Physico-Chemical Characteristics and Antimicrobial Effectiveness of a Food Grade Detergent Developed from Local Raw Materials

Abstract

Cleaning is central to any food process operation and it entails the removal of soils from processing equipment, food contact surfaces and production floor. It is done with the aid of a cleaning agent and key among several are the soaps and detergents. Most detergents currently used in the industry are petroleum based, which are not easily biodegradable. Moreover they are imported, and add costs to the operations of industry. The use of locally available material that are biodegradable to produce effective cleaning agents will offer more environmentally friendly (or “green”) alternatives. Ash derived alkalis from agricultural wastes, contain high levels of potash which are, inexpensive alternatives to imported potassium and sodium hydroxide, which form part of the key ingredients of detergents. The main objectives of this study were to develop and characterize a food grade detergent from locally available materials and examine its antimicrobial efficacy against common food borne pathogens. Dried cocoa pods, obtained from the Cocoa Research Institute (Tafo in the Eastern Region), were processed into potash. Two edible oils: palm kernel and coconut oil were mixed in various proportions (0, 30, 50, 70, and 100%). A total of five soap samples were replicated three (3) times, using a combination of both the cold and hot processes of saponification. A control food grade detergent (petrochemical based) was obtained from Cleaning Solutions Ltd –Tema, near Accra, Ghana. Differences between treatments were assessed using ANOVA procedures. The apparent viscosity of the coconut based liquid soaps were light (K=5.869 Pa.s). Addition of palm kernel oil thickened the apparent viscosity of the soaps obtained. Soaps obtained from using only palm kernel oil showed a high apparent viscosity, K of 48.057 Pa.s The flow behavior of liquid soap made using coconut oil changed from non-Newtonian, shear thinning flow and approached Newtonian, shear independent flow as the composition of palm kernel oil increased in the oil blends. The soaps made using higher proportions of coconut oil showed better foaming capacity. As the proportion of palm kernel oil increased the maximum foam capacity decreased. Increasing viscosity of the detergent decreased the foam capacity. Soaps made with high proportions of coconut oil (100-70%) exhibited characteristics of a good food grade detergent in forming good foam volumes with low foam stability. Soap made using only coconut oil showed the lowest pH (9.3) and the minimum total free alkaline (TFA). With all the different detergents formed from the various oil mixtures, the total free alkaline (TFA) levels were well below the maximum acceptable limits of 0.6% for TFA as stipulated by the Ghana Standard for alkaline soaps. Excess free alkali in the detergent will be corrosive on metallic food contact surfaces. Soap formulated using 100% coconut oil showed a much greater inhibition against bacillus species as compared to its inhibition against Salmonella and Proteus spp. The antimicrobial activity of the soaps depended on the oil type used in their formulation. The detergents with 100% coconut oil and 100% palm kernel oil soaps were relatively effective against the gram positive bacteria. Except for the detergent mixture with equal amount of both oils, all the other detergents with the oil mixtures also showed a relatively higher inhibition against the gram positive bacteria tested. There is a great potential in using local agricultural wastes and vegetable oils to develop food grade detergents with effective antimicrobial activity.