There is abundant information concerning the functional behavior of whey proteins in model systems. The data on functional properties reported by different researchers, however, reveal wide discrepancies in values. For example, in the case of comparable whey preparations, apparent solubilities may range from 10 to 100%; strength of gels from 0.3 to greater than 10 N, foam overruns from 250 to 1500%, and foam stabilities from 0.5 to 30 min. Many of the data are of limited value in assessing the true functional characteristics of different preparations, treatments, or processing effects. Reports to date are useful in indicating the relative behavior of different proteins; however, the data do not always predict the performance of such proteins in actual food systems. This reflects the fact that in foods, extensive interactions with other components may occur, resulting in modified behavior of the proteins. Harper, (1984) has advocated the testing of these various preparations in simulated food systems which should validly relate the behavior to performance in commercial systems. Emphasis on standardization of specific protocols, with regard to order of addition in ingredients, temperature, pH control, and amount of energy input during mixing, homogenization, emulsification, etc. deserves serious consideration. While this approach is justifiable in terms of providing valuable data to commercial users, it does not minimize the importance of examining these proteins in model systems where the physicochemical basis of each functional attribute can be described in molecular terms (Kinsella, 1987). Such information is necessary to expedite appropriate methods of processing in order to control compositional variability, extent of denatauration, and possible protein modification. In addition, rapid, reliable tests for routine quality assurance that can provide practical information concerning functional applications would be of great value. Whey protein preparations vary immensely in functional behavior and are presently relegated to limited use as functional ingredients in the food industry. This need not be the case since conventional and new technologies permit rigorous control of production protocols, e.g., careful control of heat treatments can result in the production of whey protein preparations with consistent, reliable functional properties (deWit, 1981, 1984; Harper, 1984; Morr, 1985). As the market for functional proteins continues to expand, the whey industry must seek the means to refine whey protein products; determine useful functional properties; develop standardized manufacturing protocols; demonstrate the effectiveness of whey as a functional ingredient; promote, and then market, whey on the basis of performance at competitive cost.

Proteins in whey: chemical, physical, and functional properties

RNA-based applications requiring high-quality, non-degraded RNA are a foundational element of many research studies. As such, it is paramount that the integrity of experimental RNA is validated prior to cDNA synthesis or other downstream applications. In the absence of expensive equipment such as microfluidic electrophoretic devices, and as an alternative to the costly and time-consuming standard formaldehyde gel, RNA quality can be quickly analyzed by adding small amounts of commercial bleach to TAE buffer-based agarose gels prior to electrophoresis. In the presence of low concentrations of bleach, the secondary structure of RNA is denatured and potential contaminating RNases are destroyed. Because of this, the 'bleach gel' is a functional approach that addresses the need for an inexpensive and safe way to evaluate RNA integrity and will improve the ability of researchers to rapidly analyze RNA quality.

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Bleach Gel: A Simple Agarose Gel for Analyzing RNA Quality

The chemistry and use of lysozyme as a food preservative and a pharmaceutical are reviewed. Lysozyme inhibits the growth of deleterious organisms, thus prolonging shelf life. Chemicals used to improve the preservative effect of lysozyme and those that inhibit the enzyme are discussed, along with the stability of lysozyme in various chemical environments. Lysozyme has been used to preserve fresh fruits and vegetables, tofu bean curd, seafoods, meats and sausages, potato salad, cooked burdock with soy sauce, and varieties of semihard cheeses such as Edam, Gouda, and some Italian cheeses. Lysozyme added to infant‐feeding formulas makes them more closely resemble human milk. Lysozyme has been used clinically in the treatment of periodontitis, administered in chewing gum, and implemented to prevent tooth decay. It has also been administered to patients suffering from cancer for its analgesic effect and has been used as a potentiating agent in antibiotic therapy.

The chemistry of lysozyme and its use as a food preservative and a pharmaceutical.

Growth factors and antimicrobial factors of bovine colostrum

Indigenous enzymes in milk: Overview and historical aspects—Part 1

SUMMARY: A Penicillium roqueforti strain produced maximal amounts of lipase when grown in 0.5% casitone-1% Proflo broth, pH 5.5, at 27°C. Addition of butteroil, com oil or olive oil to the growth medium inhibited the lipase production. Under pH stasis the partially purified lipase of P. roqueforti had an optimum pH of 8.0 and an optimum temperature of 37°C. Maximum lipolytic activity occurred with 5% butteroil emulsion as the substrate. Manganese chloride and magnesium chloride stimulated the enzyme activity. Calcium, sodium and potassium sale had no appreciable effect on lipolysis; silver, mercury and zinc salts were inhibitory. The lipase was thermolabile, being inactivated completely within 10 min at 50°C. The lipase hydrolyzed tributyrin, tricaprylin, tricaprin, tripropionin and triolein in decreasing order.

Production and properties of pencillium roqueforti lipase

Human milk ribonuclease.

Relationship between composition and stability of bovine milk lysozyme.

Simultaneous isolation of human milk ribonuclease and lysozyme.

SUMMARY –Lysozymes (mucopeptide N-acetylmuramylhydrolase, EC 3.2.1.17) isolated from human milk (HML) and bovine milk (BML) were subjected to γ-irradiation and their radiosensitivity was compared to that of egg white lysozyme (EWL). When irradiated in phosphate buffer, pH 6.2, the enzymes were fairly sensitive to γ-irradiation. Inactivation followed first order kinetics and depended upon protein concentration. BML was more radiosensitive than HML and EWL. Comparisons of the ultraviolet scans of the native and irradiated enzymes indicated that tryptophan was being destroyed in HML as it is known to occur in EWL. Hydroxy radical scavengers, cysteine and t-butanol, afforded radioprotective action for the milk lysozymes. In a dry state, both the milk lysozymes were less sensitive to γ-irradiation than in aqueous solution, requiring Mrad dosages for partial inactivation compared to Krad dosages for the same extent of inactivation in aqueous solution. However, as was observed in aqueous solution and also in the dry state, BML was more radiosensitive than HML and EWL.

R. R. Eitenmiller

Papers

Production and properties of pencillium roqueforti lipase

Human milk ribonuclease.

Relationship between composition and stability of bovine milk lysozyme.

Simultaneous isolation of human milk ribonuclease and lysozyme.

EFFECT OF γ‐IRRADIATION ON BOVINE AND HUMAN MILK LYSOZYMES