PAK. J. FOOD SCI., 24(1), 2014: 50-56 ISSN: 2226-5899 1 Pakistan Journal of Food Sciences (2014), Volume 24, Issue 1, Page(s): 50-56 Comparison and Evaluation of the Quality and Storage Stability of Soy and Peanut butter F. Matsiko 1, E. Murindwa 1 , C. Niyigena 2 , B. Hitimana 1 and H. Vasanthakaalam 1 1 Department of Food Science and Technology, College of Agriculture, Animal Science and Veterinary Medicines, University of Rwanda 2 Program of Nutrition and Rural Development, University of Ghent, Coupure links 653 Ghent, Belgium Corresponding author: matsiko12@yahoo.fr/f.matsiko@kist.ac.rw ABSTRACT Soy butter and peanut butter were processed and stored for 40 days at ambient temperature (25 o C on average) in plastic containers and analysed for comparison of their proximate composition, sensory quality, oxidation and fungal stability. Mean peroxide value was higher in soy butter (11.75meq/kg) than in peanut butter (8.50meq/kg). Maximum mean population of yeasts and moulds was greater in peanut butter (8.5 log CFU/g) than in soy butter (6.5 log CFU/g) after 20 days of storage. The average protein was significantly (p<0.05) higher in soy butter (23.25%) than in peanut butter (13.50%). Total fat was significantly (p<0.05) greater in peanut butter (52.70% on average) than in soy butter (31.40% on average). No significant (p>0.05) difference was found in ash or moisture contents between soy butter and peanut butter. The same was observed for all sensory parameters (colour, appearance, consistency, spreadability, taste and smell) evaluated by the sensory panel. It was concluded from the findings of this research work that the sensory quality of soy butter might be as acceptable as that of peanut butter to consumers. However, soy butter could be less stable to oxidation, but less prone towards fungal growth than peanut butter. Further research would be necessary to appraise available appropriate technologies to stabilise soy butter towards oxidation process and further detail the fungal spoilage of this food spread. Key words: soy butter, peanut butter, composition, acceptability, stability INTRODUCTION Soybean (Glycine max) is one of the most important crops worldwide; it is a leguminous plant related to clover, peas, and alfalfa. It belongs to the same family of leguminoasae as peanut (Arachis hypogaea) (Maria and Carelli, 2010). Its seeds are important sources of protein meal and cooking oil. The meal is used as animal feed as well. Soybeans are rich sources of protein containing about 38 % (Messina, 1999) and about 18% of oil (0.5% lecithin); are rich in polyunsaturated fatty acids (54% linoleic acid, 22% oleic acid, and 7.5% linolenic acid) but contain no cholesterol (Singh et al, 2008). They additionally contain a good number of various phytochemicals. These include but are not limited to isoflavones, catechines, p-coumaric acid, ferruric acid, gallic acid and vanillic acid (Wittanalai et al., 2012), which have a wide range of health benefits. These polyphenols and other phytochemicals are believed to play an important role in the prevention of cancer and other non-communicable chronic diseases (Messina and Barnes, 1991) and are also known for their antioxidant properties. Food that provides health benefits beyond its nutritional provision is termed as functional food. Soy beans are unique functional foods among legumes as they have the highest concentration of isoflavones (Bosman et al., 2009). Isoflavones are powerful inhibitors against tumour development and cancer cell proliferation, whilst soy proteins are known to have the lowering effect on total and LDL cholesterol (Vesanto and Brenda, 2003). Thus, soy and soy ingredients containing food products might be considered as having a protective effect against heart diseases. The use of soy as food ingredient has recently grown in food industry as a result of its health benefits, technological and functional properties (Petrak, 2008). Soybeans are used for making various food products including soy milk, tofu, soy sauce and soy cheese to just name a few. They are additionally processed into soy butter as peanuts into peanut butter, which is the most popular nut butter. However, soy butter is a good alternative for people with peanut allergy. Peanut and soy butter can best be described as typical examples of lipophilic suspensions of food that contain fine solids dispersed in a lipophilic, continuous phase (Franke and Heinzelmann, 2012). The shelf life of peanut butter and other peanuts derived products is greatly limited by rancidity that results from the oxidation of mainly unsaturated fatty acids (Nepote et al., 2006a).The oxidative and/or hydrolytic rancidity might be equally the limiting factor to the shelf life of soy butter and other soy-based products as soybeans contain large amounts of poly-unsaturated fatty acids. The oxidative and hydrolytic rancidity process is accelerated by high temperature, oxygen and enzyme. The lipolytic enzymes of yeasts and moulds are also known to