Maintaining the sensorial qualities of
Maintaining the sensorial qualities of minimally processed fruit after processing and during the chain of distribution is very difficult. The shelf-life of cut produce is very limited due to browning of the flesh and the loss of flavour (Conway et al., 2002; Toivonen, 2006; Toivonen and Delaquis, 2006). Some factors including variety, ripeness stage, and the Fmoc-Gly-OH and temperature of storage affect shelf-life during postharvest storage following processing. Modified atmosphere packaging (MAP) in combination with refrigeration temperatures is used to preserve fresh-cut produce. Low O2 and high CO2 can be used to preserve the quality of minimally processed fruit because they inhibit the bioreactions in fruit tissue that may lead to physiological decay (Rosen and Kader, 1989; Sapers and Miller, 1998). However, that gas composition may initiate fermentative pathways that release metabolites such as ethanol that cause off-flavours (Soliva-Fortuny et al., 2002). Moreover, it is known that although a high CO2 level can inhibit aerobic spoilage microorganisms, it can also allow pathogen growth (Rodriguez-Aguilera et al., 2009). Therefore, it is necessary to maintain an O2 concentration that is sufficiently low but also over the fermentation threshold (Lakakul et al., 1999).
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
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 atmosphere 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).