Effect of Processing and Storage on the Quality of Beetroot and Apple Mixed Juice

In recent years, there has been a growing interest in the development of health-promoting and disease-preventing functional foods. Beetroot is a promising vegetable because of its outstanding antioxidant activity, vivid colour, and content of bioactive compounds. In the present study, the quality of pure beetroot and apple juices as well as that of their mixture was evaluated by measuring changes of colour, betalain content, and antioxidant activity during processing and storage. No perceivable colour changes of the beetroot juice were observed after adding apple juice up to 85% of the total amount. However, the antioxidant activity was proportionally reduced with the addition of apple juice. Pasteurization negatively affected the content of betalains but did not influence the antioxidant activity. Storage led to colour modifications and reduction of betalains and antioxidant activity. Through preliminary shelf-life studies, a durability of 65 days at room temperature for apple and beetroot juice blends was calculated. The novelty of this study lies in an extended description of physico-chemical characteristics of a fresh apple and beetroot blended juice obtained from local products, in the study of the effects of processing and storage on its quality, and in the estimation of its shelf-life after storage at different temperatures.

Listeria monocytogenes Assessment in a Ready-to-Eat Salad Shelf-Life Study Using Conventional Culture-Based Methods, Genetic Profiling, and Propidium Monoazide Quantitative PCR

Listeriosis is almost entirely transmitted through foods contaminated with Listeria monocytogenes. Ready-to-eat foods present a particular challenge due to their long refrigerated shelf-life, not requiring any heat treatment before consumption. In this work, a shelf-life assessment of an industrially produced ready-to-eat salad was performed using conventional culture-based and molecular methods. L. monocytogenes isolates were confirmed and serogrouped using multiplex PCR, and genetic subtyping was performed by pulsed-field gel electrophoresis (PFGE). PMAxx-qPCR was used as an alternative method for L. monocytogenes quantification in foods. Salad samples were kept at 4 °C, 12 °C, and 16 °C for eight days and analysed. At 4 °C, acceptable results were obtained considering hygiene indicators, i.e., Enterobacteriaceae (ranging from 3.55 ± 0.15 log cfu/g to 5.39 ± 0.21 log cfu/g) and aerobic mesophilic colony counts (5.91 ± 0.90 log cfu/g to 9.41 ± 0.58 log cfu/g) throughout the study, but the same did not happen at 12 °C and 16 °C. L. monocytogenes culture-based quantification exhibited low numbers (<1 log cfu/g) for all temperatures. From 30 presumptive isolates, 10 (33.3%) were confirmed as L. monocytogenes with the majority belonging to serogroup IVb. PFGE subtyping showed that 7 of the 10 L. monocytogenes isolates had 100% of pulsotype similarity, suggesting a possible common contamination source. PMAxx-qPCR revealed a statistically higher L. monocytogenes quantification (>3 log cfu/g) when compared to the conventional culture-based method, suggesting viable but non-culturable forms. Taken together, results underline the need to combine conventional methods with more sensitive, specific, and rapid ones for L. monocytogenes assessment in ready-to-eat foods shelf-life studies to reduce the potential risk for consumers.

Degradation Kinetics and Shelf Life of N-acetylneuraminic Acid at Different pH Values

The objective of this study was to investigate the stability and degradation kinetics of N-acetylneuraminic acid (Neu5Ac). The pH of the solution strongly influenced the stability of Neu5Ac, which was more stable at neutral pH and low temperatures. Here, we provide detailed information on the degradation kinetics of Neu5Ac at different pH values (1.0, 2.0, 11.0 and 12.0) and temperatures (60, 70, 80 and 90 °C). The study of the degradation of Neu5Ac under strongly acidic conditions (pH 1.0–2.0) is highly pertinent for the hydrolysis of polysialic acid. The degradation kinetics of alkaline deacetylation were also studied. Neu5Ac was highly stable at pH 3.0–10.0, even at high temperature, but the addition of H2O2 greatly reduced its stability at pH 5.0, 7.0 and 9.0. Although Neu5Ac has a number of applications in products of everyday life, there are no reports of rigorous shelf-life studies. This research provides kinetic data that can be used to predict product shelf lives at different temperatures and pH values.

Production, Preservation and Shelf-Life Evaluation of Wine from Banana Fruit (Musa acuminata Colla)

Aims: The investigation focused on production, preservation and shelf-life study of wine from banana fruit (Musa acuminata). Study Design: This work is based on completely randomized design with two replications and the average values calculated for mean comparison. Place and Duration of Study: Food and Industrial Microbiology laboratory, Department of Microbiology, University of Port Harcourt, Nigeria, September, 2018 to March, 2019. Methodology: Analyses performed using standard methods were microbiological, physicochemical and sensory evaluations. Sodium benzoate concentrations of 5 and 25 ppm were used for shelf life studies. Banana ‘must’ was analyzed at 4 day intervals for 12 days while produced wine was analyzed at 5 day intervals for 25 days during storage. Results: Changes in total heterotrophic counts (THCs), total coliform counts (TCCs) and fungal counts (FCs) occurred during fermentation, resulting in maximum THCs of 5.02, TCCs of 3.60 and FCs of 8.87 log10 cfu ml-1 on days 4, 4 and 8 respectively. Acetobacter and Saccharomyces were pronounced in wine without preservative (control) throughout storage. Mean pH of ‘must’ was 5.8±0.30 while alcohol content was 0.28±0.03% on day 0 but as fermentation progressed, mean pH was reduced while mean alcohol content increased. Mean pH of wine preserved with 5 ppm varied slightly throughout storage but mean pH of control and 25 ppm preserved wine decreased from 3.7±0.20 on day 0 to 3.2±0.23 on day 25. Sensory attributes (overall acceptability) on day 12 was most preferred while during shelf-life studies, significant difference in overall acceptability of the different wines at P=.05 occurred. Wine preserved with 5 ppm had the best organoleptic quality but 25 ppm preserved wine showed the most acceptable microbial quality. Conclusion: Findings show that banana is a good substrate for wine production and 5 ppm sodium benzoate retained the qualities of the wine.