Process optimization of cocoa beans for the development of polyphenol rich chocolate

Abstract

newline A study was carried out with the objective to retain maximum polyphenol during fermentation and other processing steps of cocoa bean for chocolate production. The native microflora such as yeast, lactic acid bacteria and acetic acid bacteria were isolated and identified during natural fermentation in Coimbatore, Salem and Dharmapuri districts of Tamil Nadu. The isolates of yeast Saccharomyces cerevisiae, Kluyveromyces marxianus, Pichia kudriavzevii and lactic acid bacteria isolates Lactobacillus plantarum, Lactobacillus acidophilus, Lactobacillus fermentum, and acetic acid bacteria isolates Gluconobacter oxydans, Acetobacter aceti, Acetobacter pasteurianus were screened after morphological, biochemical and molecular techniques for accelerated fermentation of cocoa beans. Nine treatment combinations were formulated by orthogonal array method, out of which Treatment T6 containing Kluyveromyces marxianus, Lactobacillus fermentum, Acetobacter pasteurianus showed maximum catechin, epicatechin, total polyphenol and total flavonoid of 7.612±0.02 mg/g, 8.111±0.06 mg/g, 66.64±0.17 mg/g of GAE and 35.323±0.18 mg/g of QE respectively. The physicochemical parameters such as fermentation index, cut score, pH and temperature showed desirable values on the third day of fermentation thus decreasing days of fermentation with improved combinations of starter culture. The next level was drying of cocoa beans which was carried out in direct sun drying, tray drying and vacuum drying with different drying temperatures for tray and vacuum drying. Among the drying methods, vacuum drying at 60°C (VT6) depicted higher polyphenol and flavonoids content with required moisture content to produce chocolate. Tray drying at 70°C (TT6) showed best results among tray drying treatments and was also chosen as alternate drying method for farmers ease of adaptation. After drying, roasting and conching conditions determine the amount of polyphenols in cocoa beans. Response surface methodology (RSM) tool was utilized to determine desired solution using roasting temperature, roasting time and conching time. For VT6 the optimum roasting temperature, roasting time and conching time were found to be 135.5°C, 18 minutes and 4.5 hours respectively and 136.5 °C, 18 minutes and 3 hours respectively for TT6. In order to predict the storage stability of the chocolate, the parameters such as sensory evaluation, water activity, microbial count, total phenol, total flavonoid of the prepared dark chocolate from TT6, VT6 treatment for 150 days was analyzed. Both VT6 and TT6 showed longer shelf life with overall sensory acceptability while VT6 resulted in higher polyphenol content retention. newline newline