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Subject: search.filters.subject.Farm produce

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    Effect of bacteriophage control and artificial neural networks prediction in the inactivation of Listeria monocytogenes on fresh produce
    (2017) Oladunjoye, Adebola Olubukola; Ijabadeniyi, Oluwatosin Ademola; Singh, Suren
    There has been a global increase in fresh produce consumption, due to its attendant nutritional a nd health benefits. On the other hand, increase in the outbreak of diseases, accompanied with health and economic implications, have been traced to this deve lopment. A good number of pathogenic contaminants along the food chain have been identified as causative agent s with Listeria monocytogenes identified as one of such. Among other control strategies, the use of bacteriophage, was recommended as a palliative measure. Furthermore, the a ppli cation of artificial neural networks (ANN) in food safety remains an emerging concept in risk assessment study. Therefore, the aim of this research is to investigate the effect of bacteriophage or phage control and artificial neural network prediction in the inactivation of L. monocytogenes ATCC 7644 on fresh produce. Fresh-cut tomato and carrot were artificially inoculated with L. monocytogenes (108 CFU/ml) and subjected to antimicrobial treatment of Listex P100 bacteriophage (108 PFU/ml), sucrose monolaurate (SML at 100, 250 and 400 ppm), with chlorine (sodium hypochlorite at 200 ppm) used as control. Also, application of ANN to predict the risk effect of antimicrobial treatments of bacteriophage, sucrose monolaurate and chlorine was evaluated on the fresh-cut produce. Mathematical models were developed using a linear regression and sigmoid (hyperbolic and logistic) activation function-(120). Data sets were trained using Back propagation ANN, containing one hidden layer with four hidden neurons. Furthermore, carbon utilization profile of phage-treated L. monocytogenes using phenotypic micro array method was evaluated. In the first phase, susceptibility of L. monocytogenes subjected to certain stress-adapted conditions (acid,-adapted AA, chlorine-adapted CA, heat-adapted HA) and non-adapted-NA to phage treatment inoculated on the fresh-cut produce stored for 10 days at 4, 10 and 25oC was evaluated. The second phase investigated the combination of bacteriophage and sucrose monolaurate (using chlorine at 200 ppm as control) to inhibit the L. monocytogenes growth on the fresh-cut produce stored for 6 days at 4, 10 and 25oC. Physicochemical properties (pH, titratable acid-TTA, total soluble solids-TSS, and colour values-CIE L* a* b*) of the fresh produce after treatment were evaluated. In the third phase, ANN as a predictive tool was used to evaluate the risk involved in the relationship among the initial bacterial load, fresh-produce type, antimicrobial concentration and residual bacteria. In the final phase, 100 µL of phage-treated L. monocytogenes was introduced into a 96-micro well plate impregnated with a tetrazolium dye. The Carbon utilization profile was evaluated at intervals of 4 hours for 48 hours using a biolog micro station. Generally, L. monocytogenes grew on both fresh-cut produce and the storage temperature did not adversely affect the lytic ability of the phage treatment. Antimicrobial treatment of phage and sucrose monolaurate had minimal variations on the physicochemical properties of both fresh-cut samples. All stress-adapted and non-adapted L. monocytogenes were (p ≤ 0.05) susceptible to bacteriophage control. Phage treatment reduced non-adapted, acid adapted, chlorine-adapted, and heat-adapted L. monocytogenes population by 0.57, 0.81, 0.86 and 0.95 log CFU/ml in fresh-cut tomato, and 2.26, 2.41, 2.49 and 2.54 log CFU/ml in fresh cut carrot respectively. Furthermore, the additive effect of SML at 100 and 250 ppm had no significant effect on phage lysis. However, combination of phage with SML at 400 ppm significantly (p ≤ 0.05) resulted in 1 and 3 fold reductions in tomato and carrot respectively. Control treatment with chlorine resulted in 1-2 log reductions on both fresh produce. Algorithm data set trained using ANN gave 100% accuracy. Prediction with logistic activation function showed the highest positive correlation relationship between predicted and observed values with ~ 0.99 R2-value and MSE of 0.0831. Carbon utilization profile showed hexose and pentose sugars-ribose, glucose, fructose and sugars were maximally utilized while oligosaccharide sugars of sucrose, cellobiose and gentiobiose were similarly observed to be utilized. Notably, utilization of glucose-6-phosphate which determines L. monocytogenes pathogenicity was not very pronounced in the carbon profile. Bacteriophage application in the inactivation of L. monocytogenes contamination of fresh produce provides a safe means of control. Its perceived limitation however, can be overcome by combining with other antimicrobials. Similarly, the use of artificial neural networks prediction, remains an improved approach to harness the potential risk that could occur through this method.
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    Irrigation water and microbiological safety of fresh produce : South Africa as a case study : a review
    (Academic Journals, 2012-09-11) Ijabadeniyi, Oluwatosin Ademola; Buys, E. M.
    Irrigation water is perhaps the leading pre-harvest source of contamination of fresh produce in the world. In this review, the impact of contaminated surface irrigation water on bacterial contamination of fresh produce was examined. Some practical solutions to prevent or reduce this challenge were also considered. In South Africa, fruit and vegetables are produced on a large scale by commercial farmers who depend on surface water for their cultivation. However, the surface water, that is, rivers- has been reported to be heavily contaminated with Escherichia coli and feacal coliforms. There is a concern that contaminated surface water used for irrigation may contaminate fresh vegetables which may also have a negative effect on the export of vegetables to the EU and USA. Consumption of vegetables contaminated with foodborne pathogens presents a public health risk especially in countries like South Africa that has more than 5 million people with immune-system compromised diseases such as HIV and tuberculosis. Other groups of people that may be negatively affected because of the contaminated surface water are those who are directly and indirectly associated with the production of fresh vegetables such as pickers, handlers, packers and farmers that participate in the production of vegetables during pre-harvest and post-harvest. Prevention of contamination of fresh produce from both pre-harvest and post-harvest sources especially irrigation water still remains the only effective way to protect the public. However, for this to occur, every stakeholder in the production industry must have a culture of food safety.