Oluwatosin Ademola Ijabadeniyi

Inactivation of Listeria monocytogenes ATCC 7644 on fresh-cut tomato using nisin in combinations with organic salts

The inhibition of Listeria monocytogenes ATCC 7644 on fresh-cut tomato was investigated using nisin alone, and in combinations with organic salts. Nisin at a concentration of 5000 UI/mL was introduced alone or in combination with an organic salt (sodium citrate or sodium acetate each at 3 and 5 g/100 mL each) on fresh-cut tomato previously inoculated with 108 CFU/mL of L. monocytogenes ATCC 7644. Chlorine at 200 ppm was used as a control. The inoculated samples were incubated at different temperatures (4, 10 and 25 °C) and examined at 0, 24, 48 and 72 h. The effects of the antimicrobial treatments on quality parameters of tomato (pH, soluble solids, titratable acidity and vitamin C) were also evaluated, and colour parameters were observed at the lowest storage temperature for 10 days. Both nisin and the organic salts inhibited growth of L. monocytogenes, but the combinations of two compounds were more effective. The nisin–sodium citrate (5%) combination was significantly (p ≤ 0.05) effective, while chlorine was least effective against L. monocytogenes. The quality parameters were substantially retained, especially at 4 °C, suggesting good shelf stability at a low temperature. These results substantiate the use of the cheap and eco-friendly approach to reducing this pathogen of health concern in common fresh produce.

Food safety knowledge and microbiological hygiene of households in selected areas of Kwa-Zulu Natal, South Africa

This study was conducted to determine the level of food safety knowledge and practices during food handling and preparation at household level in selected areas in KwaZulu-Natal province of South Africa. Fifty households were selected to participate based on their monthly income, age and educational level. Samples of raw foods were randomly collected from the participating households for microbial analyses. Swabs from food contact surfaces were also collected and analyzed for the presence of pathogens. Difference in demographic data regarding food safety knowledge was tested using chi-square and microbial counts were statistically analyzed (P<0.05). Knowledge of proper cold storage temperature was found to be inadequate as over 70% of respondents had no idea of their cold storage temperatures. High risk of cross contamination was observed due to improper thawing, packaging of meat with other ready to eat foods and poor food contact material handling. Microbial analyses of raw food samples showed the presence of aerobic spore formers (1.08-1.89 log cfu/mL), anaerobic spore formers (0.29-1.83 log cfu/mL) and Staphylococcus aureus (3.31-3.96 log cfu/mL). Contact surfaces were also positive for Listeria monocytogenes, Salmonella spp and Escherichia coli. Food safety knowledge and proper food handling practices were found to be inadequate in the areas studied and urgent intervention is required to prevent fatal incidences of food borne illnesses.

Improvement of some quality attributes of soymilk through optimization of selected soybean sprouting parameters using response surface methodology

ABSTRACT This study aimed at producing functional soymilk by optimizing the sprouting conditions of soybeans using response surface methodology. Soaking (12–24 h) and germination times (48–96 h) were optimized using central complete randomized design. Responses obtained from experimental runs were fitted into second order polynomial regression model. Significance of model parameters was tested using ANOVA and R2 was evaluated. The optimum sprouting conditions of soybeans were 12 h soaking and 52 h germination using desirability concept. Soymilk made from optimized conditions had 17% increase in total proteins, 50% reduction in phytic acid, 1.7% increase in total phenolics and a color change (∆E) of 4.89 compared with the control. There was a significant reduction in trypsin inhibitor activity (0.03 mg/g TI), with increase in total amino acids and similar rheological properties in optimized soymilk. Optimized conditions obtained are adequate in the production of soymilk with improved nutritional and quality attributes.

Biocontrol of Listeria monocytogenes ATCC 7644 on fresh-cut tomato (Lycopersicon esculentum) using nisin combined with organic acids

The biocontrol of Listeria monocytogenes on fresh-cut tomato using nisin and organic acids was investigated. Fresh-cut samples inoculated with 108 CFU/mL of L. monocytogenes, treated with nisin (5,000 IU/mL), a combination of nisin and organic acids (acetic and citric acids at 3 and 5% each), with chlorine at 200 ppm as a control, and stored for six days at 4, 10, and 25°C were used to evaluate certain physicochemical qualities (pH, titratable acidity, soluble solid content, vitamin C content, and color). Nisin treatment significantly (p<0.05) reduced bacterial population by 1.91-3.07 log CFU/mL. Nisin-citric acid combination provided 2.65-3.29 log CFU/mL reduction, while nisin-acetic acid combination provided 2.93-4.15 log CFU/mL reduction. The control treatment provided <1-2 fold log reductions. Slight variations in physicochemical properties of fresh-cut tomato were observed. Nisin and organic acids can be used to improve the microbial safety of fresh-cut tomato.