Chemical and Color Changes in Tomato Juice by Heating during Processing

Abstract

The effects of heating temperature and time during processing on color, amino acid, organic acid, ascorbic acid, sugar and uronic acid in tomato juice were studied. The variety of tomato used in this study was Heinz 1370. The juice was extracted, and a part of it was frozen, the other parts were held at 90°C for 10, 40 or 90 minutes and then sterilized at 110°C for 84 seconds or at 121°C for 42 and 168 seconds.
As heating temperature became high or heating time was long, decrease of lycopene and ascorbic acid, and increase of serum color were observed. The rate of decrease of lycopene was especially rapid when the sterilization temperature was high, and decrease of ascorbic acid and increase of serum color were rapid either holding at 90°C or sterilization at above 100°C. Total amino acid content decreased and the decrease of threonine was remarkable. Glutamic acid decreased slightly, but the percentage of it in total aminoa cid increased. Peptide content obtained by dialysis did not change, but average peptide length changed from 4.36 to 3.77. Pyrrolidone carboxylic acid increased and malic acid decreased slightly. No difference was found in sugar components. Galacturonic acid decreased obviously.