Citrus fruits. Part II. Chemistry, technology, and quality evaluation. C. quality evaluation

Abstract

In Part II of this review on citrus fruits, the literature on chemistry, technology, and quality evaluation are critically considered. Sweet oranges, mandarin, grapefruit, lemon and lime are generally used for processing. The literature on chemical components of citrus fruits reviewed and discussed in Section A includes the following: sugars, polysaccharides, organic acids, nitrogenous constituents, and lipids; carotenoids which contribute to color; vitamins and minerals, and flavonoids; limonoids, some of which impart bitterness to the juice, and the volatile components which contribute to aroma. Chilled and pasteurized juices, juice concentrates, and beverages are the important products manufactured commercially, and to a limited extent powdered citrus juices, canned segments, and marmalades. The literature on the manufacture of these products as well as new types of juice and oil extractors, TASTE, and other types of evaporators, tank farms to store juice and concentrate in bulk, aseptic filling in bulk containers and retail packs, alternate flexible and rigid containers other than glass and tin and recovery of volatile flavoring constituents during juice processing are some of the important technological developments in the recent past which were discussed in Section B. Bitterness in citrus juices and its control, composition of cloud and its stability, and changes during storage have been reviewed. Essential oils, pectin, frozen and dried juice sacs, dried pulp and molasses, flavonoids, seed oil, and meal are the important by‐products, the manufacture of which is given in essential details. Generally, consumers judge the product on the basis of its sensory attributes. The quality of the finished products is dependent upon the raw materials used and control of processes. In this section, the USDA standards for different products, physico‐chemical and microbiological parameters prescribed as indices of quality of fruit, juice, concentrate, and other products, composition of essential oils, and aroma concentrates are discussed in relation to sensory quality. Analytical methods for compounds affecting quality and methods for detection of adulteration in different citrus products are briefly reviewed. The importance of sensorily evaluating quality of citrus products to select and develop quality control indices is emphasized. Areas where further research is required are indicated. A comprehensive bibliography is provided to aid further study and research.