Repetitive pulsed light treatment at certain interval on fresh-cut cantaloupe (Cucumis melo L. reticulatus cv. Glamour)

This study was done in order to investigate the effect of repetitive pulsed light (RPL) treatment at certain interval on microbiological stability, quality and physicochemical changes of fresh-cut cantaloupes during storage. Fresh-cut cantaloupes packed in polypropylene bag were exposed to RPL treatment with fluences of 0.3, 0.6, 0.9 and 1.2 J/cm² every 48 h up to 28 days of storage at 4 ± 1 °C. The microbiological quality, headspace gas composition, physical quality (firmness, fluid loss and colour), chemical quality (pH, titratable acidity, total soluble solids, total phenolic content and ascorbic acid content) and microscopic observations of fresh-cut cantaloupes were determined during storage. No significant (p > 0.05) effect was observed for firmness, colour and total soluble solids of fresh-cut cantaloupes treated with RPL throughout the storage study. Repetitive PL treatment using 0.9 J/cm² was the most effective fluence for extending the shelf life of fresh-cut cantaloupes with extension by 20 days compared to control in term of microbiological quality while maintaining all quality parameters. Negative effect of single PL treatment (SPL) (11.7 J/cm²) on tissue structure of fresh-cut cantaloupes during storage was minimised by applying RPL treatment (0.9 J/cm² for every 48 h interval).Industrial relevanceFresh-cut cantaloupes are becoming more popular due to the benefits of convenience and fresh-like quality provided. However, fresh-cut cantaloupes are susceptible to microbial contamination and deterioration as the fruit tissue is injured due to cutting of the product into pieces. Repetitive PL (RPL) treatment is an alternative application to single PL (SPL) treatment for extending shelf life of fresh-cut fruits by minimising the negative effect of SPL treatment on the tissue structure. This study demonstrates the usefulness of RPL treatment to further extend the shelf life of fresh-cut cantaloupes compared to SPL treatment. This is crucial for vending cut fruits through refrigerators equipped with RPL system. The RPL application contributes to reduced postharvest loss and increased convenience and availability of fresh-cut fruits to the public which benefit both producers and consumers.     

Adaptive self-configuring computer vision system for quality evaluation of fresh-cut radicchio

An innovative computer vision system (CVS) that extracts color features discriminating the quality levels occurring during fresh-cut radicchio storage in air or modified atmosphere packaging was proposed. It self-configures the parameters normally set by operators and completely automates the following steps adapting to the specific product at hand: color-chart detection, foreground extraction and color segmentation for features extraction and selection. Results proved the average value of a^⁎ over the white part and the percentage of light white with respect to the whole visible surface to be the most discriminating color features to significantly separate (P ≤ 0.05) the three desired quality levels (high, middle and poor) occurring during fresh-cut radicchio storage (whose true value was verified on the base of ammonium content and human evaluated visual quality). The proposed procedure significantly simplifies the CVS design and the optimization of its performance, limiting the subjective human intervention to the minimum.Industrial relevanceThe non-destructive quality control represents a valuable tool to monitor fruits and vegetables along the whole chain from production to the end-user. Increased consumers' satisfaction and reduction of waste are only two examples of benefits that can come from a frequent and consistent control of food. CVS represents the most powerful and flexible way to reach these results. The current state-of-the-art makes their design strongly related to the specific product at hand. Thresholds and features are characteristics that play a critical role in determining the final performance of the system but are generally set by designers or operators using a-priori knowledge and/or trial-and-error processes. The proposed innovative procedure allows the CVS to self-configure most of these parameters and to easily adapt to different products regardless of the number and kind of colors associated to their surface. It results of practical applications in food processing, providing a non-destructive, automatic, cheap, fast and simple technology for the quality level evaluation, whose configuration requires a reduced, less critical and less technical human intervention.     

Effect of calcium lactate and heat-shock on texture in fresh-cut lettuce during storage

Textural and microstructural changes in fresh-cut lettuce were analysed over 12 days storage. The vegetable was treated with 120 ppm chlorine and with 15 g/L calcium lactate at room temperature (∼18–20 °C) and at 50 °C (heat-shock). Texturometer analysis showed that samples washed with calcium lactate had significantly (p > 0.05) higher crispness values than samples washed with chlorine. However the use of 50 °C treatment (heat-shock) gave better textural properties at the end of storage and significantly retarded the softening process, being in agreement with the sensorial results. Cryo-SEM micrographs showed a loss of turgor (shrinkage) of the tissue cells in the samples washed with chlorine, effect not so evident in calcium lactate treated samples. The use of heat-shock in combination with calcium lactate reduced this phenomenon better than the other two treatments. Pectin methyl esterase (PME), enzyme related to textural changes, showed higher activity in samples treated with calcium lactate at 50 °C. The combination of calcium lactate and 50 °C washing temperature maintained objective and sensorial textural properties of fresh-cut lettuce better than the calcium lactate or chlorine washing treatments at room temperature.     

Nitric oxide prevents wound-induced browning and delays senescence through inhibition of hydrogen peroxide accumulation in fresh-cut lettuce

As a source of bioactive ingredients, lettuce is a preferable component of a healthy diet. In recent years the production of fresh-cut produce has become a fast growing business. However, the shreds are highly sensitive to wound-induced browning and premature senescence that substantially reduces the visual and sensory qualities and shortens the shelf life. To improve the fresh-cut quality, in this work, short pre-storage exposure of shreds from butterhead and iceberg lettuce to nitric oxide (NO) gas was applied. It was found that fumigation with 100 and 200 ppm NO for 1 or 2 h remarkably inhibited the browning of the cut surface and of other injured leaf areas; NO treatment delayed the senescence and substantially prolonged the shelf life upon storage at 4 °C and 12 °C. To obtain information on the physiological processes involved in the wound response, the generation of hydrogen peroxide (H₂O₂) and the occurrence of cell death were analyzed. The results revealed that the wounding stimulated the accumulation of H₂O₂ thus generating oxidative stress leading to cell death. A correlation between elevated H₂O₂ levels, cut surface browning, senescence and storability of the fresh-cuts was established. In comparison to mature leaves, younger leaves expressed a lesser susceptibility to wound-induced browning and the associated oxidative stress. Applied NO strongly inhibited the H₂O₂ accumulation which may explain its beneficial effects.Industrial relevanceWe demonstrate that short treatments with NO gas substantially inhibit wound-induced browning and largely improve the storability of fresh-cut lettuce. This offers an option for adopting NO treatments for optimization of the post-processing conditions. Implementation of reported findings into practice will offer innovative technological solutions for improvement of the post-harvest quality of fresh-cut lettuce applicable for the industry, distributors and retailers. Moreover, our findings indicate that the browning disorder is to a large extent dependent on the severity of the wound-induced oxidative stress and cell death occurrence. This discovery opens a possibility for the development of metabolic and morphological markers appropriate for the prediction of the quality and shelf life of fresh-cut lettuce with perspective for expanding the research and introducing the tests toward other perishable leafy vegetables.     

Quality assessment of blueberries by computer vision

Blueberry's main quality indicators associated to consumer acceptability are related to the fruit appearance and texture. To date, appearance quality assessment is determined subjectively using visual observation. Computer vision analysis is an useful tool to evaluate fruit optical properties. The objective of this work was to study quality indicators for different blueberry cultivars hand-harvested in Chile during storage using computer vision. Five cultivars were analyzed: Briggitte, Duke, Elliot, Centurion and Star; 50 individual fruit from these cultivars were stored at 4 °C and 15 °C during 21 days at 90% of relative humidity. Quality indicators: colour, presence of epicuticular wax (EW), size, dehydratation and microbial growth were determined through image analysis obtained by computer vision. Different values of each quality attribute were obtained between cultivars. Dehydratation values (measured as sample size changes during storage) at 15 °C were 2.7 and 39.6% for Briggitte and Centurion, respectively. EW presence for all was lower of 33% of the surface, which is the minimum for export, except to cv. Briggitte (75%), which was associated to low dehydratation. Colour measured with CIEL*a*b* scale showed changes from blue to red for all cultivars at both temperatures during storage. Fungal presence increased at higher temperatures, which was represented by an increased lightness. The implication of this work is that computer vision analysis is useful to objective quality evaluation of fruits such as colour, dehydratation signs and fungal growth - most important attributes for consumers- and epicuticular wax presence, which is important to protect against deteriorative changes during storage, allowing heterogeneous materials analysis and their possible application in on-line packing control.     

Calcium lactate washing treatments for salad-cut Iceberg lettuce: Effect of temperature and concentration on quality retention parameters

Salad-cut lettuce was washed in calcium lactate solution at different concentrations (0.5%, 1.5% and 3%) and temperatures (4, 25 and 50 °C) for a period of 1 min. The treated salad-cut lettuce was packaged and stored at 4 °C for 10 days. Markers of quality retention: colour, texture, browning, texture related enzymes and sensory properties, were analysed during storage. The use of high temperatures (50 °C) showed a positive effect on enzymes related to quality maintenance. It reduced the activity of the browning-related enzymes polyphenol oxidase and peroxidase but it increased the activity of pectin methyl esterase, an enzyme involved in the maintenance of texture. High calcium lactate concentrations (3%) produced a reduction in the respiration rate of the salad-cut lettuce during storage, but also a loss of luminosity and greenness (a*). The use of high temperatures and intermediate calcium lactate concentrations (1.5%) proved to be the best washing treatment to maintain the quality of salad-cut lettuce over 10 days storage. These conditions (50 °C and 1.5% calcium lactate) gave higher freshness scores and lower browning scores than conventional chlorine treatment when evaluated by a sensory panel.     

Colour and texture of apples high pressure processed in pineapple juice

Cubes of Granny Smith and Pink Lady apples were vacuum packed in barrier bags with 0% to 50% (v/v) pineapple juice (PJ) at 20°Bx and subjected to high pressure processing (HPP) at 600 MPa for 1–5 min (22 °C). The in-pack total colour change (ΔE) was observed over 4 weeks at 4 °C. Within <1 week of storage at 4 °C, texture, polyphenoloxidase, pectinmethylesterase activities, changes in ΔE and visual browning after opening the bags during air exposure (22 °C; 21% O2 ) for 5 h were also monitored. During the 4 weeks storage in bag visible colour changes were not observed. Texture and ΔE after 5 h air exposure were significantly affected by the apple variety, HPP time and % PJ used. The combined treatment significantly reduced residual PPO activity while PME activity was not affected in both varieties. Pineapple juice in combination with HPP could be used as a natural preservation system for minimally processed apples.Industrial relevanceBrowning upon opening the packs and during air exposure can adversely affect the quality of fresh-cut fruits. Combined treatment of high pressure processing (HPP) and use of pineapple juice has the potential to prevent browning for several hours giving sufficient time for presentation and use in domestic and foodservice environment where high quality fresh-like fruit is required.     

Impact of pulsed light treatments on antioxidant characteristics and quality attributes of fresh-cut apples

The effects of pulsed light (PL) treatments combined with a quality-stabilizing dip on the quality and antioxidant attributes of fresh-cut ‘Golden delicious’ apples was studied. Apple wedges were dipped into a solution of 1% w/v N-acetylcysteine and 0.5% w/v CaCl₂ and flashed with broad-spectrum light with an overall radiant exposure of 4, 8, 12 and 16 J^.cm⁻². General microbial counts, colour, firmness, phenolic compounds and vitamin C contents were evaluated over 15 days at 5 °C. More pronounced reductions of the naturally-occurring microbiota were observed as the applied PL-dose increased. The quality-stabilizing pre-treatment effectively prevented browning phenomena on the cut-tissue surface. In addition, browning and oxidation were not promoted in PL flashed samples. Indeed, the initial contents in phenolic compounds and vitamin C were even better maintained than in untreated samples. Treatments of 8 and 16 J cm⁻² were most effective for maintaining the quality and antioxidant characteristics.Industrial relevancePulsed light technology is an emerging technique with good prospects for the decontamination of foods and food contact surfaces. Application of pulse light treatments for increasing safety and extending microbial shelf life of fresh-cut produce seems feasible. However, their effects on the quality and antioxidant characteristics of fruit need to be evaluated for successfully applying the technology at an industrial level.     

Microbial safety considerations of flooding in primary production of leafy greens: A case study

This study evaluated the effects of a flood event, floodplain and climatic parameters on microbial contamination of leafy greens grown in the floodplains. Additionally, correlations between pathogenic bacteria and levels of indicator microorganisms have been also determined. To diagnose the microbial contamination after the flood event, sampling was carried out in weeks 1, 3, 5 and 7 after the flooding in four flooded lettuce fields. To assess the impact of flooding on the microbial contamination of leafy greens, indicator microorganisms (coliforms, Escherichia coli and Enterococcus) and pathogenic microorganisms (Salmonella spp., VTEC (E. coli O157:H7 and other verocytotoxin producing E. coli, O26, O103, O111, O145) and Listeria monocytogenes) were evaluated. Irrigation water, soil and lettuce samples showed levels of coliforms and E. coli higher than 5 and 3 log cfu/g or 100 mL, respectively when sampled 1 week after flooding. However, bacterial counts drastically declined three weeks after the flooding. Climatic conditions after flooding, particularly the solar radiation (6–8 MJ/m²), affected the survival of bacteria in the field. L. monocytogenes was not detected in lettuce samples, except for 2 samples collected 3 weeks after the flooding. The presence of Salmonella was detected in irrigation water, soil and lettuce by multiplex PCR one week after the flooding, but only 2 samples of soil and 1 sample of water were confirmed by colony isolation. Verotoxigenic E. coli was detected in soil and lettuce samples by multiplex PCR. Therefore, the implication of flood water as the source of VTEC contamination of soil and lettuce was not clear. E. coli counts in irrigation water were positively correlated with those in lettuce. A significant correlation (P < 0.005) was found between the presence of pathogens and E. coli counts, highlighting a higher probability of detection of pathogens when high levels of E. coli are found. The results obtained in the present study confirm previous knowledge which defined flooding as a main risk factor for the microbial contamination of leafy greens.     

Prediction of beef eating quality from colour,marbling and wavelet texture features

Beef longissimus dorsi colour, marbling fat and surface texture are long established properties that are used in some countries by expert graders to classify beef carcasses, with subjective and inconsistent decision. As a computer vision system can deliver objective and consistent decisions rapidly and is capable of handling a greater variety of image features, attempts have been made to develop computerised predictions of eating quality based on these and other properties but have failed to adequately model the variation in eating quality. Therefore, in this study, examination of the ribeye at high magnification and consideration of a broad range of colour and marbling fat features was used to attempt to provide better information on beef eating quality. Wavelets were used to describe the image texture of the beef surface at high magnification rather than classical methods such as run lengths, difference histograms and co-occurrence matrices. Sensory panel and Instron analyses were performed on duplicate steaks to measure the quality of the beef. Using the classical statistical method of partial least squares regression (PLSR) it was possible to model a very high proportion of the variation in eating quality (r² = 0.88 for sensory overall acceptability and r² = 0.85 for 7-day WBS). Addition of non-linear texture terms to the models gave some improvements.     

Chemical,instrumental and sensory characteristics of cooked pork ham

Instrumental, chemical and sensory parameters of cooked pork ham were evaluated. Principal component analysis was carried out on the basis of the instrumental variables related to colour and texture. The four PCs account for almost 94% of the total variance in the data set. The PCA only separated 3 hams with a¹ > 10. Hardness was correlated with non-collagen muscle protein (P ⩽ 0.01), gumminess (P ⩽ 0.01) and ash (P ⩽ 0.05). Sensory evaluated tenderness showed positive significant correlation with L¹ (P ⩽ 0.01). The most important colour parameter seems to be a¹, which was negatively correlated with sensory evaluated parameter colour (P ⩽ 0.01). The PCA performed on all parameters (sensory, chemical and textural) discriminated two groups of hams differing in non-collagen muscle protein content and hardness.     

Effect of immersion solutions on shelf-life of minimally processed lettuce

Prior to detailed quality and physiology evaluations, different immersion solutions (SIs) were analysed by means of a nontrained sensory panel. Each SI (calcium chloride, pectin, potassium sorbate, garlic extract and citric acid) was analysed at three concentrations. Based on at least 70% acceptance, the best mixed SI (P<0.05) was determined to be 2 g/L citric acid, 1 g/L calcium chloride and 250 g/L garlic extract (SI). The control treatment was washed only with 0.05 g/L active chlorine. Treated lettuce was stored at 5°C in darkness in sealed polypropylene bags, for 9 days. Some senescence indicators (weight loss, colour), certain enzymes related to colour (chlorophyllase and polyphenoloxidase), and a nutrient (ascorbic acid), were measured during storage. SI showed a positive effect on shelf-life of minimally processed lettuce, controlling enzymatic browning, chlorophyllase activity and weight loss. The microorganisms growth was not significantly controlled, but the fact that the organoleptic results of SI-treated lettuce showed about 80% acceptability during 9 days of storage, suggests that some slight modifications on SI could be the basis of a promising formula for minimally processed lettuce.     

Cold plasma treatment for fresh-cut melon stabilization

The aim of this study was to evaluate the effect of gas plasma treatment on fresh-cut melon stability during controlled storage. Plasma treatments of 15 + 15 and 30 + 30 min were conducted on fresh cut melon using a dielectric barrier discharge (DBD) generator. Samples were packed and stored for 4 days at 10 °C and evaluated for qualitative, metabolic and microbiological indexes. Qualitative parameters of fresh-cut melon (titratable acidity, soluble solid content, dry matter, colour, texture) were only weakly affected by plasma treatment. Peroxidase (POD) and pectin methylesterase (PME) activities were slightly inhibited by the treatment up to respectively about 17 and 7%. Tissue metabolic heat production decreased proportionally to the treatment duration, while a partial conversion to anaerobic metabolism was observed. Microbial results showed that a significant increase in microbial shelf-life was achieved following the 15 + 15 min plasma treatment due to a delayed growth of spoilage mesophilic and psychrotrophic microflora.Industrial relevanceThe demand for fresh-cut products characterized by high qualitative and nutritional values and an acceptable shelf-life has promoted the research for non-thermal treatments.Fresh-cut melon is considered to be highly perishable and potentially hazardous food because it can support the growth of spoilage microflora and several pathogens.Cold plasma has shown its potentiality as an antimicrobial treatment and has been tested on different food products, but the impact on product quality and metabolism is still scarcely known.The results obtained in this study contributed to deepen the knowledge on the effect of plasma treatment on microbial, qualitative and metabolic aspects of fresh-cut melon.     

Microstructural and morphological behaviors of asparagus lettuce cells subject to high pressure processing

To explore the mechanisms of texture change under high pressure (HP) processing, the effects of different pressures on cell microstructure and cell morphological behaviors of asparagus lettuce were investigated using different microscopy approaches. Pectin immunofluorescence labeling was adopted to analyze cell morphological change in vivo by in situ visualization of cell wall. Image analysis showed that cells in asparagus lettuce treated at lower pressures (100 MPa, 200 MPa and 300 MPa) exhibited rounder and smaller than the untreated samples. However, the shapes of cells in asparagus lettuce treated at 500 MPa were close to the control. The in situ analysis on pectin distribution by CLSM indicated that pectin was mainly restricted in the corners of tricellular junctions in the samples treated at 200 MPa and 300 MPa, whereas pectin uniformly distributed around the whole cell wall at 500 MPa. The results of cell activity staining were consistent with that of ultrastructure change of cell wall and membrane observed by TEM, which suggested that plasma membrane was ruptured at the pressure of 200 MPa, 300 MPa and 500 MPa. Meanwhile, the integrity of cell wall structure was retained under all HP conditions. Based on the above results, a 7-cell tissue model has been proposed to show the cell morphological behavior. On the one hand, moderate HP (100 MPa–300 MPa) caused an initial texture loss of asparagus lettuce tissue, probably due to the loss of turgor pressure and the loose skeleton of cell wall. On the other hand, HP (500 MPa) caused less apparent texture loss of asparagus lettuce due to the unchanged pectin distribution, which can maintain the rigid and flexible cell wall.     

Modelling kinetics of watercress (Nasturtium officinale) colour changes due to heat and thermosonication treatments

Watercress (Nasturtium officinale) colour changes due to blanching by heat and a combined treatment of heat/ultrasound (thermosonication) were studied in the temperature range of 82.5 to 92.5 °C. The application of thermosonication was intended to enable less severe blanching treatments and, therefore, improve the quality of the blanched product. The thermosonication blanching processes promoted changes of the green colour (aⁿ parameter) at a higher rate (P < 0.05), when compared with the heat blanching processes. No significant differences (P > 0.05) were detected between heat and thermosonication blanching processes in terms of the colour parameters Lⁿ, bⁿ and TCD changes. In both treatments, a fractional first order model fitted well the experimental data for Lⁿ, aⁿ and bⁿ (R_H² = 0.99; R_Ts² = 0.99) and TCD (R_H² = 0.92; R_Ts² = 0.96) colour parameters.The chlorophylls content showed no significant differences (P > 0.05) between thermally treated and thermosonicated watercress samples.The present findings will help to evaluate the effectiveness of thermosonication as a novel process to replace the classical heat treatment.Industrial relevanceConventional blanching commonly results in severe losses or destruction of nutrients due to process intensity and extended process times. Consequently, the attempts to use the synergistic effects of heat and ultrasound (at least) for enzyme inactivation are of high relevance. The results, although not conclusive, indicate, that they may aid optimization of blanching processes.     

Identification,quantification and comparison of the principal bioactive compounds and external quality parameters of two broccoli cultivars

In this research work, we aim to identify, quantify and compare the phytochemical such as vitamin C, carotenoid and chlorophyll pigments, phenolic compounds and intact glucosinolates, as well as the in vitro antioxidant activity and physical quality parameters (colour, firmness, moisture contents, weight/broccoli head and soluble solid contents) of Monaco and Parthenon broccoli cultivars. We found that the bioactive compounds were more abundant in Parthenon compared with Monaco. In fact, higher amount of chlorophylls (12.62 mg/100 g fresh weight), total phenolic compounds (147.15 mg chlorogenic acid equivalent/100 g fresh weight), and total intact glucosinolates (203.85 μmol of sinigrin equivalent/100 g fresh weight) were found in Parthenon. On the other hand, no significant differences were observed in terms of external quality parameters among the studied cultivars except in the colour and moisture contents.     

Conventional freezing plus high pressure–low temperature treatment: Physical properties,microbial quality and storage stability of beef meat

Meat high-hydrostatic pressure treatment causes severe decolouration, preventing its commercialisation due to consumer rejection. Novel procedures involving product freezing plus low-temperature pressure processing are here investigated. Room temperature (20 °C) pressurisation (650 MPa/10 min) and air blast freezing (−30 °C) are compared to air blast freezing plus high pressure at subzero temperature (−35 °C) in terms of drip loss, expressible moisture, shear force, colour, microbial quality and storage stability of fresh and salt-added beef samples (Longissimus dorsi muscle). The latter treatment induced solid water transitions among ice phases. Fresh beef high pressure treatment (650 MPa/20 °C/10 min) increased significantly expressible moisture while it decreased in pressurised (650 MPa/−35 °C/10 min) frozen beef. Salt addition reduced high pressure-induced water loss. Treatments studied did not change fresh or salt-added samples shear force. Frozen beef pressurised at low temperature showed L, a and b values after thawing close to fresh samples. However, these samples in frozen state, presented chromatic parameters similar to unfrozen beef pressurised at room temperature. Apparently, freezing protects meat against pressure colour deterioration, fresh colour being recovered after thawing. High pressure processing (20 °C or −35 °C) was very effective reducing aerobic total (2-log₁₀ cycles) and lactic acid bacteria counts (2.4-log₁₀ cycles), in fresh and salt-added samples. Frozen + pressurised beef stored at −18 °C during 45 days recovered its original colour after thawing, similarly to just-treated samples while their counts remain below detection limits during storage.     

Effects on Escherichia coli inactivation and quality attributes in apple juice treated by combinations of pulsed light and thermosonication

Pulsed light (PL) and Thermosonication (TS) were applied alone or in combination using a continuous system to study their effect on Escherichia coli inactivation in apple juice. Selected quality attributes (pH, °Brix, colour (L, a, b, ΔE), non-enzymatic browning (NEBI) and antioxidant activity (TEAC)) were also evaluated pre- and post-processing. Two PL (360 μs, 3 Hz) treatments were selected and the juice exposed to energy dosages of 4.03 J/cm² (‘low’ (L)) and 5.1 J/cm² (‘high’ (H)) corresponding to 51.5 and 65.4 J/mL, respectively. The juice was also processed by TS (24 kHz, 100 μm) at 40 °C for 2.9 min (L) or 50 °C for 5 min (H), corresponding to 1456 and 2531 J/ml energy inputs, respectively. The effect of the resulting four energy levels and sequence (PL + TS and TS + PL) was studied. When the technologies were applied individually the maximum reduction achieved was 2.7 and 4.9 log CFU/mL (for TS (H) and PL (H) respectively), while most of the combined treatments achieved reductions in the vicinity of 6 log CFU/mL, showing an additive effect for both technologies when acting in combination, regardless of the sequence applied. All treatments significantly changed the colour of apple juice and the sequence in which the technologies were applied affected colour significantly (P < 0.05). The energy level applied did not affect any of the measured quality attributes.     

Vanillin inhibits pathogenic and spoilage microorganisms in vitro and aerobic microbial growth in fresh-cut apples

The antimicrobial effect of vanillin against four pathogenic or indicator organisms; Escherichia coli, Pseudomonas aeruginosa, Enterobacter aerogenes, and Salmonella enterica subsp. enterica serovar Newport and four spoilage organisms; Candida albicans, Lactobacillus casei, Penicillum expansum, and Saccharomyces cerevisiae that could be associated with contaminated fresh-cut produce, was examined. The minimal inhibitory concentration (MIC) of vanillin was dependent upon the microorganism and this ranged between 6 and 18 mM. When incorporated with a commercial anti-browning dipping solution (calcium ascorbate, NatureSeal™), 12 mM vanillin inhibited the total aerobic microbial growth by 37% and 66% in fresh-cut ‘Empire’ and ‘Crispin’ apples, respectively, during storage at 4 °C for 19 days. Vanillin (12 mM) did not influence the control of enzymatic browning and softening by NatureSeal. These results provide a new insight for vanillin as a potential antimicrobial agent for refrigerated fresh-cut fruits and vegetables.     

The effect of high hydrostatic pressure on the microbiological quality and physical–chemical characteristics of Pumpkin (Cucurbita maxima Duch.) during refrigerated storage

Pumpkins were processed at high hydrostatic pressure (HHP) ranging from 350 to 550 MPa for 0.5 min to 30 min. Two different nonlinear mathematical models were compared to fit the inactivation kinetics. The second model consistently produced better fits to the inactivation data than the first model (Weibull model). According to the inactivation of microorganisms, pumpkin was subjected to 450 MPa/15 min and 550 MPa/10 min. The microbiological and physicochemical changes in pumpkin subjected to (HHP) and thermal-treated (854 °C/5 min) were compared during 4 °C storage. The total plate counts (TPC) treated with thermal processing, 450 MPa/15 min and 550 MPa/10 min were 5.12, 4.02 and 1.71 log₁₀ CFU/g, respectively on the 60th day. The growth of microorganisms caused the increase in ΔE, decrease in hardness in other treatments. Treatment of 550 MPa for 10 min had little effect on color during storage. There were no significant changes in the L^⁎, a^⁎ and b^⁎ values (p > 0.05). The hardness of pumpkin treated with 550 MPa/10 min decreased by 32.28% after 60 days. A greater retention of the original color, Vc and antioxidant capacity and increased total phenols were observed in 550 MPa/10 min-treated samples immediately after processing. During storage, color changed, Vc content, total phenols and the antioxidant activity were decreased. While the soluble solids content (SSC), sugars and pH value of pumpkin with HHP or thermal treatment did not show significant change immediately during 60-day storage. Based on these results, working at 550 MPa for 10 min ensures physicochemical and high standard of sanitation parameters in pumpkin.Industrial relevancePumpkin (Cucurbita maxima Duch.) is one of the popular vegetables, and fresh-cut pumpkin requires strict processing treatment and storage conditions to protect its quality. HHP is one promising novel non-thermal technique and is likely to replace thermal processes. A better knowledge of effects of storage temperature on the quality of HHP-treated pumpkin and its storage time prediction through microbiological quality and physical–chemical characteristics analysis of these changes is necessary. The available data would provide technical support for commercial application of the HHP technique in fresh-cut pumpkin processing.