ADVANCES IN THE MICROBIOLOGY OF MILK AND DAIRY PRODUCTS

The techniques of microbiology from the seventeenth century up to the present time are reviewed and the problems of disease in dairy herds with its effect on raw milk supplies assessed. Progress in the cleaning of milk vessels and sterilization is detailed and the history of pasteurization with its affect on the keeping quality of milk is shown. The introduction of starters in cheese manufacture during the last century is described and the important advances made are stressed.     

Role of Noncovalent Forces in Micellization Using Legumin from Vicia faba as a Study System

The seed storage protein, legumin, from Vicia faba interacted to form micelles and elaborate protein networks under varying conditions. Several molecular parameters correlated with observed micelle interaction parameters; these included thermal properties as indicators of protein stability and surface hydrophobicity as an assessment for potential hydrophobic interactions. The optimal pH for micelle formation ranged from 5.5 to 6.5, values at which electrostatic repulsions were minimal and surface hydrophobicites were adequate to allow hydrophobic interactions. The micelle response was affected by anions both in terms of concentration and type of anion. Finally, gradual denaturation of legumin with increasing urea concentrations had a negative impact on the micelle response.     

Role of the Thermal Denaturation-Aggregation Relationship in Determining the Rheological Properties of Heat Induced Networks for Ovalbumin and Vicilin

Heat-induced denaturation (determined by differential scanning calorimetry plus ANS fluorescence) and structure development (assessed by dynamic testing) were monitored for ovalbumin and vicilin to evaluate the importance of these processes on the rheological characteristics of resulting protein networks. Protein denaturation preceded structure development, based on an increase in the storage modulus (G′). Reduction of the temperature between denaturation and aggregation through pH manipulation or inclusion of stabilizing salts lowered G′ values in the resulting network. In contrast, in the presence of SDS, G′ values increased with (ovalbumin) or were unrelated to (vicilin) reduced temperature differences. This demonstrated the importance of a balance of attractive and repulsive forces when examining network characteristics.     

A MAJOR SOLUBLE GLYCOPROTEIN OF POTATO TUBERS1

The major soluble glycoprotein of potato tubers was isolated by chromatography on DEAE cellulose and Con A Sepharose. It contained about 5% neutral sugar and 1%hexosamine, exhibited a molecular weight of 45,000 by SDS gel electrophoresis, and consisted of 6–10 ionic forms as revealed by isoelectric focusing. This glycoprotein comprised about 20%of the soluble protein in all of the 31 tested potato cultivars.     

ISOLATION AND SOME PROPERTIES OF AN ACIDIC FRACTION OF POLYPHENOL OXIDASE FROM JERUSALEM ARTICHOKE(HELIANTHUS TUBEROSUS L.)

An acidic fraction of polyphenol oxidase (EC 1.14.18.1), representing the bulk activity, has been isolated from Jerusalem artichoke tubers by copper affinity chromatography, followed by DEAE-Sepharose ion-exchange chromatography. Isoelectric focusing analysis showed a cluster of activity bands (microheterogeneity) in the pH region of 4.5. The amino acid composition of the enzyme was also determined. The pH optimum for oxidation of chlorogenic acid, 4-methylcatechol and catechol was 6.0. Substrate inhibition was observed by high concentrations of chlorogenic acid. Thermal inactivation data indicated an apparent activation energy of 26.2 kcal/mol. Kinetics of inactivation, upon copper removal by KCN treatment, and reconstitution reactions revealed that the former is a much slower process than reactivation.     

Muscle fibre orientation and its effect on measurements of tenderness of bovine longissimus dorsi muscle

The muscle fibre orientation within a particular cooked beef steak was found to vary considerably and to be markedly affected by vacuum packaging, freezing and/or cooking. Shear force values, initial-bite tenderness (panel) and cooking loss were highly dependent on, and overall tenderness (panel) was only slightly dependent on muscle fibre orientations. These measures were affected by fibre orientation to a greater extent in tough than in tender meat. At each of three fixed muscle fibre orientation, correlations between tenderness measures were significant (P<0.05), their magnitude depending on the fibre orientation. At a fixed fibre angle correlations of tenderness measures with cooking losses were not significant. However, on a withinanimal basis, cooking loss was related to shear value and to initial-bite tenderness apparently through an effect of fibre orientation. This effect may constitute a major source of variation in the measurement of tenderness and cooking loss.     

The Lamar Underpass

For a proposal for Austin Art in Public Places, two photovoltaic-powered lightbox structures, each measuring 3 feet in height and 90 feet in length, are mounted on the concrete retaining walls of a roadway underpass in Austin, Texas.¹     

Relationship of Mineral Content and Tenderness of Meat from Cattle Differing in Breed, Sex and Age

The mineral contents and the shear values of raw and cooked meat, respectively, were determined using longissimus dorsi (LD) and semimembranosus (SM) muscles of 100 cattle, 80 of which were approximately 15 months of age and were classified by breed of sire and by sex and 20 of which were mature Shorthorn cows. Correlations between shear values and concentrations of the minerals Cu, Fe, Ca, Zn, Mg, Na and K, indicated that for the LD muscle no correlations were significant (P > 0.05) and for the SM muscle only correlations involving Ca and Fe were significant (P > 0.05). These correlation coefficients, however, were not of a magnitude to encourage the use of mineral concentrations of raw meat for the prediction of cooked beef shear value.