1081 OPTIMIZATION OF INGREDIENT AND PROCESSING PARAMETER FOR THE PRODUCTION OF Spirulina platensis INCORPORATED SOY YOGURT USING RESPONSE SURFACE METHODOLOGY Samadrita Sengupta 1 , Jayati Bhowal* 2 Address(es): 1 IIEST,Shibpur, Senior Research Fellow (PhD), SOCSAT, IIEST, Shibpur, Botanic Garden, Howrah 711 103, WB, (+91) 9903780850. 2 IIEST,Shibpur, Assistant Professor, SOCSAT, IIEST, Shibpur, Botanic Garden, Howrah 711 103, WB, (+91) 9831672455. *Corresponding author: jayatibhowal@gmail.com ABSTRACT Keywords: Spirulina platensis, sensory, viscosity, penetration, response surface methodology, soy yogurt INTRODUCTION Soy–yogurts have some adventages to consumers due to their hypolipidemic, anticholesterolemic and antiatherogenic properties as well as due to reduced allergenicity (Pourahmad and Ahanian, 2015). Protein content of soy yogurt and milk yogurt is similar (3.5 to 4.0%) and their amino acid pattern is fairly close except that soymilk is deficient in sulfur containing amino acids. Soy yogurt has about 60 to 90% nutritional value of milk yogurt and with adding small amounts of methionine to soy milk it has equivalent nutritional value to cow's milk (Abdullah et al., 2003). The high content of indigestible raffinose and stachyose, the flatulence factors, limit the consumption of soy yogurt (Tsai et al., 2006). Considerable research has been done to reduce off–flavors in soy yogurt by inhibiting formation of the isoflavones and lipid oxidation products responsible for them (Izadil et al, 2015). Using Spirulina platensis can be desirable in producing beany odour free soy yogurt. Spirulina platensis has been shown to have many advantages, especially in terms of nutritional value and contains many valuable substances in the prevention and treatment of some diseases. Spirulina platensis has been used as a food source or supplement to provide nutrition and health improvements for people because it is rich in nutrients like protein, amino acid, essential fatty acids, vitamins and minerals. (Deng and Chow, 2010). In recent years, soy yogurts have been developed with expectedly enhanced nutritional superiority by incorporating functional lipids such as Gamma linolenic acid (GLA), Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA) and also providing specific antioxidants such as oryzanol and lignans through specific edible oils (Sengupta et al., 2013; Sengupta et al., 2016). Soy yogurts enriched with Spirulina platensis to provide higher arginine and methionine content in protein part and antioxidant such as selenium, zinc, tocopherol etc. (Morsy et al., 2014). Soy yogurts have been used as the most popular carrier for incorporation of probiotic organisms (Beheshtipour et al., 2013). Unfortunately, most of the commercial products contain less probiotic bacteria than the minimum required, because these microorganisms grow slowly in milk and often show loss of viability during storage. In addition, the probiotic bacteria are sensitive to pH, lactic acid, hydrogen peroxide, and dissolved oxygen in fermented milk (Zhao et al., 2006). Some researchers have observed that growth of lactic acid bacteria in synthetic media was promoted by Spirulina platensis extracellular product (De Caire et al., 2000). Therefore, it proved to be suitable for the cost–effective manufacture of novel functional fermented non–dairy yogurts.This addition will improve sensory characteristics of the final products. To optimize process factors, an appropriate design of experiment was required, we were chosen response surface methodology (RSM) which was the key tool for reducing the number of experiments (Yaakob et al., 2012). It can help to optimize manufacturing processes involving multiple factors with different numbers of levels, especially fermentation processes and new Spirulina platensis incorporated soy yogurt developments, simultaneously and economically (Prabuthas et al., 2011).The application of RSM has not yet been adopted in studies related to soy yogurt supplemented with Spirulina platensis. Therefore, the aim of this work is to optimize the formulation ingredient and processing parameters of Spirulina platensis incorporated soy yogurt using RSM. MATERIAL AND METHODS All chemicals used were, purchased from MERCK, India. Soybean seeds were purchased from the local market (New Alipore Market, Kolkata West Bengal, India). Commercially available milk curd cultures were purchased from Microbial Type Culture Collection and Gene Bank, Chandigarh [Lactobacillus delbrueckii subsp. bulgaricus (MTCC 911) and Streptococcus thermophilus (MTCC 1938)]. Spirulina platensis was used as dry biomass having composition of protein 0.28 g, energy 1.74 Kcal, fat 0.0 g and carbohydrate 0.16 g per 500mg (SUNOVA SPIRULINA, Surya Herbal Ltd. Noida,India). In this study, response surface methodology (RSM) was employed to optimize the ingredient formulation and processing parameters of Spirulina platensis incorporated soy yogurt production such as temperature, time, and amount of Spirulina platensis on the sensory evaluation responses on 9 point Hedonic rating. Besides, the physico–chemical properties such as pH, titratable acidity, viscosity and penetration of the Spirulina platensis incorporated soy yogurt were also analysed. The analyses show that the Spirulina platensis incorporated soy yogurts have a pH from 3.43 to 5.55, acidity from 0.64 to 2.32 (%), Brookfield viscosity from 752 to 903 Centipoise and penetration from 362 to 432 1/10th mm at 25°C during the optimization process. From the analysis of variance, the R 2 of all response variables is more than 0.77 that indicates that a high proportion of variability was explained by the model. Based on the response surface 3D plot of the sensory evaluation, the optimum acceptability of the Spirulina platensis incorporated soy yogurt processing parameter are at temperature of 40°C, 12 h of the fermentation duration and 0.80% (w/w) of the Spirulina platensis. ARTICLE INFO Received 13. 10. 2015 Revised 4. 8. 2016 Accepted 18. 12. 2016 Published 1. 2. 2017 Regular article doi: 10.15414/jmbfs.2017.6.4.1081-1085