M. BARRETO and R. W. Buescher. Dept. of Food Science, Univ. of Arkansas, 2650 N. Young Ave., Fayetteville, AR 72704
Rutin (Quercetin-3-O-rhamnoglucoside), the main flavonol in pickled asparagus (Asparagus officinalis), crystallizes and deposits on stem surfaces. The appearance is objectionable causing consumer rejection and economical losses. Studies on rutin solubility and thermolability will assist with understanding the problem and its remedy. To determine effect of pH, and ionic strength on rutin solubility and the rutin thermolability in brine solutions.Rutin solubility was determined in high ionic strength solutions from pH 2 to 9, and in NaHCO3, ZnCl2 and NaCl solutions. Rutin thermostability was determined by heating for one hour in buffered salt solutions at 74, 100, and 121 °C. Rutin concentration was determined by HPLC with a Symmetry C18 column (3.9 mm ID x 150 mm L) and UV detection at 260 nm.Rutin solubility increased exponentially from 0.056 g/L to 2.3 g/L with increasing pH, from 2.5 to 9.0. Solubility was affected by ionic strength but the type of salt had a greater effect. Overall, pH was the major factor affecting solubility. Rutin thermolability in acetate buffer was low with 14 % reduction during the first 15 min of heating, at all temperatures, without significant changes after that time. Heating in 0.02 M ZnCl2 solution caused a reduction of 58 % in the rutin content.The solubility profile affected by pH demonstrates that rutin crystallization in pickled asparagus is due to its low solubility in acidic media. High pH pre-processing treatments and/or an additive in the process solution such as ZnCl2 to alter rutin could possibly reduce rutin content and the formation of rutin crystals in pickled asparagus.
Session 83D, Fruit & Vegetable Products: Processed fruit