Chalermchai Wongs-Aree

Influence of hot air fluidized bed drying on quality changes of purple rice

ABSTRACT The influence of drying using a fluidization technique on the quality of purple rice was investigated in this study. The results demonstrated that the initial moisture of rice was 28.3% dry basis (db). Compared to the sun-dried or reference purple rice samples, the influence of drying at temperatures ranging from 100 to 150°C did not affect the quality of color, anthocyanin content, total phenolic content, or antioxidant activity. At this initial moisture level, samples should be dried at 150°C air because such temperatures yield the highest drying rate. Drying at this temperature also causes an increase in the head purple rice yield because of the gelatinization of starch. In the case of an initial moisture content of 33.3% (db), the drying temperature should not exceed 130°C.

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.

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.

Assessment of three green papaya (Carica papaya Linn.) cultivars (‘Krang’, ‘Kaek Noul’, and ‘Kaek Dum’) for use as shredded fruit

Summary Immature Carica papaya fruit of three cultivars (‘Krang’, ‘Kaek Noul’, and ‘Kaek Dum’) known to be suitable for processing as papaya shreds were harvested 60 – 70 d after anthesis. ‘Krang’ had the largest fruit among the three cultivars. The mean fruit firmness values for intact ‘Krang’, ‘Kaek Noul’, and ‘Kaek Dum’ papaya fruit were 95.2 N, 99.4 N, and 109.7 N, respectively. The mean rates of respiration and ethylene production in intact fruit were not significantly different among the three cultivars. The flesh of ‘Krang’ fruit had the highest L* and hue angle (hº) values (68.1 and 112.8, respectively), and the flesh of ‘Kaek Dum’ was more yellow in colour than the flesh of the other two cultivars, expressed as a b* value of 8.9. During storage at 10ºC and 85 – 90% relative humidity, shreds of ‘Kaek Dum’ fruit flesh retained the highest average shear force values, followed by ‘Kaek Noul’ and ‘Krang’. Shreds of ‘Krang’ fruit showed a relatively higher loss of fresh weight than ‘Kaek Dum’ or ‘Kaek Noul’ (3.7 – 5.8%, 2.4 – 3.2%, and 1.1 – 2.2%, respectively), and this loss appeared to correlate with the microstructure of the parenchyma cells. The cellular morphology of shredded fruit was observed using a scanning electron microscope (SEM). The SEM revealed that parenchyma cells in ‘Krang’ were larger than those in ‘Kaek Noul’ and ‘Kaek Dum’. On day–6, fruit flesh shreds of ‘Kaek Noul’ and ‘Kaek Dum’ scored higher than those of ‘Krang’ in a trained, ten-person panel test on a nine-point hedonic scale for overall acceptance, with values of 5.0, 4.3, and 3.6, respectively. ‘Kaek Noul’ and ‘Kaek Dum’ papaya fruit were therefore better suited for processing into shreds and had a longer storage-life of 6 d. Although, initially, ‘Krang’ fruit had the best appearance and a high L* value after peeling, these features were lost during storage at 10ºC and reduced the storage–life to only 4 d.

Effect of harvest seasonal and gamma irradiation on the physicochemical changes in pineapple fruit cv. Pattavia during stimulated sea shipment

Abstract Gamma irradiation is used as a phytosanitary treatment for tropical fresh fruit from some producing countries. An experiment was carried out to study the effect of gamma irradiation and season of harvest on the quality ‘Pattavia’ pineapple fruit. Fruit harvested in the summer and the rainy cool (winter) seasons were exposed to gamma radiation at dose levels of 0 and 400–600 Gy from a 60 Cobalt source and the fruit stored at 13°C and 90% RH for up to 21 days. Gamma irradiation did not affect the ratio of TSS/TA, antioxidant content, or ascorbic acid concentration. However, gamma irradiation did delay color development and also induced internal browning over 50% of flesh discolored in fruit stored for 14 days, especially harvested winter fruit. Moreover, harvesting fruit in different seasons had a significant effect on fruit quality after harvest and during stimulated sea shipment storage. The result showed that gamma irradiation can be used as a phytosanitary treatment with minor changes in eating quality. However, the internal browning was greater if fruit were stored longer than 1 week at 13°C.

Physiological and physico-chemical changes in green papaya (Carica papaya L. ‘Kaek Noul’) shreds taken from the outer or inner mesocarp

ABSTRACT This study compared physiological and physico-chemical changes in shreds of green papaya (Carica papaya L. ‘Kaek Noul’), taken from inner and outer mesocarp tissues, during storage at 7ºC for up to 8 d. Reductions in the flesh firmness of shreds, microstructure, colouration, dry matter content (DMC), and fresh weight (FW) loss, and in the rates of respiration, ethylene production, and enzyme activities were measured. The rapid loss of firmness of green papaya ‘Kaek Noul’ shreds taken from the inner mesocarp was attributed to the larger and more loosely arranged cells of the inner mesocarp compared to the smaller and compact cells of the outer mesocarp. Shreds taken from the outer mesocarp had a higher DMC [6.21–6.77% (w/w)] than those from the inner mesocarp [5.83–6.34% (w/w)] during storage at 7ºC. FW loss was higher for shreds from the inner mesocarp than from the outer mesocarp (0.89–1.12% vs. 0.39–1.00%, respectively). Colour values (h°) were lower at the end of storage for shreds from the inner mesocarp than shreds from the outer mesocarp (104.38° and 111.94°, respectively). Moreover, scanning electron micrographs of shreds from inner mesocarp and outer mesocarp tissues showed that the slower loss of firmness in shreds from the outer mesocarp could be attributed to having smaller and more compact cells, as well as to lower ethylene production by the outer mesocarp. However, this was not related to cellulase activity. This study indicated why processors prefer to use shreds from the outer mesocarp of green papaya.