Citrus quality standards

During the past half-century, the citrus industry has grown world-wide and quality standards, both local and international, have continually become more comprehensive and rigorous. 

W. L. Chen (China Agric. Univ., China) stressed the importance of education and stewardship on the part of farmers in China and other Asian nations in achieving a high level of compliance for foods exported to Japan. H. W. Ewart (California Citrus Quality Council, USA) emphasized the difhculties faced by growers and exporters in complying with disharmonized MRL standards of various trading... 

Gas chromatography provides a rapid analysis of citrus oil quality. This technique can be further enhanced to determine quantitative levels of individual compounds. Compounds can be measured based on the FID response. A standard curve with known concentrations is used to extrapolate an unknown concentration. 

The quality of extracted citrus juices depends on enzyme reactions that occur not only in the fruit during the development period, but also in the juice during processing. When juice is extracted from citrus fruit, enzymes are released from their normal restraint in the cell. Several of these enzymes catalyze reactions that adversely affect taste and appearance of the juice. Unless the reactions are controlled, the juice products will not meet the standards of quality set up by the USDA Food Safety and Quality Service. The two reactions of commercial importance are the hydrolysis of pectin to pectic acid, which clarifies juice, and the lactonization of limonoic acid A-ring lactone to the bitter compound, limonin. Research efforts to identify and characterize the reactions, to isolate and purify the enzymes, and to develop methods to control the reactions are described in this review. 

Fresh Citrus Juice. Freshly extracted commercial orange juice may contain a high peel oil content making sensory evaluation of this product very difficult because of the overriding, biting and even bitter flavor effect of the peel oil. This is one of the reasons why in certain plants, minimal attention is paid to the flavor quality of the juice until the product is standardized either in retail or bulk form (2). 

The purpose of quality control or quality assurance in the citrus industry is to help provide for the production of a uniform, high quality and commercially acceptable product. For most of the major qualitative characteristics, standardized, accurate and simple methods have been developed, and high and low limits have been carefully been established. Some of these include Brix, acid, color, recoverable oil, and free and suspended pulp. For each of these criteria, a simple and rapid assay has been developed and good correlation exists between the objective assay results and the subjective quality evaluations. 

An examination of the developments in the design of citrus fruit processing machinery shows quite clearly that the quality of the juice was more important than the quality of the oil, the only exception being oil of bergamot. Nevertheless, oil quality improved during the last decades and complies with the requirements of ISO standards. The expressed pulp of the more valuable kind fruit is very often treated with high-pressure steam to recover additional amounts of colorless oils of variable composition. The kinds of fruit treated in this manner are bergamot, lemon, and mandarin. 

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