The impact of a cold chain break on the survival of Salmonella enterica and Listeria monocytogenes on minimally processed ‘Conference’ pears during their shelf life

BACKGROUND: In recent years, improved detection methods and increased fresh-cut processing of produce have led to an increased number of outbreaks associated with fresh fruits and vegetables. During fruit and vegetable processing, natural protective barriers are removed and tissues are cut, causing nutrient rich exudates and providing attachment sites for microbes. Consequently, fresh-cut produce ismore susceptible to microbial proliferation than whole produce.The authors are grateful to the University of Lleida, Grupo Alimentario Citrus and Banco Santander for a PhD grant (UdL-Impuls Program) to Pilar Colás Medà, and to the Spanish Government (Ministerio de Economia y Competitividad, research project AGL-2012-38671) for its financial support

Inactivation of Escherichia coli, Salmonella enterica and Listeria monocytogenes on apple peel and apple juice by ultraviolet C light treatments with two irradiation devices

Following the market trends, the consumption of fresh and cold-pressed juice in Europe is increasing. However, a primary concern – particularly in apple juice – is the related outbreaks caused by food-borne pathogens. One of the challenges is to find methods able to reduce pathogenic loads while avoiding deterioration of nutritional properties and bioactive compounds that occur in thermal pasteurization processes. In this study, the inactivation of Escherichia coli, Salmonella enterica and Listeria monocytogenes was evaluated under different ultraviolet C (UVC254nm) light treatments (up to 10,665.9 ± 28.1 mJ/cm2), in two different steps of the production chain (before and after juice processing): on apple peel discs and in apple juice. The systems proposed were a horizontal chamber with UVC254nm emitting lamps treating the product disposed at a distance of 12 cm, and a tank containing UVC254nm lamps and in which the product is immersed and agitated. Final reductions ranged from 3.3 ± 0.5 to 5.3 ± 0.4 logarithmic units, depending on the microorganism, matrix and used device. The survival curves were adjusted to Weibull and biphasic models (R2-adj ≥ 0.852), and UVC doses needed for the first decimal reduction were calculated, being lower for the apple peel discs (0.20 to 83.83 mJ/cm2) than they were for apple juice (174.60 to 1273.31 mJ/cm2), probably for the low transmittance of the apple juice compared to the surface treatment occurring on the peels. Within the treatments evaluated, the UVC254nm irradiation of apple peels immersed in water was the best option as it resulted in a reduction of the tested microorganisms of ca. 2–3 log units at lower UVC254nm doses (< 500 mJ/cm2) when compared to those occurring in apple peel treated with the UVC chamber and in juice. As contamination can proceed from apples, the sanitization of these fruit prior to juice production may be helpful in reducing the safety risks of the final product, reducing the drawbacks related to the poor transmittance of the fruit juices.This research was funded by the Spanish Ministry of Science and Innovation (MICINN), research project QUALISAFEJUICE [PID2019- 106645RB-I00], and the Spanish Ministry of Economy, Industry and Competitiveness (MINECO), with a postdoctoral orientation period grant [BES 2017 079779] (I. Nicolau-Lape ̃na)

Effect of ripeness stage during processing on Listeria monocytogenes growth on fresh-cut "Conference" pears

There are several factors that affect the shelf life of fresh-cut fruit, including the cultivar, the ripeness stage of the fruit during processing and the fruit's storage atmosphere and temperature. The effect of fruit ripeness during processing on the survival and growth of Listeria monocytogenes on fresh-cut 'Conference' pear slices at different temperatures (5, 10 and 20 °C) was studied. The four ripeness stages studied in this work (assessed by a fruit's firmness) were mature-green (5460 N), partially ripe (4353 N), ripe (3142 N) and overripe (<31 N). In our studies, pH, acidity and soluble solids content did not significantly change during conditioning at 20 °C. L. monocytogenes grew under all experimental conditions, showing an increase of approximately 2 log CFU g−1 after 8 days of storage at 5 °C. There were significant differences in the L. monocytogenes population between different ripeness stages at the end of the experiments at 10 and 20 °C. Regardless of the ripeness stage of a fresh-cut pear, the growth potential of L. monocytogenes increased with increasing temperature. A pear's ripeness stage during processing is an important consideration to ensure the quality of a fresh-cut pear, but it is not as important for preventing L. monocytogenes growth at common storage temperatures.The authors are grateful to the University of Lleida, Grupo Alimentario Citrus and Banco Santander for Pilar Colas Meda PhD grant (UdL-Impuls Program) and to the Spanish Government(Ministerio de Economia y Competitividad, research project AGL- 2012-38671) for its financial support

Bacterial Spore inactivation in orange juice and orange peel by ultraviolet-C light

Spore-forming bacteria are a great concern for fruit juice processors as they can resist the thermal pasteurization and the high hydrostatic pressure treatments that fruit juices receive during their processing, thus reducing their microbiological quality and safety. In this context, our objective was to evaluate the efficacy of Ultraviolet-C (UV-C) light at 254 nm on reducing bacterial spores of Alicyclobacillus acidoterrestris, Bacillus coagulans and Bacillus cereus at two stages of orange juice pro13 duction. To simulate fruit disinfection before processing, orange peel was artificially inoculated with each of the bacterial spores and submitted to UV-C light (97.8-100.1 W/m2) with treatment times between 3 s and 10 min. The obtained product, the orange juice, was also tested by exposing artificially inoculated juice to UV-C light (100.9-107.9 W/m2 16 ) between 5 and 60 min. A three-minute treatment (18.0 kJ/m2 17 ) reduced spore numbers on orange peel around 2 log units, while more than 45 min (278.8 kJ/m2 18 ) were needed to achieve the same reduction in orange juice for all evaluated bacterial spores. As raw fruits are the main source of bacterial spores in fruit juices, reducing bacte20 rial spores on fruit peels could help fruit juice processors to enhance microbiological quality and safety of fruit juices

Studies on the biocontrol mechanisms of Pseudomonas graminis strain CPA-7 against food-borne pathogens in vitro and on fresh-cut melon

The present study was aimed at gaining insight into the mode of action of the antagonistic bacteria Pseudomonas graminis CPA-7, which has been previously identified as an effective biocontrol agent against Listeria monocytogenes, Salmonella enterica and Escherichia coli O157:H7 on fresh-cut fruit. In vitro experiments did not reveal any antimicrobial or proteolytic activity on solid media or any biosurfactant activity on hydrophobic surfaces. Metabolites produced by CPA-7 in two different culture media and on 'Galia' melon were unable to inhibit L. monocytogenes populations on 'Galia' melon plugs at 25 °C or 5 °C. In contrast, at 25 °C the population of this pathogen on 'Galia' plugs was reduced by 2.1 and 3.3 log-units when co-inoculated with the antagonist in water, after 24 and 48 h, respectively. CPA-7 did not form biofilms after 72 h at 25 °C (OD = 0.03) or at 30 °C (OD = 0.01) on polystyrene plates and the production of alginate was close to the negative control. Studies of nutritional profiles showed high overlap (NOI > 0.9) between CPA-7 and E. coli O157:H7 regarding the use of carboxylic acids. This functional group could also contain putative targets for competiveness between CPA-7 and S. enterica, although overlapping was not restrictive enough (NOI = 0.83).The authors are grateful to the Catalan departmental government for the Phd. FI-DGR-2015-0004 grant (Cyrelys Collazo) and to the Spanish central government for the FDPI-2013-1583 grant (Dr. Ingrid Aguiló-Aguayo)

Aloe vera gel: An update on its use as a functional edible coating to preserve fruits and vegetables

Aloe vera L. is a common succulent plant that has been used for centuries regarding their healing properties and health benefits. Nowadays, scientific investigations on its gel have gained more attention because of its interesting antioxidant and antimicrobial properties. Also, the food industry encounters the need to preserve safety and quality of fresh produce; fruits and vegetables are in high demand due to their reported health benefits, and fresh-cut products are a new trend that meets the restless needs of the society. Edible coatings are an effective way to maintain freshness of these products, extend their shelf life, and even act as an alternative to modified atmosphere packaging to be used in conventional packaging. Aloe vera gel is a natural hydrocolloid, composed mainly by polysaccharides, that has been applied in the last years on fruits and vegetables. It can act as a semipermeable barrier for gases and water vapor, decreasing the respiration and ripening processes of the fruit, thus maintaining weight, firmness and valuable compounds. Its antioxidant and antimicrobial properties make it also an interesting material for increasing the shelf-life of fruits and vegetables. This review aims to describe the preparation and preservation of Aloe vera gel as well as the properties and compounds that are effective against oxidation and microbial growth. Moreover, the recent findings of its use – with or without additives – as an edible coating on fruits and vegetables have been widely detailed, showing that Aloe vera gel is a promising preservative method in this industry.Nicolau-Lapeña is in receipt of a predoctoral grant (BES 2017 079779) awarded by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO). Dr. I. Aguiló-Aguayo thanks the National Programme for the Promotion of Talent and Its Employability of MINECO and the European Social Fund for her Postdoctoral Senior Grant ‘Ramon y Cajal’ (RYC-2016-2019 949). This work was supported by the CERCA Programme of Generalitat de Catalunya

Development of a fresh-cut product based on pears and the subsequent evaluation of its shelf life under commercial conditions and after a cold chain break

Processing of pears as a fresh-cut product could offer added value and introduce a product into the market that offers greater convenience and health benefits for consumers. Cultivar selection is one of the most important considerations for fresh-cut fruit processing because characteristics such as flesh texture, skin colour, and browning potential can vary greatly among cultivars. Four pear cultivars (‘Flor de invierno’, ‘Passe-Crassane’, ‘Ercolini’ and ‘Conference’) and four antioxidant treatments, that is, (NS) 50 g L-1 NatureSeal® AS1 (Agricoat) solution, (AsAc) 20 g L-1 ascorbic acid + 10 g L-1 citric acid + 10 g L-1 calcium chloride solution, (CaAs) 20 g L-1 calcium ascorbate + 10 g L-1 calcium chloride solution and (NaAs) 20 g L-1 sodium ascorbate + 10 g L-1 calcium chloride solution, were tested to obtain a high-quality fresh-cut pear. For the selected cultivar and treatment, the nutritional changes and physicochemical, microbial and sensorial quality were evaluated under conditions that simulated commercial application followed by storage at 4 °C and a simulated cold chain break at 8°C. The ‘Conference’ pear was selected as the best cultivar based on its physicochemical characteristics (high levels of soluble solids content and low acidity), low increase in browning index, and visual acceptance after 7 days of storage. The results demonstrated that CaAs maintained the fresh-cut pear quality after 8 days of storage at 4°C and also after a cold chain break. Furthermore, application of the selected treatment produced an increase in the ascorbic acid content, total phenolic content and antioxidant activity of minimally processed pear samples. These values were reduced during shelf life, but the total phenolic content at the final sampling point was higher than that of fresh-cut pears after processing without treatment.The authors are grateful to the University of Lleida, Grupo Alimentario Citrus and Banco Santander for the Pilar Colás Medà PhD grant (UdL-Impuls Program) and to the Spanish Government (Ministerio de Economia y Competitividad, research project AGL-2012-38671) for financial support. L. Plaza thanks the National Institute for Agronomic Research (INIA) for the DOC-INIA research contract

Control biológico de las enfermedades fúngicas en poscosecha de fruta. Situación actual y perspectivas futuras

Tradicionalmente el control de las enfermedades fúngicas en poscosecha de frutas se ha venido realizando mediante fungicidas químicos de síntesis. Sin embargo, la fuerte demanda por parte de los consumidores de fruta libre de residuos de plaguicidas y las nuevas estrictas regulaciones sobre su registro y aplicación, han propiciado la aparición de alternativas a los productos químicos. Dentro de las alternativas, el control biológico se presenta como una de las más prometedoras. En los últimos 35 años de investigación de los agentes de biocontrol en poscosecha se han llevado a cabo considerables avances y la comercialización de algunos productos. No obstante, todavía existen numerosos desafíos y obstáculos que dificultan la implementación de su uso como una estrategia de control a gran escala

Potencial de la radiación ultravioleta para el control de podredumbres en postcosecha de frutas y hortalizas

Se estima que más de un 20% de las frutas y hortalizas se desperdician antes de su consumo, siendo las podredumbres fúngicas una de las principales causas. El uso de la radiación ultravioleta puede ser una alternativa a los fungicidas químicos que está mostrando resultados prometedores, ya sea actuando directamente sobre el moho o incrementado la resistencia de los vegetales a las podredumbres. A continuación, se revisarán los avances más recientes sobre el uso de la radiación ultravioleta en frutas y hortalizas

Ultraviolet applications to control patulin produced by penicillium expansum CMP-1 in Apple products and study of further patulin degradation products formation and toxicity

Patulin is a mycotoxin whose presence in apple-derived products and fruit juices is legally regulated, being its maximum limits established in the legislation of multiple countries. However, the management of contaminated batches is still an issue for producers. This investigation aims to evaluate ultraviolet light (254 nm, UV-C254nm) irradiation to find solutions that can be applied at different stages of the apple juice production chain. In this regard, 8.8 (UV-1) and 35.1 (UV-2) kJ m−2 treatments inactivated spores of Penicillium expansum CMP-1 on the surface of apples. Although the same treatments applied to wounded apples (either before the infection or after the infection, immediately or when the lesion had appeared) did not show any effect on the growth rate of P. expansum during storage (up to 14 days, at 4 or 25 °C), they reduced patulin content per lesion size in apples treated after the infection had occurred (patulin decreased from 2.24 (control) to 0.65 µg kg−1 cm−2 (UV-2 treated apples)). Additionally, the treatment of juice with patulin with ultraviolet light up to 450.6 kJ m−2 resulted in more than 98 % reduction of patulin. Degradation products of patulin after UV-C254nm treatments were tentatively identified by HPLC–MS, and toxicity and biological activities were assessed in silico, and results indicated that such products did not pose an increased risk when compared to patulin.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This research was funded by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO), with a postdoctoral orientation period grant [BES 2017 079779] (I. Nicolau-Lapeña)