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OBJECTIVE METHOD OF ESTIMATING ANTHOCYANIN CONTENT FOR DETERMINING COLOR GRADE OF GRAPES
Author(s) -
WATADA ALLEY E.,
ABBOTT JUDITH A.
Publication year - 1975
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1975.tb01071.x
Subject(s) - alley , citation , library science , engineering , advertising , operations research , computer science , business , civil engineering
THE USDA COLOR GRADE of hand-harvested grapes is determined visually (USDA, 1965). Such a subjective technique is not satisfactory for grading the color of mechanicallyharvested grapes because the skins are often separated from the pulp and the harvest consists of a mixture of skin, pulp, whole fruit and juice in a 4 ft X 4 ft X 4 ft plastic-lined bin. Fresh grapes must have adequate color if they are to produce concentrated frozen juice of satisfactory color. The USDA color grade of the frozen concentrated sweetened juice is based on absorbance of the juice (pH 3.2) at 430 and 52.0 nm (USDA, 1957). Absorbance at 430 nm indicates degree of degradation, and at 520 nm indicates the anthocyanin (Acy) content. Since the color of concentrated frozen juice is based on Acy content, juice color should be satisfactory if the fresh grapes contain adequate Acy. This study was to establish a rapid objective optical method for estimating Acy content, which could be used to grade the color of mechanically-harvested grapes. The study was designed so that macerates prepared for USDA grade determination of soluble solids could also be used for Acy analyses. For soluble solids determination, samples are collected randomly from bins and macerated together.