Showing papers in "Critical Reviews in Food Science and Nutrition in 1994"

The microbiology of minimally processed fresh fruits and vegetables

Abstract: Minimally processed fresh (MPF) fruits and vegetables are good media for growth of microorganisms. They have been involved in outbreaks because of the consumption of products contaminated by pathogens. They are also sensitive to various spoilage microorganisms such as pectinolytic bacteria, saprophytic Gram-negative bacteria, lactic acid bacteria, and yeasts. Contamination of MPF fruits and vegetables occurs at every stage of the food chain, from cultivation to processing. Polluted environments during cultivation or poor hygienic conditions in processing increase the risk of contamination with foodborne pathogens. Although MPF fruits and vegetables may harbor psychrotrophic microorganisms such as fluorescent pseudomonads or Listeria monocytogenes, good control of refrigeration temperature limits growth of spoilage and pathogenic microorganisms. Modified atmospheres are often efficient to maintain or improve visual organoleptic quality of MPF fruits and vegetables, but their effects on microorganisms are inconsistent. Chemical disinfection can partially reduce the initial bacterial contamination; irradiation seems to be more efficient. The applications of legislations and quality assurance systems to control contamination, survival, and growth of foodborne pathogens in MPF fruits and vegetables are discussed.

Implications of antinutritional components in soybean foods

Abstract: There are a number of components present in soybeans that exert a negative impact on the nutritional quality of the protein. Among those factors that are destroyed by heat treatment are the protease inhibitors and lectins. Protease inhibitors exert their antinutritional effect by causing pancreatic hypertrophy/hyperplasia, which ultimately results in an inhibition of growth. The lectin, by virtue of its ability to bind to glycoprotein receptors on the epithelial cells lining the intestinal mucosa, inhibits growth by interfering with the absorption of nutrients. Of lesser significance are the antinutritional effects produced by relatively heat stable factors, such as goitrogens, tannins, phytoestrogens, flatus-producing oligosaccharides, phytate, and saponins. Other diverse but ill-defined factors appear to increase the requirements for vitamins A, B12, D, and E. The processing of soybeans under severe alkaline conditions leads to the formation of lysinoalanine, which has been shown to damage the kidneys of rats. This is not generally true, however, for edible soy protein that has been produced under milder alkaline conditions. Also meriting consideration is the allergenic response that may sometimes occur in humans, as well as calves and piglets, on dietary exposure to soybeans.

Enzymatic browning reactions in apple and apple products

Abstract: This review examines the parameters of enzymatic browning in apple and apple products that is, phenolic compounds, polyphenoloxidases, and other factors (ascorbic acid and peroxidases), both qualitatively and quantitatively. Then the relationships between intensity of browning and the browning parameters are discussed, including a paragraph on the methods used for browning evaluation. Finally, the different methods for the control of browning are presented.

Endogenous skeletal muscle antioxidants

Abstract: Skeletal muscle is susceptible to oxidative deterioration due to a combination of lipid oxidation catalysts and membrane lipid systems that are high in unsaturated fatty acids. To prevent or delay oxidation reactions, several endogenous antioxidant systems are found in muscle tissue. These include alpha-tocopherol, histidine-containing dipeptides, and antioxidant enzymes such as glutathione peroxidase, superoxide dismutase, and catalase. The contribution of alpha-tocopherol to the oxidative stability of skeletal muscle is largely influenced by diet. Dietary supplementation of tocopherol has been shown to increase muscle alpha-tocopherol concentrations and inhibit both lipid oxidation and color deterioration. Dietary selenium supplementation has also been shown to increase the oxidative stability of muscle presumably by increasing the activity of glutathione peroxidase. The oxidative stability of skeletal muscle is also influenced by the histidine-containing dipeptides, carnosine and anserine. Whereas carnosine and anserine are affected by diet less than alpha-tocopherol and glutathione peroxidase, their concentrations vary widely with species and muscle type. In pigs, beef, and turkey muscle, carnosine concentrations are greater than anserine, while the opposite is true in rabbit, salmon, and chicken muscle. Anserine and carnosine are found in greater concentrations in muscle high in white fibers, with chicken white muscle containing over fivefold more anserine and carnosine than red muscle. Anserine and carnosine are thought to inhibit lipid oxidation by a combination of free radical scavenging and metal chelation.

Biochemical, microbiological, and nutritional aspects of kimchi (Korean fermented vegetable products)

Abstract: Kimchi is a traditional, fermented Korean food that is prepared through a series of processes, including pretreatment of oriental cabbage (or radish), brining, blending with various spices and other ingredients, and fermentation. The characteristics of kimchi differ depending on the kimchi varieties, raw materials used, process, fermentation, and preservation methods. However, kimchi has typical biochemical, nutritional, and organoleptic properties and health-related functions. Kimchi fermentation is initiated by various microorganisms originally present in the raw materials, but the fermentation is gradually dominated by lactic acid bacteria. Numerous physicochemical and biological factors influence the fermentation, growth, and sequential appearance of principal microorganisms involved in the fermentation. Complex biochemical changes occur depending on the environmental conditions before, during, and after fermentation. The most important characteristics are the compositional changes of sugars and vitamins (especially ascorbic acid), formation and accumulation of organic acids, and texture degradation and softening. Nutritionally, kimchi is an important source of vitamins, minerals, dietary fiber, and other nutrients. This review covers in some detail the biochemical, microbiological, and nutritional characteristics of kimchi.

Chemistry of Amadori rearrangement products: Analysis, synthesis, kinetics, reactions, and spectroscopic properties

Abstract: The chemistry of the key intermediate in the Maillard reaction, the Amadori rearrangements product, is reviewed covering the areas of synthesis, chromatographic analyses, chemical and spectroscopic methods of characterization, reactions, and kinetics. Synthetic strategies involving free and protected sugars are described in detail with specific synthetic procedures. GC- and HPLC-based separations of Amadori products are discussed in relation to the type of columns employed and methods of detection. Applications of infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy for structural elucidation of Amadori products are also reviewed. In addition, mass spectrometry of free, protected, and protein-bound Amadori products under different ionization conditions are presented. The mechanism of acid/base catalyzed thermal degradation reactions of Amadori compounds, as well as their kinetics of formation, are critically evaluated.

Psychrotrophs in dairy products: Their effects and their control

Abstract: Health concerns and technological effects of psychrotrophic bacteria in dairy products are reviewed, as well as methods to control their presence and development. The various Gram-negative and Gram-positive psychrotrophic species are listed and, with respect to pathogenic psychrotrophs, emphasis is given on Listeria monocytogenes, Yersinia enterocolitica, and Bacillus cereus. The influence of psychrotrophic bacteria on the quality of raw milk, pasteurized and UHT milks, butter, ice cream, cheese, and powders is examined. Public health considerations of Listeria monocytogenes, Yersinia enterocolitica, and Bacillus cereus of these various dairy products are also presented. Methods that can be used to eliminate or control the development of psychrotropic bacteria include low or high temperatures, chemicals, gases, the lactoperoxidase system, lactic acid bacteria, microfiltration, bactofugation, lactoferrin-related proteins, sanitation, flavors, and naturally occurring spore germinants.

Antioxidants and hormone-mediated health benefits of whole grains.

Abstract: Lignans and phytoestrogens have been associated with protective effect against hormone‐related diseases, for example, cancer of the breast and prostate, and potential mechanisms for this effect have been reported Antioxidants also appear to have some protective effect against diseases associated with reactive free radicals such as coronary heart disease and cancer Whole grains contain some of these substances particularly the mammalian lignan precursors, vitamin E, other phenolic compounds, Se, and phytic acid These substances may in part be responsible for the reduced risk of cancer and coronary heart disease associated with intake of high‐fiber diets containing whole grains Because they are more associated with the fiber in the outer layers of the grain, the intake of whole vs refined grain is emphasized for optimum health benefits

Effect of preheating on potato texture

Abstract: Preheating potatoes at 50 to 80°C has a firming effect on the cooked potato tissue. This effect is particularly pronounced at a preheating temperature of 60 to 70°C followed by cooling. Several theories have been presented in the literature to explain this firming effect: retrogradation of starch, leaching of amylose, stabilization of the middle lamellae and cell walls by the activation of the pectin methylesterase (PME) enzyme, and by the release of calcium from gelatinized starch and the formation of calcium bridges between pectin molecules. Most probably, none of these theories alone can explain the phenomenon and more than one mechanism seems to be involved. Some of these mechanisms seem to be interdependent. As an example, calcium could be considered as a link all the way through release after starch gelatinization to cross‐linking pectin substances in the cell wall and the middle lamellae, which has been demethylated by the PME enzyme. More research and “clear cut” experiments are needed in...

Myofibrillar protein from different muscle fiber types : implications of biochemical and functional properties in meat processing

Abstract: Texture, moisture retention, and tenderness of processed muscle foods are influenced by the functionality of myofibrillar protein. Recent studies have revealed large variations in processing quality between red and white muscle groups that can be attributed to differences in the functional properties of myofibrillar protein associated with the type of fiber. Myofibrillar proteins from fast- and slow-twitch fibers exhibit different biochemical and rheological characteristics and form gels with distinctly different viscoelastic properties and microstructures. The existence and wide distribution of the numerous myosin isoforms in different muscle and fiber types contribute to the various functional behaviors of myofibrillar protein. The different sensitivities of fast and slow myofibrillar proteins to pH, ionic environment, temperature, and other external factors have been well documented and illustrate the importance of adjusting meat processing conditions, according to fiber type profile to achieve maximum protein functionalities, and hence, uniform quality of the final muscle foods.

Nisin as a model food preservative

Abstract: Nisin is a ribosomally synthesized peptide that has broad-spectrum antibacterial activity, including activity against many bacteria that are food-spoilage pathogens. Nisin is produced as a fermentation product of a food-grade bacterium, and the safety and efficacy of nisin as a food preservative have resulted in its widespread use throughout the world, including the U.S. Nisin is a member of the class of antimicrobial substances known as lantibiotics, so called because they contain the unusual amino acid lanthionine. Lantibiotics, in general, have considerable promise as food preservatives, although only nisin has been sufficiently well characterized to be used for this purpose. As the number of known natural lantibiotics has increased and their useful characteristics have been explored, it has become desirable to synthesize structural analogs of nisin and other lantibiotics that do not occur naturally. The fact that lantibiotics are gene-encoded peptides synthesized by transcription and translation allows structural variants to be generated by mutagenesis. This review focuses on the progress that has been made in the construction and biological expression of genetically engineered nisin structural analogs. For example, a host-vector pair has been engineered that permits the construction of mutants of the structural gene for subtilin, which is a naturally occurring structural analog of nisin. The vector is designed in such a way that the mutant gene can be substituted for the natural subtilin gene in the chromosome of Bacillus subtilis, which in turn directs the transcription, translation, posttranslational modifications, and secretion of the mature form of the structural analog. Several structural analogs have been constructed, and their properties have provided insight into some of the structure-function relationships in lantibiotics, as well as their mechanism of antimicrobial action. These advances are assessed together with potential problems in the future development of nisin analogs as valuable new food preservatives.

Deamidation of food proteins to improve functionality.

Abstract: Many proteins, particularly those in plants, require structural modifications to improve their functional properties for expanded use. Several chemical and enzymatic methods are described for food protein deamidation to improve solubility, emulsification, foaming, and other functional properties of the proteins. The use of enzymes in protein modification is more desirable than chemical treatments because of their speed, mild reaction conditions, and their high specificity. Transglutaminase, protease, and peptidoglutaminase (PGase) are the only enzymes reported in the literature for protein deamidation. Of these, PGase appears to be the most feasible for practical application. PGase production, purification, and use in deamidation are discussed.

Optimizing the diet with whole grains

Abstract: Dietary recommendations may be perceived by the general population as causing a shift to less food and perhaps to less aesthetically pleasing foods often resulting in noncompliance. Technology can play a key role in this scenario by creating new formulated foods as well as by utilizing technology to modify whole foods or foods containing whole foods and enhancing both their health benefits and acceptability. At present we have evidence for a positive role in health of nutrients and many nonnutrients in foods, such as whole grains. However, all the linkages between dietary components and disease are not clear. Therefore, it is critical to design not only appealing formulated foods, but to also ensure adequate consumption of whole foods in order to obtain those compounds we know to be linked to good health, as well as those yet‐unknown compounds or interactions in food that are also linked to good health. In all cases, the technical and functional properties of food, as well as the nutritional, mus...

Nutrition, endothelial cell metabolism, and atherosclerosis.

Abstract: The vascular endothelium that forms an interface between the blood and the surrounding tissues is continuously exposed to both physiologic and pathophysiologic stimuli. These stimuli are often mediated by nutrients that can contribute to the overall function of the endothelial cell in the regulation of vascular tone, coagulation and fibrinolysis, cellular growth and differentiation, and immune and inflammatory responses. Therefore, nutrient-mediated functional changes of the endothelium and the underlying tissues may be significantly involved in the atherosclerotic disease process. There is evidence that individual nutrients or nutrient derivatives may either provoke or prevent metabolic and physiologic perturbations of the vascular endothelium. Preservation of nutrients that exhibit antiatherogenic properties may, therefore, be a critical issue in the preparation and processing of foods. This review focuses on selected nutrients as they affect endothelial cell metabolism and their possible implications in atherosclerosis.

Whole grains--impact of consuming whole grains on physiological effects of dietary fiber and starch.

Abstract: Much of the present research on the physiological effects of dietary fiber and starch has been done on sources isolated from the parent material, and it is not clear whether they have the same effects if fed in the intact or whole grain. For dietary fiber, physiological effect depends on extent of fermentation in the large intestine, and this is influenced by chemical composition, solubility, physical form, and presence of lignin or other compounds. All of these factors are altered by isolation of a fiber source from the whole grain, and hence effects of eating fiber vary. Similarly, physical form and presence in the whole grain will affect digestibility of starch in the small intestine, which in turn influences the glycemic response and colonic effects determined by the extent of malabsorption and entry into the colon. Starch that enters the colon is fermented and produces short-chain fatty acids, particularly butyrate, which is necessary to maintain a healthy mucosa. Hence, their presence within the whole grain may have important implications for health for both dietary fiber and starch. Evidence indicates that such effects are beneficial and that whole-grain consumption should be encouraged.

Epidemiological evidence for the impact of whole grains on health

Abstract: Current dietary advice suggests consumers increase consumption of whole‐grain products because of their potential role in prevention of chronic disease. Whole grains are important sources of nutrients that are in short supply in our diet, including dietary fiber, resistant starch, trace minerals, certain vitamins, and other compounds of interest in disease prevention, including phytoestrogens and antioxidants. Despite dietary recommendations to increase intake of whole grains, little epidemiological evidence is available to support the physiological importance of whole‐grain intake. Most epidemiological studies focus on nutrients, rather than whole foods, so little attempt has been made to evaluate the contribution of whole grains in disease. Further, studies on vegetarians that show decreased risk of degenerative diseases are unable to separate the contribution of fruit and vegetable intake when compared with whole‐grain intake and protection from disease. The few epidemiological studies that ha...

Achieving dietary recommendations: whole-grain foods in the Food Guide Pyramid.

Abstract: The Food Guide Pyramid illustrates USDA's food guide developed to help people follow the Dietary Guidelines for Americans. Unlike earlier food guides, the new food guide specifies foods for a total diet; that is, it addresses both concerns about adequacy and moderation. The food guide recommends increased intakes of the vegetable, fruit, and grain groups with special emphasis on dark‐green leafy vegetables, legumes, and whole‐grain products. These foods are important sources of several vitamins and minerals, complex carbohydrates, and dietary fiber, and they are generally low in fat. Analyses of expected nutrient levels provided by the food guide diet patterns indicate that the nutrient contribution of whole‐grain products is particularly important for diets at lower calorie levels. In these diets, it is recommended that at least half the number of servings in the grain group be whole‐grain products. In all diets, it is recommended that several servings of whole‐grain products be included each da...

A report of the proceedings of an MSG workshop held august 1991

Abstract: This report of the proceedings of a workshop on monosodium glutamate (MSG) represents the output of an exchange of scientific information, discussed and debated, by a group of experts representing a variety of disciplines. Experts in the areas of food science, potential adverse reactions to foods, pharmacology, neuroscience, biochemistry, nutrition, pediatrics, and anatomy reviewed the current scientific literature relative to the safe use of MSG in foods. These proceedings supplement the extensive literature compiled by various prestigious international expert committees since the flavor‐enhancing properties of MSG were identified around the turn of the century.

Dietary patterns vs. dietary recommendations: identifying the gaps for complex carbohydrate.

Abstract: Dietary guidelines of the U.S. and Canada recommend that 55% of dietary calories of individuals should come from carbohydrates, especially complex carbohydrates. However, they generally fail to describe how much should come from complex carbohydrates. Undoubtedly, this is because of confusion about the composition of complex carbohydrate foods and incomplete knowledge of the health benefits of all components of grain products. With the intent of shifting dietary food selection to increase carbohydrate consumption above the current 46% of calories, food guides recommend 5 to 12 servings per day from grain products. Current estimated intake for adults is between four to five servings of grain products, of which less than one is from whole grain, in an average 2000-kcal adult diet. To follow the advice of the U.S. Food Guide Pyramid, which suggests half the bread (grains) group should be whole-grain products, adult Americans should increase their intake of whole-grain products four- to fivefold and double their intake of total grain products.

Narrowing the gap: practical strategies for increasing whole-grain consumption.

Abstract: Overcoming consumer confusion and doubt regarding nutrition recommendations is key to communicating the message to increase whole‐grain foods in the diet Nutrition communicators may do that more successfully by using four tactics to fashion messages about whole grains: (1) present a positive message; (2) keep it short and simple; (3) keep the message practical and flexible; (4) speak with a united voice The quantitative recommendation to eat at least three servings of whole‐grain foods daily also must be integrated into national nutrition documents, such as Healthy People 2000, Dietary Guidelines for Americans, the Food Guide Pyramid, Nutrition Recommendations for Canadians, and Canada's Food Guide to Healthy Eating, if we are to be truly successful in communicating the need to increase whole‐grain consumption

Darwinian evolution patterns in food products and beverages

Abstract: Although the development and survival of food products are regulated by mechanisms that bear little resemblance to those operating in the living world, their general evolutionary patterns share certain common features. These include punctuated equilibria, convergent evolution, coevolution, the equivalence of symbiosis, and, rarely, even parasitism. The evolution of food products, like that of living organisms and other systems, is a nonlinear process. Consequently, its path can be affected not only by major events that drastically alter the environment but also by very minor events that may be unnoticeable at the time of their occurrence.

The regulatory environment past and future : incentive or impediment to developments in food science and technology : a perspective from FDA

Abstract: The best system for protecting public health is one that involves two layers of control before food reaches the consumer. The first layer of control is the industry's clear responsibility to prepare food that is safe. The second layer of control is the monitoring that is provided by government to ensure that the industry is doing its job and is in fact producing safe food. While some may view this “second layer” as an impediment in the development and marketing of new technologies, there is another way to look at the “regulatory environment”. The regulatory environment itself, is not an impediment to the development of food science and technology. The regulatory environment, with all its components — scientists, consumers, industry, and Congress — defines “safety” within the context of today's technology, scientific capability, and tolerance level of the lay public. The entire regulatory environment serves to guide the development of food science and technology by providing signposts, in the form...

The brave new world of FDA nutrition regulation — some thoughts about current trends and long‐term effects∗

Abstract: This article reviews long‐term trends at the U.S. Food and Drug Administration (FDA) concerning regulation of nutrition, and considers how these trends may affect products of the food industry in the decades ahead. Among the topics discussed are the FDA's rules concerning the provision of basic, standard format nutrition information (“nutrition labeling”) on food products. These rules have changed dramatically over the past 50 years from a period when no information was required to a period when information was required only if a nutrient claim was made or if a nutrient was added to the product to the new FDA regulations that become effective in 1994, which require standardized nutrition labeling on most food products in interstate commerce. There have also been important shifts in the procedures concerning government regulation of nutrition‐related labeling. In general, previously a food company was free to provide truthful and nonmisleading labeling claims about the nutrition content of a food ...

Regulatory environment: incentive or impediment to developments in food science and technology.

Abstract: The regulatory environment is one of several key factors that impact successful technological development and commercialization. The current process of developing and implementing regulations is extremely complex and does not always apply the principle of benefit:risk and balance protection with progress. Although the current system is effective in protecting consumers, it tends to impede technological innovation. To help improve balance and effectiveness, an independent "food regulatory board" is recommended.