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 ºC to 22.5 ºC 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.
| Original language | English |
|---|---|
| Pages (from-to) | 1817-1825 |
| Journal | Food Science and Nutrition |
| Volume | 6 |
| Issue number | 7 |
| Early online date | 13 Aug 2018 |
| DOIs | |
| Publication status | Published - 16 Oct 2018 |
Keywords
- Orange juice
- E. coli
- Flow cytometry
- Viable but non-culturable
- Amino acids