Delia B. Rodriguez-Amaya’s research while affiliated with State University of Campinas (UNICAMP) and other places

The substitution of synthetic food dyes with natural colorants continues to be assiduously pursued. The current list of natural carotenoid colorants consists of plant-derived annatto (bixin and norbixin), paprika (capsanthin and capsorubin), saffron (crocin), tomato and gac fruit lycopene, marigold lutein, and red palm oil (α- and β-carotene), along with microalgal Dunaliella β-carotene and Haematococcus astaxanthin and fungal Blakeslea trispora β-carotene and lycopene. Potential microalgal sources are being sought, especially in relation to lutein, for which commercial plant sources are lacking. Research efforts, manifested in numerous reviews and research papers published in the last decade, have been directed to green extraction, microencapsulation/nanoencapsulation, and valorization of processing by-products. Extraction is shifting from conventional extraction with organic solvents to supercritical CO2 extraction and different types of assisted extraction. Initially intended for the stabilization of the highly degradable carotenoids, additional benefits of encapsulation have been demonstrated, especially the improvement of carotenoid solubility and bioavailability. Instead of searching for new higher plant sources, enormous effort has been directed to the utilization of by-products of the fruit and vegetable processing industry, with the application of biorefinery and circular economy concepts. Amidst enormous research activities, however, the gap between research and industrial implementation remains wide.

Stimulated by their multifaceted functions and actions, carotenoids have been among the most investigated food components, producing a voluminous, complicated, and sometimes inconsistent literature. This review puts into context developments in the last decade to have a comprehensive current knowledge on these valuable food constituents. Carotenoid analysis continues to show the wide biodiversity of carotenogenic foods and the many factors that affect the composition. Because of their instability, subject to multiple influencing factors, retention of carotenoids during processing and storage of food has been a daunting task. Since thermal processing may result in substantial carotenoid losses, thermal processes that are much faster than the conventional methods and nonthermal processing have been introduced. The processing conditions of nonthermal processing should, however, be well established so that microbial and enzymatic inactivation is achieved while maintaining nutrients and bioactive compounds. Instead of losses, higher carotenoid levels and bioaccessibility are sometimes reported for both thermal and nonthermal processing, attributed to greater extractability of carotenoids during analysis and greater release from the food matrix during digestion. Carotenoids differ markedly in their susceptibility to degradation, the epoxycarotenoids being most degradable. Results are mixed, however, in relation to the comparative stability of hydroxycarotenoids and carotenes. E-Z isomerization at sterically unhindered double bonds is now well documented. There is also more information about oxidative degradation, although more work is needed on this topic. It consists of epoxidation, cleavage to apocarotenoids and finally fragmention to low mass compounds. Enzymatic and non-enzymatic cleavage of carotenoids forms important aroma compounds but can also produce off-flavor.

Anthocyanins, betalains, carotenoids, and chlorophylls confer the attractive colors of plant-derived foods. These natural pigments, however, are unstable and prone to chemical changes during processing and storage, resulting in loss of color and biological activities. Anthocyanins suffer hydrolysis, nucleophilic attack by water, ring cleavage, and polymerization. Betacyanins undergo hydrolysis, C15 isomerization, dehydrogenation, and decarboxylation. Carotenoids are susceptible to geometric isomerization, epoxidation, and cleavage to apocarotenals and, eventually, to volatile compounds. Chlorophylls are epimerized and transformed to pheophytin, pyropheophytin, chlorophyllide, pheophorbide, and pyropheophorbide. The factors that enhance or inhibit these chemical alterations have been widely investigated. Considering the importance of these pigments to food quality and their potential health-promoting effects, the wealth of knowledge that has been accrued should be used to guarantee retention of these valuable compounds during processing and storage of food.

Lipid oxidation is the principal cause of nonmicrobiological deterioration of food. It can occur through autoxidation (oxidation with ³O2), photooxidation (oxidation with ¹O2) and enzymatic oxidation. Both autoxidation and photooxidation occur with the formation of hydroperoxides as primary products and their decomposition to secondary products, which are mostly low-mass aldehydes, ketones, alcohols, acids, esters, epoxides, and hydrocarbons. Singlet oxygen reacts directly with the unsaturated fatty acids while ³O2 needs an initiation step. Many factors influence lipid oxidation, such as the nature of the lipids, nature and composition of the food matrix, physical structure and physicochemical characteristics, availability and type of oxygen, transition metals, light, temperature, water activity, other food components, and additives, processing and storage conditions. Strategies to minimize lipid oxidation include vacuum packaging or controlled atmosphere, low-temperature storage, encapsulation of sensitive added compounds, addition of antioxidants. Lipid oxidation frequently limits the shelf-life of foods with the development of unpleasant rancid odor and taste. Negative effects on human health include loss of nutrient value and functionality and accumulation of compounds potentially toxic to humans.

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.

Upon processing or storage foods almost invariably undergo chemical changes that lead to a dramatic discoloration known as nonenzymatic browning or Maillard browning, along with the development of volatile, soluble, and insoluble products bearing far-reaching consequences on the food sensory properties and the long-term health of consumers. This chapter summarizes the chemistry underlying the complex network of different types of reactions, collectively known as the “Maillard reaction.” It is explained how each type of reaction imparts the changes and affects human health emphasizing the molecular events they promote in the body. An updated evaluation is made of both the positive and negative effects highlighting the possible connection between ingested preformed AGEs and the higher susceptibility of elderly individuals to the SARS-type viral infections. The means to control the reactions are reviewed seeking a balance between the technological gains and the health consequences, rather than the nutritional losses.

Incorporation of a vast number of additives in foods is permitted to fulfill a wide range of functions. During processing and storage, they may undergo chemical alterations in line with their intended actions. Examples are the reaction of nitrite with myoglobin to produce the reddish-pink color typical of cured meat and the reaction of sulfite with intermediates of the Maillard reaction and ascorbic acid oxidation to prevent nonenzymatic browning. On the other hand, degradation of additives may occur, such as the degradation of carotenoids and citral, resulting in loss of color and flavor, respectively. Additives may also undergo unintended interactions with other additives and food constituents, with desirable or undesirable consequences on food quality and human health. This chapter discusses the chemical changes, reactions, and interactions of some additives: antioxidants, colorants, flavorings, sulfites, and nitrites/nitrates. This type of information is vital to the food sector, since it provides the necessary background so that beneficial alterations can be enhanced and detrimental effects minimized.

Carotenoids are among the most investigated bioactive compounds of food. Numerous epidemiological studies and intervention trials have been conducted, and in spite of some inconsistencies in the results obtained, there is scientific support for carotenoids’ action against certain types of cancer, cardiovascular diseases, macular degeneration, and cataract. Carotenoids differ in their efficacy; lycopene is associated with reduced risk of prostate cancer while lutein and zeaxanthin are credited with lower risk of macular degeneration and cataract. Other potential health effects of carotenoids are emerging, such as protection of the skin from sunlight and maintenance of cognitive function. The most studied carotenoids have been β-carotene, α-carotene, β-cryptoxanthin, lycopene, lutein and zeaxanthin, and the carotenoids most commonly found in foods, but other carotenoids, such as astaxanthin, crocetin, bixin, and fucoxanthin, are being increasingly investigated. There is a continuous call for well-designed, long-term, large-scale human clinical trials, which require months of costly, laborious, complicated, challenging research with high probability of inconsistent or inconclusive results.