Evaluation of Apple Juice Authenticity by Organic Acid Analysis

Abstract

An organic acid profile provides valuable information regarding authenticity of apple juice. The presence of D-malic acid is a clear indication of adulteration because this isomer does not occur naturally. Fumaric and citric acid levels above trace amounts are also inconsistent with pure apple juice; therefore, measurement of these organic acids may also be used as an authenticity check. Citric acid, total malic acid, and fumaric acid were determined in a single scan by liquid chromatography (LC) for 30 known pure apple juice samples. The L-isomer of malic acid was measured by an enzyme-specific method, and the D-isomer was calculated as the difference between total malic acid and L-malic acid.

INFLUENCE OF COMMERCIAL SHIPPING ON THE COLOR AND COMPOSITION OF APPLE JUICE CONCENTRATE1

“…The titratable acidity, while being on the low side of Mattick and Moyer's range (0.15-0.91 g 100 mL), is typical for the Delicious and Spur varieties grown in the Rio Negro valley. The malic acid content is within the range of values reported by Evans et al (1983). while the citric acid content is higher than the maximum reported by Evans et a!.…”

Geographic Variability of Sugars and Organic Acids in Selected Wild Fruit Species

“…From a technological perspective, they are very important for formation of gel consistency in gelatin products [33] and in production of juices and nectars, since they define sweetness index [34]. The representation of individual sugars and organic acids serves also as an indicator of authenticity of fruit products [35][36][37]. In addition, sugars participate in polyphenol biosynthesis [38]; thus, higher sugar content in fruit implies higher polyphenol concentration [39,40], which is exceptionally important from the perspective of a nutrient-enriched diet.…”

A Rapid Method for Separation and Quantitation of D‐Malic Acid in Fruit Juice

“…that D-malic acid could be resolved and quantitated. The procedure is simple and is less prone to error than the indirect determination of D-malic acid by difference methodology (Evans et al, 1983).…”

“…L-malic acid can be quantitated by enzymatic procedures (Mollering, 1974) and DL-malic acid by HPLC (Coppola and Starr, 1986). The presence of the D-enantiomer is indirectly determined by difference (Evans et al, 1983). An inter-laboratory study (Zyren and Elkins, 1985) showed that the precision of this procedure was good; however, synthetic DL-malic acid had to be added to the 20% level before the apple juice could be classified as adulterated at a 95% confidence levels.…”