Kin‐Chor Kwok

Abstract Ferulic acid (4‐hydroxy‐3‐methoxycinnamic acid), an effective component of Chinese medicine herbs such as Angelica sinensis, Cimicifuga heracleifolia and Lignsticum chuangxiong , is a ubiquitous phenolic acid in the plant kingdom. It is mainly conjugated with mono‐ and oligosaccharides, polyamines, lipids and polysaccharides and seldom occurs in a free state in plants. Ferulic acid is a phenolic acid of low toxicity; it can be absorbed and easily metabolized in the human body. Ferulic acid has been reported to have many physiological functions, including antioxidant, antimicrobial, anti‐inflammatory, anti‐thrombosis, and anti‐cancer activities. It also protects against coronary disease, lowers cholesterol and increases sperm viability. Because of these properties and its low toxicity, ferulic acid is now widely used in the food and cosmetic industries. It is used as the raw material for the production of vanillin and preservatives, as a cross‐linking agent for the preparation of food gels and edible films, and as an ingredient in sports foods and skin protection agents. Ferulic acid can be prepared by chemical synthesis and through biological transformation. As polysaccharide ferulate is a natural and abundant source of ferulic acid, preparation of ferulic acid from plant cell wall materials will be a prospective pathway. Copyright © 2004 Society of Chemical Industry

There have been many reports concerning the role of dietary fiber in lowering postprandial serum glucose, and the main mechanism was regarded as the viscosity of different dietary fibers in hampering diffusion of glucose and postponing absorption and digestion of carbohydrates. In this paper, two kinds of water-insoluble dietary fibers, water-insoluble dietary fiber of wheat bran and enzyme-resistant starch of maize amylose, and four kinds of water-soluble dietary fibers, water-soluble dietary fiber of wheat bran, carboxymethyl cellulose, guar gum, and xanthan gum, were used to investigate their postprandial serum glucose lowering mechanism in vitro. The results showed that these dietary fibers lowered postprandial serum glucose levels at least by three mechanisms. First, dietary fibers increase the viscosity of small intestine juice and hinder diffusion of glucose; second, they bind glucose and decrease the concentration of available glucose in the small intestine; and, third, they retard alpha-amylase action through capsuling starch and the enzyme and might directly inhibit the enzyme. All of these decreased the absorption rate of glucose and the concentration of postprandial serum glucose.

Summary Heating conditions are the most important variables in the processing of soymilk. the heat treatments given to soymilk during extraction, cooking, and subsequent pasteurization or sterilization, principally influence (1) the yields and nutritive quality of solids and proteins, (2) destruction of spoilage microorganisms, and (3) the colour and the flavour of the milk. the qualities of other soy products derived from soymilk, e.g. the texture of tofu and the suitability for lactic acid fermentation, may also be affected by the net heat treatment received by the milk. Excess heating generally leads to the destruction of amino acids and vitamins, browning and the development of cooked flavour. Considerable research efforts have been devoted to establish the effects of heat on the elimination of off‐flavours, inactivation of antinutritional factors such as trypsin inhibitors, and the recovery of solids and proteins in soymilk. Other heat‐induced chemical changes such as loss of vitamins, Maillard reaction and protein denaturation have not been studied as extensively. Published studies show that higher temperature heating and UHT treatment may have beneficial effects on the yields of solids and proteins, retention of the nutrients, and minimizing chemical changes in soymilk, provided that optimum processing conditions are used. Process optimization is only possible if data on the kinetics of various chemical reactions involved are available. However, such data are lacking, especially in the UHT range. The principal objective of this review article is to compile a comprehensive description of heat‐induced changes occurring in soymilk. Attention has been given to the analysis of published data relating to the kinetics of various reactions. Such an analysis would permit the evaluation of kinetic parameters (such as rate constants and activation energies), and would form the basis for reaction engineering studies leading to the design of optimum heat exchangers for the processes.

Mathematical and kinetic models were set up for heat-induced quality changes in soy milk, including inactivation of trypsin inhibitor activity (TIA) and degradation of thiamin, riboflavin, color, and flavor over a wide range of time-temperature combinations with particular interest in the ultrahigh-temperature (UHT) range. On the basis of these models, multiresponse optimization of the thermal processes for soy milk was carried out to obtain the following effects simultaneously: (1) maximum destruction of bacterial spores, (2) maximum inactivation of TIA, and (3) minimum degradation of sensory and nutritional qualities. By a suitable selection of high temperatures and extended heating times, for example, 143 degrees C/60 s, it is possible to use a single-step UHT process to produce a commercially sterile soy milk with satisfactory TIA inactivation, highly acceptable color and flavor, and thiamin retention between 90 and 93%.