36E-93 |
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K. Y. YOON, E. E. Woodams, and Y. D. Hang. Food Science & Technology, Cornell Univ., New York State Agricultural Experiment Station, 630 W. North St., Geneva, NY 14456-1371 The Brix/acid ratio is commonly used as a measure of fruit maturity and palatability. The organic acid content of a fruit significantly affects the Brix/acid ratio. Acid limes have low pyrophosphatase activity, while sweet limes exhibit higher pyrophosphatase activity. In a recent study, we observed an inverse relationship between the acid phosphatase activity and the acidity in apples. The objective of the present study was to determine the relationship between the Brix/acid ratio and the acid phosphatase activity in stone fruit such as cherries. Eleven cultivars of cherries grown at the New York State Agricultural Experiment Station in Geneva, NY were harvested in 2003 and 2004. Acid phosphatase was extracted by blending fruit with acetate buffer (pH 5.0) containing 5% polyethylenglycol, 0.1% beta-mercaptoethanol and 0.2 N NaCl. The soluble fraction obtained by centrifugation was used as crude enzyme. The enzyme activity was measured with 0.2% p-nitrophenyl phosphate as substrate. One unit is the amount of enzyme capable of producing 1 umol p-nitrophenol/h at pH 5.0 and 25 o C. Brix was measured with a refractometer. Acidity expressed as citric was determined by titration. High-acid, low-phosphatase cultivars (Karneol, Northstar, Kroeker, Danube Montmorency, Oblinska and Topas) exhibited low Brix/acid ratios, while low-acid, high-phosphayase cultivars (Balatron, Sweet heart, Hedelfingen, and Hudson) had high Brix/acid ratios. The coefficients of correlation for acid phosphatase and Brix/acid ratio of cherries harvested in 3003 and 2004 were 0.8760 and 0.8361, respectively. A positive relationship exists between the Brix/acid ratio and the acid phosphatase activity in stone fruit such as cherries. Acid phosphatase thus could serve as a genetic marker for breeding new fruit cultivars with a desirable ratio for commercial applications.
Session 36E, Fruit & Vegetable Products: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |