Use of flow cytometry and total viable count to determine the effects of orange juice composition on the physiology of Escherichia coli

Abstract

Orange juice (OJ) contains numerous compounds some of which are known to play key roles in growth and survival of bacteria. This study aimed to investigate the effects of natural or processing‐induced variations in OJ composition on the physiology of Escherichia coli. OJ and model OJ (MOJ) samples containing various sugars, organic acids, amino acids, or ascorbic acid were inoculated with E. coli K‐12 MG1655 in different growth phases. The culturability, viability, and physiology of the cells were investigated during storage using plate counting and flow cytometry. Generally, stationary‐phase cells displayed the greatest survival in both MOJ and OJ. Increase in incubation temperature from 4 to 22.5ºC caused a significant decrease in both healthy and culturable cell populations. Supplementation of MOJ with ascorbic acid and amino acids increased both the viability and culturability of the cells. Similar trends were observed in amino acid‐supplemented OJ, albeit at a slower rate. In contrast, variations in sugar or organic acid composition had negligible effects on the physiological status of the cells. In summary, natural variation in ascorbic acid or amino acid concentrations could potentially have an adverse effect on the microbiological safety of orange juice.

Integrated approach of ultrasound with mild heat treatment on the quality characteristics of yacon (Smallanthus sonchifolius) tuber juice

“…For TVC, serial dilutions of the juice were prepared and plated on PCA. The plates were then incubated at an appropriate temperature (usually 30–37°C) for 48 h, and the colonies were counted to determine the number of viable bacteria present in the juice (Anvarian et al, 2018).…”

“…W: weight; b: bias; ANN: artificial neural network; TSYJ: thermosonicated yacon tuber juice; TSS: total soluble solids; TA: titratable acidity; AA: ascorbic acid; AOA: antioxidant activity; TPC: total phenolic content; TFC: total flavonoid content; TCC: total carotenoid content; TVC: total viable content; YM: yeast and mold count. been reported in both thermosonicated orange and pineapple juice (Anvarian et al, 2018;Mala et al, 2021). The thermoresistant spore-forming nature of YM growth may be the cause of its presence.…”

“…After incubation, the colonies were counted to determine the number of Y&M present in the juice. The results were expressed as colony-forming units per milliliter (CFU/ml) of juice for TVC and Y&M count (Anvarian et al, 2018).…”

Flow cytometry and growth‐based analysis of the effects of fruit sanitation on the physiology of Escherichia coli in orange juice

“…Orange juice was obtained from a local retailer and centrifuged at 17,696 g for 40 min (Beckman J2‐21, Beckman Coulter) to remove pulp. The pulp‐free supernatant was then filtered through a sterile filter paper of 1.2 μm pore size (Whatman, Maidstone, UK) to prevent the interference of OJ cloud particles with bacterial detection using FCM, as previously described (Anvarian, Smith, & Overton, ; Anvarian et al., ).…”

Bacterias viables, pero no cultivables: Cuando los patógenos están presentes, pero no son detectados por los análisis convencionales

“…En bebidas, los autores Anvarian et al (2018) reportaron que al inocular E. coli en jugo de naranja natural y adicionado con diferentes niveles de azúcar, ácido ascórbico y/o ácidos orgánicos en simulación a las diferentes concentraciones que se pudieran encontrar según la variedad o la temporalidad del fruto del que se extrajo el jugo, entre otras. Los resultados mostraron que al incrementar la temperatura de refrigeración (4°C) a temperatura ambiente (22.5°C) disminuyó el número de bacterias viables y cultivables; las variaciones de azúcar y de la composición de los ISSN en línea: 2789-3855, febrero, 2023, Volumen 4, Número 1, p. 945.…”