Prediction and Measurement of the Water Activity of Selected Saturated Salt Solutions at 5°C and 10°C

A theoretical approach, based on the thermodynamic properties of strong electrolyte aqueous solutions, was used to calculate the a_w at 5°C and 10°C of selected saturated salt solutions frequently used as standards in the range of microbial growth. The results agreed very well with experimental measurements at both temperatures for most salts studied, which included NaBr, NaCl, SrC1₂, (NH₄)₂SO₄, KCl, BaCl₂, and K₂SO₄. For KNO₃ the agreement was somewhat less satisfactory and the reasons are discussed.     

MULTIVARIATE STATISTICAL ANALYSIS OF VOLATILE COMPOUNDS AS A CRITERION FOR SELECTING TECHNOLOGICAL PARAMETERS IN THE OSMOTIC DEHYDRATION OF PINEAPPLE

Principal component analysis and cluster analysis of volatile compounds were used for selecting technological parameters in the osmotic dehydration of pineapple. Assessment of volatile losses permitted differentiation between samples obtained by different osmotic treatments. Treatments at 30C for 1 h at atmospheric pressure or under vacuum and at 30C or 40C for 1 to 3 h with pulsed vacuum (1 cycle) produce the lowest losses of volatile compounds. Apparently, pulsed vacuum allows higher aromatic volatiles retention than two other pressure modes. It also allows increases in both process temperature and time without an important increase in losses.     

MULTIVARIATE ANALYSIS FOR CLASSIFICATION OF COMMERCIAL GRAPEFRUIT JUICE PRODUCTS BY VOLATILE CONSTITUTES

Isolation of volatile constituents from fresh and processed grapefruit juice by a simple technique afforded up to 20 components in each juice type. Many of these constituents are known to contribute to grapefruit juice flavor. Multivariate analysis utilizing the concentration data of twelve constituents allowed classification of the juice samples according to processing conditions. The classification corresponded to expected flavor quality.     

Application of 2-Thiobarbituric Acid Reaction to Exudates of Frozen and Refrigerated Meats

Lipid oxidation in frozen and refrigerated meats was followed by application of the TBA test to their deproteinized exudates obtained by meat centrifugation and TCA addition. Use of meat-exudate avoided drastic treatments which could alter 2-thiobarbituric acid reactive substance (TBARS) content. Differences in the absorption spectra of the extracts assayed by Tarladgis and modified Matsushita reactions are described. Recovery factors of malonaldehyde (MAL)-injected meats were lower than those in which an intimate contact was not allowed. The modified Matsushita reaction gives better results than the Tarladgis reaction in determine TBA numbers in meat exudates.     

PROTEIN AGGREGATION IN INTACT AND DISRUPTED PEROXIDIZING ERYTHROCYTE MEMBRANES

The effects of molecular organization on the interaction of peroxidizing lipids with proteins were studied by using human red cell membranes. Intact and chloroform-disrupted membranes were oxidized. Disruption of membranes was achieved by treatment with chloroform and subsequent elimination of the solvent. Lipid oxidation rates and SDS-electrophoretic protein patterns in the two types of membranes were compared. Specific ³H-DIDS label of band 3 allowed the study of the role of intrinsic proteins in the aggregation process. Lipid oxidation rate is not greatly affected by chloroform disruption although disrupted membranes show a higher rate of protein aggregation. α-Tocopherol decreases lipid oxidation and protein aggregation rates. Band 3 protein dimers (188,000 M.W.) appear earlier than the higher molecular weight protein aggregates (400,000 M.W.). The results suggest that native membrane organization prevents protein damage upon lipid peroxidation.