Lee H S, Wrolstad R E
Oregon State University, Department of Food Science and Technology, Corvallis 97331.
J Assoc Off Anal Chem. 1988 Jul-Aug;71(4):795-7.
The 13C:12C ratios of 8 authentic apple juice samples and their subfractions were determined by mass spectrometry. Apples from Argentina, Mexico, New Zealand, and the United States were processed into juice; pulp was collected from the milled fruit and seeds were collected from the press-cake. Sugars, nonvolatile acids, and phenolics were isolated from the juice by treatment with ion-exchange resins and polyvinylpyrrolidone (PVPP). The mean value for all juice samples was -24.2% which is close to the values reported by other investigators. Juice from apples grown in Argentina, Mexico, and New Zealand did not differ from U.S. samples. The isotopic composition of the subfractions ranged from -22.0 to -31.0%. The values for the pulp were essentially the same as for juice. The sugar fraction was slightly less negative than the juice; the nonvolatile acid and phenolic fractions were more negative. The levels of nonvolatile acids and phenolics in apple juice are low, however, so these compounds contribute little to overall delta 13C values in juice.
通过质谱法测定了8个正宗苹果汁样品及其亚组分的13C:12C比率。将来自阿根廷、墨西哥、新西兰和美国的苹果加工成果汁；从磨碎的水果中收集果肉，从滤饼中收集种子。通过用离子交换树脂和聚乙烯吡咯烷酮（PVPP）处理，从果汁中分离出糖、非挥发性酸和酚类物质。所有果汁样品的平均值为-24.2%，这与其他研究人员报告的值相近。来自阿根廷、墨西哥和新西兰种植的苹果制成的果汁与美国样品没有差异。亚组分的同位素组成范围为-22.0%至-31.0%。果肉的值与果汁基本相同。糖组分的负值略低于果汁；非挥发性酸和酚类组分的负值更大。然而，苹果汁中非挥发性酸和酚类物质的含量较低，因此这些化合物对果汁中整体δ13C值的贡献很小。
