Effect of preharvest melatonin applications at dusk on quality and bioactive compounds content of early sweet cherries.

BACKGROUND: Early sweet cherries have a high economic impact on cherry growers but have poorer quality characteristics and shorter shelf-life than late cherries. Melatonin has been proposed as a biostimulant that regulates plant and fruit growth and increases fruit quality and shelf-life but, in general in fruit and vegetables, there is controversy about its effects. Therefore, this work aimed to evaluate the impact of exogenous preharvest melatonin applications at dusk on the quality and bioactive compounds of two early sweet cherry cultivars. RESULTS: The M3 and M5 (3 × 10-4 and 5 × 10-4 mol L-1 melatonin, respectively) treatments effectively enhanced the endogenous melatonin and hydroxycinnamic acid concentration, enhancing the functional properties of the fruit. Additionally, the M5 treatment enhanced skin colour and consumer acceptance of 'Samba' cherries, while the M3 treatment improved cherry size in 'Sandon Rose'. CONCLUSION: Preharvest melatonin applications at dusk could be included in the scheduled preharvest treatments for early cherry cultivars in order to improve the quality and to stimulate the functionality of the fruit. However, further studies are needed to adjust the concentration depending on the cultivar and the objective pursued. © 2023 Society of Chemical Industry.

Impact of Pre-Storage Melatonin Application on the Standard, Sensory, and Bioactive Quality of Early Sweet Cherry.

Melatonin (N-acetyl-5-methoxytryptamine) is involved in multiple functions in plants. However, its role in some metabolic pathways and exogenous application's effect on fruits is still unclear. Furthermore, the effects of pre-storage melatonin treatment on sensory traits and consumer acceptance of cherries have yet to be studied. For this reason, the early sweet cherry cultivar 'Samba' harvested at the commercial ripening stage was treated with different melatonin concentrations (0.1, 0.3, and 0.5 mmol L-1) and stored for 21 days under controlled cold temperature and humidity. The standard quality, respiration rate, postharvest aptitude, sensory quality, phenols, and antioxidant systems (non-enzymatic and enzymatic) were analysed at 14 and 21 days of storage. Postharvest treatment with melatonin 0.5 mmol L-1 improved firmness and reduced weight loss and non-commercial fruit percentage while increasing respiration rate, lipophilic antioxidant activity, and ascorbate peroxidase enzyme activity. Furthermore, the treated cherries showed better sensory qualities, such as uniformity of colour and skin colour, as well as being sourer and showing better consumer acceptance and liking after 14 days of storage. Therefore, we conclude that the 0.5 mmol L-1 concentration is effective on the standard, sensory, and bioactive quality of early sweet cherries and can be considered an eco-friendly tool for maintaining the postharvest quality of early cherries.

Control of toxigenic Aspergillus spp. in dried figs by volatile organic compounds (VOCs) from antagonistic yeasts.

Aspergillus flavus and Aspergillus niger are fungi which can contaminate dried figs before and after harvest and consequently produce aflatoxins (AFs) and ochratoxin A (OTA). Many approaches have been applied to minimise the growth of these filamentous fungi, mainly involving the use of synthetic fungicides which are limited due to their negative impact on human health and the environment. In this context, biocontrol is a recent approach that needs to be explored. This study evaluated the potential of three volatile organic compounds (VOCs), octanoic acid (OA), 2-phenylethyl acetate (2PEA) and furfuryl acetate (FA), produced by Hanseniaspora uvarum and Hanseniaspora opuntiae yeasts on the growth, germination, gene expression and production of AFs and OTA by A. flavus M144 and A. niger M185 on dried fig-based agar and the incidence rates in dried figs. Two of the three VOCs evaluated (2PEA and FA) effectively controlled A. flavus M144 and A. niger M185 by using at least amounts of 50 µL (715 µL/L in the headspace) for FA and 100 µL (1430 µL/L in the headspace) for 2PEA in dried figs. One of the mode of actions of both compounds consists in early repressing the expression of genes involved in the biosynthesis of AFs (aflR) and OTA (pks) of A. flavus and A. niger, respectively. The results of this study support the application of 2PEA and FA at the early post-harvest stages of dried figs to control mycotoxin accumulation.

Evaluation of fungal hazards associated with dried fig processing.

The processing of dried figs in the industry involves a number of stages that present a significant risk of filamentous fungal infection of the fruit and subsequent mycotoxin contamination, due to the changes in temperature and water activity (aw) to which dried figs are exposed. In this study, the environmental conditions and the physicochemical parameters of dried figs at different processing stages were evaluated in 3 different industries, and were associated with fungal counts and the presence of toxigenic moulds and their mycotoxins. For this, dried figs at 5 relevant stages of industrial processing (curing, sizing, blanching, storage, and final product) in 3 industries located in Extremadura (Spain) were sampled. Changes in moisture content and aw of dried figs during processing were observed and they influenced the mycological quality of figs. Among the fungal genera, Aspergillus spp. predominated in most stages except blanching, where Penicillium spp. prevailed. About 10% of the dried fig samples were contaminated with aflatoxins (AFs) and 6% with ochratoxin A (OTA). Based on findings, longer drying times are necessary after blanching to reduce aw and to avoid the development of toxigenic moulds. In addition, all stages covering industry processing, final storage, and retailing of dried figs are advisable to be conducted at refrigeration conditions and controlled relative humidity to avoid mycotoxin production. The enumeration of AFs- and OTA- producing moulds by real-time PCR seems to be a good indicator for integration into prevention strategies to control filamentous fungal hazards and subsequent mycotoxin synthesis during the processing of dried figs.

Identification of the Causal Agent of Aqueous Spot Disease of Sweet Cherries (Prunus avium L.) from the Jerte Valley (Cáceres, Spain).

The pre and postharvest disease named 'aqueous spot' is an emerging risk for sweet cherries growing in Jerte Valley (Cáceres, Spain). Early stages of the disease appear in the tree, but it is usually detected after harvesting, during the postharvest period. Symptoms include the appearance of skin discolouration and translucency in the shoulder areas. At the most advanced stages, a mycelium of white colour partially or completely covers the fruit. This manuscript provides a detailed description of the microbes involved in this disease, such as bacteria, yeasts, and moulds. Microbes of different cherry cultivars were studied during two consecutive seasons (2019 and 2020). The counts of bacteria and yeast in damaged tissues were higher (7.05 and 6.38 log10 CFU/g for total aerobic mesophilic microbes and yeasts, respectively) than sound tissues (6.08 and 5.19 log10 CFU/g, respectively). The Enterobacterales order dominated the bacteria population. Among yeasts, Yarrowia lipolytica, in 2019, and Metschnikowia pulcherrima and Metschnikowia viticola, in 2020, were consistently isolated from all samples. The presence of moulds was inconsistently detected at the early stage of this disease by plate counts. However, microscopic observations revealed the presence of hyphae in cherry flesh. Different pathogenic moulds were identified, although white mycelium, identified as Botrytis cinerea by molecular methods, was consistently isolated at later stages. Inoculation tests confirmed the involvement of white-mycelium B. cinerea in the development of this new postharvest disease in the Jerte Valley. Its combination with Enterobacterales enhanced the evolution of rotting, whereas the combination with yeasts decreased and delayed the symptoms. This work presents the first report of a consortia of microorganisms implicated in the development of 'aqueous spot', an emerging disease in sweet cherry cultivars in the Jerte Valley.

Effect of Temperature during Drying and Storage of Dried Figs on Growth, Gene Expression and Aflatoxin Production.

Dried fig is susceptible to infection by Aspergillus flavus, the major producer of the carcinogenic mycotoxins. This fruit may be contaminated by the fungus throughout the entire chain production, especially during natural sun-drying, post-harvest, industrial processing, storage, and fruit retailing. Correct management of such critical stages is necessary to prevent mould growth and mycotoxin accumulation, with temperature being one of the main factors associated with these problems. The effect of different temperatures (5, 16, 25, 30, and 37 °C) related to dried-fig processing on growth, one of the regulatory genes of aflatoxin pathway (aflR) and mycotoxin production by A. flavus, was assessed. Firstly, growth and aflatoxin production of 11 A. flavus strains were checked before selecting two strains (M30 and M144) for in-depth studies. Findings showed that there were enormous differences in aflatoxin amounts and related-gene expression between the two selected strains. Based on the results, mild temperatures, and changes in temperature during drying and storage of dried figs should be avoided. Drying should be conducted at temperatures >30 °C and close to 37 °C, while industry processing, storage, and retailing of dried figs are advisable to perform at refrigeration temperatures (<10 °C) to avoid mycotoxin production.

Anti-fungal activity of phenolic sweet orange peel extract for controlling fungi responsible for post-harvest fruit decay.

There is a growing interest in finding safe and natural anti-microbial compounds as a valid alternative to conventional chemical treatments for managing post-harvest fruit diseases. This study investigated the anti-fungal capacity of orange peel polyphenolic extract (OPE) against three relevant post-harvest fungal pathogens, Monilinia fructicola, Botrytis cinerea and Alternaria alternata. OPE extract at 1.5 g/L inhibited (100%) the mycelial growth and conidial germination of the three target fungi. At lower concentration, the effect varied, depending on the dose applied and target fungi. When the anti-fungal activity of the main phenolic compounds in sweet orange peel, namely, the flavonoids (naringin, hesperidin and neohesperidin) and phenolic acids (ferulic and p-coumaric), were evaluated, ferulic acid and p-coumaric acid displayed significantly higher inhibitory capacity in synthetic medium, while the activity of flavonoids was limited. Synergism between compounds was not detected, and the inhibitory activity of OPE may be attributed to an additive effect of phenolic acids. Interestingly, in peach-based medium, ferulic acid remained active against M. fructicola and A. alternata and was more efficient than p-coumaric to control B. cinerea. These results highlight peel orange waste as an excellent source of anti-fungal compounds, suggesting the possibility of using ferulic acid or ferulic acid-rich extracts, either alone or in combination with other post-harvest treatment, as a natural alternative to reduce post-harvest losses and, also, enhance the shelf-life of fruit.

Evaluation of the Physicochemical and Sensory Characteristics of Different Fig Cultivars for the Fresh Fruit Market.

Physicochemical and sensory properties of nine fig cultivars: 'San Antonio' (SA), 'Blanca Bétera' (BB), 'Brown Turkey' (BT), 'Tres Voltas L'Any' (TV), 'Banane' (BN), 'Cuello Dama Blanco' (CDB), 'Cuello Dama Negro' (CDN), 'Colar Elche' (CE), and 'De Rey' (DR), were compared at three different ripening stages. Weight, size, titratable acidity, pH, skin and flesh colours, firmness, maturation index (MI), and volatile compounds were determined in samples from two consecutive seasons, in addition to both descriptive and hedonic sensory analysis. The mechanical behaviour of figs determined by firmness analysis and colour changes in both skin and flesh was the most important trait for the discrimination of ripening stages. Notable differences among cultivars were found in most of the parameters studied, in particular the inter-cultivar differences highlighted for MI, pH, acidity, and skin colour analyses, followed by volatile compounds. Principal component analysis (PCA) indicated that MI, pH, colour parameters of flesh (h and L*), and terpenes were the best physicochemical indices to determine overall acceptability which is highly correlated with the sensory attributes flesh colour and fruit flavour. The results suggested that CDN and SA showed huge consumer acceptability among the fig cultivars studied.

Characterization of microbial population of breba and main crops (Ficus carica) during cold storage: Influence of passive modified atmospheres (MAP) and antimicrobial extract application.

The purpose of this work was to study the changes of bacterial and fungal population of breba fruits such as 'Banane' and 'San Antonio' as well as 'Cuello Dama Negro', 'Cuello Dama Blanco' and 'San Antonio' fig cultivars stored in passive modified atmospheres (MAP) by the use of three different microperforated films (M10 with 16 holes; M30 with five holes and M50 with three holes). Moreover the effects of the application of aqueous soy polyphenolic antimicrobial extract (APE), alone or combined with MAP, were also studied for 'Cuello Dama Negro' and 'Cuello Dama Blanco' fig cultivars. Bacteria and fungi isolates were identified by PCR-RFLP of 16S rRNA and ITS regions, respectively, and subsequently sequence of the different patterns obtained. The results indicated that Pseudomonas gessardii, Pantoea agglomerans and Enterobacter asburiae were the main species of bacteria found in all the treatments studied. The fungal species identified were Aureobasidium pulullans, Cladosporium cladosporioides and Alternaria alternata, which were found in a lower percentage in fruit stored in MAP and fruits treated with antimicrobial extracts, as this treatments allowed to reduce the microbial growth of moulds and yeasts. Thus, the application of treatments such as M30, M50 or the combination of MAP with antimicrobial extract was highly effective to control fruit spoilage in fig and breba crops.

Preservation of different fig cultivars (Ficus carica L.) under modified atmosphere packaging during cold storage.

BACKGROUND: The effect of modified atmosphere packaging (MAP) on the stability of 'Cuello Dama Blanco' (CDB), 'Cuello Dama Negro' (CDN) and 'San Antonio' (SA) figs during post-harvest cold storage was evaluated by using three different films with a diverse number of microperforations (diameter, ø = 100 µm): M10 (16 holes), M30 (five holes) and M50 (three holes). A macroperforated film was used as control (five holes, ø = 9 mm). Gas composition, weight loss, percentage disorder, microbial counts and physico-chemical parameters were monitored during cold storage for 21 days. Furthermore, sensory quality was also evaluated. RESULTS: MAP has allowed the extension of cold storage and distribution time for the three different cultivars of figs, minimising weight loss and delaying pathological disorders related to endosepsis, smut, and souring. Of the three cultivars, the M50 batch (one hole per 50 mm) showed the best efficiency in terms of physico-chemical quality and delay of post-harvest decay, although the M30 batch was also found to be suitable for delaying the post-harvest decay, especially for the CDB cultivar. CONCLUSION: MAP is a useful tool to extend the storability with optimal quality properties for CDN and SA during 21 days of cold storage and 14-17 days of cold storage for CDB.

Antioxidant and antimicrobial activity of natural phenolic extract from defatted soybean flour by-product for stone fruit postharvest application.

BACKGROUND: Fresh fruit is highly perishable during storage and transport, so there has been growing interest in finding safe and natural antimicrobial compounds as a control tool. Phenolic compounds are secondary metabolites naturally present in vegetable material and have been associated with antimicrobial and antioxidant properties. Therefore, the aim of this study was to investigate the antioxidant capacity and potential antimicrobial effect of phenolic extract obtained from defatted soybean flour against selected pathogenic bacteria and microorganisms responsible of fruit decay. RESULTS: Analysis of phenolic composition by HPLC-MS showed the presence of a wide range of compounds, with isoflavones and phenolic acids the main polyphenols identified. Furthermore, the phenolic extract had important antioxidant activity by two different assays. Related to antimicrobial activity, in vitro experiments demonstrated that phenolic extract displayed a high activity against the main foodborne pathogens, while a moderate inhibition was found against five spoilage yeasts and Monilia laxa and a scarce effect for Penicillium glabrum, Cladosporium uredinicola and Botrytis cinerea. Interestingly these compounds considerably inhibited the mycelial growth of Monilia laxa, in both in vitro and in vivo experiments. CONCLUSION: The results of the present study revealed that defatted soybean flour is an important source of phenolic compounds with remarkable antimicrobial and antioxidant activity, suggesting the possibility of using them as natural additives in postharvest treatments to extend the shelf life of fruit.

Study of microbiological quality of controlled atmosphere packaged 'Ambrunés' sweet cherries and subsequent shelf-life.

The objectives of this study were to evaluate the effect of different controlled atmospheres, containing 3% O2+10% CO2, 5% O2+10% CO2 and 8% O2+10% CO2, on changes in microbial population of 'Ambrunés' sweet cherries throughout storage during 30days and subsequent shelf-life, as well as to identify the main genera of yeast, mould, lactic acid bacteria, Staphylococcus spp., Pseudomonas spp., Enterobacteriaceae spp., and coliforms. The results indicated that controlled atmospheres with 5% O2+10% CO2 and 8% O2+10% CO2 were highly effective to control the growth of mesophilic aerobic bacteria, psychrotrophs, Pseudomonas spp., yeasts, and moulds after 15days of storage, showing, in the case of yeasts and moulds, counts that ranged between <1 and 1.75logCFU/g. The genera of yeasts, moulds, lactic acid bacteria, Enterobacteriaceae spp., and coliforms identified were Aureobasidium spp., Penicillium spp., Leuconostoc spp., and Rahnella spp., respectively. In addition, the genera Staphylococcus spp. and Pseudomonas spp. were also identified. On the other hand, cherries of Stage 3 ripening presented the highest counts for all microbial groups.

Effect of the commercial ripening stage and postharvest storage on microbial and aroma changes of 'Ambrunés' sweet cherries.

The purpose of this work was to investigate the effect of the commercial ripening stage and postharvest storage on microbial and aroma changes of 'Ambrunés' sweet cherries. The microbial counts and volatile profile of sweet cherry batches automatically sanitized and classified in three commercial ripening stages were studied for five postharvest storages. The batches were also evaluated sensorially, and the correlations between volatile compounds and aroma quality were determined. The microbial counts provided evidence that 21 days of cold storage is near the maximum extension of 'Ambrunés' sweet cherry storage in maintaining the minimal microbial quality during their shelf-life period. Relevant changes associated with longer cold storages were found in different aroma constituents with a negative impact on flavor. These changes were more evident in less ripened sweet cherries, including a decrease of (E)-2-hexenal and 1-hexanol and an increase of 2-methyl-propanal and 2-methyl-butanal. These compounds could constitute a good tool to predict flavor quality in 'Ambrunés' sweet cherries during the cold-storage process.

Safety and functional aspects of pre-selected lactobacilli for probiotic use in Iberian dry-fermented sausages.

The purpose of this study was to investigate lactobacilli for potential probiotic use in Iberian dry-fermented sausages. A total of 18 strains, previously selected, isolated from different sources were evaluated according to safety and functional characteristics including biogenic amines and d-lactic acid production, antibiotic susceptibility, haemolysis, cell adhesion, and antimicrobial activity against food-borne pathogens. The strains Lactobacillus reuteri PL519, L. reuteri PL542, and Lactobacillus fermentum HL57 were able to establish their self on the intestinal epithelium, and an inhibition of such pathogenic bacteria as Listeria monocytogenesin vitro. These strains were also considered safe to be used with regard to their low aminogenic potential and d-lactic acid production, antibiotic resistance pattern and haemolytic activity. Thus, they were selected as a potential probiotic meat starter culture suitable for manufacture of dry-fermented Iberian sausages.