Monitoring studies of the occurrence of fire blight pathogen in Kazakhstan and identification of antagonistic microorganisms suppressing its development.

The paper presents data on phytosanitary monitoring of garden cenoses for fire blight in the Turkestan, Zhambyl, and Almaty regions of Kazakhstan. The purpose of this study is to assess the phytosanitary situation in various regions of Kazakhstan, determine the extent of fire blight spread, and isolate and identify the fire blight pathogen. During the study, methods such as hypersensitivity, pathogenicity, and fluorescent simplification-based specific hybridization polymerase chain reaction (FLASH-PCR) were used. It was found that in all the surveyed areas, disease foci were identified. For the first time, the fire blight pathogen was detected on fruit crops such as plum, peach, cherry plum, and quince, as well as on wild apricots. 274 plant samples were collected from which microorganisms were isolated. Isolates related to the fire blight pathogen Erwinia amylovora were identified by methods of hypersensitivity, pathogenicity, and FLASH-PCR diagnostics. Of the 156 isolates of microorganisms isolated from apple tree plant samples, 21 inhibited the in vitro growth of E. amylovora to varying degrees. Isolates 16.2 and 19.2 with maximum antagonistic activity were selected, where the pathogen growth inhibition zones were 52.2 ± 2.58 mm and 45.6 ± 0.55 mm, respectively. Based on the obtained sequence of nucleotides of the 16SpRNA gene site, it was found that the selected isolates with high antagonistic activity belonged to the Pseudomonas genus. In the future, based on these isolates, a new biological product for fire blight control can be created and adapted to the natural and climatic conditions of Kazakhstan.

Alicyclobacillus spp. in fruit-based products: Isolation, identification, quantitative assessment (SPME/GC-MS) of spoilage compounds and spore's resistance to thermal shocks.

Alicyclobacillus spp. is the cause of great concern for the food industry due to their spores' resistance (thermal and chemical) and the spoilage potential of some species. Despite this, not all Alicyclobacillus strains can spoil fruit juices. Thus, this study aimed to identify Alicyclobacillus spp. strains isolated from fruit-based products produced in Argentina, Brazil, and Italy by DNA sequencing. All Alicyclobacillus isolates were tested for guaiacol production by the peroxidase method. Positive strains for guaiacol production were individually inoculated at concentration of 103 CFU/mL in 10 mL of orange (pH 3.90) and apple (pH 3.50) juices adjusted to 11°Brix, following incubation at 45 °C for at least 5 days to induce the production of the following spoilage compounds: Guaiacol, 2,6-dichlorophenol (2,6-DCP) and 2,6-dibromophenol (2,6-DBP). The techniques of micro-solid phase extraction by headspace (HS-SPME) and gas-chromatography with mass spectrometry (GC-MS) were used to identify and quantify the spoilage compounds. All GC-MS data was analyzed by principal component analysis (PCA). The effects of different thermal shock conditions on the recovery of Alicyclobacillus spores inoculated in orange and apple juice (11°Brix) were also tested. A total of 484 strains were isolated from 48 brands, and the species A. acidocaldarius and A. acidoterrestris were the most found among all samples analyzed. In some samples from Argentina, the species A. vulcanalis and A. mali were also identified. The incidence of these two main species of Alicyclobacillus in this study was mainly in products from pear (n = 108; 22.3 %), peach (n = 99; 20.5 %), apple (n = 86; 17.8 %), and tomato (n = 63; 13 %). The results indicated that from the total isolates from Argentina (n = 414), Brazil (n = 54) and Italy (n = 16) were able to produce guaiacol: 107 (25.8 %), 33 (61.1 %) and 13 (81.2 %) isolates from each country, respectively. The PCA score plot indicated that the Argentina and Brazil isolates correlate with higher production of guaiacol and 2,6-DCP/2,6-DBP, respectively. Heatmaps of cell survival after heat shock demonstrated that strains with different levels of guaiacol production present different resistances according to spoilage ability. None of the Alicyclobacillus isolates survived heat shocks at 120 °C for 3 min. This work provides insights into the incidence, spoilage potential, and thermal shock resistance of Alicyclobacillus strains isolated from fruit-based products.

Diversity and metabolomic characterization of Penicillium expansum isolated from apples grown in Argentina and Spain.

Apples (Malus domestica) are one of the most consumed fruits globally. It is a relevant crop in Argentina and Spain, and one of the main fruits for export and industrialization in these countries. Quality control of apples, fundamentally in the postharvest stage, is critical to prevent fungal diseases. The blue mould, caused by Penicillium expansum, is responsible for great economic losses due to the deterioration of the fruit and mycotoxin production. Many studies have characterized this pathogen; however, little is known about the differences between populations from distant geographical origins. The objective of the present study was to characterize two P. expansum populations, from Argentina and Spain, through morphological, metabolomic and molecular approaches, and to evaluate the existence of differences related to their geographical source. A total of 103 isolates, 53 from Argentina and 50 from Spain were studied. Their morphological features were consistent with the species description. The secondary metabolite profiles revealed low chemical diversity. All 103 isolates shared the production of 13 compounds, namely andrastins, aurantioclavine, chaetoglobosins, communesins, expansolides, roquefortine C and patulin. Penostatins and citrinin were produced by 102 and 101 isolates, respectively. A region of the ß-tubulin gene was selected to analyse the diversity of the P. expansum isolates. No substantial differences were observed between isolates of different geographical origins through morphology, patulin accumulation, secondary metabolite profiles and phylogenetic analysis. However, the analysis of polymorphisms revealed 29 haplotypes with a relative separation between isolates of both populations; 13 haplotypes contained Argentinean isolates, while Spanish isolates were separated into 16 haplotypes. The diversity indices of Shannon (H'=2.075; H'=2.402) and Simpson (SiD = 0.850; SiD = 0.895) for isolates from Argentina and Spain, respectively, indicated that the diversity of P. expansum is greater in Spain than in Argentina. This distribution could be explained both by the existence of haplotype exchange between both countries, with the ancestral haplotypes originating in Spain, and the subsequent adaptation to the environmental conditions or apples varieties grown in each region.

Morphological and chemical characterization of Alternaria populations from apple fruit.

Alternaria is a frequent contaminant of apple fruit, causing severe economic losses. It can produce external lesions and mouldy core, characterised by a rotten area in the apple core. In the present study, morphological and chemical characterization of Alternaria from apples was performed, evaluating differences related to agricultural practices and type of disease. A low morphological diversity was observed; most of the isolates were identified as A. tenuissima sp.-grp. (95 %). A. arborescens sp.-grp. and A. gaisen sp.-grp. were present in a proportion of 1 %, and 3 % of the isolates showed intermediate characteristics between these sp.-grps. and were identified as Alternaria sp. The chemical diversity was greater; 27 secondary metabolites were produced by the apple isolates. The most frequents were altertoxin-I (85 %), altechromone A (76 %), tentoxin (69 %), and tenuazonic acid (68 %). The alternariols were produced in a lower frequency when comparing with isolates from other crops; alternariol, 58 % and alternariol monomethyl ether, 57 %. The predominant secondary metabolite profile included compounds from different chemical families, such as dibenzopyrones, tetramic acids, perylene quinones, and cyclic tetrapeptides. A wider metabolomic capacity was observed in isolates from conventional apples when compared to those from organic fruit, with the predominance of strong producers of altertoxins and alternariols. The isolates from mouldy core showed higher ability to produce metabolites from different chemical families than those from external lesions. The wide chemical diversity of the Alternaria apple population should be considered to assess the health risk associated with apple by-products.

Antibacterial activity of Ricinus communis plant extract against antibiotic resistant Helicobacter pylori and Gluconobacter oxydans isolated from fresh apple juices samples.

Bacteria were isolated from samples of Fresh Apple juices from shops of three different localities of Lahore. Analysis of samples from Liberty, Anarkali and Yateem khana Markets show different levels of contamination. There were pathogenic and non-pathogenic bacteria in all samples and were identified by the morphological and biochemical tests. Most of the plasmids of pathogenic bacteria were 4kb in their molecular size. Ribotyping of 16S ribosomal RNA gene sequencing was done to confirm Helicobacter pylori strain and Gluconobacter oxydans. The highest sensitivity of 210mm was shown by Enterobacter sp. against Aztheromysine disk (15µg) while Micrococcus sp. was highly resistant against all of the Antibiotics applied. The antibiotic resistance of pathogenic bacteria was also checked against Ricinus communis plant's extracts, all isolated bacterial pathogens were resistant but only, E.coli was inhibited at 300µl of the extracts. Presence of pathogenic bacteria in Apple juice samples was due to contamination of sewage water in drinking water while some of these pathogenic bacteria came from Apple's tree and other from store houses of fruits.

Kosakonia radicincitans and Cryptococcus laurentii controlled Penicillium expansum rot and decreased patulin production at 4 and 25 °C.

In the present work, we evaluated the effects of a mixture of biocontrol agents against two toxigenic strains of Penicillium expansum isolated in Argentine Patagonia from pome fruits. The two strains, INTA-5 and INTA-10, were previusly selected among ten strains coming from the Alto Valle (Rio Negro-Argentina) for their high production of patulin. For the biocontrol, Kosakonia radicincitans, Cryptococcus laurentii, and Rhodosporidium fluviale were tested in vitro experiments on Potato Dextrose Agar (PDA) dishes against the INTA-5 and INTA-10 strains. The bacterium K. radicincitans and the yeast C. laurentii were selected to be used in a mixture due to their capacity to control the fungus and reduce the mycotoxin severely. In vitro assays with the mixture showed a high antagonism against P. expansum INTA-5 and INTA-10, at 21 d of incubation at 25 °C and a patulin reduction of 98%. The mixture of microorganisms was also effective in apples stored at 25 °C for 10 d and 4 °C for 30 d. At cold storage, the mixture controlled moderately the development of rot and decreased patulin concentration. At 25 °C, the pathogen's optimal growth temperature, the mixture of Biological Control Agent (BCAs) assured both the control of rot and decrease of patulin concentration. The combination of two microorganisms, with different requirements and abilities, resulted in a mix with a strong antagonism against P. expansum with the capability to decrease the patulin concentration. Treatment with the selected mixture could be a good option for controlling strains with different behaviours and in different environmental conditions.

Use of non-Saccharomyces yeasts in cider fermentation: Importance of the nutrients addition to obtain an efficient fermentation.

The isolation of autochthonous yeast species presents a good strategy to select new microorganisms for developing an adequate inoculum to carry out fermentations and generate representative products of the cider production zone. However, non-Saccharomyces yeasts have been considered to have low capacity to carry out a complete fermentation as Saccharomyces cerevisiae. In this work, five autochthonous yeasts from a cider fermentation process were isolated and identified as Saccharomyces cerevisiae, Kluyveromyces marxianus, Pichia membranaefaciens, P. kluyveri and Zygosaccharomyces rouxii. A series of fermentations were developed at laboratory level, using each species individually and it was observed that only S. cerevisiae was able to finish the process. K. marxianus consumed less than 50% of the sugars; P. kluyveri and Z. rouxii consumed less than 70% and P. membranaefaciens consumed more than 90% but the yield (ethanol produced for sugar consumed (YP/S)) was 0.39. Nevertheless, the addition of magnesium, zinc and nitrogen increased the fermentative capacity of almost all species: K. marxianus, Z. rouxii and P. kluyveri, showed an increase in ethanol production when nutrients were added, obtaining more than 80 g/L of ethanol, and showing that those nutrients are necessary to complete the fermentation. This work describes the potential use of different non-Saccharomyces species to carry out fermentation of apple juice and highlights the importance of certain nutrients to enable an efficient alcoholic fermentation and the generation of desirable volatile compounds for cider production.

Evaluation of cryotolerant yeasts for the elaboration of a fermented pear beverage in Patagonia: Physicochemical and sensory attributes.

The production of pome fruits as pears and apples, as well as their derived industries, is of great economic importance in North Patagonia. The elaboration of fermented beverages as cider or perry has evidenced a substantial diversification during the last years, with the evaluation of different fruit varieties, yeast starters and technological changes. In this work, two cryotolerant yeasts belonging to the species Saccharomyces uvarum were evaluated at laboratory and pilot scale in sterile and no-sterile pear must. One of the strains was originally isolated from apple chicha (strain NPCC1314) and the other from apple cider (strain NPCC1420) in Patagonia. Both physicochemical and sensory features of the fermented products were evaluated. Both strains were able to successfully complete the fermentations, although strain NPCC1420 showed the better kinetic properties including a faster sugar consumption than the strain NPCC1314. Both strains showed excellent implantation capacity, but the fermented products showed different chemical profiles. The perry fermented with the strain NPCC1314 was characterized by better sensory attributes as assessed by trained panelists and a greater acceptance for untrained public than the same fermented with the strain NPCC1420. The two strains were able to consume sorbitol, both in pear must and in agar-plates supplemented with sorbitol as the sole carbon source. This ability is described for the first time in S. uvarum, at least for the two strains evaluated in this work.

Attachment and survival of bacteria on apples with the creation of a kinetic mathematical model.

The estimation of growth or inactivation of bacterial population in fruits during preservation and storage provides useful information for the improvement of the safety of fresh-cut fruits and vegetables. This paper addressed the attachment to the surface and the growth in the flesh of apple fruits of four bacterial cultures (Escherichia coli, Bacillus cereus, Staphylococcus aureus and Pseudomonas aeruginosa). The growth of the bacterial cultures in apple flesh was monitored at particular time intervals, and Gompertz parameters, i.e. maximum number of bacteria (Pm), the maximum growth rate of bacteria rp,m, and lag time tl, were used to determine the growth kinetics. After the immersion, the highest number of P. aeruginosa and the lowest number of B. cereus adhered to the apples. After washing and swabbing, E. coli was reduced from the surface of apples to the highest extent (by 3.34 log cfu g-1), while the number of B. cereus was reduced to the lowest extent (1.66 log cfu g-1). Fitted curves of the Gompertz model corresponded quite well to the measured values of the number of microorganisms with R2 = 0.92-0.98. The values of the standard error (0.17-0.37) and extremely low p values of the Fischer test (p < 0.0001) indicated strict dependence between the model predicted and the maximum population density. The predicted values of the maximum number of microorganisms (Pm) correspond almost exactly to the actual values. A similar conclusion can be drawn for the maximum growth rate of microorganisms (rp,m), with the measured value being slightly higher than predicted values.

Effects of combined application of high-pressure processing and active coatings on phenolic compounds and microbiological and physicochemical quality of apple cubes.

BACKGROUND: In recent years the use of high-pressure processing (HPP) of fruit products has steadily increased due to its antimicrobial effectiveness and the retention of nutritional and quality attributes compared to conventional thermal technologies. Edible coatings are already being used to enhance the quality of minimally processed fruits. Thus, apple cubes (AC) and alginate-vanillin-coated apple cubes (AVAC) were subjected to HPP (400 MPa/5 min/35 °C). The microbiological and physicochemical parameters were evaluated and the bioactive compounds were monitored before and after HPP of apple cubes. Also, an in vitro gastrointestinal digestion (GID) was conducted. RESULTS: HPP left L. monocytogenes counts below the detection limit (2 log UFC g-1 ), regardless of the presence of coating. For E. coli, HPP + active coating showed a synergism affording the greatest reduction (>5 log) for AVAC-HPP. Firmness was maintained in AVAC-HPP samples, while AC-HPP samples suffered reductions of 35%. Colour attributes were also better retained in AVAC-HPP samples. In general, HPP led to a decrease in phenolic compounds. Regarding the effects of GID, vanillin-based active coating exerted a protective effect on some phenolics. Thus, p-coumaroylquinic acid concentration was maintained for AVAC and AVAC-HPP during GID. Epigallocatechin, the compound with the highest concentration in apple cubes, increased for AVAC (106%) and AVAC-HPP (57%). Also, phloridzin concentration increased for AVAC-HPP (17%). At the end of GID, procyanidin B1 and epigallocatechin were the main phenolic compounds for all samples, AVAC showing the highest concentration. CONCLUSIONS: This work demonstrates that the combined application of HPP and active coatings on apple cubes could be used to obtain a safe and good-quality product. © 2021 Society of Chemical Industry.

Effect of pasteurization on Aspergillus fumigatus in apple juice: Analysis of the thermal and electric effects.

Fungal spoilage in fruit juices is a currently relevant issue considering that recent reports have found unacceptable fungal levels even after traditional pasteurization processes. Ohmic heating demonstrated to be a good alternative process to conventional pasteurization, as it can promote higher heating rates and additional cell damage in some scenarios (nonthermal effects). However, the application of ohmic processing for fungi inactivation has not been properly investigated. The objective of this study was to analyze the inactivation of Aspergillus fumigatus, a highly distributed fungi species, in apple juice by ohmic and conventional heating at 75, 80, 85, 90 and 94 °C. Predictive primary and secondary models were fitted and the Weibull-Mafart models were the most accurate to describe the experimental behavior considering the statistical indices applied. Statistical differences between both thermal processes were found in the three lower analyzed temperatures (75, 80 and 85 °C), which is possibly related to nonthermal effects. When ohmic heating was applied, processing time was up to 23% shorter. The resulted model was successfully validated in two distinct temperatures (83 and 92 °C) and could be applied to obtain adequate processing times for apple juice pasteurization. This study contributes to deepen the knowledge concerning the use of ohmic heating for fungi inactivation.

Modeling the inactivation of Aspergillus fischeri and Paecilomyces niveus ascospores in apple juice by different ultraviolet light irradiances.

The present work aimed to evaluate and to model the influence of UV-C light treatments with different irradiances (6.5, 13, 21, and 36 W/m2) on Aspergillus fischeri and Paecilomyces niveus ascospores inactivation in clarified apple juice. Approximately 5.0 and 6.0 log CFU/mL spores of P. niveus and A. fischeri, respectively, were suspended in 30 mL of clarified apple juice (pH 3.8, 12 ± 0.1°Brix) and exposed to UV-C light at different irradiances (as above) and exposure times (0 to 30 min). The first-order biphasic model was able to describe the experimental data with good statistical indices (RMSE = 0.296 and 0.308, R2 = 0.96 and 0.98, for P. niveus and A. fischeri respectively). At the highest irradiance level tested (36 W/m2), the UV-C light allowed the reduction of 5.7 and 4.2 log-cycles of A. fischeri and P. niveus ascospores, respectively, in approximately 10 min. P. niveus was the most UV-C resistant mould. The results showed that, to a defined UV-C fluence, a change in the level of either time or UV-C irradiance did not affect the effectiveness of UV-C light for A. fischeri and P. niveus inactivation. Thus, the modeling of the inactivation as a function of the UV-C fluence allowed the estimation of the primary model parameters with all experimental data and, consequently, no secondary models were needed. The model parameters were validated with experiments of variable UV-C fluences. Accordingly, experimental results allowed to conclude that UV-C treatment at the irradiances tested is a promising application for preventing A. fischeri and P. niveus spoilage of juices.

Poly(lactic acid) nanocapsules containing lemongrass essential oil for postharvest decay control: In vitro and in vivo evaluation against phytopathogenic fungi.

The increased demand for pesticide-free foods has also increased the search for healthier and environmentally friendly alternatives in agriculture. Essential oils are known to possess natural antifungal properties, becoming a reliable alternative for commercial fungicides, especially for postharvest decay control. However, essential oils are volatile and photodegradable, which reduces their long-term activities. This work presents the development of a lemongrass essential oil-containing poly(lactic acid) nanocapsules. They have shown in vitro antifungal activity against Colletotrichum acutatum and Colletotrichum gloeosporioides with a MIC dosage of 0.1% (v/v) for both phytopathogens. In the in vivo assay with postharvest apples, the ones treated with encapsulated essential oil showed bitter rot lesions three times smaller than the ones treated with non-encapsulated essential oil, or in comparison to the apples in positive control. The methodology led to stable nanocapsules with spherical morphology, a mean diameter of 96.4 nm, and with an encapsulation efficiency of 99%.

From field to process: How storage selects toxigenic Alternaria spp. causing mouldy core in Red Delicious apples.

Apple is a major crop in Argentina where 50% of the production is derived to by-products. Industries process either recently harvested apples or fruit stored for up to 9 months. This crop is susceptible to fungal diseases both external and internal, such as mouldy core (MC). The incidence of fungal pathogens changes during storage, as well as the risk associated with their presence since some contaminants belong to mycotoxigenic genera. The objective of this study was to characterize the fungal contaminants of Red Delicious apple fruit in Argentina evaluating their evolvement from field to process, with main interest on MC causal agents and mycotoxigenic species. A total of 240 apples were analysed; 140, recently harvested and intended for fresh consumption (C), and 100 stored for 9 months in a refrigerated chamber (0-3 °C) and destined to industrialization (I). The 86% of fresh consumption apples showed external fungal lesions, and only 14% were undamaged; MC incidence was 34%. High biodiversity was observed; Penicillium was the predominant genus (54%), followed by Alternaria spp. (41%). Only 3% of industrialization fruit were undamaged, 48% had external lesions and 51% MC. However, biodiversity was lower in these apples. Alternaria spp. was recovered from 60% of apples, mainly causing MC, while Penicillium spp. took second place (34%). All the Alternaria isolates belonged to Section Alternaria with A. tenuissima as the predominant species-group. Alternariol was synthesised by 75% of the isolates, while both alternariol monomethyl-ether and tenuazonic acid by 76%. From the 100 I apples, 93 were contaminated with at least one of these mycotoxins. Alternaria was the main causal agent of MC in Argentinean Red Delicious apples, and fruit affected by this disease might be incorporated into the process line, with a consequent risk of mycotoxin contamination in apple by-products.

The combined effect of high pressure processing and dimethyl dicarbonate to inactivate foodborne pathogens in apple juice.

Novel processing technologies can be used to improve both the microbiological safety and quality of food products. The application of high pressure processing (HPP) in combination with dimethyl dicarbonate (DMDC) represents a promising alternative to classical thermal technologies. This research work was undertaken to investigate the combined effect of HPP and DMDC, which was aimed at reaching over 5-log reduction in the reference pathogens Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes inoculated in apple juice. Different strains of each species were tested. The pressure (ranging from 100 to 600 MPa), dwell time (from 26 to 194 s), and DMDC (from 116 to 250 mg/L) were tested based on a central composite rotatable design. The dwell time, in the studied range, did not have a significant effect (p > 0.1) on the pathogens´ reduction. All treatments achieved a greater than 5-log reduction for E. coli O157:H7 and L. monocytogenes. The reductions for S. enterica were also greater than 5-log for almost all tested combinations. The results for S. enterica suggested that it is more resistant to HPP and DMDC compared with E. coli O157:H7 and L. monocytogenes. The findings of this study showed that DMDC at low concentrations can be added to apple juice to reduce the parameters conventionally applied in HPP. The combined use of HPP and DMDC was highly effective under the conditions of this study.

Pathogen Dispersal and Glomerella Leaf Spot Progress Within Apple Canopy in Brazil.

Glomerella leaf spot (GLS) of apple is caused by three different Colletotrichum species complexes. This study evaluated the dispersal of Colletotrichum spores related to GLS temporal progress and defoliation. Spores were monitored by air and water runoff in different plant heights, and the temporal progress of GLS and defoliation were assessed. Spores of the pathogen were first cached in the lower part of the tree closer to the ground, confirming the importance of dead leaves on the ground as main source of primary inoculum. In plots with high primary inoculum, the disease increases exponentially during favorable weather conditions. The highest initial inoculum was found in the lower part of the tree, but the highest rate of the disease progress in the upper.

Sensitivity of the Colletotrichum acutatum Species Complex From Apple Trees in Brazil to Dithiocarbamates, Methyl Benzimidazole Carbamates, and Quinone Outside Inhibitor Fungicides.

Glomerella leaf spot (GLS) and bitter rot (BR) on apples are often caused by Colletotrichum acutatum in Paraná State, Brazil. GLS control is difficult because of its rapid development, with an incubation period of only 2 days under favorable conditions. Therefore, producers use successive fungicide applications every season; however, failure to control GLS has been commonly reported. The objectives of this study were to determine the sensitivity of isolates of the C. acutatum species complex obtained from apple orchards in Brazil to mancozeb, thiophanate-methyl, and azoxystrobin fungicides. Isolates from the different parts of the plant (leaves, flowers, buds, and twigs) and cultivars (Gala and Eva) showed different levels of sensitivity to mancozeb, thiophanate-methyl, and azoxystrobin. For mancozeb, the frequencies of isolates were 25% highly resistant, 50% low-resistance, and 25% sensitive. For thiophanate-methyl, the frequencies of isolates were 72.2% highly resistant, 11.1% resistant, and 16.7% moderately resistant. For azoxystrobin, the frequencies of isolates were 11.1% highly resistant, 5.6% resistant, and 83.3% sensitive. Interestingly, no mutations in the ß-tubulin and cytochrome b genes were observed in any of the isolates resistant to thiophanate-methyl and azoxystrobin fungicides.

Effect of soluble solids concentration on Neosartorya fischeri inactivation using UV-C light.

Ascospores of Neosartorya fischeri are heat-resistant and can survive thermal commercial treatments normally applied to the juices, as apple juice. Non-thermal processing of food such as exposure to ultraviolet light (UV-C) is reported to induce minimal quality changes while reduces microbial load. The main objective of this study was to determine the effect at different soluble solids concentration (12, 25, 30, 40, 50, 60 and 70 °Brix) on N. fischeri ascospores inactivation in apple juice, using UV-C light intensity (38 W/m2). Weibull model was fitted to experimental data. Then, a secondary model was used to describe how the inactivation kinetic parameters varied with the changes in soluble solids concentration. Results showed that the UV-C light had influence on N. fischeri ascospores inactivation in apple juice even at the highest soluble solids concentrations used, reaching approximately 4 log reductions at all concentrations used. The inactivation parameters, obtained by Weibull model, were δ (dose for the first decimal reduction) and p (the shape factor). Exponential model was chosen to describe the influence of soluble solids concentration on δ and p parameters. It can be concluded that UV-C light is a promising treatment with a drastic impact on the loads of N. fischeri, especially when low soluble solids concentration is used and a model was obtained to describe Brix effect.

Control of Autochthonous Spoilage Lactic Acid Bacteria in Apple and Orange Juices by Sensorially Accepted Doses of Citrus Spp. Essential Oils Combined with Mild Heat Treatments.

This study assessed the compromised acceptance threshold (CAT) and rejection threshold (RT) of Citrus lemon (CLEO) and Citrus reticulata essential oil (CREO) in apple and orange juices. The efficacy of CLEO and CREO concentrations below the RT were evaluated alone and combined with mild heat treatment (MHT) (54 °C, up to 12 min) to inactivate the autochthonous spoilage bacteria Lactobacillus brevis, Lactobacillus plantarum, and Leuconostoc mesenteroides in apple and orange juices. The CAT of CLEO and CREO varied from 0.15 to 0.17 µL/mL in orange and apple juices. The RT of CLEO was approximately 0.58 µL/mL in apple and orange juices, and the RT of CREO was 0.68 µL/mL in both juices. When CLEO and CREO were assayed alone, the highest concentration (0.50 µL/mL) decreased counts of all strains approximately 2 log10 CFU/mL after 12 min of exposure to 54 °C. All concentrations of CLEO or CREO in combination with MHT acted synergistically against L. brevis, L. plantarum, and L. mesenteroides. Decreases in counts varied with the strain, CLEO and CREO concentrations, juice type, and exposure time to the combined treatment. CREO was more effective than CLEO in combination with MHT against the strains in apple and orange juices. Effective combinations of CLEO or CREO with MHT to control the autochthonous spoilage bacteria did not compromise the quality parameters (°Brix, pH, and titratable acidity) that characterize unsweetened juices. These results indicate CLEO or CREO at concentrations below the sensory RT in combination with MHT as a feasible technology to control autochthonous spoilage bacteria in fresh fruit juices. PRACTICAL APPLICATION: The present study provides novel information concerning the efficacy of sensorially accepted doses of CLEO and CREO combined with MHT against autochthonous spoilers in fruit juice. The valuable synergistic effects that can be observed when combining CLEO and CREO with MHT reveal a feasible preservation technology and alternative to traditional treatments that are successful because they help reduce treatment intensity, thereby avoiding adverse effects on the sensory, physicochemical, and nutritional properties of these products.

Antimicrobial effect of nisin electrospun amaranth: pullulan nanofibers in apple juice and fresh cheese.

Nisin-loaded amaranth protein isolate:pullulan (API:PUL) nanofibers were prepared by the electrospinning method. The nisin release kinetic was evaluated at pH 3.4 and 6.1 and the antimicrobial effectiveness of the electrospun mats was evaluated in apple juice and fresh cheese. The nisin API:PUL fibers with 120 nm average diameter reached 81.49% and 43.85% nisin release after 12 h at pH 3.4 and 6.1, respectively. The encapsulation of nisin in electrospun fibers allowed complete bactericidal activity against Salmonella Typhimurium, L. monocytogenes and L. mesenteroides inoculated in apple juice after 48, 20 and 48 h, respectively. When nisin API:PUL fibers were applied to fresh cheese, microorganism inactivation was complete after 142, 120 and 170 h, respectively. The results demonstrated that nisin API:PUL electrospun fibers significantly reduce the bacterial population and can be used in food products for microbiological safety.