S. Kanlayanarat

Effect of chitosan on ripening, enzymatic activity, and disease development in mango (mangifera indica) fruit

Abstract The effects of chitosan on mycelial growth and spore germination of Colletotrichum gloeosporioides were investigated on potato dextrose agar (PDA) containing 0%, 0.5%, 1.0%, 1.5%, and 2.0% (w/v) chitosan dissolved in 0.5% acetic acid. Complete inhibition of mycelial growth and spore germination was observed in the medium containing only 0.5% acetic acid. Media containing chitosan were less inhibitory, but the highest concentrations of chitosan, at 1.5% and 2.0%, were more inhibitory than the lower concentrations (0.5% and 1.0%). Chitosan treatment (0.5%, 1.0%, 1.5%, and 2.0%) of mangoes {Mangifera indica) previously inoculated with C. gloeosporioides resulted in a lower rate of disease progression compared with the controls. Chitosan concentrations of 0.5% and 1.0% had stimulatory effects on chitinase and P‐l,3‐glucanase activities. Additionally, chitosan coatings in mangoes delayed ripening and reduced respiration rate, ethylene production, and the loss of weight, ascorbic acid, and total titratable acidity. However, the firmness of mangoes treated at concentrations above 1% caused a perceptible decline in sensory quality.

Changes in physical characteristics and polyamines during maturation and storage of rambutans

Abstract Polyamine concentrations were measured in skin, pulp, and seeds of the late-harvest cultivar ‘Rongrien’ and the early harvest cultivar ‘Seechompoo’ rambutan ( Nephelium lappaceum L.) fruit. Skin weight increased steadily until harvest in both cultivars. The pulp weight increased rapidly from 84 to 105 DAFB (harvest) in Rongrien and from 70 to 91 DAFB (harvest) in Seechompoo. Putrescine (Put) was the major polyamine in the skin, pulp, and seeds of rambutan. In general, it decreased early and increased late in fruit development. The increase of Put in the pulp coincided with that of the fresh weight. At harvest, total polyamine concentrations in the skin and pulp in late-harvest Rongrien were higher than those in early harvest Seechompoo. When Rongrien rambutan fruit were stored at 8 or 13°C, chilling injury (CI) was detected in the skin of fruit stored 4 days or more at 8°C, and the CI index increased with days of storage. Put concentrations in the skin at 8°C were higher than those at 13°C, but Put concentrations did not rise correspondingly to the degree of CI. CI was not observed in the pulp, and the Put was much higher in the pulp than in the skin. These results suggest that Put concentration may be associated with the fruit growth and CI of rambutan.

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.

Relationship between ABA and chilling injury in mangosteen fruit treated with spermine

Theeffects of spermine on abscisic acid (ABA), hardening, and browning in storedmangosteen fruit were investigated. The hardening and browning, which areassociated with chilling injury (CI), were observed in only the skin of fruitstored at 7 °C. However, the hardening of skin was notaccompanied by moisture loss. The spermine treatment decreased the browning andhardening of the skin and extended storage time. Carbon dioxide(CO2)production from stored fruit gradually increased with d in storage(DIS). The increase of CO2 may be associated with the moisture lossbecause these levels coincided. ABA concentrations in the skin were highest infruit stored at 7 °C, followed by spermine treatment at 7°C, and the lowest at 13 °C. That is, thespermine treatment inhibited the increase of ABA in the skin of stored fruit.ABA concentrations in the skin may be associated with the degree of CI becausetheir fluctuations coincided. ABA metabolism in fruit stored at 7°C or 13 °C was also examined. The PA-DPApathway may not be the primary pathway of ABA metabolism because theconcentrations of PA and DPA were very low compared with those of ABA. ABAconcentrations in the aril were not significantly different between 7°C and 13 °C. This may be related to the lackof CI observed in the aril. ABA metabolism was different at each temperature.The decrease of ABA and the increase of DPA correlated at 13°C, however this correlation was not observed at 7°C. ABA metabolism may be influenced by temperature.

Abscisic acid metabolism during development and maturation of rambutan fruit

SummaryEndogenous abscisic acid (ABA), its 2-trans isomer (trans-ABA), phaseic acid (PA) and dihydrophaseic acid (DPA) were quantified in the skin, pulp and seed of the late-harvest cultivar Rongrien and the early-harvest cultivar Seechompoo to clarify the pathway of ABA metabolism in rambutan fruit (Nephelium lappaceum L.) and the relationship between ABA and fruit maturation. In the skin of ‘Rongrien’, ABA concentration reached a maximum 70.d after full bloom (DAFB) before maturation and then decreased torwards harvest. Trans-ABA and PA concentrations also followed a similar pattern to ABA. DPA increased from 84 DAFB and peaked at 98 DAFB. In the skin, although DPA increased after the decrease of ABA and PA, there was a long time lag, and the amount of increase was slight compared with the decrease of ABA. These results demonstrate that PA and DPA may not be the major metabolic pathway of ABA in rambutan skin. ABA metabolism in the seed of both cultivars followed a similar pattern. ABA and PA in the see...

Pasting properties by near-infrared reflectance analysis of whole grain paddy rice samples

A rapid predictive method based on near-infrared reflectance spectroscopy (NIRS) of paddy rice was developed to measure the pasting properties of rice. The paddy rice samples were scanned by a near-infrared reflectance spectrometer in the wavelength region of 1400–2400 nm and preprocessed by mathematical pretreatments prior to pasting properties analysis using a rapid visco-analyzer (RVA). The results indicated that the developed models of setback (SB), peak viscosity (PV), breakdown (BD) and consistency (CS) provided good prediction results with relatively high correlation coefficients (0.81–0.96). In addition, the validity of the calibration models was statistically tested. Standard error of prediction (SEP) and bias were small enough without any significance at 95% confidence interval. Nonetheless, this study proved that the use of NIRS for predicting pasting properties was feasible in paddy rice and could be applied in commercial trade and research.

THE BIOLOGICAL ACTIVITIES OF TROPONOIDS AND THEIR USE IN AGRICULTURE A REVIEW

Abstract Chemical compounds containing the tropone structure (2,4,6-cycloheptatrien-1-one), in their molecule, called troponoids, characterized by a seven-membered ring, are distributed in some plants, bacteria and fungi, although they are relatively rare. ß-Thujaplicin (2-hydroxy-4-isopropyl-2,4,6-cycloheptatrien-1-one), also known as hinokitiol, is a natural compound found in several plants of the Cupressaceae family. Besides hinokitiol, related compounds were identified in Cupressaceae trees. It has been demonstrated that hinokitiol and its derivatives have various biological effects, such as antibacterial, antifungal, insecticidal, antimalarial, antitumor, anti-ischemic, iron chelating and the inhibitory activity against polyphenol oxidase activity. Activity similar to ß-thujaplicin has tropolone and its derivatives, which are not present nature. Due to the high scientific and practical interest, synthetic ß-thujaplicin and other troponoids have been produced for many years. In this review, the major biological effects of troponoids, mostly ß-thujaplicin and tropolone, on tyrosinase and polyphenol oxidase activity, ethylene production, antibacterial, antifungal and insecticidal activities, and biotransformation of ß-thujaplicin by cultured plant cells are presented. Accumulation of ß-thujaplicin and related troponoids has been shown in cell cultures of Cupressus lusitanica and other species of Cupressaceae. The biosynthetic pathway of the troponoids in plants, bacteria and fungi has been also briefly described.

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.

Cell wall metabolism during development of rambutan fruit

Summary Cell wall metabolism during fruit development in ‘Rongrien’ rambutans (Nephelium lappaceum L.) was investigated. Around 80% of the cell wall composition in the skin and around 60% in the pulp was cellulose. The firmness of skin increased towards harvest. In the skin, water-soluble pectic substances (WSP), hemicellulose and cellulose decreased with days after full bloom (DAFB), but hexametaphosphate-soluble pectic substances (HMP) increased. Cellulose concentrations were high throughout fruit development, that is, they never fell below 27 g kg–1 FW. The inconsistency of the skin firmness with cellulose and hemicellulose suggests that if they remained at a certain minimum level, their concentrations might not be reflected in the firmness. In the skin, HMP concentrations may influence firmness. Pectin esterase (PE) activity in the skin decreased towards harvest, but endo-polygalacturonase (PG) activity increased. Thus their activities may not be associated with the cell wall polyuronide degradation in the skin. The firmness of pulp decreased towards harvest, and coincided with the changes of HMP, hemicellulose and cellulose, but WSP increased. From 56 DAFB to 98 DAFB (harvest), cellulose decreased 70% from 10 g kg–1 FW and hemicellulose decreased 60% from 5 g kg–1 FW. Although PE activity in the pulp did not change during fruit development, endo-PG increased towards harvest. This result suggests that endo-PG may relate to cell wall polyuronide degradation in the pulp. However, the WSP concentration was very low compared with other components. In contrast to the skin, the decreases of cellulose and hemicellulose may be related to the softening of pulp.

Assessment of volatile and non-volatile organic compounds in the liquid endosperm of young ‘Nam Hom’ coconut (Cocos nucifera L.) at two stages of maturity

SUMMARY Young coconut (Cocos nucifera L.) fruit collected 6–8 months after anthesis (MAA) contain a high volume of water [20% (w/w)] and can provide a refreshing drink. The present study investigated volatile organic compounds (VOCs), as aroma components, and physico-chemical changes in the liquid endosperm of young ‘Nam Hom’ coconut at two stages of maturity: the one-layer stage (6 MAA) and the two-layer stage (7.0–7.5 MAA) of the flesh. The liquid endosperm of coconut fruit becomes sweeter and more turbid late during maturation. Lauric acid (C12:0) and myristic acid (C14:0) were the main free fatty acids in the liquid endosperm of coconut. Short-chain fatty acid (C10–C12) concentrations increased slightly, and longer-chain fatty acid (C14–C18) concentrations declined when fruit matured from the one- to the two-layer stage of flesh. Solvent extractions showed a 1.4-fold increase in the total concentration of VOCs in the liquid endosperm during fruit development. This was related to a major increase in squalene and sterols, to 21.7% (w/w) of the total VOC and non-volatile organic compounds, whereas the concentrations of terpenes and esters remained stable. Although a series of alkanes existed in the liquid endosperm of coconut, the main aroma components were 2-methyl-1-butyl acetate and terpenes such as D-limonene, α-pinene, and 3-carene. We conclude that, when coconut fruit developed from the one- to the two-layered flesh stage, the liquid endosperm not only became sweeter and contained higher concentrations of aroma volatile and non-volatile components, but also became oily and less translucent.