Concerning firmness postharvest calcium dips for whole fruit

Concerning firmness, postharvest calcium dips for whole fruit have been demonstrated to preserve firmness, cell wall structure (Glenn and Poovaiah, 1990), nutritional quality (Goldberg, 1984) and fruit flavour (Ortiz et al., 2009). Similarly, combinations of calcium treatment (0.5–4%) with packaging under modified atmospheres and low storage temperature (<5 °C) are generally effective for extending the shelf-lives of minimally processed products. The aim of this study was to evaluate the antagonistic effect of CPA-7 against Salmonella and L. monocytogenes on fresh-cut pear treated with CaCl2 after harvest under conditions simulating commercial applications (under MAP and in presence of an antioxidant solution) at 5 ± 1 °C. In addition, the effect of CPA-7 on some quality parameters, including ethanol and acetaldehyde contents and the volatile profile, were evaluated throughout storage.
Materials and methods
Results
Discussion In previous studies (Iglesias et al., 2018), we demonstrated that CPA-7 was effective against S. enterica and L. monocytogenes on pear wedges at air temperatures of 20, 10 and 5 ± 1 °C and determined the antioxidant solution and film best used for commercial applications. In this work, we have focused on the antagonistic activity of CPA-7 against foodborne pathogens under conditions that simulate commercial applications and how the presence of CPA-7 and the CaCl2 postharvest treatment influences several pear quality parameters, including the contents of several volatile compounds. After harvest of the fruit, cold storage and a controlled Finasteride receptor are essential for delaying the ripening process. Moreover, postharvest dipping in CaCl2 prior to storage extends the commercial life for both whole and minimally processed fruit (Ortiz et al., 2009; Trentham et al., 2008). Calcium can penetrate fruit flesh through lenticels, but cracks in the cuticle play a significant role in calcium entrance into the fruit (Conway et al., 2002; Ortiz et al., 2009). In general, CaCl2 treatment after harvest did not improve CPA-7 effectiveness against foodborne pathogens evaluated; nevertheless, the CPA-7 population was higher on pear wedges treated with CaCl2 after harvest than it was on untreated samples. Microorganisms need calcium for their development, survival and physiological processes (Corbin et al., 2008). Tiwari et al. (1992) observed that an increase in extracellular Ca2+ caused an increase in the growth rate of Rhizobium melitoti. In addition, Onoda et al. (2000) demonstrated that in absence of Ca2+, E. coli stopped growing and cells became unusual in form and could lyse and die. However, it has been demonstrated that the amount of calcium required for bacteria depends on the growth conditions (Youatt, 1993). CPA-7 was not observed to have antagonistic activity against S. enterica under MAP at 5 ± 1 °C, and no pathogen growth was observed. Similarly, Alegre et al. (2013a) did not observe an antagonistic effect against Salmonella on apple wedges. Regarding L. monocytogenes, we observed an antagonistic effect from CPA-7 after 9 days of storage at 5 ± 1 °C, and it caused reductions of approximately 1-log unit. Alegre et al. (2013a) also demonstrated an antagonistic effect of CPA-7 against L. monocytogenes on apple wedges; however, the effect was greater under air conditions than under MAP; a similar effect was observed by Abadias et al. (2014) for fresh-cut melon. According the review by Siroli et al. (2015a) some biocontrol agents were also able to control spoilage microorganisms naturally present in minimally processed fruits and vegetables. In our work, the effect of CPA-7 on the spoilage microorganisms was not evaluated. No visible symptoms of microbial spoilage were observed neither in CPA-7 and control fresh-cut pears during the shelf-life (9 days at 5 °C), so we could not reach to a clear conclusion. We observed significant differences in the SSC values of untreated and CPA-7-treated fresh-cut pear regardless of postharvest CaCl2 treatment, except after 6 days of storage in the case of the CaCl2-treated pear wedges. The SSC values of pear wedges treated with CPA-7 were 1% lower than those of untreated pear, which could be perceived by the consumers as a less sweet taste. Regarding the TA values, significant differences were observed after 6 and 9 days of storage between the CaCl2-treated pear inoculated with CPA-7 and non-inoculated samples. It is known that consumers can perceive differences in the TA if the variation is higher than 0.08% (Harker et al., 2002). In our case, the differences found after 6 and 9 days of storage were lower than this value and therefore could not be perceived by consumers. Alegre et al. (2013a) and Abadias et al. (2014) did not report significant differences in SSC or TA values among fruit (apple wedges or fresh-cut melon) untreated and treated with CPA-7.