Abstract
Oxidative enzymes are responsible for changes in flavor, texture, color and also in some nutritive properties of several fruits and vegetables processed in industries. The present investigation aimed to study the activity of Peroxidase (E.C. 1.11.1.7) and Polyphenoloxidase (E.C. 1.10.3.1) in tomato fresh pulp in natura and in three different trademarks of tomato puree sold in supermarkets. Crude extracts of peroxidase (POD) and polyphenoloxidase (PPO) enzymes, from both fresh tomato pulp in natura and processed tomato puree, purchased in supermarkets, were prepared, by using sodium phosphate buffer at different pHs. The best pH values for extraction of peroxidase and polyphenoloxidase were 6.2 and 7.5, respectively. Protein precipitations were carried out using acetone at the ratio of 1:2 enzymatic extract/acetone. The enzymatic extract from Santa Clara tomato cultivar was concentrated 10 times, before being applied to the chromatographic column packed with Sephacryl 100-HS. From the samples eluted, one isoenzyme was isolated (A1) and the molecular weight and isoelectric point (pI) was determined (MW 45 kDa and pI 4.5). The fraction with A1 was stored at -18 o C, and later used for thermostability studies. A decrease in the enzymatic activity was observed at 85 and 90C, in the enzymatic extracts obtained from fresh tomato pulp; nevertheless, in the processed tomato purees the loss of activity was more significant.
Highlights
Peroxidase (POD) and polyphenoloxidase (PPO) are enzymes found abundantly in fruits and vegetables
The aim of the present investigation was to study the relationship between peroxidase and polyphenoloxidase action in fresh tomato pulp in natura and in tomato purée processed by food industries
Samples of fresh tomato pulp and processed tomato purée were analyzed in the present investigation: one sample of fresh tomato pulp in natura and three samples of tomato purée processed by three different food industries
Summary
Peroxidase (POD) and polyphenoloxidase (PPO) are enzymes found abundantly in fruits and vegetables. The action of PPO and POD is connected with the enzymatic darkening and loss of flavor when fruits and vegetables undergo industrialization processes to be turned into canned and/or frozen products (CLEMENTE, 1993). During the processing or industrialization of tomatoes, lipoxygenase (LPO), peroxidase (POD) and polyphenoloxidase (PPO) enzymes can cause deterioration in the product, changing characteristics, such as color, aroma composition and nutritional properties of the product, especially causing a reduction of provitamin A (ESKIN, 1990). The processed tomato purée suffers a thermal treatment similar to the fresh tomato pulp treatment, with the objective of inactivating the oxidative enzymes, which are present in the product. The aim of the present investigation was to study the relationship between peroxidase and polyphenoloxidase action in fresh tomato pulp in natura and in tomato purée processed by food industries
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