The quality of red chilli is based on colour, pungency and their retention during storage. The development of red colour is attributed to the presence of about 20 carotenoids, of which cap-santhin is the major one. Pungency is due to the mixture of seven homologous branched chains of alkyl vanillyl amides, namely, capsaicinoids (Hoffman et al., 1983) and these are produced in the glands of the fruit's placenta.
Factors affecting the quality of red chilli during storage
Colour loss during storage makes red chilli unacceptable to consumers, even though no change occurs in flavour and aroma. It has been found that colour impairment in red chilli starts when the fruits have lost about one-third of their water content and become over-ripe (Biacs et al., 1989; Daood et al., 1989). This colour impairment is accelerated several-fold as a result of the grinding and storage of paprika (Czinkotai et al., 1989) and is probably due to the development of heat at the time grinding. Positive correlations with high regression coefficient values have been obtained between colour retention by paprika powders and the initial concentrations of tocopherol and ascorbic acid (Biacs et al., 1992). Further, cultivars have showed substantial variability with respect to carotenoid composition and endogenous antioxidant content (Usha Rani, 1996; Gomez et al., 1998) and those with higher levels of ascorbic acid and tocopherol have shown greater colour stability during storage in powder form. Although there is an inverse relationship between the degree of pungency and the amount of deterioration during storage, no such correlation between capsanthin content and reduction in quality could be established (Usha Rani, 1996).
Fruit drying is the most important step that determines the final quality of the product. In India, chilli growers of small holdings dry the fruits using traditional methods. The methods involve sun drying by spreading fruits on either a cement floor, a mud floor, a floor smeared with cow dung, a zinc sheet, a polythene sheet, a granite floor or on the roof of red tiles. In a study involving these traditional methods, including oven drying at 65°C, it has been observed that drying the fruits on the plant itself and in a hot air oven was found to be better as these methods have resulted in a lower percentage of whitened fruits compared to the other methods (Nagaraja et al., 1998a). However, drying fruits on the plants may not always be possible because of bad weather conditions. Among the traditional methods, drying under house shade or on open ground and even on cement floors were found to be better and practically feasible, especially for large scale drying of fruits, particularly in the tropical countries where sunlight is not a limiting factor. Moreover, this type of drying would reduce the percentage of whitened fruits.
The industrial drying of pepper fruits for paprika production involves mainly two methods (Minguez et al., 1994) namely, oven drying and smoke drying. Each of the drying processes has its own merits and demerits that effect the stability of the final product. One such disadvantage of rapid oven drying at high temperature is the loss of colour stability during storage (Ramakrishnan and Francis, 1973). On the other hand, slow drying using wood smoke could result in degradative processes which are associated with the post-harvest physiology, as well as rotting arising from breakage, infection, etc. The possible colour stability produced by drying at low temperatures can be diminished by the presence of highly reactive chemicals formed during the smoking process, but these can provide an efficient protection against any infection (Minguez et al., 1994). However, the same authors in another study comparing the two industrial drying processes noticed a greater loss of carotenoid content in oven drying than in smoke drying. In fact, they have also observed an increase in concentration of some of the pigments during smoke drying, although the final carotenoid content of the dried fruits is less than that of fresh fruits. The loss of carotenoid content during drying and storage is attributed to a drastic reduction in the concentration of antioxidants, such as tocopherol and ascorbic acid, as a result of the antioxidation process (Daood et al., 1996). Further, the rate of pigment degradation is greater at a higher storage temperature and lower relative humidity (Gomez etal, 1998).
These studies suggest that the loss of fruit quality in terms of vitamins and their precursors during drying is very much dependent on the temperature and the rate of drying. Further, drying processes also determine the subsequent storability of chillies.
Dried chillies, when stored, are often attacked by the drugstore beetle Stegobium paniceum L. and the cigarrette beetle Lasioderma serricorne (Fabricius). The Arthrodeis species feed on dried chillies, though the loss caused by them is negligible. If the quantity of chillies infested by these storage pests is small, spreading the fruits in thin layers and exposing them to sunlight will eliminate the infection. If large quantities are infested with these pests, fumigation is the only remedy. Any good fumigant like ethyl dibromide or methyl bromide at one gram per 30 cubic metre space may be used. Fumigation should be done in airtight containers for the effective control of these stored pests (Dhamo et al., 1984).
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