Citrus are nonclimacteric fruits that are allowed to mature on the tree, since postharvest maturation will not occur. The indices of fruit maturity include °Brix, acid content, and the Brix/acid ratio. Major U.S. citrus producing regions, such as California, Florida, and Texas, all have legal maturity standards. Typically, oranges range from 7 to 14, grapefruit from 10 to 12, and tangerines from 16 to 17 °Brix . Citric acid is the major acid present in citrus fruit. At maturity, concentrations of total acid for oranges, grapefruit, and tangerines are 0.5 to 1.5%, 1.0 to 2.0%, and 0.6 to 2.3%, respectively. The U.S. Department of Agriculture (USDA) has published standards for grades of orange juice. Brix standards for pasteurized juice are 11° for grade A and 10.5° for grade B. An acid concentration or pH standard is not established. However, Brix/acid minimum and maximum ratios are given for grade A and grade B juice. The typical pH range for most citrus juice is from 3.0 to 4.0 and cannot be legally altered by added acidulants .
Typical aerobic microbial load on citrus fruit is approximately 4.0 log CFU/cm2 [17-19]. Yeast and mold populations measured alone seem to show greater variability than total aerobic populations, but have been reported as nearly as high as total aerobic microbial load. In citrus juices, acidic conditions, coupled with higher sugar content, result in a microbiological population made up primarily of acidolactic bacteria, yeasts, and molds. Lactic acid bacteria are reported to be the major spoilage organisms [16,20,21]. Populations found in fresh citrus juices are reduced compared to populations found on fruit when appropriate sanitation and extraction methods are used .
Was this article helpful?