Journal of Food Technology 6 (5): 217-220, 2008 ISSN: 1684-8462 © Medwell Journals, 2008 Corresponding Author: Ogbonnaya Chukwu, Department of Agricultural Engineering, Federal University of Technology, PMB 65, Minna, Niger State, Nigeria 217 Storage Stability of Groundnut Oil and Soya Oil-Based Mayonnaise Ogbonnaya Chukwu and Yahaya Sadiq Department of Agricultural Engineering, Federal University of Technology, PMB 65, Minna, Niger State, Nigeria Abstract: The objectives of this study are the production of mayonnaise from groundnut and soya oils and the determination of the storage stability of the mayonnaise by monitoring the development of rancidity and increase in peroxide values. Mayonnaise was prepared from groundnut and soya oils with the level of oils varied from 65-78%. The mayonnaise produced was stored for a period of 6 weeks and then analyzed for changes in free fatty acid (FFA) and peroxide values. The results showed that on storage the peroxide values of the mayonnaise products increased. This shows their susceptibility to go rancid with time. It was also found out that the 65 and 78% soya oil mayonnaise had shelf-life of 40 days and 32 days, respectively while the 65 and 78% groundnut oil mayonnaise had shelf-life of 34 days and 26 days in that order at room temperature. Sensory evaluation carried out by a team of panelists on the mayonnaise products showed that mayonnaise produced from 65% soya and groundnut oils was more preferred to that produced from 78% soya and groundnut oils. Key words: Free fatty acid, groundnut oil, mayonnaise, peroxide value, shelf-life, soya oil, storage stability INTRODUCTION In Nigeria, some of the major oil sources are palm oil, Mayonnaise comes under the class of foods seed oil. Kolowsky (1993) showed that salad oil can be commonly referred to as salad dressings or salad cream. prepared from palm oil by fractional crystallization method In Nigeria, the consumption of salad dressings has in isopropyl alcohol. Despite the fact that salad dressing increased tremendously in the last 30-40 years principally is much consumed in Nigeria, not much attention has because of their widespread adoption as spreads for been given to its development from local oils. The bread as well as other uses. A salad dressing is an oil-in- suitability of groundnut oil for preparation of a stable water emulsion where oil is the discontinuous phase and mayonnaise emulsion is not very certain. Different water is the continuous phase. Mayonnaise is a semi- researchers appear to have different ideas about solid emulsion of edible vegetable oil, egg yolk or whole groundnut oil as a salad oil. Weiss (1990) stated that egg, acidifying ingredients (vinegar, lemon or lime juice), groundnut oil solidifies to an extent that it cannot be seasoning (e.g. salt, sweeteners, mustard, paprika), citric winterized hence it cannot be used for salad dressings. acid and maleic acid to preserve its colour and flavour. It Binsted et al. (1983) on the other hand enumerated is less perishable than butter or margarine, more mobile, groundnut oil as one of the salad oils in use. easy to handle and fast to spread. The finished product, Winterization is used to remove the higher melting mayonnaise, contains about 65% and above of edible glyceride of oil before it may be classified as a salad oil vegetable oil. Since mayonnaise consists largely of oil, its (Mattil, 1984). The standard method of evaluating the production actually depends on or represents a method of winterization of salad oils is the cold test of the American converting liquid oil to a plastic product competitive with oil chemist’s society (Mounts et al., 1981). Other tests butter and margarine. In the production of mayonnaise, usually carried out on oils to be used as salad dressing the choice of oil is very important and the oils used are and mayonnaise are: organoleptic (checking of flavour referred to as salad oils. In some cases the oil used are and odour), free fatty acid, peroxide value and colour. different from the normal cooking oils. Salad oils usually Free fatty acid test serves as a quality factor. The remain substantially liquid when refrigerated at 4.5-7.2°C presence of free fatty acid in oil is an indication of lipase and produces mayonnaise which is stable at relatively low activity or other hydrolytic action (Brown and Morton, temperatures (Finberg, 1995). 1989) and is important in order to obtain maximum shelf groundnut oil, palm kernel oil, soyabean oil and melon