ABSTRACT Size dispersion in farmed fish has a substantial impact on production’s bioeconomic performance, directly affecting net profits. This work’s objective was to develop a bioeconomic model based on experimental data to identify the optimal harvest time (OHT) for Nile tilapia Oreochromis niloticus. The bioeconomic model considered four minimum marketable sizes (Mms = 350, 400, 450, and 500 g). Organisms were selected by size with different coefficients of variation (CV). Therefore, they were reared under two growth strategies: heterogeneous size (HT = 44-155 g; CV 25.5%) and homogeneous size (HM = 87-112 g; CV 5.9%). The HT system-generated tradable biomass of 99.30% in an OHT of 196 days with a net profit of USD 3,551.61 and a Mms of 350 g. However, the HM system achieved greater marketable biomass (99.53%) in less time (OHT = 181 days) with a net profit of USD 3,327.96 for the same Mms. The Mms of 500 g had the lowest net benefit in both systems. The HM strategy earned an additional 10.66% of incomes, indicating that the reduction in size dispersion positively impacted profits. The developed model provides a new perspective regarding the management of heterogeneity and size homogeneity in commercial production of Nile tilapia in intensive systems.

ABSTRACT Despite the increasing reports on the incidence of fresh vegetables and fruits as a possible vehicle for human pathogens, there is currently limited knowledge on the growth potential of Escherichia coli O157:H7 on different plant substrates. This study analyzed the selective adhesion and growth of E. coli O157:H7 on chili habanero (Capsicum chinense L.), cucumber (Cucumis sativus), radish (Raphanus sativus), tomato (Lycopersicon esculentum), beet (Beta vulgaris subsp. vulgaris), and onion (Allium cepa L.) under laboratory conditions. The Gompertz parameters were used to determine the growth kinetics. Scanning electron microscopy was used to visualize the adhesion of E. coli O157:H7 on the epicarp of the samples. Predictive models were constructed to compare the growth of E. coli O157:H7 on the samples with different intrinsic factors and to demonstrate the low selectivity of the pathogen. No significant difference was observed in the lag-phase duration (LPD), generation time (GT), and exponential growth rate (EGR) of the pathogen adhered to the samples. The interaction between the microorganism and the substrate was less supportive to the growth of E. coli O157:H7 for onion, whereas for tomato and cucumber, the time for the microorganism to attain the maximum growth rate (M) was significantly longer than that recorded for other samples.

Abstract There are no precedents concerning the quality of Octopus maya during chilled storage. This study evaluated the shelf life of the red octopus in chilling storage (4oC) and the correlation of the sensory quality index with microbiological counting and the biochemical indicators (hypoxanthine, histamine and volatile amines). A total of 112 whole raw octopi (average weight of 896 g) were randomly selected from seven batches and exposed to 4°C for 18, 24, 48, 72, 84, 96, and 100 h. The histamine concentration (91.7%), followed by the counts of psychrotrophic bacteria (5.5%) and hypoxanthine (2.2%), were the predictors from the redundancy analysis that better explained the changes taking place during the chilling hours. After 72 h of chilling, the microbial count was determined to be log 4.7 CFU/g, and the octopus samples were classified as B quality (minor sensory quality defects) based on the sensory quality scale. Although the samples were not classified as unacceptable at 100 h of refrigeration by the sensory index, the level of histamine reached the defect action level (5 mg/100 g) as ruled by the International Food Safety Authorities. The shelf life of the red octopus in chilling storage was predicted to be 119 h.