EFFECTS OF ROASTING ON THE CHEMICAL COMPOSITION, AMINO ACID AND FATTY ACID PROFILE OF CASHEW (Anacardium occidentale) SEED AND OIL

Abstract

The cashew nuts were collected from Ada in Osun State and identified at Crop Soil and Pest Management laboratory of Federal University of Technology, Akure. The samples were air dried and the seeds were removed from the nut manually. Some of the seeds were roasted at a temperature of 92oC until they became brown while the rest left raw. Both were ground into powder, stored in an air tight container and kept in the refrigerator at 4oC prior to analysis. The sample, cashew seed (Anacardium occidentale) both raw and roasted, were analyzed for proximate composition, minerals, phytochemical properties, amino acid components and the extracted oil were analyzed for their physicochemical properties, fatty acid contents and antimicrobial activities on some micro organisms like Escherichria coli, Bacillus cereus, Candida albican, Bacillus subtilis, Pseudomonas aeruginosa , Pseudomonas syringiae and Xanthomonas oxinopoides using standard methods. From the results, the mean values for proximate composition (%) for raw and roasted samples respectively were moisture (3.67 ± 0.05 and 2.0 ± 0.00), crude protein (43.80 ± 0.00 and 42.87 ± 0.05), crude fat (42.70 ± 0.00 and 46.73 ± 0.05), ash (2.30 ± 0.00 and 2.23 ± 0.05), organic matter (97.70 ± 0.00 and 97.77± 0.05) , crude fibre (3.37 ± 0.05 and 1.40 ± 0.00), carbohydrate (4.10 ± 0.00 and 4.80 ± 0.00) and energy (575.90 ± 0.00 and 611.25 ± 2.50 KJ/mol). The sample is rich in phosphorous, potassium, calcium, magnesium, iron and zinc. The phytochemicals that were present in the sample were alkaloids, steroid, saponin, flavonoid, terpernoid, cardiac glycoside while tannin and phlobatannins were absent. The samples contained nutritionally useful quantities of most essential amino acids like aspartic acid, glutamic and methioine. The physicochemical properties of the extracted oil from raw and roasted samples respectively were refractive index (1.46 ± 0.00 and 1.46 ± 0.00), specific gravity (0.87 ± 0.00 g/dm3 and 0.86 ± 0.01 g/dm3) , viscosity (50.28 ± 0.00 and 48.12 ± 0.01 pal/sec), acid value (1.68 ± 0.00 and 1.29 ± 0.00), free fatty acid (0.84 ± 0.00 and 0.65 ± 0.00 mg/g), saponification value (201. 96 ± 0.00 and 171.10 ± 0.00 mgKOH/g), unsaponifiable matter (1.64 ± 0.00 and 1.42 ± 0.00 mg/g), iodine value (43.15 ± 0.00 and 36.17 ± 0.00 mg/g) and peroxide value (0.92 ± 0.00 and 0.60 ± 0.00 mg/g). The most abundant fatty acids in the samples were linoleic, oleic, palmitic acid, and stearic. Unsaturated fatty acids dominated essential fatty acids and they constituted seventy percent of the total fatty acid present in the sample. The antimicrobial test showed that the oil has antimicrobial agent that stop the growth of chosen microorganisms like E. coli, B. subtilis, B. cereus C. albican P. aeruginosa, P. syringe and X. anthropodes. Although, there was no zone of inhibition in E. coli and P. aeruginosa on the roasted oil this may be due to the loss of some active ingredients during roasting. The results showed that roasting has positive effect on the sample; The roasting reduced the moisture content, physicochemical parameters like viscosity, acid value, free fatty acid ,saponification value ,unsaponifiable matter, iodine value, and peroxide value .This shows that the roasted oil will have long shelf life without growing mould. Also the phytochemicals e.g. flavonoid, saponin,and terpenoid reduced and the non essential amino acid with some fatty acid also reduced by roasting .Roasting increased fat, energy, essential amino acid and fatty acid .The roasted oil has higer inhibitory effect on the tested microorganisms