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1.
Food Sci Technol Int ; 25(4): 271-281, 2019 Jun.
Article in English | MEDLINE | ID: mdl-30545245

ABSTRACT

Biological preservation methods with bacterial antagonists have emerged as alternatives to chemical sanitizers for extending shelf-life and reducing the population of pathogenic microorganisms. In addition, calcium plays an important role in maintaining the quality of fruit, and postharvest calcium treatments might determine the potential of fruit for processing. The objective of this work was to evaluate the effect of the postharvest application of calcium and biopreservation with the CPA-7 strain of Pseudomonas graminis on the quality parameters of fresh-cut pears. After harvest, whole pears were dipped in calcium chloride solution (1%, w/v) or water (control) for 10 min at 25 ℃ and stored for five months at temperatures ranging from 0 to -0.5 ℃. Both batches of fruit were minimally processed and dipped in a solution containing CPA-7 and an antioxidant solution or kept untreated, and both groups were stored at 4 ℃ for six days. The postharvest calcium treatment had no remarkable effect on the quality of the whole and fresh-cut pears. The enzymatic activities (PPO, PME and PG) related to browning and softening were constant in fresh-cut pears after storage, and the application of P. graminis CPA-7 had a positive effect on the activity of PPO. Finally, a combined effect of the biocontrol agent and calcium treatment was not demonstrated.


Subject(s)
Food Preservation/methods , Fruit/chemistry , Nutritive Value , Pseudomonas/physiology , Pyrus/chemistry , Anti-Infective Agents , Antioxidants , Ascorbic Acid/analysis , Calcium/analysis , Calcium Chloride , Food Handling/methods , Phenol/analysis
2.
Food Microbiol ; 76: 226-236, 2018 Dec.
Article in English | MEDLINE | ID: mdl-30166146

ABSTRACT

The application of microorganisms to control the growth of foodborne pathogens is an alternative to the use of chemical additives. In this work, Pseudomonas graminis CPA-7 was tested as a biocontrol agent against Salmonella enterica and Listeria monocytogenes on fresh-cut pear under conditions that simulate its commercial application at 5 ±â€¯1 °C (under a modified atmosphere and antioxidant solution). The quality of the fresh-cut fruit, including the ethanol and acetaldehyde contents and the volatile profile, was determined. After the storage period, the L. monocytogenes population was reduced by 1-log unit by the presence of CPA-7; however, CPA-7 was not found to have antagonistic activity against S. enterica. The fruit quality (total soluble solids content and titratable acidity) was not negatively affected by CPA-7. The ethanol and acetaldehyde contents increased during the shelf-life of the fruit regardless of the presence of CPA-7. Some volatile compounds were key factors for discriminating samples from the two groups (the control group and the group that was inoculated with CPA-7). Some components are common in the volatile profile of pear (methyl acetate, 3-methylbutyl acetate, 1-butanol, 1-hexanol, and hexanal), and thus increases in their contents could enhance consumers flavour perception.


Subject(s)
Antibiosis , Biological Control Agents/pharmacology , Listeria monocytogenes/physiology , Pseudomonas/physiology , Pyrus/microbiology , Salmonella enterica/physiology , Acetaldehyde/analysis , Colony Count, Microbial , Ethanol/analysis , Flavoring Agents/analysis , Food Microbiology , Fruit/chemistry , Fruit/microbiology , Humans , Listeria monocytogenes/pathogenicity , Pyrus/chemistry , Salmonella enterica/pathogenicity , Volatile Organic Compounds/analysis , Volatile Organic Compounds/metabolism
3.
J Sci Food Agric ; 98(13): 4978-4987, 2018 Oct.
Article in English | MEDLINE | ID: mdl-29577335

ABSTRACT

BACKGROUND: Biological preservation with probiotic bacteria has arisen as an alternative to control the growth of foodborne pathogens on food. The objective of this work was to evaluate the effect of postharvest calcium application and biopreservation with Lactobacillus rhamnosus GG on the quality and bioaccessibility of total phenolic content and antioxidant activity in fresh-cut pears. RESULTS: The immersion of whole pears in a calcium chloride solution did not provide added value. Despite the increase in observed activity of PME and PPO enzymes in fresh-cut pears during storage, the browning index and firmness values were constant for all samples. The antioxidant properties, including antioxidant activity, total phenolic content and vitamin C content, were maintained during storage, but a significant decrease was observed after in vitro simulated digestion. Ca/LGG samples showed the lowest calcium content (1.75 ± 0.00 g kg-1 ) after 9 d of storage at 4 °C. In general, the overall visual quality scores were higher in fresh-cut pears treated with L. rhamnosus GG than in non-treated pears, with the highest values in the NoCa/LGG (7.7 ± 0.2) samples after 9 d at 4 °C. CONCLUSION: Fresh-cut pears with a postharvest treatment of calcium and immersed in a solution containing antioxidant agents and probiotic bacteria could be a suitable alternative to dairy products for maintaining the overall quality of fruit for up to 9 d of storage. © 2018 Society of Chemical Industry.


Subject(s)
Calcium Chloride/pharmacology , Food Preservation/methods , Food Preservatives/pharmacology , Fruit/chemistry , Lacticaseibacillus rhamnosus/physiology , Pyrus/chemistry , Antibiosis , Ascorbic Acid/analysis , Food Storage , Fruit/microbiology , Phenols/analysis , Plant Diseases/microbiology , Plant Diseases/prevention & control , Pyrus/microbiology , Quality Control
4.
Int J Food Microbiol ; 262: 55-62, 2017 Dec 04.
Article in English | MEDLINE | ID: mdl-28964998

ABSTRACT

To further gain insight into the mechanism by which the biopreservative bacterium Pseudomonas graminis CPA-7 develops its antimicrobial activity, we have examined the effect that the prior interaction stablished by this bacterium and two foodborne pathogens on fresh-cut pear, has on their capacity to colonize human epithelial cells (Caco-2 cell line) which is crucial for establishing infection. CPA-7 inhibited the growth of L. monocytogenes and S. enterica subsp. enterica ser. Enteritidis by 5.5 and 3.1 log10, respectively, after 7d of interaction at 10°C. Furthermore, CPA-7 attenuated the adherence of S. enterica to Caco-2 cells by 0.8 log10 regardless of the pre-adaptation on the fruit. Conversely, the adhesiveness of L. monocytogenes was not influenced by the interaction with the antagonist but it was reduced by 0.5 log10 after incubation on the food matrix. Pathogen-antagonist-food matrix interaction was associated to a significant reduction of the relative invasiveness of both pathogens, by 1.3 log10 in the case of L. monocytogenes and to an undetectable level (below 5CFU/g fruit) for S. enterica. CPA-7 can adhere to and internalize into intestinal epithelium which enables it for competition. Its adherence positively correlates to the multiplicity of infection (MOI) with respect to Caco-2 cells, increasing by 0.6 log10 in an MOI range of 0.1:1 to 100:1. For the same levels of inoculum, internalized cells could only be detected after 7d of pre-adaptation in the fruit (pH4.5-5.0). However, the combination of gastrointestinal digestion and habituation on the fruit resulted in a significant reduction of CPA-7 populations (by 2 log10 more after 7d of incubation than on inoculation day) as well as in the decrease of its adhesiveness (by 0.8 log10) and invasiveness (to undetectable levels).


Subject(s)
Bacterial Adhesion/physiology , Caco-2 Cells/microbiology , Fruit/microbiology , Listeria monocytogenes/growth & development , Probiotics/metabolism , Pseudomonas/physiology , Pyrus/microbiology , Salmonella enterica/growth & development , Cell Line, Tumor , Colony Count, Microbial , Foodborne Diseases/microbiology , Gastrointestinal Tract/microbiology , Humans
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