Browning of sultana grape berries during drying

Abstract

Berries of Vitis vinifera L . cv. Sultanina (Sultana, Thonpson Seedless) were partly immersed in commercial oil emulsion before drying in an oven at 40"c. The treatedpart dried to a yellow colour without visible surface bloom, which is characteristic of firlly treared berries, while the untreatedpart dried to a bluish-violet cotour with surface bloom characteristic of untreated berries. Colour development was prevented in partly treated berries if they were fully immersed in oil emulsion before they had lost about 50% of their fresh weight. The browning reaction was inhibited in isolated grape skins by sodium diethyldithiocarbamate. The results support the hypothesis that browning of sultanas during drying under mild conditions is caused by o-diphenol oxidase (E.C.1.10.3.1) acting on substrates released from cell compartments when cell integrity is lost. Uneven colour development in commercially produced, dried sultanas can be prevented by a second spraying with oil emulsion within 7 days of the first.

Diphenol Oxidases, Enzyme-catalysed Browning and Plant Disease Resistance

“…However catecholase action is not always a problem in the food industry and in some circumstances its action is desirable or even essential; for example, in the manufacture of black tea (Takeo, 1966;Opie etal., 1995), sultanas (Grncarevic and Hawker, 1971), prunes (Vamos-Vigyazo, 1981), coffee (De Amorim and Silva, 1968) and cider (Walker, 1975(Walker, , 1995.…”

Time Course ofPPO-Related Browning of Yams

“…The incidence of tissue browning is desirable in the manufacture of black tea (Takeo 1966), tobacco (Sheen and Calvert 1969) and in the processing of sultana grapes and prunes (Grncarevic and Hawker 1971). It is undesirable in the processing of fruits juices (Wolfrom et a1 1974), yam (Anosike and Ikediobi 1985) plantain and grain flour (Lamkin et al 1981) because of production of undesirable colour, odour and astringent flavours which reduce the commercial value of the product (Sciancalepore and Longone 1984; Lee et a1 1990).…”

Monitoring and Optimization of the Process of Drying Fruits and Vegetables Using Computer Vision: A Review

“…For example, a high level of melanins, which are enzymatic browning products, is responsible for the brownish color and off-flavor. One exception is made for Sultana grapes, because consumers seem to prefer brown dried grapes [62]. Several solutions were adopted to inhibit enzyme activity: the use of heat as pre-treatment, to inactivate the enzyme, and the use of sulfur dioxide or sulfites, which are able to complex an intermediate product, the o-quinones [63].…”