Showing papers in "Critical Reviews in Food Science and Nutrition in 1989"

Modified atmosphere packaging of fruits and vegetables.

Abstract: Modified atmospheres (MA), i.e., elevated concentrations of carbon dioxide and reduced levels of oxygen and ethylene, can be useful supplements to provide optimum temperature and relative humidity in maintaining the quality of fresh fruits and vegetables after harvest. MA benefits include reduced respiration, ethylene production, and sensitivity to ethylene; retarded softening and compositional changes; alleviation of certain physiological disorders; and reduced decay. Subjecting fresh produce to too low an oxygen concentration and/or to too high a carbon dioxide level can result in MA stress, which is manifested by accelerated deterioration. Packaging fresh produce in polymeric films can result in a commodity-generated MA. Atmosphere modification within such packages depends on film permeability, commodity respiration rate and gas diffusion characteristics, and initial free volume and atmospheric composition within the package. Temperature, relative humidity, and air movement around the package can influence the permeability of the film. Temperature also affects the metabolic activity of the commodity and consequently the rate of attaining the desired MA. All these factors must be considered in developing a mathematical model for selecting the most suitable film for each commodity.

Food colorants: Anthocyanins

Abstract: Interest in food colorants as shown by the number of patents has doubled in recent years with natural pigments outnumbering synthetics by five to one The natural colorant area can be subdivided into anthocyanins, betalains, chlorophylls, carotenoids, flavonoids, polyphenols, Monascus, hemes, quinones, biliproteins, safflower, turmeric, and miscellaneous All involve different groups of chemical compounds which may be used directly as colorants, or may be chemically modified to produce different hues or increased stability All usually involve a method of collection, extraction, purification, possibly stabilization, and formulation A variety of hues can be obtained ranging from green through yellow, orange, red, blue, and violet, depending on the source of colorant Similarly, water or oil‐soluble formulations can be prepared depending on the type of colorant

Occurrence and content of hydroxycinnamic and hydroxybenzoic acid compounds in foods.

Abstract: Phenolic acid compounds seem to be universally distributed in plants. They have been the subject of a great number of chemical, biological, agricultural, and medical studies. Hydroxycinnamic acid compounds occur most frequently as simple esters with hydroxy carboxylic acids or glucose, while the hydroxybenzoic acid compounds are present mainly in the form of glucosides. Furthermore, phenolic acids may occur in food plants as esters or glycosides conjugated with other natural compounds such as flavonoids, alcohols, hydroxyfatty acids, sterols, and glucosides. Also, hydroxycinnamic acid amides appear to be common constituents. The occurrence of the different natural phenolic acid compounds in foods is reviewed, and data of the content in fruit, vegetables, and spices are given. The distribution of the main phenolic acid compounds in food plants as well as their changes during development and maturation of fruits are considered. Furthermore, the hydroxycinnamic acids bound to cell wall polymers, the phenolic...

Nutritional and toxicological aspects of the Maillard browning reaction in foods.

Abstract: The Maillard, or nonenzymatic, browning reaction between carbonyl and amino groups is a common reaction in foods which undergo thermal processing. The Maillard reaction is a desirable consequence of many industrial and domestic processes and is responsible for the attractive flavor and brown color of some cooked foods. An early recognized consequence of the Maillard reaction was the destruction of some essential amino acids, such as lysine. More recently, research interest has focused on the production of toxic and antinutritive compounds. This review examines the nutritional and toxicological consequences of the Maillard reaction in light of the findings of such research. In particular, the effect of Maillard reaction products on the digestion, absorption, and excretion of nutrients is considered. The cytotoxicity, mutagenicity, and immunochemical aspects of selected Maillard reaction products are also examined and suggestions are made for future areas of investigation.

Nutritional improvement of cereals by sprouting

Abstract: Cereal grains form a major source of dietary nutrients for all people, particularly those in the developing countries. However, the nutritional quality of cereal grains and sensory properties of their products are inferior due to lower protein content, deficiency of certain essential amino acids, lower protein and starch availabilities, presence of certain antinutrients, and the coarse nature of the grains. The consumption of sprouted cereals is becoming popular in various parts of the world. Sprouting of grains for a limited period causes increased activities of hydrolytic enzymes, improvement in the contents of certain essential amino acids, total sugars, and B-group vitamins, and a decrease in dry matter, starch, and antinutrients. The digestibilities of storage proteins and starch are improved due to their partial hydrolysis during sprouting. The magnitude of the nutritional improvement is, however, influenced by the type of cereal, seed quality, sprouting conditions, and it is not large enough to account for in feeding experiments with higher animals. In this review, the available literature concerning the nutritional improvement of cereals by sprouting and utilization of sprouted cereals in traditional and processed foods has been compiled and is critically reviewed.

Nutritional improvement of cereals by fermentation

Abstract: Cereal grains form a major source of dietary nutrients for all people, particularly those in the developing countries. However, compared with animal foods, nutritional quality of cereal grains is inferior due to lower protein content, deficiency of certain essential amino acids, lower protein and starch availabilities, and the presence of some antinutritional factors. Fermentation of cereals for a limited period of time improves amino acid composition and vitamin content, increases protein and starch availabilities, and lowers the levels of antinutrients. In this review, the available literature concerning the nutritional improvement of cereals by fermentation has been compiled and is critically analyzed. The traditional foods prepared by fermentation of cereals in different parts of the world are briefly described and future research needs to improve their nutritional contribution are addressed.

Cuphea: a new plant source of medium-chain fatty acids.

Abstract: The plant genus Cuphea (family Lythraceae) promises to provide a new source of industrially and nutritionally important medium-chain fatty acids, especially of lauric acid now supplied exclusively by coconut and palm kernel oils from foreign sources. The seed lipids of Cuphea were first discovered in the 1960s to contain high percentages of several medium-chain fatty acids, including caprylic, capric, lauric, and myristic acid. Research is still in the early stages, but it is intensifying toward the goal of developing the genus into a new temperate climate crop for production of specialty oils. Given the diversity of Cuphea seed lipid composition and the wide ecological and distributional range of the genus, it may be possible to tailor crops to produce selected fatty acids on demand under a variety of growing conditions. Cuphea comprises about 260 species, most native to the New World tropics. Its morphology, classification, chromosome numbers, distribution, ecology, and folk uses are presented. Seed structure is described and seed lipid composition for 73 species is summarized. Problems in domestication and agronomic progress are reviewed. Knowledge of the biosynthetic mechanism controlling the lipids produced by Cuphea remains very limited. Future research in this area, and particularly successful employment of gene transfer techniques, may allow genes controlling the mechanism to be transferred to an already established seed oil producer such as rapeseed. Presently, both traditional plant breeding techniques and newer biotechnological methods are directed toward Cuphea oilseed development.

Folates in foods: reactivity, stability during processing, and nutritional implications

Abstract: Nutritional deficiencies are eminent at all socioeconomic levels of the world population and have created a critical need for a reevaluation of the nutritional quality of the food supply. A particular group of vitamers, collectively referred to as folates, has received a great deal of attention due to their significance in human metabolism, their prevalent deficiency worldwide, as well as their complexity of analysis. Severe folate deficiency may result in megaloblastic anemia and is generally attributed to low dietary intake, although it may also result from malabsorption. Such concerns have instigated increased interest in food-fortification programs. In order to ensure appropriate levels of nutrient fortification and optimization of food processes for maximum folate retention, it is of great importance to have a basic understanding of the kinetic behavior of individual vitamers with respect to processing parameters and various environmental conditions. This article reviews kinetic stability of folates as affected by processing conditions, discusses problems associated with current methodology for folate analyses, and integrates this information with the nutritional aspects of folates.

Surface activity, film formation, and emulsifying properties of milk proteins.

Abstract: This overview indicates that simple, reliable standardized methods for measuring emulsifying activity and for determining ES are not yet available. One of the major shortcomings of most of the current methods is the inability to detect very small fat globules (less than 0.5 micron), which may be very important in stable emulsions. Several of the methods are time consuming and destructive. To minimize the time required to evaluate emulsions, techniques that monitor instability under the influence of accelerated aging (increased temperature and gravitational field) have been used with varying degrees of success. These methods, e.g., centrifugation, are useful, but processes occurring during centrifugation or heating may not be characteristic of those occurring in a stored emulsion. Generally, there is no method that simultaneously determines changes in emulsions due to the aggregation coalescence, flocculation, creaming, of the droplets and/or oiling off. No single criterion of emulsion instability is sufficient to characterize all the changes occurring in the system. A nonintrusive technique that can monitor dynamic changes in emulsions is needed. Ideally, it should be simple, rapid, inexpensive, and applicable to both diluted and concentrated emulsions. Scientists must continue research to develop such a standard universal method for determining ES, because data from different laboratories cannot currently be validly compared. Reliable methods are also required to elucidate relationships between the physical properties of proteins as emulsifiers and their performance in food emulsions. There is a need for opportunities for systematic research to determine the interfacial behavior of food emulsifiers, particularly food proteins. Research to describe the kinetics and thermodynamics of adsorption at an interface, the extent of unfolding, the degree of packing and polypeptide interactions in an interface during film formation, and information concerning the physical and mechanical properties of interfacial films is needed to describe emulsifying behavior of different proteins. The effects of components in the continuous and discontinuous phase, parameters of manufacture, and interactions between different types of surface-active materials that occur in food need to be studied.

Pleurotus mushrooms. Part III. Biotransformations of natural lignocellulosic wastes: commercial applications and implications.

Abstract: Species of Pleurotus are endowed with the capacity to degrade unfermented natural lignino-cellulosic wastes. From the time the substrate is spawned until the end of cropping, there occurs a spectrum of qualitative and quantitative changes in the various substrate constituents, viz., cellulose, hemicellulose, lignin, sugars, amino acids, phenols, ash, nitrogen, etc. In general, cellulose, hemicellulose, and lignin are degraded, solubility of the substrate is increased, phenolic content is decreased, sugar and amino acid contents are increased, as is the ash content due to a constant utilization of the organic matter. The ability of Pleurotus to effect these degradative changes is discussed under both sterile (monoculture) and nonsterile culturing conditions. The enzymatic aspects affecting these various chemical changes in the lignino-cellulosic substrates are brought out. The various commercial applications and implications of the spent substrate, such as use as an upgraded form of ruminant feed, production of biogas, manufacture of paper/cardboard, recycling into Agaricus compost, garden fertilizer, production of single cell proteins, etc., are critically evaluated.

Effect of dietary protein and minerals on calcium and zinc utilization.

Abstract: The utilization of most minerals can be altered not only by varying the dietary levels of protein, carbohydrate, fiber, fat, and vitamins but also by varying the forms of macronutrients fed. Interactions among minerals are frequent and sometimes complex. Thus, all assessments of mineral requirements should include discussions of the effects of interactions on mineral bioavailability. Some of these interactions occur in the gut and affect the absorption of minerals. Other interactions affect the metabolism, transport and storage of minerals, and ultimately their excretion in urine or in endogenous gut secretions.

Improved wheat for baking

Abstract: To bakers, wheat quality means the performance characteristics of the flour milled from the wheat when used in specific wheat products. The tremendous increase in the number of wheat cultivars grown in the U.S. in recent years, along with the unusual climate, new advances in milling technology, and increased automation of baking lines, have resulted in bakery production problems partly attributed to wheat flour quality. In this review various factors affecting wheat quality are explained. Concerns of bread and cookie/cracker manufacturers on deterioration of the wheat quality are discussed, and, finally, some solutions are proposed.