Ethylene has undesirable effects on the retention of quality in fruits and vegetables. Many ethylene absorbents and ethylene scrubbers are available. However, their effects have not yet been well confirmed. Activated carbon, molecular sieve and palladium (Pd), which are commonly used as ethylene absorbents, were examined for their efficiency. The activated carbon and the molecular sieve 4A, 5A and 13X were effective in reducing ethylene, however, some amount of ethylene remained. The molecular sieve 3A had no effect on the removal of ethylene. The other molecular sieves were significantly affected by a humid environment, and they lost efficiency. The activated carbon as well as the molecular sieve, released the absorbed ethylene when it was moistened by water. On the other hand, the removal of ethylene by PdCl₂ was accelerated under highly humid conditions or by the presence of water. PdCl₂ converted most of the ethylene into acetaldehyde. Palladium carbon and palladium activated carbon were more effective under dry conditions than a highly humid environment, and they functioned as a catalyzer rather than an absorbent.

View full abstract

Pineapples were stored at 10°C and 30°C, and the influence of temperature on synthesis of volatile compounds was examined. Volatile compounds of whole fruits were trapped by the headspace method using a Tenax TA column, and components over ten were detected by gas liquid chromatography. Main components were identified as esters, such as methyl n-hexanoate, methyl acetate, and ethyl acetate, and also as ethyl alcohol. When pineapples were stored at 10°C, the level of trapped volatiles was very low and the volatiles increased only slightly during storage, however, almost all the volatiles increased sharply during storage at 30°C following the low temperature storage. The pattern of the increase in the volatiles differed among the components, and the degree of increase in methyl n-hexanoate became smaller as the low temperature storage precedent was prolonged. On the contrary, methyl acetate and ethyl alcohol increased more significantly as the low temperature storage was prolonged. These changes in metabolism of the volatiles seem to play an important role in weakening the flavor of pineapples stored at low temperatures.

View full abstract

The occurrence of bitterness, changes in the production of bitter compounds, and sugar contents were measured to determine the effects of ethylene (C₂H₄) treatment and/or cutting on different tissues (different part of phloem or xylem) of partially processed carrot (PPC) during storage. Carrots (Daucus carota L. var. sativa DC, cv : unknown) were sliced with 1 cm thickness and stored at 20°C with or without C₂H₄ (100ppm) in air. Phloem or xylem of PPC were divided into three portions (A : part located at 0-1.5mm from cut surface, B : 1.5-3.0 mm, and C : 3.0-5.0), respectively, and the occurrence of bitterness and contents of phenols and sugar in these portions were determined. Neither C₂H₄-treated nor un-treated PPC showed apparent decay during 3 days of storage, but brown pitting injury on the surface of phloem was markedly associated with C₂H₄ treatment. This was not so for xylem tissue. The occurrence of bitterness increased apparently in phloem treated with CO₂H₄ and the xylem was less sensitive than phloem. Bitterness in A was significant and moderate in B and C of phloem. The contents of isocoumarin and phenols, bitter compounds, did not show apparent changes in phloem and xylem of un-treated PPC. The accumulation of these compounds were induced significantly in phloem and moderately in xylem by C₂H₄ treatment. This increase was greatest in A, followed by B and C in both tissues. An increase in reducing sugar content and a decrease in total sugar content were observed in phloem but not in xylem of C₂H₄ treated PPC, while neither phloem nor xylem in un-treated PPC showed apparent changes during storage. We conclude that the occurrence of bitterness and the accumulation of bitter compounds in PPC are induced by C₂H and cutting and propose the importance of PPC storage without C₂H₄.

View full abstract

In 1995, insoluble polyvinylpolypyrrolidone (PVPP) was approved in Japan for use as an additive for preserving wine. In this paper, retaining quality of white wine with PVPP was investigated. (1) When PVPP was added to white wine which was produced from 'Koshu' grapes in concentrations between 200 to 2000 mg/L, the removal rate of polyphenol in the wine with PVPP increased gradually with an increase in the concentration of PVPP. Eleven polyphenols were detected in this wine, and the contents of each polyphenol were reduced at the same rate by treatment with PVPP. When PVPP was added to commercial wines at a concentration of 500 mg/ L, the maximum removal rate of polyphenol was about 20%. (2) Added PVPP in white wine exerted an inhibitory effect of protein clouding, and wine treated with PVPP maintained quality for 4 days during storage at 60°C, and for 120 days during storage at 27°C

View full abstract

The influence of the high-pressure treatment on the activity of the trypsin and chymotrypsin was examined. Both enzymes showed the remaining activity of about 92% after the high-pressure treatment of 600MP and both enzymes showed a very high pressure resistance.
The Km value of both enzymes showed almost constant values. It was suggested that Vmax decrease after the high-pressure treatment.
Moreover, it was showed that the second structure of enzyme had been changed from the result of CD and NIR by the high-pressure treatment of 600MPa. The results of UV spectrum and hydrophobicity strongly suggested that the enzymes' surface structure were changed after pressure treatment. It was found that the reactive behavior of both enzymes had been changed because the structure around the catalytic site of the surface structure of the enzymes been influenced by the high-pressure treatment of 600MPa.

View full abstract

We examined the vibrating characteristics of bunches and berries of grape 'Pione' (Vitis vinifera x V. labrusca) by giving horizontal and vertical shakings with some different frequencies (Hz) and G values, and studied the effects of the treatment of KT-30 (synthetic cytokinin) and uses of a styrofoam net on the reduction of berry-drop. It was confirmed that bunches and berries of the grapes vibrated violently under the condition based on Japanese Industrial Standards, and they vibrated more intensively by horizontal shaking than by vertical shaking. At the fine of the vertical shaking fixed at 1.0G, berries vibrated slightly at 5 Hz, but bunches vibrated violently at 9-11Hz. In the case of the shaking at fixed 10Hz, berries vibrated slightly at 0.2G, bunches vibrated violently at 0.6G, and whole bunches vibrated more violently and vertically at 1.0G. Berry-drop occurred at 1.4G, and bunches sprang up at 1.6G. At the fine of horizontal shaking, berries vibrated more violently at a low frequency than by the vertical shaking. Treatment with KT-30 considerably prevented immediate berry-drop after the shaking. Berry-drop of treated grapes occurred several at the fine over 2 days after the shaking, but the number of berry-drops was below 50% of that in the grapes not treated with KT-30. The number of berry-drops of grapes treated with 20 ppm of KT-30 was less than that of grapes treated with 5 ppm of KT-30. It is postulated that the cause of the decrease of berry-drop may be the increase of strength against pulling off berry from the peduncle. As the treatment with high concentration of KT-30 brought about a delay of berry-coloring and the decreases in Brix and sugar-acid ratio, it was considered that the treatment with 5 ppm of KT-30 was preferred as the practical concentration. By using a Styrofoam net as a shock absorber, the number of berry-drops decreased to below 50% over a 2 day period after the shaking. The above results indicate that the number of berry-drops is reduced with treatment of KT-30 or a Styrofoam net. By combining these treatments, berry-drop seems to be reduced even more. As the treatment with KT-30 is favorable to decrease berry-drop, that is appropriate for elongation of the harvest period.

View full abstract

The changes of peroxide content and enzyme activities involved in hydrogen peroxide metabolism of stored mitsuba (Japanese hornwort, Cryptotaenia japonica Hassk. cv. Senkaku) leaves were studied to elucidate the role of peroxides in leaf yellowing. The peroxide content in mitsuba leaves decreased significantly during storage at 25°C. Glycolate oxidase activity increased for the first 2 days of storage at 25°C and then decreased with leaf yellowing, while superoxide dismutase activity showed a decline during storage. Catalase and peroxidase activities decreased in stored mitsuba leaves, the decrease being greater in catalase than in peroxidase. These results suggest that the oxidation process in which the peroxides, including hydrogen peroxide, are involved, might enhance leaf yellowing in stored mitsuba.

View full abstract

Volatile components of citrus fruits were trapped and measured by the head space method with using a Tenax, and the difference in the composition among the varieties, and specificity the variety based on the main component analysis were examined. D-Limonene has the highest composition ratio in the volatiles in every varieties. The percentage of d-limonene were in a range of 80 to 93 in the many varieties, but 47 to 72 in Shiikuwasha, Kabosu, and Lisbon lemon. Myrcene or γ-terpinene was higher especially in Kabosu or Shiikuwasha, respectively and showed a ratio value of 27 or 32, respectively. The main component analysis based on the first (X-axis) and the second (Y-axis) component scores revealed that fruits of navel orange, tangerine-tangelo, or satsuma mandarin were plotted in the limited and small area on the scattergram. Fruits of Shiikuwasha, Ohtani-Iyo, or Lisbon lemon gathered in a certain area far from the zero point, and showed a different specificity from those of the other citrus fruits.

View full abstract