V. Srilaong

Biochemical and physiological changes during chlorophyll degradation in lime (Citrus aurantifolia Swingle cv. ‘Paan’)

Summary Lime (Citrus aurantifolia Swingle cv. ‘Paan’) native to South East Asia, has a distinct flavour and quality characteristics. Maintenance of the green colour in the peel of lime is a desirable quality attribute during storage. Post-harvest chlorophyll degradation in lime was studied in fruit stored at room temperature (30°C) at a relative humidity (RH) of 70 – 85%. Within 7 d of storage, the total chlorophyll content decreased to 53.9% of its initial level. The highest chlorophyllase activity (1.68 units mg–1 protein) was observed after 4 d of storage and declined thereafter. Peroxidase activity differed from chlorophyllase activity and increased significantly to 6.25 units mg–1 protein after 9 d of storage, (i.e., at the late maturity stage). Respiration rate and 1-aminocyclopropene-1-carboxylic acid (ACC) oxidase activity did not significantly affect the chlorophyll degradation process in lime.The total nitrogen content of lime peel was inversely correlated with its chlorophyll content. A higher soluble protein content was observed in yellow peel than in mature green peel. A colour index chart was developed for maturity stages 1–4 in lime based on peel colour changes from mature green to full-yellow, and its correlation with chlorophyll content and fruit quality attributes.

Oxygen action on respiratory processes in cucumber fruit (Cucumis sativus) stored at low temperature

Summary Respiratory processes in cucumber fruit stored in 5%, 21% (air control) and 100% O2 at 5°C were studied. Storage in 100% O2 at 5°C was most effective for suppressing the respiratory rate in cucumber fruit, the rate being lower than in fruit stored in either 5% O2 or air. Succinate dehydrogenase (SDH) activity in cucumber fruit stored in 100% O2 was lower than in other storage conditions. Only slightly different SDH activity was recorded between the control and 5% O2-treated fruit. Cucumber flesh pH in all three atmospheres increased during storage. pH showed similar increasing trends and more than one pH unit change from the initial value was recorded in control and 5% O2-treated fruit. Fruit kept in 100% O2 had a lower pH than fruit stored in 5% O2 and air. Pyruvate concentration in all three storage atmospheres increased during storage. The pyruvate concentration in 100% O2 was higher than in other storage atmospheres. The increase in pyruvate concentration in control fruit was similar to that in 5% O2 stored fruit. However, the pyruvate concentration in air-stored fruit increased sharply after day 11 and finally reached a higher level than that in 100% O2-treated fruit. Thus, the elevated O2 concentration suppressed SDH activity. This effect may be due to a reduction in fruit pH change. Consequently, reduced SDH activity in the 100% O2 treatment resulted in pyruvate accumulation which was not associated to any off-flavours. High O2 treatment has the potential to help maintain the quality of cucumber fruit. This is discussed.

Analysis of cost and execution efficiency of selected inbound logistics parameters in baby corn supply chains in Thailand

The inbound logistics for baby corn supply chain in Thailand were analysed to determine the factors that contribute to improve execution effi ciency. Three provinces accounted for more than 80% of the countrys total baby corn production. A survey covering 102 growers and 16 suppliers from three provinces randomly selected following the sample size principle was conducted using pretested. Relative effi ciency was determined following the Data Envelopment Analysis (DEA) using the Win4DAEP programme. Only 9 growers obtained the highest relative effi ciency of 1.0. Four of these growers had large planting area and all were GAP-certifi ed and engaged in contract farming.

Alleviation of browning and lignification in minimally processed sweet bamboo (Dendrocalamus asper) shoots by packaging

Abstract Browning at the cut surface of minimally processed sweet bamboo (Dendrocalamus asper) shoots is a limiting factor for shelf life and consumer preference. We studied the effect of two different packaging systems, polyvinyl chloride (PVC)‐wrapped foam trays and vacuum polyethylene (PE) bags, on storage attributes of bamboo shoot slices held at 4°C. Both packaging methods reduced weight loss, lignification and browning symptoms, and preserved the quality of fresh‐cut bamboo shoots, compared to unwrapped controls. Vacuum packaging was most effective in reduction of weight loss, respiration rate, activities of polyphenol oxidase and peroxidase, as well as least browning and lignification but PVC wrapping is recommended for general use because it is practical and less costly.

Influence of 1-methylcyclopropene on pectic enzyme activities, gene expression, and cell wall modification in papaya (Carica papaya cv. ‘Sunrise’) fruit

SUMMARY ‘Sunrise’ papaya fruit harvested at two stages of maturity [colour break (< 10% yellow peel colour) and 25% yellow peel colour] were treated with 100 nl l–1 1-methylcyclopropene (1-MCP) to determine its effects on ripening, on the activities and levels of gene expression of polygalacturonase (PG), pectin methyl esterase (PME), and βgalactosidase ( βGal), and on the degradation of cell wall components. 1-MCP delayed ripening and the onset of the climacteric, although the peak in the respiration rate was almost the same as that in untreated control fruit. Colour-break fruit treated with 1-MCP exhibited a continuous increase in ethylene production, but at a lower rate than in control fruit. Consequently, 1-MCP-treated fruit ripened with a concomitant reduction in firmness, which was accompanied by an increase in PG and βGal enzyme activities and gene expression. On the other hand, fruit treated with 1-MCP at the 25% yellow stage exhibited lower levels of ethylene production and developed pulp with a rubbery texture at the ripe stage which was attributed to reduced PG, βGal, and PME enzyme activities and gene expression. This was consistent with the higher level of cell wall polysaccharides measured in 1-MCP-treated fruit. The above results indicated that ‘Sunrise’ papaya fruit can be treated with 1-MCP at the colour break stage since they have a greater capacity to recover from the effects of 1-MCP than fruit treated at the 25% yellow stage.

Salt Tolerance in Apple Seedlings is Affected by an Inhibitor of ABA 8′-Hydroxylase CYP707A

The effects of an ABA 8′-hydroxylase inhibitor, (±)abscinazole-E2B (Abz-E2B), were examined in “Fuji” apple seedlings exposed to sodium chloride (NaCl). Water potential, stomata aperture, and endogenous ABA, proline, and sodium (Na+) levels were analyzed, along with expression of the 9-cis-epoxycarotenoid dioxigenase (MdNCED) and ABA 8′-hydroxylase (MdCYP707A) genes. Water potential and stomatal aperture in the leaves treated with Abz-E2B and NaCl (Abz-E2B+NaCl+ group) were lower than those in the untreated controls, but remained higher than those in the leaves treated with NaCl alone (Abz-E2B−NaCl+ group). Endogenous ABA levels were higher in the Abz-E2B+NaCl+ leaves at 4 days after treatment, whereas those in the Abz-E2B−NaCl+ leaves increased with time and peaked at 12 days after treatment. Expressions of the MdNCED1 and MdNCED2 genes remained lower in Abz-E2B+NaCl+ compared with Abz-E2B−NaCl+ leaves, especially at 12 days after treatment. Proline levels increased sharply at 100-mM NaCl, and Na+ levels increased with time. The Na+ concentrations in the Abz-E2B−NaCl+ leaves increased fourfold compared to those in the Abz-E2B+NaCl+ leaves. The expressions of MdCYP707A1 and MdCYP707A2 were higher in Abz-E2B+NaCl+ at 4 days, but declined at 12 days. The present data suggest that the increased endogenous ABA during the early stages of Fuji apple cultivation under salinity-stress conditions might be a good approach to prevent long-lasting damage and allow plants to recover.