Showing papers in "Critical Reviews in Food Science and Nutrition in 2003"

Tea catechins and polyphenols: health effects, metabolism, and antioxidant functions.

Abstract: Increasing interest in the health benefits of tea has led to the inclusion of tea extracts in dietary supplements and functional foods. However, epidemiologic evidence regarding the effects of tea consumption on cancer and cardiovascular disease risk is conflicting. While tea contains a number of bioactive chemicals, it is particularly rich in catechins, of which epigallocatechin gallate (EGCG) is the most abundant. Catechins and their derivatives are thought to contribute to the beneficial effects ascribed to tea. Tea catechins and polyphenols are effective scavengers of reactive oxygen species in vitro and may also function indirectly as antioxidants through their effects on transcription factors and enzyme activities. The fact that catechins are rapidly and extensively metabolized emphasizes the importance of demonstrating their antioxidant activity in vivo. In humans, modest transient increases in plasma antioxidant capacity have been demonstrated following the consumption of tea and green tea catechins. The effects of tea and green tea catechins on biomarkers of oxidative stress, especially oxidative DNA damage, appear very promising in animal models, but data on biomarkers of in vivo oxidative stress in humans are limited. Larger human studies examining the effects of tea and tea catechin intake on biomarkers of oxidative damage to lipids, proteins, and DNA are needed.

Chitin--the undisputed biomolecule of great potential

Abstract: Of the truly abundant polysaccharides in Nature, only chitin has yet to find utilization in large quantity. Chitin is the second most abundant natural biopolymer derived from exoskeletons of crustaceans and also from cell walls of fungi and insects. Chitin is a linear beta 1,4-linked polymer of N-acetyl-D-glucosamine (GlcNAc), whereas chitosan, a copolymer of GlcNAc (approximately 20%) and glucosamine (GlcN, 80%) residues, is a product derived from de-N-acetylation of chitin in the presence of hot alkali. Chitosan is, in fact, a collective name representing a family of de-N-acetylated chitins deacetylated to different degrees. Both chitin/chitosan and their modified derivatives find extensive applications in medicine, agriculture, food, and non-food industries as well. They have emerged as a new class of physiological materials of highly sophisticated functions. Their application versatility is a great challenge to the scientific community and to industry. All these are the result of their versatile biological activity, excellent biocompatibility, and complete biodegradability in combination with low toxicity. Commercial availability of high-purity forms of chitin/chitosan and the continuous appearance of new types of chitin/chitosan derivatives with more and more useful and specific properties have led to an unlimited R&D efforts on this most versatile amino polysaccharide, chitin to find new applications, which are necessary to realize its full potential. Incidentally, this too has become an environmental priority. No doubt, chitin is surely an undisputed biomolecule of great potential.

Production, properties, and some new applications of chitin and its derivatives.

Abstract: Chitin is a polysaccharide composed from N-acetyl-D-glucosamine units. It is the second most abundant biopolymer on Earth and found mainly in invertebrates, insects, marine diatoms, algae, fungi, and yeasts. Recent investigations confirm the suitability of chitin and its derivatives in chemistry, biotechnology, medicine, veterinary, dentistry, agriculture, food processing, environmental protection, and textile production. The development of technologies based on the utilization of chitin derivatives is caused by their polyelectrolite properties, the presence of reactive functional groups, gel-forming ability, high adsorption capacity, biodegradability and bacteriostatic, and fungistatic and antitumour influence. Resources of chitin for industrial processing are crustacean shells and fungal mycelia. Fungi contain also chitosan, the product of N-deacetylation of chitin. Traditionally, chitin is isolated from crustacean shells by demineralization with diluted acid and deproteinization in a hot base solution. Furthermore, chitin is converted to chitosan by deacetylation in concentrated NaOH solution. It causes changes in molecular weight and a degree of deacetylation of the product and degradation of nutritionally valuable proteins. Thus, enzymatic procedures for deproteinization of the shells or mold mycelia and for chitin deacetylation were investigated. These studies show that chitin is resistant to enzymatic deacetylation. However, chitin deacetylated partially by chemical treatment can be processed further by deacetylase. Efficiency of enzymatic deproteinization depends on the source of crustacean offal and the process conditions. Mild enzymatic treatment removes about 90% of the protein and carotenoids from shrimp-processing waste, and the carotenoprotein produced is useful for feed supplementation. In contrast, deproteinization of shrimp shells by Alcalase led to the isolation of chitin containing about 4.5% of protein impurities and recovery of protein hydrolysate.

Tomatoes and cardiovascular health.

Abstract: Diet is believed to play a complex role in the development of cardiovascular disease, the leading cause of death in the Western world. Tomatoes, the second most produced and consumed vegetable nationwide, are a rich source of lycopene, beta-carotene, folate, potassium, vitamin C, flavonoids, and vitamin E. The processing of tomatoes may significantly affect the bioavailability of these nutrients. Homogenization, heat treatment, and the incorporation of oil in processed tomato products leads to increased lycopene bioavailability, while some of the same processes cause significant loss of other nutrients. Nutrient content is also affected by variety and maturity. Many of these nutrients may function individually, or in concert, to protect lipoproteins and vascular cells from oxidation, the most widely accepted theory for the genesis of atherosclerosis. This hypothesis has been supported by in vitro, limited in vivo, and many epidemiological studies that associate reduced cardiovascular risk with consumption of antioxidant-rich foods. Other cardioprotective functions provided by the nutrients in tomatoes may include the reduction of low-density lipoprotein (LDL) cholesterol, homocysteine, platelet aggregation, and blood pressure. Because tomatoes include several nutrients associated with theoretical or proven effects and are widely consumed year round, they may be considered a valuable component of a cardioprotective diet.

Nonthermal preservation of foods using combined processing techniques.

Abstract: In the last 2 decades, consumer demand for fresher, higher quality, and safer food has promoted research on nonthermal methods of food preservation for the inactivation of microorganisms and enzymes as an alternative to thermal processes. However, the high resistance of certain enzymes and microorganisms to nonthermal processes, especially bacterial spores, limit their application. To expand the use of nonthermal processes in the food industry, combinations of these technologies with traditional or emerging food preservation techniques are being studied. The use of nonthermal processes in combination with other preservation technologies presents a number of potential benefits to food preservation. The purpose of this article is to review some successful combinations of different nonthermal technologies, such as high hydrostatic pressure, ultrasound, pulsed electric fields, and irradiation, with traditional or emerging food preservation technologies.

The Study of Phenolic Compounds as Natural Antioxidants in Wine

Abstract: Plant phenolics present in fruit and vegetables, and that are particularly rich in red wine, have received considerable attention because of their potential antioxidant activity. Human consumption of antioxidants has many alleged health benefits, including protection against cardiovascular diseases, and, most recently, cancer. Red wines contain a variety of polyphenolic antioxidants. Five samples of commercial red wines from Spain and four phenolic compounds of red wine: gallic acid, trans-resveratrol, quercetin and rutin, have been studied. The total phenolics content and the total antioxidant activity (TAA) of wines was determined. The total phenolic content, determined according to the Folin-Ciocalteu method, varied from 1800 to 2300 mg/L, expressed as gallic acid equivalents (GAE). The antioxidative effects of wine phenolics were determined using a system based on the inhibition by antioxidants of the absorbance of the radical cation. The relationship between antioxidant activity of phenolic comounds, as hydrogen donating free radical scavengers, and their chemical structures was studied. Furthermore, the total antioxidant activity of the wines investigated was well correlated with phenol content. Thus, the results confirm that red wine polyphenols are, in vitro, significant antioxidants.

The physiological effects of dietary boron.

Abstract: Boron may be an essential nutrient for animals and humans. Dietary boron influences the activity of many metabolic enzymes, as well as the metabolism of steroid hormones and several micronutrients, including calcium, magnesium, and vitamin D. Boron supplementation in rats and chicks has been shown to increase bone strength. Boron may also play a role in improving arthritis, plasma lipid profiles, and brain function. Additional research is necessary to further clarify boron's influence in human and animal physiology, as well as determine a dietary requirement for humans.

Radio frequency heating of foods: principles, applications and related properties--a review.

Abstract: Radio frequency (RF) heating is a promising technology for food applications because of the associated rapid and uniform heat distribution, large penetration depth and lower energy consumption Radio frequency heating has been successfully applied for drying, baking and thawing of frozen meat and in meat processing However, its use in continuous pasteurization and sterilization of foods is rather limited During RF heating, heat is generated within the product due to molecular friction resulting from oscillating molecules and ions caused by the applied alternating electric field RF heating is influenced principally by the dielectric properties of the product when other conditions are kept constant This review deals with the current status of RF heating applications in food processing, as well as product and system specific factors that influence the RF heating It is evident that frequency level, temperature and properties of food, such as viscosity, water content and chemical composition affect the dielectric properties and thus the RF heating of foods Therefore, these parameters should be taken into account when designing a radio frequency heating system for foods

A review on biological control and metabolism of aflatoxin.

Abstract: The series of events that led to the discovery of aflatoxin as a potent carcinogen, its biosynthesis, mechanism of action, structure-function relationship provide interesting insight into the economical and technological factors involved in the development of an effective control measure for the toxin. Scientists all over the world are making continuous efforts to explore a generalized process of detoxification, which can bring down the toxin content in heterogeneous commodities to a threshold level. In this article biological control methods with special emphasis on in vivo and in vitro enzymatic detoxification of aflatoxin have been reviewed. Future areas of research involving large-scale enzymatic detoxification and modified atmosphere storage are also discussed. Referee: Dr. F. S. Chu, 16458 Denhave Court, Chino Hills, CA 91709

Nutritional Responses to the Presence of Inulin and Oligofructose in the Diets of Domesticated Animals: A Review

Abstract: Inulin and oligofructose are prebiotic oligosaccharides fermented in the large intestine. This article provides an extensive review of the effects of these oligosaccharides on gastrointestinal characteristics (microflora, pathogen control, epithelial cell proliferation, putrefactive compound production, fecal characteristics, and nutrient digestibility) and systemic metabolism of carbohydrates, nitrogen, lipids, and minerals in dogs, cats, horses, calves, pigs, poultry, and rabbits. In addition, intake of inulin and oligofructose and considerations in their supplementation to animal diets are discussed. Growth performance and meat production in livestock in response to inulin and oligofructose supplementation are addressed. Finally, the possible substitution of antibiotics with fructans in animal diets and directions for future research are presented.

Caviars and Fish Roe Products

Abstract: Fish roe products are extremely valuable and currently enjoy expanding international and domestic markets. Caviars represent the best-known form of fish roe products; however, several other product forms are also consumed, including whole skeins and formulations with oils and cheese bases. Caviars are made from fish roe after the eggs have been graded, sorted, singled-out, salted or brined, and cured. Most caviar is marketed as a refrigerated or frozen food. Several types of caviar from different fish species are marketed as shelf-stable products. Market preferences for lower salt content have raised food safety concerns. Descriptions of and processing technologies for many delightful fish roe and caviar food products are presented here.

Peptides From Milk Proteins and Their Properties

Abstract: This review has attempted to study the literature pertaining to peptides derived from milk proteins. Hydrolysis of milk proteins to generate peptides has been practiced for a long time and it was recognized early on in this process that the taste of hydrolyzates might hinder use of these products in food formulations. Modification of protein is necessary to form a more acceptable or utilizable product, to form a product that is less susceptible to deteriorative reactions and to form a product that is of higher nutritionall quality. Modifications may be achieved by a number of chemical and enzymatic means. This review has considered only enzymatic modification of dairy proteins. Modified proteins contain peptides and some of these peptides have been purified and their functionalities have been compared with unmodified proteins. This paper has examined the literature pertaining to improvement in functionality of enzyme-modified proteins. Improvements in solubility, emulsification, foaming and gelation were examined. There is limited information available on the sequence of the peptides necessary to improve the functional characteristics of proteins. Knowing the sequences of desirable functional peptides can lead to genetic alteration of proteins to improve functionality. Addition of synthetic peptides to intact proteins may be another way in which the functionality of proteins can be augmented. Some of the peptides in milk proteins are capable of affecting biological functions of an organism. These effects can be antimicrobial and probiotic, i.e., prevent the growth and proliferation of undesirable and pathogenic organisms, or they may promote the growth of desirable bacteria in the digestive tract of humans and animals. Peptides derived from milk protein have been shown to exert digestive and metabolic effects as well. They may also influence the immune system. These biological effects may play an important role in the development of medical foods that treat or mitigate the effects of diseases. Proteins are allergens and therefore it is possible that products derived from modification of proteins may also be allergens. The known literature about the allergenicity of peptides derived from milk proteins has been examined in this article. Last, but not the least, the taste attributes of peptides is also considered. Bitterness of hydrolyzates is a common occurrence and the origins of these bitter peptides and possible ways of mitigating this sensory defect has been discussed. Many of the peptides that enhance functionality and exert biological activity are likely to be bitter. Therefore, the bitter taste of hydrolysis products has to be dealt with in boosting the functional or nutraceutical aspects of foods containing these peptides. Analytical techniques for sequencing peptides have become more accessible and purification of peptides is commercially feasible. Computer based modeling techniques have aided the prediction of structures in these peptides. These advances, coupled with the advances in biotechnology, promise to revolutionize the future of nutraceutical and functional foods.

New trends in food processing.

Abstract: In this work some of the newest trends in food processing are reviewed. This revision intends to provide an updated overview (including works published until February 2001) on the newest food processes, including food manufacturing, preservation, and control. Modern processes for food and food ingredients manufacturing based on membrane technology, super-critical fluid technology, and some applications of biotechnology are presented, mainly applied to obtain functional foods, "all-natural" enriched foods, probiotics and prebiotics. Also included is a critical assessment concerning non-thermal preservation techniques used for food preservation, such as high hydrostatic pressure, pulsed electric fields, ultrasound, pulsed light, hurdle systems, etc. Finally, a group of new analytical techniques (i.e., molecular techniques such as Polymerase Chain Reaction (PCR), food image analysis, and biosensors) and their use for food and process control is reviewed.

Effects of combined pressure and temperature on enzymes related to quality of fruits and vegetables: from kinetic information to process engineering aspects.

Abstract: Throughout the last decade, high pressure technology has been shown to offer great potential to the food processing and preservation industry in delivering safe and high quality products. Implementation of this new technology will be largely facilitated when a scientific basis to assess quantitatively the impact of high pressure processes on food safety and quality becomes available. Besides, quantitative data on the effects of pressure and temperature on safety and quality aspects of foods are indispensable for design and evaluation of optimal high pressure processes, i.e., processes resulting in maximal quality retention within the constraints of the required reduction of microbial load and enzyme activity. Indeed it has to be stressed that new technologies should deliver, apart from the promised quality improvement, an equivalent or preferably enhanced level of safety. The present paper will give an overview from a quantitative point of view of the combined effects of pressure and temperature on enzymes related to quality of fruits and vegetables. Complete kinetic characterization of the inactivation of the individual enzymes will be discussed, as well as the use of integrated kinetic information in process engineering.

Exopeptidases and their application to reduce bitterness in food: a review.

Abstract: When exopeptidases catalyze hydrolysis of peptide bonds, the product(s) may have a less bitter taste, and the free amino acids or small peptides formed may function in food as pleasant-tasting flavor compounds or as flavor precursors. There are several classes of exopeptidase based on specificity for hydrolysis of synthetic substrates. Exopeptidases in food-stuff may be of natural origin or may be extrinsic, that is, produced by microorganisms or parasites. Exopeptidases used to modify foods are also becoming increasingly available in the industrial enzyme market. Exopeptidases contribute to a variety of quality changes in postharvest fruit, meats, and food fermentations. Foodstuff impacted by these enzymes during processing include cocoa, beer, aged and cured meat products, koji, fish sauce, ripened cheeses, and protein hydrolysates. An important role of exopeptidases in food is the hydrolysis of hydrophobic, bitter peptides. The relationship between peptide structure and sensory transduction/receptor models is discussed. Research on the use of exopeptidases to reduce bitterness is reviewed.

Low-glycemic-load diets: impact on obesity and chronic diseases.

Abstract: Historically, carbohydrates have been thought to play only a minor role in promoting weight gain and in predicting the risk of development of chronic disease. Most of the focus had been on reducing total dietary fat. During the last 20 years, fat intake decreased, while the number of individuals who were overweight or developed a chronic conditions have dramatically increased. Simultaneously, the calories coming from carbohydrate have also increased. Carbohydrates can be classified by their post-prandial glycemic effect, called the glycemic index or glycemic load. Carbohydrates with high glycemic indexes and high glycemic loads produce substantial increases in blood glucose and insulin levels after ingestion. Within a few hours after their consumption, blood sugar levels begin to decline rapidly due to an exaggerated increase in insulin secretion. A profound state of hunger is created. The continued intake of high-glycemic load meals is associated with an increased risk of chronic diseases such as obesity, cardiovascular disease, and diabetes. In this review, the terms glycemic index and glycemic load are defined, coupled with an overview of short- and long-term changes that occur from eating diets of different glycemic indexes and glycemic loads. Finally, practical strategies for how to design low-glycemic-load diets consisting primarily of low-glycemic carbohydrates are provided.

Mechanisms and prevention of plant tissue collapse during dehydration: a critical review.

Abstract: The appearance and functional properties are primordial in the quality assessment of semifinished fruit and vegetable products. These properties are often associated with shrunken, shriveled, darkened materials of poor rehydration ability after been subjected to air-drying--the most used drying method in the food industry. Fruits and vegetables are cellular tissues containing gas-filled pores that tend to collapse when subjected to dehydration. Collapse is an overall term that has different meanings and scale-settings in the literature depending on whether the author is a plant physiologist, a food technologist, a chemical engineer, or a material scientist. Some clarifications are given in this particular but wide field. The purpose of this work was to make a state-of-the-art contribution to the structural and textural effects of different types of dehydration on edible plant products and give a basis for preventing this phenomenon. The plant tissue is described, and the primordial role of the cell wall in keeping the structural integrity is emphasized. Water and its functionality at macro and micro levels of the cellular tissue are reviewed as well as its transport during dehydration. The effects of both dehydration and rehydration are described in detail, and the term "textural collapse" is proposed as an alternative to structural collapse.

Towards sustainable production of protein-rich foods: appraisal of eight crops for Western Europe. PART II: Analysis of the technological aspects of the production chain.

Abstract: Increased production of plant protein is required to support the production of protein-rich foods which can replace meat in the human diet to reduce the strain that intensive animal husbandry poses on the environment. The suitability of lupin (Lupinus spp.), pea (Pisum sativum), quinoa (Chenopodium quinoa Willd.), triticale (x Triticosecale), lucerne (Medicago sativa), grasses (Lolium and Festuca spp.), rapeseed/canola (Brassica napus) and potato (Solanum tuberosum) for protein production in Western Europe was studied on the basis of a chain-approach. The technological aspects, which are considered in this paper, are the processing methods, and the functional and nutritional properties of the derived protein products. The overall evaluation of the technological prospects of the eight crops as a protein source for Western Europe leads to the conclusion that this part of the production chain is not decisive for that choice. Pea and lupin have a slight advantage over the other crops, because their concentrates and isolates are already commercially available.

Lipase Mediated Upgradation of Dietary Fats and Oils

Abstract: In the present scenario, fats and oil modification is one of the prime areas in food processing industry that demands novel economic and green technologies. In this respect, tailored vegetable oils with nutritionally important structured triacylglycerols and altered physicochemical properties have a big potential in the future market. In this context, it is well established that lipases especially microbial lipases, which are regiospecific and fatty acid specific, are of immense importance and hence could be exploited for retailoring of vegetable oils. Further, of the bulk available, cheap oils could also be upgraded to synthesize nutritionally important structured triacylglycerols like cocoa butter substitutes, low calorie triacylglycerols, PUFA-enriched and oleic acid enriched oils. It is also possible to change the physical properties of natural oils to convert them into margarines and hard butter with higher melting points or into special low calorie spreads with short or medium chain fatty acids. Today, by and large, fat and oil modifications are carried out chemically following the method of directed inter-esterification. The process is energy intensive and non-specific. Lipase mediated modifications are likely to occupy a prominent place in oil industry for tailoring structured lipids since enzymatic modifications are specific and can be carried out at moderate reaction conditions. However, as a commercial venture, lipases are yet to be fully exploited. Once the technologies are established, the demand of lipases in oil industry is expected to increase tremendously in the near future for specific modifications of fats and oils to meet the changing consumers' dietary requirements.

Implementation of Chemometrics for Quality Control and Authentication of Meat and Meat Products

Abstract: Multivariate analysis has been established as a very powerful and effective tool in classifying and grouping individual products. Principal Component Analysis, Canonical analysis, Cluster and Partial Least Squares were found to be indispensable for classifying food products according to variety and/or geographical origin. Meat and meat products were correctly classified for authentication purposes to various groups following instrumental and/or sensory analyses.

Calculation of the non-isothermal inactivation patterns of microbes having sigmoidal isothermal semi-logarithmic survival curves.

Abstract: Sigmoidal isothermal semi-logarithmic survival curves are of two main types; starting with a downward and changing to upward concavity and vice versa. Both can be described by a variety of mathematical models having 3-4 adjustable parameters. The temperature dependence of these models' parameters can be described by empirical models, which account for the progressive change in the sigmoidal shape, including its disappearance at either high or low temperatures. If the temperature history of a heat-treated population of microbial cells or spores ('temperature profile') can be described algebraically, then there is a way to estimate the survival pattern under these non-isothermal conditions without invoking the traditional D and z values, which require forcing straight lines through the curved experimental data. The described method is based on the assumption that the local slope of the non-isothermal survival curve is that of the isothermal curve at the momentary temperature, at a time, which corresponds to the momentary survival ratio. It is similar to the method previously proposed for microbial populations with a 'power law' type isothermal survival curves, except that the time, which corresponds to the momentary survival ratio, is calculated either symbolically or numerically as a procedure incorporated in the governing differential equation. The method's capabilities are demonstrated with simulated survival curves under temperature histories that resemble thermal processing of foods. They include heating to different target temperatures and starting the cooling at different times.

Novel approaches and application of contemporary sensory evaluation practices in iron fortification programs.

Abstract: Iron deficiency is the leading nutritional deficiency in the U.S. and the rest of the world, with its highest prevalences in the developing world. Iron fortification of food has been proposed as a strategy to reduce the high prevalence of iron deficiency. Poor consumer acceptance, unacceptable taste, and discoloration of the iron-fortified foods have been frequently listed as causes of unsuccessful iron fortification programs. An excellent prospect for improving consumer acceptance of iron-fortified foods is the incorporation of a thorough, organized, and unified approach to sensory evaluation practices into iron fortification programs for product optimization. The information gained from systematic sensory evaluation allows for the manipulation of the sensory attributes, and thus improvement of the sensory properties of the fortified food. However, iron fortification programs have not systematically measured the effect of fortification on the sensory quality of the food. Because sensory evaluation is an important criterion in successful iron fortification, an integrated approach is necessary. Therefore, nutritionists and sensory scientists should work closely with each other to select the most suitable sensory tests and methods. The objectives of this article are to: (1) critically review and discuss some traditional and contemporary approaches and applications of sensory evaluation practices in iron fortification programs, and (2) demonstrate the importance of incorporating a multidisciplinary, systematic sensory evaluation approach in iron fortification programs.

Development of hazard analysis by critical control points (HACCP) procedures to control organic chemical hazards in the agricultural production of raw food commodities.

Abstract: Hazard Analysis by Critical Control Points (HACCP) is a systematic approach to the identification, assessment, and control of hazards in the food chain. Effective HACCP requires the consideration of all chemical, microbiological, and physical hazards. However, current procedures focus primarily on microbiological and physical hazards, while chemical aspects of HACCP have received relatively little attention. In this article we discuss the application of HACCP to organic chemical contaminants and the problems that are likely to be encountered in agriculture. We also present generic templates for the development of organic chemical contaminant HACCP procedures for selected raw food commodities, that is, cereal crops, raw meats, and milk. Referee: Dr. Michal Voldrich, Department of Food Preservation, Institute of Chemical Technology, Technikca 6, 166 28 Prague 6, Czech Republic