engleski

Opimization of canding orange peel

Oranges, which are among the most cultivated citrus fruit, usually consumed as fresh fruit, but in some high-production countries, most of the crop is processed primarily in the juice. Juice production generates large amounts of peel. Because peel is known as source of many valuable components a lot of by-products derived from it. For example, oil from the outer layer of the peel, flavedo, is one of the major sources of flavour products. Also, pectin obtained from inner layer of the peel, albedo, mostly is used in food industry for gelling products. But nutritional and health properties of some peel components such as pectin, flavonoids, carotenoids or limonene are the reason to use whole peel and produce high valuable peel product, such as candied peel. Due to its highly porous structure, orange peel is suitable for impregnation by sugar. The process of sugar impregnation should be optimized to reduce bitterness of peel and losses of valuable components, what could be achieved with appropriate pre-treatment, sugar solutions, utilizing some additives and optimal temperature and specially by using the vacuum. The aim of this research work was to optimize canding of orange peel with emhasis on pre-treatment and pressure used. Three samples were produced: (i) pre-treatment by NaCl addition during cooking peel, impregnation in water sugar solution on 60oC, as control ; (ii) pre-treatment by cooking peel in sugar solution and immersing that peel in emulsion of water, sunflower oil and sodium-bicarbonate (E), vacuum impregnation in orange juice with sugar addition on 30oC (VI) ; (iii) pre-treatment by ultrasound in E and VI. During the process mass increase, dry matter, total phenolic compunds, antioxidant activity, and total carotenoids were monitored. Samples were sensory evaluated by quantitative descriptive method. The best procedure was the second one (ii), so this procedure could be recommended for canding orange peel.058

candying; orange peel; vacuum impregnation; phenolics; carotenoids

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