EFFECT OF INTERMITTENT FRYING ON FATTY ACIDS, VITAMIN E, LIPID OXIDATION AND ACRYLAMIDE IN OILS AND PLANTAIN CHIPS COLLECTED FROM SMALL- SCALE PRODUCERS IN CAMEROON

Deep-fat frying is susceptible to induce the formation of undesirable products as lipid oxidation products and acrylamide in fried foods. Plantain chips produced by small-scale producers are sold to consumers without any control. The objective of this study was to evaluate the quality of plantain chips from local producers in relation to production process parameters and oils, and to identify the limiting factors for the production of acrylamide in plantain chips. Samples of frying oils and plantain chips prepared with either palm olein or soybean oil were collected from 10 producers in Yaoundé. Quality parameters determined in this study were: fatty acid composition of the oils, determined by gas chromatography (GC) of free acid methyl ester; trans fatty acids, determined by Fourier transform infra-red spectroscopy; Tocopherols and tocotrienols as markers of nutritional quality were analyzed by High Performance Liquid Chromatography in isocratic mode. Free fatty acids and acylglycerols as markers of lipid hydrolysis were analyzed by GC of trimethylsilyl derivatives of glycerides. Conjugated dienes, Anisidine value and viscosity as markers of lipid oxidation and thermal decomposition of the oils; acrylamide which is formed through Maillard reaction and identified as a toxic compound in various fried products. Asparagine content of the raw fresh plantain powder was also determined. Fatty acid composition of palm oleins was stable within a day of intermittent frying. In soybean oils, about 57% and 62.5% of linoleic and linolenic acids were lost but trans fatty acids were not detected. Soybean oils were partly hydrolysed leading to the formation of free fatty acids, monoacylglycerols and diacylglycerols. In both oils, tocopherols and tocotrienols contents decreased significantly by about 50%. Anisidine value (AV) and polymers contents increased slightly in fried palm oleins while conjugated hydroperoxides, AV and polymers greatly increased in soybean oils. Acrylamide was not detected in the chips. This is explained by the absence of asparagine in the raw plantains, the other acrylamide precursors being present. This study shows that the plantain chips prepared at the small-scale level in Yaounde with palm olein are of good quality regarding oxidation and hydrolysis parameters and the absence of acrylamide. In contrast, oxidation developed with soybean oil whose usage for frying should be questioned. Considering that asparagine is the limiting factor for the formation of acrylamide in plantain chips, its content depending on several factors such as production parameters and maturity stage should be explored.

NUTRITIONAL COMPOSITION AND ANTIOXIDANT PROPERTIES OF RAPHIONACME SPLENDENS (SCHL.) TUBERS

People of Western Kordofan (Sudan) are endowed with a deep knowledge concerning the use of wild plants. Tubers of Raphionacme splendens Schl. subspecies splendens Flickr (family Apocynaceae), locally known as Elfayo, are used as a food reserve during times of famine or poor harvest. The aim of this study was to analyze the nutritional composition and antioxidant capacity of root tubers of R. splendens. Samples were collected from South-West Kordofan. Analyses included determination of moisture, carbohydrate, crude protein, fat, fibre, ash, minerals, vitamin C, amino acids and fatty acids composition. Antioxidant activity was determined by the DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS (2.2’-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) assays. The total phenolic content was also assessed. The results, which are referred to as (%) dry weight, showed that the tubers contained 3.2% protein, 18% carbohydrate, 0.5% lipid, 2.4% crude fibre, 3.5% ash, 79.2% moisture and gross energy 101.7 kJ/g. The total amino acids were 10776 mg/100g where the essential amino acids represented 28.2%. The more abundant essential amino acids were leucine (792mg/100g), isoleucine (712mg/100g) and threonine (536mg/100g). Methionine and lysine were the limiting amino acids. Minerals were potassium (259mg/100g), calcium (183mg/100g), magnesium (64mg/100g), phosphorus (37mg/100g), copper (3.6mg/100g), manganese (2.4mg/100g), zinc (1.8mg/100g) and iron (1.2mg/100g). Total saturated fatty acids were 45.6% whereas total unsaturated fatty acids were 54.4%. Oleic acid (32.56%) and palmitic acid (30.23%) were the most abundant fatty acids. Tubers displayed good antioxidant activity with IC50 values 0.987 and 1.559mg/mL against DPPH and ABTS radicals respectively. Vitamin C was 31.5mg/100g and total phenolic content was 60mg gallic acid equivalent (GAE) per 100g dry sample and they could be the main contributor to the antioxidant capacity of the tubers. In conclusion, the results of this study suggested that tubers of R. splendens could have beneficial effect for food and/or nutraceutical application for normal growth and adequate protection against diseases associated with reactions of free radicals.