Morphological and histochemical changes of tissue structures in persimmon leaves were investigated using a fresh leaf, a freeze - dried powder and a semi-purified dietary fiber preparation isolated from the powder. Concentration and composition of dietary fiber (DF) and other chemical components in the latter two samples were also analyzed. Morphological observation showed that the fresh persimmon leaf distributed palisade and spongy parenchyma between the upper and lower epidermis. It was observed by histochemical techniques that the cell walls and vacuoles of the cells were stained strongly by Periodic Acid Schiff (PAS) reagent. The PAS reaction with the cell walls and vacuoles of May and July leaves was much stronger than those of the September leaf. The cell walls of all fresh leaves each month were stained by Alcian Blue (AB, pH2.5 or pH1.0) with almost the same intensity. The cells in the freeze-dried specimen were found to be morphologically nearly intact and the cell walls were stained by PAS and AB reagents with the same intensity as those of fresh leaves. The existence of polysaccharides, which were stained by PAS and AB reagents, was also observed in the semi-purified DF preparation. The freeze-dried specimen contained from 41 to 43% (dry basis) DF which consisted of almost equal amounts of lignin, cellulose and hemicellulose. These results suggest that persimmon leaves are constituted by 4 main tissues and contain dietary fiber with a complex structure consisting of nearly an equal amount of major plant fiber components and a small amount of pectic substance and mucopolysaccharide-like substances as acid polysaccharides in the cell walls.

View full abstract

The respiration rate, the chemical components including ascorbic acid and sugar, and the quality stability of Welsh onion (A llium fistulosum L.) harvested in summer (July, '95), autumn (November, '95), winter (January, '96) and spring (April, '96) were investigated during storage at room temperature or at 15°C. A nearly second order regression equation (Y = a + b * T+c * T²) with high relative coefficient (R = 0.987 - 0.991), was established between respiration rate (mgCO₂ /kg/hr) (Y) and temperature of Welsh onion (T). At the same temperature, Welsh onions harvested in the winter season showed a higher respiration rate than those harvested in the summer season. In the Welsh onion harvested in the summer and stored at room temperature conditions, ascorbic acid content decreased markedly and the score of leaf tip withering increased. These results indicate that Welsh onions harvested in the summer season and stored at room temperature do not retain good quality. Ascorbic acid and sugar contents in Welsh onion harvested in winter were maintained for 6 days, suggesting that good quality is retained during storage room temperature. On the other hand, summer season Welsh onions stored at 15°C indicated much better quality stability than those of the winter season. There was a correlation between the respiration rate of Welsh onions and quality stability, meaning that the lower was the respiration rate, and the higher was the quality stability.

View full abstract

The effects of a functional corrugated cardboard box coated with a mixture of alginate and pullulan (polysaccharide film) on maintaining freshness of rape inflorescences (Brassica campestris L.) were examined. Rape inflorescences were packaged in a functional or conventional corrugated cardboard box and stored at 20°C for 4 days. Atmospheric condition in a conventional corrugated cardboard box was almost the same as surrounding atmosphere, whereas gas composition in the functional corrugated cardboard box were kept at lower oxygen and higher carbon dioxide during storage. Therefore, these facts suggest that the changes in gas composition are affected by the gas permeability corrugated cardboard box and respiration of rape inflorescences. The rape inflorescences in the functional corrugated cardboard box kept its freshness with high ascorbic acid and chlorophyll contents during storage at 20°C, and no change in color, flavor and total polyphenol content of rape inflorescences were observed. These results suggest that the storage of rape inflorescences in the functional corrugated cardboard box coated with polysaccharide films is effective for keeping freshness and nutritional quality at 20°C for 4 days.

View full abstract