CRC critical reviews in food science and nutrition最新文献

About 15 million children under 5 years of age die each year due to suppressed immunity and the resulting increased infection. In severely malnourished children and animals some immune systems such as T-cell function, secretory IgA and complement are significantly suppressed. Other systems, such as the serum IgG or IgA, are normal or even elevated. Some of these changes are apparently caused by nutritional stress while others may be due to stimulation by increased incidence of infection and antigen load. On the other hand, marginal malnutrition stimulates increased phagocytosis and T-cell function with increased immunity to cancer but decreased resistance to certain microbial agents. The mechanisms of immune suppression by malnutrition, persistence of these effects after renutrition, and the effect of maternal malnutrition on newborn immunity are critically reviewed. Possible non-nutritional means of rapid immunological restoration of malnourished children are described.

The production of high fructose corn syrups was greatly facilitated by the use of immobilized glucose isomerase. Similarly, in Japan, the fermentation industry proved its processing efficiency for amino acids through the use of immobilized amino acid acylase. This article discusses the use of soluble enzymes in the food industry followed by a section on the various available methods to immobilize enzymes. Once enzymes are immobilized, many of their operational parameters could be altered. Rationale for the determination of the effects of immobilization is provided. A relatively new concept is the use of a single matrix for immobilizing more than one enzyme. Immobilized multi-enzyme systems offer many attractive advantages; however, such a process also raises some interesting questions about kinetics. These questions and their suggested answers are discussed in the penultimate section. The major emphasis of this article is on the use of immobilized enzymes in the food industry. Two systems--amino acylase and glucose isomerase--have been demonstrated to be techno-economically feasible. Immobilization of other enzymes, such as glucoamylase, lactase, protease, and flavor modifying enzymes, has received some attention. The potential of these new systems are also discussed.

Fructose has recently received much attention due to renewed interest in natural sweeteners. In addition, fructose has some advantages to sucrose in sweetness, solubility, viscosity, and dental health characteristics. Fructose is deposited as storage fructans of the inulin (beta-1,2) type in tubers and rhizomes of the Compositae family. The utilization of the Jerusalem artichoke (Helianthus tuberosus) tuber as a source of fructose syrup is discussed. This plant has the potential to produce more sugar per acre than corn or sugar beets. In addition, the artichoke has higher frost resistance and lower heat unit requirements than corn and is somewhat more tolerant to low moisture conditions than sugar beets. A high quality fructose syrup can be produced from artichoke tubers. The extraction step was found to be particularly important since development of adverse colors and flavors must be prevented. The fructans may be acid or enzyme hydrolyzed but the latter method gave a higher quality syrup. Ion-exchange resins and activated charcoal were effective in removing coloring and flavoring materials, and also reduced other noncarbohydrate constituents. Since the enzymatic hydrolysis of the fructans is an attractive alternative to acid hydrolysis, a process was developed for producing and purifying a special beta-fructofuranosidase (inulase) from Saccharomyces fragilis. Inulase has a much higher specificity for fructans than commerically available beta-fructofuranosidase (invertase).

Determining vitamin D content in foods is difficult because in natural foods of highest vitamin D activity, and even in vitamin D-fortified foods, only small quantities are present, and many other compounds are extracted along with vitamin D that cause difficulties in purifying the extract or in the spectrophotometry or colorimetry that follows. Several physicochemical methods--such as spectrophotometric, colorimetric, thin-layer chromatographic, adsorption, partition, gas-liquid, and high-performance column chromatographic--have been tried for assay foods for vitamin D, but none of them have been accepted for official or routine use; they are time consuming and expensive, or lack the required sensitivity, precision, or accuracy. Curative biological assays, based on degree of healing of a leg bone of rats previously made rachitic, is the generally accepted method to determine vitamin D content of foods. However, that method also requires too much time and is expensive. The recently developed high-performance liquid chromatographic method may offer the most for establishing a satisfactory physicochemical method for determining vitamin D in foods. Many of the difficulties and problems in assaying foods for vitamin D are discussed.

The formation of flavor in fermented beverages is due to various biosynthetic mechanisms. In wine, flavors arise as the result of compounds: 1. Originating from the native fruit (grap) 2. Which are formed or altered during the various processes employed in production 3. Which are developed or transformed by yeast during fermentation 4. Arise during the aging process In this review the results of investigations on the development of flavors in grape and wine will be discussed. Special attention will be devoted to the effects of specific processes in winemaking on the development of flavor.

Obesity, a common disorder causing excess mortality due to the development of cardiovascular disease, hypertension, respiratory illness, and diabetes, is difficult to control by simple dieting techniques. Low calorie foods, which can facilitate newer weight reduction approaches such as behavior modification, often lack adequate palatability due to the absence of carbohydrate or fat. Various low calorie bulking agents that can replace the traditionally used carbohydrates and fats are discussed in terms of caloric value, utility, and regulatory status. Methods of measuring caloric utilization of bulking agents in test animals and humans are evaluated. For fat, no really satisfactory replacement is currently available, although several promising are under development. Dietary fiber sources such as microcrystalline cellulose are receiving considerable attention as flour replacements. While the polyols have many desirable attributes, as sucrose replacements, their caloric utilization values generally prevent a significant caloric reduction when they are used in foods. Several experimental sucrose replacements are described.

This article is an attempt to study the metabolic functions of vitamin C and E together. Such a study must necessarily be imcomplete owing to the extreme richness of the literature. The increasing importance of the work on free radical reactions, their toxicity and carcinogenic action, and also their relation to the metabolism of metals, particularly iron, copper, selenium, and zinc, shows a number of metabolic pathways with which both vitamins interact. It is hoped that this article will indicate future research possibilities.

Furan represent a class of compounds that have been reported in a wide variety of foods. Normally, they result from thermal decomposition reactions, and, as such, are important in foods. They also possess unique sensory properties and, thus, can significantly contribute to food flavor. This review shall attempt to summarize their food occurrences, organoleptic properties, and formation pathways.

Ergot is caused by a fungus (Claviceps species) which has been found on hundreds of plants in almost every country of the world. The fungus can adapt itself to form many different varieties. New species of the fungus and new hosts are still discovered today. The alkaloids in ergot have caused hundreds of thousands of deaths in the Middle Ages after consumption of contaminated cereal grains, but during the last two decades there has not been a recorded outbreak of ergotism. Grain standards in most countries are very strict and do not permit grain which contains ergot to reach commercial food channels. All involved in cereal grain production and ulilization should be cognizant of the potential danger, however, since ergot contamination at levels above those permitted by grain standards cannot necessarily be detected by the normal evaluation of a flour sample in the cereal chemistry laboratory. There always have been and always will be ergot infections and a possible danger to human health, but man has learned to minimize the potential problem by using proper agricultural practices. Futhermore, techniques for the removal of ergot from contaminated grains have been developed. While human ergotism is a disease of the past, ergotism in animals still occurs frequently. The problem is not a simple one because of many unanswered questions. What is the tolerance of different breeds or species of livestock to ergot? What are the effects of low-level long-term ingestion of ergot on livestock? What is the difference in toxicity to animals of ergot from different cereal ingestion of ergot on livestock? What is the difference in toxicity to animals of ergot from different cereal grain varieties? What is the effect of storage and processing of cereal grain products on the potential ergot toxicity? The last and most important chapter in the history of ergot concerns ergot as a source of pharmacologically useful alkaloids which have found applications in internal medicine and obstetrics. The future promises to bring some new ergot alkaloids and some new uses. Recent research data indicate the possibility of using ergot alkaloids in contraceptives, which would be truly remarkable.

Dietary fiber was extensively discussed in an article by G.A. Spiller and R.J. Amen in this journal in 1975 (Volume 7 Issue 1). The progress in this field has been tremendous in the past 2 years. What was an uncertain field in 1975 and what at that time to some investigators still appeared as a hypothesis or fad without much proof has turned into a much more respected part of nutritional sciences. The scientific quality of recent studies on dietary fiber in human nutrition shows a great deal of sophistication and care. Improved analytical methodologies are being used more extensively. Many nutritionists and clinicians have accepted the fact that a reasonable increase in the dietary fiber intake in the U.S. and U.K would be advisable. In this article, the possible beneficial effects of dietary fiber on health, the possible harmful side effects, and the food science aspects are carefully discussed after an update on chemistry, analytical procedures, and nomenclature. Undoubtedly, dietary fiber has found a new niche in the sciences of nutrition, medicine, epidemiology, and foods.