This study aims at investigating the effect of high pressure treatment on the heat-induced gelation of mixture of actomyosin and soy 11S globulin (soyl 1S) by changing protein concentration (actomyosin 20mg/g, soy 11S 0-100mg/g), heating temperature (30-90t), pressure intensity (0-600MPa), pH (5. 5-7. 5), concentration of N-ethylmaleimide (NEM, 1-8mM).When mixtures were in low salt concentration (0. 2M KCl) without pressure treatment, the gel-formation was not recognized at 70t which is the critical gel-forming temperature of actomyosin. However, good gel was formed when pressure-treatment was applied to the same samples. At 90t, the critical gel-forming temperature of soy 11S, the gel-formation was observed in the non-pressurized samples. However, when pressure treatment was exercised on the same samples, firmer gel was formed. These results show clear pressurization effect. The gel-formation was not observed in the samples with pH above 7.5. However, strong gel-formation was observed within the pH range between 6.0-7.0. The gel strength and work done values increased as the pressure from 100 to 400 MPa was exercised on the samples. Over 400 MPa, however, the gel-formation dropped dramatically. The gelation was inhibited by the addition of NEM. These results show that SH-groups play an important role in the formation of heat-induced gelation after actomyosin and soy 11S mixture samples had a pressure treatment.

View full abstract

Macadamia nuts at four different stages of development, namely 3, 5, 7 and 9 months after flowering were examined for their physical and physiological characteristics. There were no significant differences among shell sizes and nut-in-shell weight at different growth stages. However, moisture contents were remarkably different among different development stages. Kernel of 3 month stage contained remarkably high amount of moisture and low total lipids (P<0.05). A remarkable decrease in moisture observed from 5 months after flowering, while total lipids significantly increased. The major lipid classes were found to be triacylglycerols for neutral lipids, and phosphatidylcholine and phosphatidylethanolamine for polar lipids at all development stages. The composition of polar lipids changed remarkably during kernel development, especially after 3 months. Fatty acid composition of total lipids at 3 months stages showed significantly higher amounts of myristic, palmitic and linoleic acid (P<0.05), while contents of stearic and oleic acid increased as the nuts grew further. A ratio of unsaturated to saturated fatty acid contents changed from 4.3 to 6.6 with kernel development and this was mainly due to an increase in oleic acid.

View full abstract

Moderate heat treatment may increase thermotolerance and induce sublethal injury in bacterial cells. The effects of heating conditions on the thermotolerance and the extents of sublethal injury of Escherichia coli JCM 1649^T were examined. Test organism was heated slowly from 20°C to 55°C at a definite speed of 0.5°C/min and then held at 55°C for 180min (slow heat treatment), or heated to 55°C within a few seconds and then held for the same period (rapid heat treatment). The thermotolerance of the slowly heated cells was higher than that of the rapidly heated ones due to stress response. It was shown that the majority of survived cells after heat treatments by both method were sublethally injured (desoxycholate-sensitive). The highest injury percentage (calculated from the detectable viable counts on both of nutrient agar ; NA and desoxycholate agar; DESO) was observed at the early stage of both heat treatments (5-30 minutes after the heating temperature reached to 55°C). With lengthening the heating time, the rate considerably decreased. Selective detection rate of the sublethally injured E. coli by DESO was improved satisfactorily by the preliminary incubation in NA at 37°C for 2hr.

View full abstract

The cardboard shipping container for broccoli was improved to raise gas barrier. The broccoli packaged in expanded polystyrene container, cardboard shipping container, cardboard shipping container lining polyethylene, functional cardboard shipping container and the improved cardboard shipping container were stored at 15t for 8 days. The yellowing occurred after storage of 4 or 6 days with broccoli in the usual container or the functional container, but not in the improved cardboard shipping container during storage of 8 days. The level of decrease in chemical components including chlorophyll, total sugar and ascorbic acid of broccoli in the improved cardboard shipping container was also less than that in usual or functional cardboard shipping container. The concentrations of carbon dioxide and oxygen in the improved cardboard shipping container were 9-11% and 10-12%, respectively throughout the storage period. The oxygen concentration was lower and carbon dioxide concentration higher as compared to that in a usual cardboard shipping container or functional cardboard shipping container with both sides plastic film lining. These results suggest that the quality of broccoli in the cardboard shipping container was successfully kept due to modifying the atmosphere in the container.

View full abstract