Ferulic acid and peroxidase infusion into disparate vegetables and its effect on texture

The texture quality of canned fruits and vegetables can be severely degraded or softened due to thermal processing. Increased ferulic acid cross-linking and cell-cell adhesion has been associated with increased firmness of texture in fruits and vegetables. In order to test such a theory for maintaining firmness and cross-linkages of ferulic acid after thermal processing, vegetables were pre-treated/infused with peroxidase enzyme and ferulic acid. Carrots, beets and Chinese water chestnuts were chosen for their extreme differences in texture. Various methods for measuring texture were tested. Flat head compression was selected as the most sensitive method of assessing texture. Various infusion methods were tested including osmotic (marinating), vacuum and high-pressure. High-pressure was selected as the most effective method of infusion. Various high-pressure levels were tested. 20K psi showed the highest effective enzyme activity (balance of infusion vs. enzyme degradation by high pressure) and the most promising texture improvement.; Sliced raw carrots and beets were high-pressure infused at 20K psi for 10 min with 0.05 mg/ml peroxidase enzyme with and without 0.1 mg/ml added ferulic acid followed by vacuum infusion of 1.5% hydrogen peroxide for 30 min. Samples were then vacuum packaged in military tri-laminate pouches and thermally sterilized at 115.5°C (240°F) for 6 min. Texture effects of various treatments were assessed and compared to relative amounts of non cross-linked esterified ferulic acid versus cross-linked ferulic acid by HPLC separation and analysis within prepared isolated plant cell walls. Texture improvements were seen in peroxidase-infused carrot and beet samples, with additional firming seen in the peroxidase/ferulic acid infused beets. The amount of cross-linked ferulic acid increased in the peroxidase infused beets. Chromatograms support a possible theory explaining the additional firming seen in the peroxidase/ferulic acid infused beets. Very little ferulic acid cross-linking was seen in the carrots. There was good correlation between cross-linked ferulic acid and improved texture for the beet. Fluorescence was used to confirm ferulic acid solution cross-linking with both peroxidase/hydrogen peroxide and laccase enzymes. A fluorescence shift was also seen in peroxidase-infused beets possibly indicating ferulic acid cross linking.