STORAGE STABILITY OF MILKFAT GLOBULE MEMBRANE

To investigate changes in structure and function of milk fat globule membrane (MFGM) components due to oxidation of membrane lipids, freeze-dried MFGM were stored under controlled temperature and relative humidity (RH) conditions. It was found that while membranes underwent extensive lipid oxidation when stored under air, fluorescent compounds were formed. These compounds exhibited fluorescence with excitation maxima at 350 nm and emission maxima at 440 nm; which were similar to those of the fluorescent substances derived from the reaction of oxidized fatty acids and primary amines. Formation of high molecular weight proteins was detected by SDS-PAGE in samples stored under air, but not in samples stored under nitrogen and was also affected by time and relative humidity. Activity of xanthine-oxidase, an important prooxidative agent, was greatly influenced by temperature and complete inactivation was observed when MFGM's were stored at 37°C, 50% RH for 1 day.     

Color Stability of Radappertized Cured Meat

Porcine semimembranosus muscles were cured (with different levels of nitrite, nitrate, and their combination), smoked, and irradiated with 3.2 Mrad gamma radiation at ?40°C. Subjective studies by a trained panel, objective studies of total color difference (calculated from tristimulus values), and behavior of residual nitrite and nitrate show that radiation alters the pink color of cured meats (radiation- induced fading). Contrary to prior reports, nitrate affects neither color development nor post-irradiation fading. Color of nitrate- cured samples, like uncured samples, become bright red when irradiated, due to reduction of globin myohemichromogen (indistinguishable from pink color of cured meat), and therefore are more desirable.     

Solvent Techniques for the Direct Colorimetric Determination of Copper and Iron in Oils

SUMMARY— The standard procedure for determining trace metals in biological materials requires the ashing of the sample to obtain an aqueous solution. Once this sample is prepared, numerous methods may be employed to determine the metal content. With oils the common ashing techniques lead to serious errors because of spattering, foaming, and volatilization of the sample. In the past, several methods have been developed to eliminate the ashing procedure but large samples (20–50 g) or special equipment was necessary. To allow use of very small oil samples (0.5–2 g) for determining iron and copper, solvent procedures which eliminated the ashing step were developed. The iron procedure is based on the standard aqueous 1,10-o-phenanthroline method modified to employ an initial solvent extraction procedure. Comparison of this method with the aqueous ash procedure on oils of known iron content showed the methods to be equivalent in precision. The solvent procedure is capable of determining 0.1 ppm of iron in the oil. The direct solvent copper procedure based on the sodium-diethyldithiocarbamate aqueous method showed similar results. Because of the ease of performance and the small sample size required, these tests would be useful in food and biological research.     

FLUIDIZED-BED APPARATUS FOR CRYSTAL GROWTH RATE MEASUREMENTS AND ITS TESTING WITH COPPER SULPHATE

Apparatus for measurement of crystal growth rate in a fluidized bed has been modified. The improvement consists of a new way of introducing and removing seeds, which substantially speeds up the measurement and, due to better stability of the temperature regime, leads to improved reliability of results. Growth rates of CuSO₄ · 5H₂O in aqueous solutions, measured in the original and improved apparatus, are compared and they demonstrate the advantages of the new version of the equipment.     

Oxidation Effects in a Freeze-Dried Gelatin-Methyl Linoleate System

SUMMARY– We studied oxidation of a freeze-dried model system consisting of methyl linoleate and gelatin by incubating the model system in air at 50°C for up to 10 days in the dry state or at controlled relative humidities. Incubation for 5-10 days caused a drop in the viscosity of gelatin solutions, an increase in the solubility of gelatin in ethanol-rich solvent mixtures, an increase in the retention time of gelatin on a Sephadex G-150 column, and a reduction in the melting point of a standard gelatin gel. There were no such changes in the viscosity and solubility properties of gelatin when incubation was at a relative humidity of approximately 60%. In some instances, incubation at high relative humidity led to partial insolubilization of gelatin in water or in acetate buffer. The oxidation effects in the dry state were consistent with the hypothesis that gelatin undergoes oxidative degradation. The effects of oxidation showed similarities to effects of ionizing radiations.     

LOW-TEMPERATURE DESTRUCTION OF Trichinella spiralis USING LIQUID NITROGEN AND LIQUID CARBON DIOXIDE

The destruction of Trichinella spiralis by low temperature treatment has been demonstrated to be an effective tool in combatting this parasite in fresh pork products. Current procedures, however, require a holding period under varying times and temperatures to accomplish this destruction. Freezing with cryogenic materials offers the opportunity to attain ultra low temperatures and, thus, eliminate post–freezing holding periods. Four trials were conducted using trichina-infected fresh pork patties approximately 9 mm thick and 88 mm square. In trials 1, 2 and 3 the patties were frozen with LN, using a modified Heath freezing tunnel to final equilibrated temperatures of –12C, –14°C, –20°C, –23°C, –25°C, –28°C, –29°C, –39°C and −47°C. In trial 4 the patties were frozen in a Certified Multideck tunnel using liquid CO₂ as a refrigerant to −10°C, –17°C, –23°C, –29°C and –39°C. Patties were thawed immediately and checked for viable T. spiralis. No positive samples were found at temperatures of –29°C or below.     

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.