本研究では,神奈川県が育成したトマト品種「湘南ポモロンレッド」の日焼けによる品質低下(着色不良)を抑制するため,果実を早期収穫した後の適切な追熟条件を検討するとともに,カロテノイド代謝系の遺伝子発現について解析した.催色期で収穫したトマトを各温度で追熟させた結果,20°C~25°Cの温度帯で追熟を行うことでリコペンが多く蓄積し,またその際に,カロテノイド生合成関連遺伝子の一つPSYおよびプロリコペンをリコペンへと異性化する遺伝子であるCRTISOの発現量も高くなることが明らかとなった.また蛍光灯の照射がカロテノイドの生合成に与える影響としては,照射によりリコペン,β-カロテンの蓄積が高まり,果実の着色も早くなることが明らかとなった.カロテノイド生合成遺伝子の発現も高まっており,蛍光灯の照射がカロテノイド生合成経路を活発化させることが明らかとなった.これらの結果より,「湘南ポモロンレッド」における最適な追熟温度,さらに光照射によるリコペンおよびβ-カロテンの蓄積増大を表現型および遺伝子発現レベルで明らかにした.

Reconstruction of cell wall polysaccharide is necessary for fruit development and ripening. Arabinose is the one of neutral sugars constituting wall polysaccharides and arabinose-containing polysaccharides play an important role in cellular attachment. In this study, expression patterns of α-l-arabinofuranosidase genes were examined in three tomato cultivars, the processing type ‘OSKAR’, fresh market type ‘Ailsa Craig’, and their hybrid ‘Shonan Pomoron Red’, to elucidate the function of α-l-arabinofuranosidase in fruit traits such as shape, growth, firmness, and juiciness. While there was no significant difference in fruit diameter among the cultivars, longitudinal elongation was observed in ‘OSKAR’ with increasing fruit weight. The hybrid ‘Shonan Pomoron Red’ showed intermediate longitudinal growth. Compared to ‘OSKAR’ at the red ripe stage, fruit flesh softened more in ‘Ailsa Craig’ and much water was released from the pericarp disk. The rate of water release in ‘Shonan Pomoron Red’ was intermediate. The α-l-arabinofuranosidase genes, SlArf/Xyl2, LeXYL1 and LeXYL2, were highly expressed in the young fruits and SlArf/Xyl1 and LeXYL1 were up-regulated when ripening initiated. However, their expression levels did not appear to cause the difference in fruit traits such as growth rate, fruit shape, and firmness among the cultivars. On the other hand, expression levels of SlArf/Xyl1, LeARF1 and LeXYL2 were consistent with the rate of water release from ripe fruit. Therefore, α-l-arabinofuranosidase could influence fruit flesh texture and juiciness in fresh market and processing cultivars.

The vibration characteristics, contact load, and breaking strength of Satsuma mandarin stacked in a triple-wall fiberboard box under a vibration treatment (2-30 Hz, 0.6 G) were investigated for evaluating the feasibility of using a bulk container (BC) for fresh produce transportation

An unidentified compound was detected in sweet pea (Lathyrus odoratus L. 'Diana') petals by HPLC analysis using a cation-exchange column for soluble carbohydrate analysis. This compound was identified as 2-cyanoethyl-isoxazolin-5-one (2-CEIX) using H-1-NMR, C-13-NMR, and CI-MS and ESIMS. 2-CEIX was detected in the petals, leaves and stem. Amino acid and other nitrogenous compound contents in these organs were compared with 2-CEIX. The content of asparagine was highest, followed by 2-CEIX in the petals, and 2-CEIX was highest among nitrogenous compounds in the stem and leaves. The 2-CEIX content in the petal decreased during flower opening, but those in the petals and the other floral parts increased during senescence regardless of sucrose treatment. These trends differed from those of monosaccharides, sucrose and cyclitols. Thus, the role of 2-CEIX appears to differ from those of soluble carbohydrates. 2-CEIX was not detected in phloem and xylem saps. The results suggest that 2-CEIX is a major nitrogenous compound of low molecular weight and is likely to be produced in situ in various organs in sweet pea.

The damage (abrasion) and vibration characteristics of 5-layer stacked Japanese radishes in a triple-wall fiberboard box under sinusoidal vibration (2, 10, 15, 20, and 30Hz, 0.6G) were investigated here. The influence of packaging conditions on the vibration characteristics was also examined. A larger damage area ratio and positional changes were found at a vibration frequency of 10-20Hz. The peak frequencies of the acceleration transmissibility and the rotation angle were close to 10 and 15Hz, respectively. A positive correlation between the damage area ratio of the upper layer of Japanese radish and acceleration transmissibility (r2＝0.92), as well as between the rotation angle and the fifth layer (r2＝0.66), was observed. Tight wrapping, using an inner bag, lowered the acceleration transmissibility and rotation angle at the peak frequency. The peak frequency of the acceleration transmissibility and the rotation angle differed depending on the floor materials used (corrugated fiberboard, polypropylene ［PP］ sheet, polyethylene foam sheet). Because the rotation angle tended to increase when a2-mm thick PP sheet was used, as compared to that when other floor materials were used, use of the former material should be avoided. Overall, it is important to choose the appropriate packaging material (inner bag and floor material) depending on the purpose for use and the transport conditions. In addition, an index that combines the acceleration transmissibility and the rotation angle may be useful to estimate the damage to Japanese radish during bulk container distribution.

The damage characteristics of five layers of Japanese radishes stacked in a triple-wall fiberboard box under a vibration treatment (2～30Hz, 0.6G), which was considered a transport model of a newly developed bulk container, are investigated. The differences in the vibration treatment period (0.5, 3, 5, 10, 20, and 40min) and the position of the Japanese radishes in the stack significantly affected the type and the severity of the damage. Various types of damage, including abrasion, peeling, and bruising of Japanese radishes, are observed differently, depending on the stacking layers. Abrasion and peeling symptoms are found on the upper layers of the stack of the Japanese radishes owing to a non-synchronized movement, whereas bruise symptoms are found on the lower layers. Further, the acceleration transmissibility test of the Japanese radishes against a vibrating table revealed resonant frequencies close to 15Hz in all the layers. The higher the stacking layer, the higher is the acceleration transmissibility. Moreover, the contact stress index obtained from a multipoint pressure sensor revealed that both the maximum and the minimum values at the lower layers are significantly higher than those at the upper layers (maximum value: P＜0.05 (15Hz, 20Hz, and 25Hz are excluded) ; minimum value: P＜0.01). A reduction in the load from the upper layers, caused by the non-synchronized movement, most likely results in lower values of the contact stress index of the Japanese radishes in the middle/upper layers. Overall, it appears that the restriction of the free movement of Japanese radishes in the upper layer without any additional stress facilitates the prevention of damages such as abrasion and peeling. Moreover, we need to find an acceptable stacking height to avoid bruising in the lower layers. Further research on the design of packaging conditions for the actual transport condition will enable us to distribute Japanese radishes by using the newly developed bulk container without any unacceptable damages.

Because the mechanical damage caused by postharvest handling (including bulk storage and transport) plays an important role in the yield and the postharvest quality of fresh produce, the effect of postharvest impact stress on the physiological and chemical properties of cabbage (Brassica oleracea var. Capitata L.) was investigated in this study. To simulate the impact stress occurrence during the bulk handling practice, cabbage picked at commercial harvest stage was dropped from different heights (10, 20, 40, and 80cm) onto a flat, rigid concrete floor. The effects of the dropping treatment on the respiration rate and on the content of various sugars (sucrose, glucose, and fructose) were evaluated during storage at 20℃ for 6 days. Shortly after the dropping treatment, an increased rate of respiration correlated with a higher dropping height. However, a decreased respiration rate was observed after one day of storage. The sugar content of all samples changed slightly at days 1 and 3. At day 6, cabbages dropped from 80 and 40cm showed the lowest content of fructose and total sugar (the sum of sucrose, glucose, and fructose). The major effects of impact stress on cabbage heads include increases in the respiration rate and a loss of sugar content. In addition, tests of controlled atmosphere (CA) treatment on dropped cabbages showed that CA likely inhibited the severe damage caused by impact stress on cabbages because it reduced the rise in respiration rate and slowed the loss of sugar content in dropped cabbages during storage at 20℃. Overall, impact stress obviously affects the postharvest physicochemical properties of cabbage just after impact occurrence (respiration rate) and during storage (sugar content). These changes are also influenced by the strength of the stress level (height of dropping treatment) and the time period after the application of the stress treatment. Rapid and appropriate postharvest handling and storage management, therefore, will delay the onset of deterioration of cabbage quality and extend its shelf life.