madison, Cottage Grove, WI, United States

Abstract

During the past 80 years, a vast volume of science and technological know-how has been assembled to enable food processing to comply with its fundamental commitment of providing food security to society (i.e., food availability, accessibility, safety, and nutritional security). Food processing has additionally been expected to meet society’s demands for palatability, convenience, health benefits beyond nutrition, and sustainability. Such an enormous task has required the participation of professionals from multidisciplinary food science, technology, and engineering, working in cooperation with other sectors such as agriculture, industry, and government. Notwithstanding the integrated approach, feeding the world is an ever-increasing challenge because of such problems as an expanding world population, constraints on agricultural production, and the constant dependence on corporate and personal responsibilities. Striving always for further improvement, food processing will continue to serve present and future societies. A world without processed foods would be as hard to imagine as one that would depend only on natural medicines.

Keywords

Society and processed foods; food security; nutritional security; food safety; sustainability; consumer’s benefits; corporate responsibility; individual responsibility; multidisciplinary solutions

Contents

Outline

1.1 Introduction 1

1.2 Addressing food security 3

1.2.1 Food availability and accessibility 3

1.2.2 Nutritional security 4

1.2.3 Food safety 6

1.3 Meeting other societal needs and demands 8

1.3.1 Palatability and other sensory attributes 9

1.3.2 Convenience 9

1.3.3 Sustainable food systems 10

1.4 Present and future challenges 11

1.4.1 Unhealthy diet 11

1.4.2 Constraints on food production 12

1.4.3 Chemical alterations during processing and storage 13

1.4.4 Individual and corporate responsibility 14

1.4.5 Facing the future 15

References 17

1.1 Introduction

Food processing is a vital operation to provide society with a sufficient, safe, and nutritious food supply. If processed foods are removed from grocery stores and supermarkets around the world (Fig. 1.1), not many food products will be left on the shelves.

Figure 1.1 Supermarket alleys displaying hundreds of industrialized food items, most of which are variations of traditional home recipes, first from western-world kitchens, later from all over the world. Vast scientific knowledge has been put in to improve traditional recipes to make them safer, healthier, and more accessible to consumers. Although the original motivation was food preservation and food safety, about 60%–70% of total calories purchased by consumers in western and some Asian societies correspond to processed foods because the continued appeal for convenience is predominant.

Worded differently, should the option of having processed food cease to exist in today’s world, it would be impossible for society to sustain life as we know it.

Processing is accomplished by using one or more process operations, including washing, grinding, mixing, cooling, storing, heating, freezing, filtering, fermenting, extracting, extruding, centrifuging, frying, drying, concentrating, pressurizing, irradiating, microwaving, and packaging (Floros et al., 2010). Some foods can be eaten raw (e.g., fruits and some vegetables), but most foods are exposed to one or more processes. Grain crops, for example, have limited edibility in their natural state. Processing, such as milling and grinding, turns grains into flour, which can then be made into breads, cereals, pasta, and other edible grain-based products.

The societal role of food processing goes beyond transforming raw materials into edible products. With the exception of natural calamities, food shortages around the world are a result of a lack of importance given to the binomial nature of food production–preservation. It is true that for food security to be attained, the world needs a strong agricultural production sector, but agricultural production alone will not save the world from uncontrolled food insecurity without the input of food processing.

In the early 20th century, farmers and a growing population demanded a way to make cow’s milk widely available to be consumed, reducing losses at the farm level and curbing the dissemination of communicable diseases from consuming raw milk. In the 1950s, cow’s milk was conveniently made available to American suburban and city dwellers, first unprocessed, and later, pasteurized, solving a public health problem and significantly improving child nutrition. Preserving foods by canning had to surmount technical barriers, like controlling the browning reaction that deteriorated powdered milk and powdered eggs, before it became a successful industrial practice. Likewise, scores of processes, ingredients, additives, and packaging materials have been proposed, developed, and used commercially for most foods following a diversity of safety criteria, but those that were successful are controlled by food laws and regulations.

Food scientists are aware of the crucial importance of food processing as the best strategy to make foods safer and more nutritious. During the past 100 years, food science and technology have gone through a series of learning stages and introduced immense improvements in the safety of foods. Safety was primarily improved by removing or transforming harmful substances or preventing unwholesomeness by controlling both spoilage and pathogenic microbes. However, this does not mean that today’s best processes are perfect and cannot be improved, nor does it mean that the search for better processes should be curtailed.

Today, the food supply chain is dynamic and highly complex, influenced by globalization of the market, flow of raw materials, ingredients, and products among countries, and immense diversification of food products.

1.2 Addressing food security

Feeding the constantly increasing world population is an endless, daunting task. It is predicted that the world will face even more serious food security problems in the coming years as the population increases from the current 7.3 billion to 9.1 billion in 2050. It is projected that the world will need 70%–100% more food by 2050 (World Bank, 2008XXX).

Food security exists when all people, at all times, have physical, social, and economic access to sufficient, safe, and nutritious food that meets their dietary needs and food preferences for an active and healthy life (FAO, IFAD, and WFP, 2015). Food security therefore encompasses availability and access to food, nutritional security, and food safety.

1.2.1 Food availability and accessibility

1.2.1.1 Without food processing, will there be enough food for everyone?

By inhibiting microbiological and biochemical changes that lead to spoilage, processing extends the time during which a food remains wholesome (shelf-life). This shelf-life provides ample time for distribution and storage. Along with adequate packaging, food processing has facilitated transport to places distant from the site of agricultural production. Additionally, processing seasonal crops during harvest reduces postharvest losses and makes seasonal food available year-round.

Without processing, the population would be restricted to what is produced locally, limiting food availability and accessibility. Food supply would fluctuate, being plentiful during harvest seasons and scarce between seasons. The uneven distribution of food, today held responsible for hunger in some areas of the world while others have too much to eat, would be aggravated. Food loss, which is currently inadmissibly high, would be even greater.

Almost 870 million people were chronically undernourished in 2010–12 (FAO, WFP, and IFAD, 2012XXX), decreasing to 795 million in 2014–16 (FAO, IFAD, and WFP, 2015). The number of hungry people in the world remains unacceptably high. It is therefore unbelievable that about one-third of food produced for human consumption is lost or wasted globally, amounting to 1.3 billion tons/year (Gustavsson et al., 2011XXX) with the estimated value of US$ 1 trillion annually at the global level (FAO, 2015XXX).

Food is lost or wasted throughout the supply chain, from initial agricultural production to final household consumption. In low-income countries, food is lost during early and middle stages of the food supply chain; much less food is wasted at the consumer level. In medium- and high-income countries, food is wasted to a significant extent at the consumption stage. Suggested measures to reduce food loss in the former countries include investments in infrastructure, transportation and storage facilities, farmer education, diversification of production, increased use and efficiency of processing and packaging, and improved market facilities. In the latter countries, enhancing consciousness, planning of purchasing, adequating consumption habits, package size, and restaurant portions are actions that should be undertaken by consumers, processors, and restaurants.

Industrial processing generates much less total solid waste than home preparation. Storage losses in fresh foods are also generally greater than those associated with food processing.

Food processing can reduce the cost of food products and make them available to the population at affordable prices. By increasing the shelf-life of food and decreasing the amount of waste, food processing can reduce the overall cost of food production. Moreover, mass production of food tends to be cheaper than individual preparation of meals from raw ingredients.

1.2.2 Nutritional security

1.2.2.1 Without food processing, will the population be able to meet its requirements for nutrients and avoid nutritional deficiencies?

Food processing can enhance nutritional quality in many ways. Unstable nutrients can be preserved, important vitamins and minerals added, antinutrients transformed or removed, and nutrient bioavailability increased.

Processing such as freezing preserves the nutrients that are naturally present in foods. Freezing is usually done with freshly harvested crops when the nutritional quality is at its best. Thus in many cases frozen fruits and vegetables have higher nutrient content than the raw produce sold at the markets.

On the other hand, numerous papers have reported the loss of nutrients and bioactive compounds during thermal processing of foods, the extent of which depends mainly on the processing technique and conditions (especially time and temperature). Optimization of processing to achieve maximum retention of these valuable food components has been pursued (Lund, 1982XXX; Ling et al., 2015XXX; Preedy, 2014XXX; Rodriguez-Amaya, 2015; Rodriguez-Amaya and Amaya-Farfan, 2018XXX). Investigation of nutrient losses often focuses on industrial processing and storage. However, losses during home preparation/cooking and storage can be substantial, and may surpass those incurred in the food industry.

An example of what industrial processing can do that home preparation cannot do is the simple hydration operation and cooking of grains in order to obtain high bioconversion of bioactive compounds and nutrient retention. Before cooking, kidney beans, lentils, and other grains need to be hydrated for heat to be efficiently transmitted to the interior of the seed, an operation that has been traditionally accomplished by immersing the seeds in excess water for several hours. Unfortunately, this practice also leads to losses of soluble nutrients by leaching and, more importantly, it misses the opportunity to activate the endogenous glucosidase that carries out the isoflavone bioconversion to aglycones using the natural strategic enzyme-substrate arrangement in some beans. By precisely controlling hydration, Salces et al. (2018)XXX succeeded in converting close to 50% of the isoflavones to bioavailable aglycones while still guaranteeing high yields of daizein, which is the precursor of equol (an isoflavandiol estrogen-like hormone important in bone health).

Precision hydration is a simple technology that has other applications in production of minimally processed convenience foods. Examples include nutrification of grains and reduction of phytates in precooked soybean for salads and precooked chickpeas. Precision hydration, however, is a process not amenable to implementation in the limited space of a home kitchen.

Alternative food preservation technologies have been developed during the past several decades to meet the demand of consumers for fresh-like foods. Increasingly, these processes have also been shown to maintain or result in only slight or insignificant losses of nutrients and bioactive compounds (e.g., Al-juhaimi et al., 2018XXX). These technologies include thermal processes such as microwave and ohmic heating, which are much faster than the traditional canning method in producing shelf-stable foods. Methods that do not use heat as a primary mode of inactivating microorganisms in foods have also been introduced, such as high-pressure and high-intensity pulsed electric field processing (Bermúdez-Aguirre and Barbosa-Cánovas, 2011XXX; Chauhan, 2019XXX; Jan et al., 2017XXX).

Enrichment (replacing nutrients lost in processing) and fortification (adding nutrients at higher amounts than naturally found in the food) have been used globally as a public health measure to deal with population-level nutrient deficiencies. Early on, the targets were deficiencies such as goiter, rickets, beriberi, and pellagra. More recently, folate and neural tube defects, zinc and child growth, and selenium and cancer are being addressed (Samaniego-Vaesken et al., 2012XXX). Examples of enriched foods are grain products, especially breads. Examples of fortified foods include ready-to-eat cereals (fortified with B vitamins, folate, iron, and other nutrients) and milk (fortified with vitamins A and D).

In an assessment of the nutritional impacts of processed foods, Weaver et al. (2014) concluded that processed foods are nutritionally important to American diets, contributing to both food security (ensuring that sufficient food is available) and nutrition security (ensuring that food quality meets human nutrient needs). Analyses of the National Health and Nutrition Examination Survey 2003–08 showed that processed foods provided nutrients specified in the 2010 Dietary Guidelines for Americans, contributing 55% of dietary fiber, 48% of calcium, 43% of potassium, 34% of vitamin D, 64% of iron, 65% of folate, and 46% of vitamin B-12.

Using dietary data for 1989–91, an earlier paper had already confirmed that fortification made major contribution to intakes of all nutrients examined (nine vitamins and minerals), except calcium, in all age/gender groups but especially in children in the United States (Berner et al., 2001XXX). The breakfast cereal category was responsible for nearly all the intake of nutrients from fortified foods, except vitamin C, for which juice-type beverages made as great or greater contribution.

It is now widely accepted that a healthy diet means eating a variety of nutritious foods from the different food groups. Foods differ in their nutrient composition and no single food can provide all the nutrients. A more varied diet is more likely to provide all the nutrients required for good health, enabling consumers to reach their recommended daily intakes. The impressively varied modern diet has only been made possible through food processing.

Another benefit of thermal processing is the deactivation of thermolabile antinutritional factors. For example, heating inactivates protease inhibitors found in peas, beans, or potatoes (Damodaran, 2008XXX). These inhibitors are globular proteins that inhibit the action of the human digestive enzymes trypsin and chymotrypsin, which hydrolyze dietary proteins. Prolonged heating also inactivates lectins, glycoproteins present in legumes such as red kidney beans. Lectins bind and damage intestinal mucosa cells and interfere with the absorption of amino acids.

It is well known that heat treatment enhances digestibility of food. For example, denatured proteins are generally more digestible than proteins that are not denatured. Gelatinized starch can be hydrolyzed by amylase enzymes. As shown with carotenoids (Gärtner et al., 1997XXX; Rock et al., 1998XXX; Stahl and Sies, 1992XXX), processing boosts bioavailability of nutrients and bioactive compounds, attributed to the softening or breaking of cell walls/membranes and denaturing proteins complexed with carotenoids, thereby facilitating the release of carotenoids from the food matrices. Thus processing conditions are optimized to increase bioavailability while minimizing degradation of the carotenoids.

1.2.3 Food safety

1.2.3.1 Without food processing, can food safety be ensured?

Processed foods are regulated in both developed countries and developing countries. However, the food industry’s attention to food safety is not only in terms of compliance with legislation but also motivated by financial liabilities. Food safety can be a competitive factor and the consequences of a food safety failure can be commercially devastating, including product recalls, damage to reputation, and punitive lawsuits. Consumer confidence in the safety of food products is one of the key elements in brand loyalty, which determines success and profitability.

Processing techniques ensure the safety of foods by reducing the microbial count, particularly of harmful microorganisms. Drying, pickling, and smoking reduce the water activity and alter the pH of foods, thereby restricting the growth of pathogenic and spoilage microorganisms and retarding enzymatic reactions. Other techniques such as canning and pasteurization destroy microorganisms through heat treatment. Processing also addresses chemical and physical hazards.

It is widely recognized that the greatest food safety threats come from pathogenic microorganisms. Foodborne illnesses are a burden to public health and contribute significantly to the cost of health care. For example, the American food supply is considered among the safest in the world, but the Food and Drug Administration estimates that there are about 48 million cases of foodborne illness annually—the equivalent of sickening 1 in 6 Americans each year. And each year these illnesses result in an estimated 128,000 hospitalizations and 3000 deaths (FDA, 2019).

Processing reduces the incidence of foodborne diseases. As shown below, unprocessed food, such as fresh produce and raw meat, are more likely to harbor pathogenic microorganisms capable of causing these illnesses. Below are major examples of these diseases together with the food sources (FDA, 2019):

• Salmonellosis—eggs, poultry, meat, unpasteurized milk or juice, contaminated raw fruits and vegetables.

• Campylobacteriosis—unpasteurized milk, raw or undercooked poultry, and contaminated water.

• Hemorrhagic colitis or Escherichia coli O157:H7 infection—undercooked beef (especially hamburger), unpasteurized milk and juice, raw fruits and vegetables (e.g., sprouts), contaminated water.

• Listeriosis—raw and undercooked meats, unpasteurized milk, soft cheeses made with unpasteurized milk, ready-to-eat deli meats, and undercooked hot dogs.

• Botulism—improperly canned foods, especially home-canned vegetables, fermented fish, and baked potatoes in aluminum foil.

Processing eliminates and reduces microbial contamination responsible for foodborne diseases while packaging and postprocessing storage control recontamination.

The use of additives in food processing represents another safety concern. Food additives are added for a specific purpose, such as to extend shelf-life, ensure food safety, add nutritional value, or improve food quality. They are important in preserving the freshness, taste, appearance, texture, and wholesomeness of foods. For example, antioxidants prevent fats and oils from becoming rancid and emulsifiers stop peanut butter from separating into solid and liquid fractions. The use of additives is subject to laws and regulatory practices; approved additives are permitted for use in food products at specific levels. Food additives are discussed in detail in Chapter 12, Reactions and Interactions of Some Food Additives.

Attempts to reduce or eliminate food allergenicity through food processing have met with mixed results (Sathe et al., 2005XXX). The allergenic activity may be unchanged, decreased or even increased by food processing (Besler et al., 2001XXX). The identification of specific variables that could be used to reliably determine how processing will influence protein allergenicity has been difficult (Thomas et al., 2007XXX). Food allergens are discussed in greater detail in Chapter 2, Denaturation of Proteins, Generation of Bioactive Peptides, Alterations of Amino Acids.

1.3 Meeting other societal needs and demands

Fig. 1.2 illustrates the major stages of evolution and the expectations of food processing, which essentially reflect the increasing demands of society, as well as the increasing responsibilities of the food technologist. Aside from being available, affordable, nutritious, diverse, and safe, as discussed above, today’s consumers also expect food to be attractive, tasty, convenient, health promoting, and environmentally sustainable. The factors that influence consumers’ food choice include quality, price, appearance, taste, health, family preferences, habits, safety, production methods, country of origin, brand name, availability, and avoiding food allergens. Consumers increasingly wish to be informed about the safety of their food, its origin, and the sustainability of the processes that have produced and delivered it (Wognum et al., 2011XXX).`

Figure 1.2 Mounting responsibilities of the food processor through the last 80 years.

1.3.1 Palatability and other sensory attributes

Flavor, appearance, and texture remain the overriding consideration in consumers’ food acceptance, the emphasis on healthy foods, convenience, etc., becoming secondary.

Flavor is a nonnegotiable attribute, meaning if there is an undesirable or no flavor, the food is rejected by the consumer.

The sensory quality of some foodstuffs benefits directly from processing techniques.

Food processors have been impressively creative in changing basic raw materials into a range of attractive and tasty foods that provide an interesting and vast variety in the diets of consumers. Process-generated flavors are discussed in Chapter 9, Generation of Process-Derived Flavors and Off-flavors.

1.3.2 Convenience

As more and more women join the workforce and the fast pace and pressures of the modern world cut leisure time, consumers look for ways to ease the burden of food preparation. Processing and packaging technologies have provided a range of convenience foods, allowing consumers to enjoy varied and nutritious meals that take little time to prepare and also practically eliminate the need to clean up. Further, consumers save time from shopping less frequently by stocking up on a wide range of foods.

Convenience food products include complete meals for almost instant serving from freezer to microwave or conventional heating to table, frozen pizzas ready for the oven, special mixes for pastries and breads, bagged salads, and sliced and canned fruits and vegetables.

1.3.2.1 Health benefits beyond basic nutrition

In recent years, consumers have become more health conscious and interested in maintaining or improving their health through their diets. A prominent consequence of this trend is the intense research and development of functional foods worldwide.

Functional foods are conventional or modified foods that have a potentially positive effect on health beyond basic nutrition. Functional food combinations may promote better health and help reduce the risk of chronic, noncommunicable diseases (e.g., cancer, cardiovascular diseases).

In developed countries, research activities and the market have centered on:

• Bioactive ingredients (e.g., fiber, omega-3 fatty acids, isolated soy and milk proteins, probiotic, tomato concentrate, tea extracts, fruit extracts)

• Bioactive-enriched foods (e.g., prebiotic enriched foods, dairy products with probiotics)

• Naturally functional foods (e.g., flax, nuts, cranberry, whole grains)

In developing countries, the focus has been on:

• Optimization of naturally functional traditional foods (e.g., quinoa, amaranth seeds, yerba mate)

• Processing native, often unexploited, plant species with high levels of bioactive components (e.g., tropical fruits)

There is a consensus that high-quality, safe, and stable functional foods with proven efficacy can be achieved only when there is an appropriate and effective regulatory framework in operation. For these foods, not only safety should be proven but efficacy should be demonstrated.

Modern food manufacturing has also provided foods for individuals with specific health conditions, offering modified foods to meet their needs. Examples are sugar-free foods sweetened with natural sweeteners such as stevia and thaumatin for diabetic and celiac patients, gluten-free and lactose-free foods for those who are sensitive to these food components.

1.3.3 Sustainable food systems

Sustainability is gaining importance in the food industry (e.g., Mattsson and Sonesson, 2003XXX). Food production and consumption are increasingly based on global and ecological perspectives in which minimal environmental impact and efficient utilization of natural resources are important criteria for development of food products and selection of food systems.

Recognizing the urgent need to develop and implement policies and practices that provide universal access to healthy food choices for a growing world population, while reducing the environmental footprint of the global food system, Lindgren et al. (2018)XXX cited two challenges: reduction of the yield and nutritional quality of crops (in particular, vegetables and fruits) due to climate change, and trade-offs between food production and industrial crops.

Sustainability requires maximum utilization of all raw materials including their by-products and integration of activities throughout the entire production-to-consumption stages (Floros et al., 2010). To maximize the conversion of raw materials into consumer products, postharvest losses are reduced and the utilization of by-products increased. Food processors are striving to minimize the environmental impact of processing and products including efforts to reduce air, water, and solid waste emissions and reduce the environmental impact of packaging by using recycled and recyclable materials and reducing the weight of packaging.

Nonetheless, the food processing industry needs to further improve the use of agricultural food materials and the use of energy resources. There are many potential uses for processing wastes, at the same time avoiding a waste disposal problem. For example, there is interest in extracting the protein from wheat bran, a by-product of wet milling of wheat, for use as an ingredient in food and for conversion into bioactive peptides (Balandrán-Qunitana et al., 2015XXX). Processing wastes (e.g., peel) of the fruit and vegetable industry are richer in carotenoids and other bioactives than the processed products (Rodriguez-Amaya, 2015). The tomato processing industry generates waste that contains substantial amounts of lycopene. Components in apple pomace such as dietary fiber and phenolic compounds may be extracted and subsequently utilized in the food chain (Rabetafika et al., 2014XXX).

The food systems approach is considered the sustainable solution for a sufficient supply of healthy food (van Berkum et al., 2018XXX). Food systems consist of all the processes associated with food production and food utilization: growing, harvesting, packing, processing, transporting, marketing, consuming, and disposing of food remains.

1.4 Present and future challenges

1.4.1 Unhealthy diet

While food processing has provided the means to a healthy diet as discussed above, it is also blamed for giving rise to an unhealthy diet. The past few decades have seen alarming increases in obesity and chronic diseases such as diabetes, cardiovascular diseases, and cancer. An unhealthy diet, high in fat, added sugar and salt, and low in fiber may increase the risk for these diseases. The same assessment showing that processed foods provided nutrients to the American population (Weaver et al., 2014) also concluded that processed foods contributed constituents that need to be limited according to the 2010 Dietary Guidelines for Americans: 52% of saturated fat, 75% of added sugars, and 57% of sodium. Eating only refined grains, instead of whole grains, may increase the risk for type 2 diabetes, cardiovascular diseases, and weight gain (Liu et al., 2003XXX; Ye et al., 2012XXX). Eating more whole-grain foods is an important health recommendation; most consumers will need to reduce their current consumption of refined grains to no more than one-third to one-half of all grains in order to meet the targets for whole-grain foods (Williams, 2012XXX).

Many food companies have responded to this situation. More bread and cereal products are now available that are made from whole grains and have higher fiber content. Food processing techniques have been applied to offer low fat or fat-free, low salt, low sugar, and high fiber versions of many foods, which enable consumers to make food choices suitable for their individual health requirements.

Several countries have introduced sugar (MacGregor and Hashem, 2014XXX) and salt (He and MacGregor, 2009XXX; Webster et al., 2014XXX, 2015XXX) reduction programs, working with industry voluntarily or mandatorily. Food categories include bread, breakfast cereals, soups, and sauces. In Australia, salt levels in bread were estimated to be reduced by 9%, in cereals by 25%, and in processed meat by 8% during the period 2010–13 (Trevena et al., 2014XXX).

Trans fat (i.e., containing trans fatty acids) has been incorporated in many foods, such as snack and deep-fried foods, baked goods, margarines, crackers, cookies, pie crusts, doughnuts, and frozen pizza. The primary dietary source is partially hydrogenated oils, produced by adding hydrogen to the double bonds of unsaturated fatty acids of vegetable oils, thereby increasing the degree of saturation of the fat and altering its hardness and oxidative stability. Partially hydrogenated fats have been used to obtain desirable texture and palatability and to increase the resistance of oils to oxidation during deep frying. The process, however, introduces unnatural trans fatty acids.

Trans fat increases the risk of developing heart disease, stroke, and diabetes (Bhardwaj et al., 2011XXX; Brownell and Pomeranz, 2014XXX; Dietz and Scanlon, 2012XXX; Mozaffarian et al., 2006XXX; Stender and Dyerberg, 2004XXX). Thus strict regulations for limiting and removing trans fatty acids from the food supply are being implemented across the world. In 2003, Denmark was the first country to introduce a law that limited trans fatty acid content in food; thereafter other countries followed suit.

Weaver et al. (2014) listed the following challenges for food processing, especially in relation to nutrition and health: reduce calories, enhance gut health, reduce salt intake, enhance health benefits of foods, improve food safety, reduce food waste, reduce allergens, promote fresh but stable foods, and produce age-specific products.

1.4.2 Constraints on food production

Food production is now beset with almost insurmountable obstacles: less land available for agricultural production; limited access to water; higher costs of production, transport, and storage; climate change; soil degradation and desertification; more resistant pests; and overexploitation of fisheries. With continuing population growth, the global demand for food will increase amidst stiff competition for land, water, and energy, in addition to the urgent requirement to reduce the impact of the food system on the environment. Climate change will have far-reaching impacts on crop, livestock, and fisheries production, and will modify the prevalence of crop pests (Campbell et al., 2016XXX).

Both the agricultural production and the food processing sectors will be challenged to produce greater quantities of existing foods with fewer resources and develop innovative new foods that are nutritionally appropriate for the promotion of health (Augustin et al., 2016XXX).

Another challenge is the large and growing food security gap between industrialized countries and the developing world. Science-based improvements in agricultural production, food science and technology, and food distribution systems are critically important in decreasing this gap (Floros et al., 2010). Lack of technology, poor skilled labor, and underdeveloped infrastructure remain as daunting challenges in developing countries.

1.4.3 Chemical alterations during processing and storage

Processing causes changes in the components of food that may be either beneficial or detrimental. Examples are:

• Denaturation of proteins, generation of bioactive peptides

• Oxidation of proteins and lipids

• Starch gelatinization and retrogradation

• Maillard reaction and caramelization

• Alterations of natural pigments

• Generation of process-derived flavors

• Generation of process-induced toxicants

• Generation and alteration of bioactive compounds

• Reactions and Interactions of food additives

Research in food chemistry has generated a voluminous literature on these chemical changes, discussed in depth by the different chapters in this book, including the reaction mechanisms, the influencing factors, and the effects on food quality and human health. The food industry needs and should make good use of this wealth of information so that desirable changes can be stimulated and undesirable changes prevented, leading to the production of safe, nutritious, and health-promoting foods with satisfactory sensory attributes.

Thermal processing is the most established and widely used processing technique to reduce microbial load on food, and is also the most investigated in terms of its effects on food during processing. Beneficial effects of thermal processing include inactivation of detrimental constituents, improved digestibility and bioavailability of nutrients, improved palatability, taste, texture and flavor, and enhanced functional properties (van Boekel et al., 2010XXX). Unintentional undesired consequence, aside from losses of certain nutrients, is the formation of toxic compounds (e.g., acrylamide, furan, heterocyclic aromatic amines, polycyclic aromatic hydrocarbons) or compounds with negative effects on flavor perception, texture, or color. Process-generated toxicants are discussed in Chapter 10, Generation of Process-induced Toxicants.

1.4.4 Individual and corporate responsibility

Especially in developed countries processed foods are strictly regulated based on scientific evidence and reasonable practicality. Those laws and regulations come into being through a consultative process involving scientists, industry, non-governmental organizations such as consumer groups, and governmental regulatory agencies. It has been a long-standing desire on the part of consumers that laws and regulations are based on sound science, upon which the public at large can rely with regard to food quality and food safety.

Recently, however, confidence in science has been badly shaken. As this applies to food, consider two examples from the United States. In 2011, research in support of resveratrol, a flavonoid in red grapes that is good for the heart, was revealed to have been fabricated and falsified (Wood, 2019XXX). The result was that several manuscripts were retracted by the journals, the researcher was fired, and federal funds for the research were returned to the funding agency. More recently there was the revelation that six research papers on the relationship between satiety and food consumption were retracted with the professor abruptly retiring (Butler, 2018XXX).

The assumption is that scientists, corporations, and governmental agencies are honest, ethical, moral, and can be trusted. The problem is that greed or individual success may become an overwhelming driving force to be dishonest. This can happen to individual scientists, corporations, and government leaders.

To regain public trust, the science community is aggressively applying fundamental principles in conducting research. First, when research is conducted and reported, the scientist should identify any conflicts of interest or bias. Second, the public and the scientific community should have access to the data, methods, and interpretation of the data so the research can be reproduced and the conclusions drawn from the data verified. Guidelines have been published on (1) avoiding conflict of interest (Rowe et al., 2009XXX), (2) conducting public–private partnerships (Rowe et al., 2013XXX), and (3) a scientific resource guide on scientific integrity (Kretser et al., 2017XXX).

It is not only scientists who need guidelines for behavior but also corporations. For corporations, those guidelines are laws and regulations. However, in addition to obeying the letter of the law, corporations have an obligation to act responsibly and morally. Many corporations have credos that compel them to be responsible corporate citizens. If corporations want the consumer to trust them, then they must act in an ethical and moral way.

Finally, there certainly exist governmental institutions that are complicit in putting the public’s health in danger through the food system. They should be held to the same standards for moral and ethical behavior as scientists and private industry.

The contributions of food science and technology to society through the years have been immeasurable, thanks to countless dedicated, hard-working, responsible, and honest food science and technology professionals in academia, government agencies, and industry. The dishonesty and over ambitious agenda of a few should not be allowed to negate the significance of such endeavors.

1.4.5 Facing the future

According to an IFT Scientific Review (Floros et al., 2010), the solution to the challenge of meeting the food demands of our future world population lies clearly in the following principal goals:

• Increased agricultural productivity everywhere, but particularly among poor farmers, of whom there are hundreds of millions.

• Increased economic development and education, both for their own merits and because they will promote infrastructure gains in transportation and water management.

• Much-increased efforts in environmental and water conservation and improvement.

• Continued improvements in food and beverage processing and packaging to deliver safe, nutritious, and affordable food.

• Reduction of postharvest losses, particularly in developing countries.

All of these goals must be achieved if we are to deliver a sustainable diet.

In 2010XXX, the FAO defined sustainable diets as diets with low environmental impacts which contribute to food and nutrition security and to healthy life for present and future generations. Sustainable diets are protective and respectful of biodiversity and ecosystems, culturally acceptable, accessible, economically fair and affordable; nutritionally adequate, safe and healthy; while optimizing natural and human resources. The major determinants of sustainable diets fall into five categories: (1) agriculture, (2) health, (3) sociocultural, (4) environmental, and (5) socioeconomic (Johnston et al., 2014). Promoting sustainable diets will require an inclusive approach that reflects the multidisciplinary determinants.

There has been a constant call for integrated multisectorial (academia, government, industry, consumers), and multidisciplinary (agriculture, food science and technology, nutritional sciences, medical sciences, environmental sciences, social sciences, economics) approaches (Fig. 1.3) to address the complex, multifaceted challenge to feed the world and minimize global food insecurity (Dwyer et al., 2012XXX; Godfray et al., 2010XXX; Johnston et al., 2014; Lowe et al., 2008XXX; van Mil et al., 2014XXX; Wu et al., 2014XXX). Engagement and effective communication among all stakeholders along the food supply chain is considered essential for delivering innovative and effective solutions.

Figure 1.3 From the farm to the dining table: the multidisciplinary strategy by which food science and technology bridges the various disciplines that are responsible for feeding populations.

Agriculture alone can no longer provide food security as it did in the past. An increase in agricultural production provides greater availability of food, but not necessarily an improvement in the nutritional status of the population. Agriculture should be nutrition sensitive (e.g., including nutrient/bioactive levels as criterion for choosing varieties for commercial production, along with yield, resistance to pests and adverse climatic conditions, and sensory attributes). Fortunately, the agriculture–nutrition–health linkage is now widely acknowledged. But there is a bridge between agriculture and the nutritional/medical sciences that needs to be recognized and improved (Fig. 1.3; Table 1.1). It is food science and technology that brings food from the farm to the table. To quote the IUFoST Cape Town Declaration (2010), …the problem of food insecurity…will not be solved by Food Science and Technology alone …but it will certainly not be solved without the contribution of Food Science and Technology. Because communication with consumers, costs, and environmental impact are important components for a successful strategy, other fields such as social sciences/behavioral sciences, economics, and environmental science must be included.

Table 1.1

Food processing has solved significant challenges, resulting in improved food availability and quality. As new challenges emerge, however, other advancements in science and technology are becoming available to food scientists in their quest for safer foods both in the short and long term. Examples include the various instances in which molecular biology has shown precisely how an ingredient or a process may become harmful to health after prolonged consumption, thus extending the significance of innocuousness and the power of classical food toxicology. By detecting minute changes in the intestinal microbiota or in the hypothalamus, for instance, food scientists are now in a position to readily predict the potential harm of a particular food item or diet. Such avenues of research should certainly shorten the systematic search for alternative solutions.

Food processing has accomplished great benefits for humankind, and responsible food processors are striving to improve it. Processed foods will continue to be an essential part of our future. A world without processed foods is as senseless as a world without manmade or transformed medicines.

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Chapter 2

Denaturation of proteins, generation of bioactive peptides, and alterations of amino acids

Jaime Amaya-Farfan,    Food & Nutrition Program, School of Food Engineering, University of Campinas, Campinas, SP, Brazil

Abstract

Chemical changes introduced in foods during processing can modify the roles laid down by nature for amino acids, peptides and proteins when they stop supporting life in the organism that synthesized them to start supporting life in the organism that took them in as food. It first focuses on the chemical uniqueness of the amino-carboxyl system, the peptide bond and the obligatory adoption of spatial configurations and new properties as the molecule increases in size. Protein denaturation is treated in an intuitive manner to emphasize the order that exists within ‘chaos’ and the predictability of the sequence of alterations that a food technologist can expect when manipulating the complex food matrices. While chemical changes, such as the cleavage of peptide bonds and the development of numerous compounds from amino acids during processing are advantageous, many chemical alterations can be detrimental to health. Considering that perhaps the most outstanding advancement of recent times on the role of proteins is that all proteins encode metabolic signals deliverable to the consuming organism upon digestion, this class of nutrients should be studied under the perspective that higher living beings reached high degrees of metabolic sophistication by delegating clerical yet vital metabolic tasks to incoming food proteins. With such biological approach, the chemical changes introduced by millennial techniques as fermentation, maturation and heating, or even modern hydrolytic and non-conventional processes, this chapter draws examples of what processing can do to proteins and what the consumed protein can do for the consumer in terms of functionality and health. Current data continue to support the classical notion that food processing can complement and improve the core metabolic functions of food proteins, but also suggest that research ahead should give special attention to the long-term health effects of undigestible degradation products and the altered sequential order of peptide release as they may have a role in chronic non-communicable diseases.

Keywords

Modified food proteins; health consequences of food processing; protein degradation and health; health significance of food bioactive peptides

Contents

Outline

2.1 Introduction—proteins as multifunctional food components 21

2.2 The unique features of amino acids and the structuring of proteins 23

2.2.1 The primary structure 24

2.2.2 Secondary structure 25

2.2.3 Tertiary structure 25

2.2.4 Quaternary structure 26

2.2.5 Do fibrous proteins not have tertiary and quaternary structures? 26

2.2.6 The critical role of hydrophobic interactions in structuring 28

2.3 Protein denaturation 29

2.3.1 The intuitive approach to follow denaturation 30

2.3.2 Means of denaturation and relevance to health 33

2.4 Bioactive peptides 38

2.4.1 Bioactive peptide formation. Why and how are they formed? 39

2.4.2 From proteins to functional peptides or amino acids and back to proteins 41

2.4.3 Where do bioactive peptides display their actions? 45

2.4.4 The relevance of chemical transformations to health 48

2.4.5 Processing-induced changes and the quality of bioactive peptides 48

2.5 Alterations of food proteins and amino acids caused by classical processing 50

2.5.1 Extended effects of protein denaturation on amino acid reactivity 50

2.5.2 Common chemical modifications and most reactive groups 51

2.5.3 Primitive and conventional processes 58

2.6 Impact of nonconventional processes on protein and nonprotein amino acids 72

2.7 Concluding observations 76

Acknowledgments 77

References 78

2.1 Introduction—proteins as multifunctional food components

Processing emerged in prehistoric ages as a necessary means to preserve and avoid the spoilage of foods thus guaranteeing survival during times of scarcity. Food processing and storage have made possible the organization of man into societies, the development of specialization of trades and professions, and, equally important, these technologies contributed to a sustainable food supply, food security, nutrition, and health of populations (Weaver et al., 2014XXX). Throughout this chapter we will be concerned with describing the key chemical changes that occur in proteins, peptides, and amino acids, as well as both the beneficial and adverse chemical changes that food processing—from primitive to modern—and storage can modify the health value of proteinaceous components occurring in the human diet.

For studying the great number of chemical changes that a food system can undergo during processing and storage, it is important to bear in mind that proteins will most likely participate in