In this study, we investigated the postharvest changes in glutamine synthetase (GS; EC 6. 3. 1. 2) activity in relation to ammonia content, respiration rate and pod color changes after harvest of young soybeans (Glycine max Merr of the 'Ajigen' and 'Fuuki' varities) stored at 5 and 20°C for up to 10 days. GS activity slightly increased throughout the experimental period for both storage temperatures and cultivars. Ammonia content increased approximately 2-fold after a 10-day storage. Postharvest ammonia content increased was enhanced with storage. This phenomenon followed the same trend as that for other perishable vegetables, such as broccoli and asparagus. GS activities in these vegetables usually decreased during storage. Thus, the increase in GS activity in soybean implies that GS has a role in protein synthesis. The low-temperature storage of soybeans at 5°C resulted in the retention of good bean pod color and quality because it effectively decreased respiration rate and suppressed ammonia accumulation after harvest.

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The exposure of a commodity to varying temperature during postharvest handling and marketing affects product quality. In this study, we investigated the physio-biochemical changes in broccoli heads held under simulated retail market conditions by keeping broccoli heads at 1°C for 7 and 14 days prior to exposure to 20°C. The visual quality and color of the heads were maintained during cool storage regardless of storage duration. Respiration rate abruptly increased after exposure to 20°C. One day after removal from cool storage, glutamine synthetase (GS; EC 6. 3. 1. 2) activity in the florets with prior 7-day cool storage was almost maintained whereas it slightly increased for 14-day storage. Thereafter, GS activity for both storage durations decreased continuously with corresponding ammonia accumulation. In the branchlet portion, GS activity and ammonia content slightly decreased with storage time. Furthermore, glutamate dehydrogenase (GDH; EC 1. 4. 1. 2) activity in this portion continuously decreased throughout the experimental period. Almost similar patterns of postharvest physio-biochemical changes were observed under both storage conditions.

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The influence of lipoteichoic acid (LTA), which is the negatively charged component of the cell surface, on the bacteriostatic effect of bovine milk lactoferrin (bLF) was investigated. Cell agglutination in suspensions of 18 strains of Clostridium by iron-free and iron-saturated bLF (apo-bLF and Fe-bLF) was observed. The cell agglutination of Clostridium species by apo-bLF and Fe-bLF showed a significant correlation with the extent of the negative charge on the bacterial cell surface. The degree of cell agglutination of C. perfringens JCM1290 by bLF decreased with increasing LTA concentration. The growth suppressive ratio of bLF in the presence of LTA was also lower than that in the absence of LTA. The growth suppressive effect of bLF on C. perfringens JCM1290 was closely related to the cell agglutination by this protein. These results suggest that the direct interaction of bLF with the cell surface is necessary for the bacteriostatic effect of bLF.

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