Effect of Some Preservatives on Nutritional Quality and Sensory Characteristics of Pickled African Walnut (Tetracarpidium conophorum)

This study was carried out between July-September, 2017 at Food and Industrial Microbiology Laboratory, University of Port Harcourt, Port Harcourt Nigeria. 1 %, 3 % and 5 % citric acid were separately added to brine solution containing pickled African walnut inside three glass jars, and sterilised. Similarly, 1 %, 3 % and 5 % lactic acid was added to already sterilised pickled African walnut mixed with brine solution. Pickled African walnut without preservative was the control sample. The entire setup was stored for 6 Wks at room temperature (28±2°C). At 1 Wk interval, pH of the samples was monitored. Proximate composition and antinutrients in freshly cooked African walnut (FCAW) and pickle from each glass jar were determined using standard methods after 6 Wks storage period and sensory characteristics by 9 point Hedonic scale. The antinutrients, fibre, ash and carbohydrate content of FCAW were higher than that of pickled samples after 6 weeks storage period. The protein content of the pickles ranged between 24.12-25.20 %, ash 2.88-3.22 %, moisture 31.55-33.33 %, fat 28.30-29.24 %, fibre 0.90-1.21 % and carbohydrate 10.08-10.49 %. All the parameters evaluated showed significant differences (P = .05) among the samples. Very strong correlation exist between the proximate composition of the pickles preserved with same concentration of citric and lactic acid but level of antinutrients and sensory evaluation scores of the pickles exhibited weaker correlations with few exceptions. During storage, pH of FCAW steadily increased from 5.6-7.0 but that of pickled samples which ranged between1.8-4.0 decreased. The pickles met U.S. Code of Federal Regulations (21 CFR Part 114) which stipulate that acetic acid added to food products must maintain its pH at 4.6 or below. Sensory evaluation revealed that pickled African walnut preserved with 5 % lactic acid was most preferred. Pickled African walnut preserved with citric and lactic acid is well acceptable to consumers. The preservatives slightly affected its nutritional composition, reduced its pH and level of antinutrients.