Limonin Bitterness in Citrus Juices

Abstract

Juices and their derivatives are by far the most important products made from the major citrus varieties. Among citrus fruits, oranges are the leading variety utilized for juice production. “Single-strength juice,” also known as 100% juice, is either not from concentrate (NFC) juice, or juice reconstituted from a concentrate by dilution with water to the natural single-strength Brix. There are two fundamentally different systems of raw material procurement for the industry. In the “industry only” or the “industrial orchard” system, nearly all the crop is sent to the factory to be processed. This system accounts for a great part of citrus production in Florida, Brazil, and parts of China. The second system is the “fresh/industry mix” system, the objective of which is to maximize the proportion of crop marketed as fresh fruit, processing only the fruit that cannot be sold as such, for reasons of external quality, fruit size, trade barriers, or excess production. After harvesting and transporting to the processing plant, the fruit is graded and washed. Juice extraction systems may be separated into two groups: those where the fruit is cut into two halves before juice extraction and those where the juice is extracted from whole fruit without halving. In the first group the essential oil is separated from the whole fruit before juice extraction. In the second group the essential oil is obtained simultaneously with juice extraction. Three leading industrial systems of juice extraction are described in detail. Excess pulp is removed by different methods of screening and the juice is pasteurized to inactivate cloud-breaking enzymes and spoilage microorganisms. Deaeration and homogenization before pasteurization are frequently practiced options. Several nonthermal stabilization processes are described. The pulp wash processes for the recovery of soluble fruit solids from pulp are explained. The production of single-strength juice by dilution of concentrates and of various modified juices is discussed.