Postharvest quality and storage life of 'Makapuno' coconut (Cocos nucifera L.)

Makapuno is a high-value commercial coconut with distinct sensory attributes, however the postharvest conditions required to maintain quality are unknown. To address this, partially de-husked mature Makapuno coconut fruit were stored at 2, 5 or 30°C and were then evaluated after transferring to 30°C for 3 days to simulate conditions in retail markets. During storage at 30°C, the fruit showed a moderate respiration rate of 40-60mgCO2kg-1h-1, a low ethylene production rate of 0.6-0.8μLC2H4kg-1h-1 and storage life was 3 days. In contrast, storage at 2°C or 5°C markedly reduced respiration rates to 4 and 20mgCO2kg-1h-1, respectively, and storage-life increased dramatically from 3 days to 6 weeks. Generally, cold storage delayed fruit deterioration by limiting weight loss, kernel browning and malondialdehyde content, however, after the fruits were transferred to 30°C, those previously held at 2°C showed signs of chilling injury, while those held at 5°C did not. Modified atmosphere packaging (MAP) using high oxygen transmission rate (OTR) bags in combination with 5°C storage extended fruit storage-life 20-fold, from 3 days at ambient conditions to 10 weeks. The combination of MAP and 5°C storage reduced weight loss (4-fold), the incidence of surface mold and the quality parameters measured were comparable to values in freshly harvested fruit. © 2014 Elsevier B.V

Postharvest quality and storage life of 'Makapuno' coconut (Cocos nucifera L.)

Makapuno is a high-value commercial coconut with distinct sensory attributes, however the postharvest conditions required to maintain quality are unknown. To address this, partially de-husked mature Makapuno coconut fruit were stored at 2, 5 or 30°C and were then evaluated after transferring to 30°C for 3 days to simulate conditions in retail markets. During storage at 30°C, the fruit showed a moderate respiration rate of 40-60mgCO2kg-1h-1, a low ethylene production rate of 0.6-0.8μLC2H4kg-1h-1 and storage life was 3 days. In contrast, storage at 2°C or 5°C markedly reduced respiration rates to 4 and 20mgCO2kg-1h-1, respectively, and storage-life increased dramatically from 3 days to 6 weeks. Generally, cold storage delayed fruit deterioration by limiting weight loss, kernel browning and malondialdehyde content, however, after the fruits were transferred to 30°C, those previously held at 2°C showed signs of chilling injury, while those held at 5°C did not. Modified atmosphere packaging (MAP) using high oxygen transmission rate (OTR) bags in combination with 5°C storage extended fruit storage-life 20-fold, from 3 days at ambient conditions to 10 weeks. The combination of MAP and 5°C storage reduced weight loss (4-fold), the incidence of surface mold and the quality parameters measured were comparable to values in freshly harvested fruit. © 2014 Elsevier B.V

Enzymatic browning in banana blossoms and techniques for its reduction

Banana blossoms are rich in fiber and nutrients and are a popular plant-based, vegan alternative to fish. However undesirable browning, usually visible at the peduncle cut-end, negatively impacts consumer acceptability of banana blossoms. The aim of this work was to develop safe alternatives to prevent browning in banana blossoms. First, the activities of primary enzymes associated with tissue browning, i.e., polyphenol oxidase (PPO), peroxidase (POD) and phenylalanine ammonia lyase (PAL), were assayed. Our data showed that PPO and POD were the key enzymes responsible for blossom browning as they increased in activity, reaching a maximum at pH 7, as browning developed. In contrast, PAL activity decreased, and total phenolic content did not change as browning progressed, indicating PAL was not induced by cutting and may not be involved in blossom browning. Second, to find antibrowning agents for banana blossoms that can substitute for the use of sodium metabisulfite (SMS), different organic acids of varying concentrations were tested. Among organic acids studied, treatment with 3% (w/v) oxalic acid was the most effective method and thus could be a safe substitution for SMS to prevent browning in banana blossoms

Overexpression of GSK3-like Kinase 5 (OsGSK5) in rice (Oryza sativa) enhances salinity tolerance in part via preferential carbon allocation to root starch

Rice (Oryza sativa L.) is very sensitive to soil salinity. To identify endogenous mechanisms that may help rice to better survive salt stress, we studied a rice GSK3-like isoform (OsGSK5), an orthologue of a Medicago GSK3 previously shown to enhance salinity tolerance in Arabidopsis by altering carbohydrate metabolism. We wanted to determine whether OsGSK5 functions similarly in rice. OsGSK5 was cloned and sequence, expression, evolutionary and functional analyses were conducted. OsGSK5 was expressed highest in rice seedling roots and was both salt and sugar starvation inducible in this tissue. A short-term salt-shock (150mM) activated OsGSK5, whereas moderate (50mM) salinity over the same period repressed the transcript. OsGSK5 response to salinity was due to an ionic effect since it was unaffected by polyethylene glycol. We engineered a rice line with 3.5-fold higher OsGSK5 transcript, which better tolerated cultivation on saline soils (EC=8 and 10dSm-2). This line produced more panicles and leaves, and a higher shoot biomass under high salt stress than the control genotypes. Whole-plant 14C-tracing and correlative analysis of OsGSK5 transcript with eco-physiological assessments pointed to the accelerated allocation of carbon to the root and its deposition as starch, as part of the tolerance mechanism

Effects of Timing and Severity of Salinity Stress on Rice ( Oryza sativa

The aim of this work was to examine agronomic, compositional, and functional changes in rice (Oryza sativa L. cv. Nipponbare) grains from plants grown under low-to-moderate salinity stress in the greenhouse. Plants were grown in sodium chloride-containing soil (2 or 4 dS/m(2) electrical conductivity), which was imposed 4-weeks after transplant (called Seedling EC2 and EC4) or after the appearance of the anthers (called Anthesis EC2 and EC4). The former simulates field conditions while the latter permits observation of the isolated effect of salt on grain filling processes. Key findings of this study are the following: (i) Plants showed adaptive responses to prolonged salt treatment with no negative effects on grain weight or fertility. Seedling EC2 plants had more panicles and enhanced caryopsis dimensions, while surprisingly, Seedling EC4 plants did not differ from the control group in the agronomic parameters measured. (ii) Grain starch increased in Seedling EC4 (32.6%) and Anthesis EC2 (39%), respectively, suggesting a stimulatory effect of salt on starch accumulation. (iii) The salinity treatment of 2 dS/m(2) was better tolerated at anthesis than the 4 dS/m(2) treatment as the latter led to reduced grain weight (28.8%) and seed fertility (19.4%) and compensatory increases in protein (20.1%) and nitrogen (19.8%) contents. (iv) Although some salinity treatments led to changes in starch content, these did not alter starch fine structure, morphology, or composition. We observed no differences in reducing sugar and amylose content or starch granule size distribution among any of the treatments. The only alterations in starch were limited to small changes in thermal properties and glucan chain distribution, which were only seen in the Anthesis EC4 treatment. This similarity of compositional and functional features was supported by multivariate analysis of all variables measured, which suggested that differences due to treatments were minimal. Overall, this study documents the specific response of rice under defined conditions, and illustrates that the plasticity of plant response to mild stress is complex and highly context-dependent, even under greenhouse conditions in which other potential environmental stress impacts are minimized