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Yaguang Luo - One of the best experts on this subject based on the ideXlab platform.
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Genome Sequences of Brevundimonas naejangsanensis Strain FS1091 and Bacillus amyloliquefaciens Strain FS1092, Isolated from a Fresh-Cut-Produce-Processing Plant
Microbiology resource announcements, 2020Co-Authors: Narjol Gonzalez-escalona, Yaguang Luo, Jie Zheng, Samantha Bolten, Abdullah I. Mafiz, Maria Sanchez Leon, Xiangwu NouAbstract:ABSTRACT The complete genome sequences of Brevundimonas naejangsanensis strain FS1091 and Bacillus amyloliquefaciens strain FS1092, which were isolated from a commercial Fresh-Cut-Produce-processing facility, were determined. Both FS1091 and FS1092 have one circular chromosome of approximately 3.15 and 4.24 Mb, respectively.
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Dynamic changes in the physicochemical properties of Fresh-Cut Produce wash water as impacted by commodity type and processing conditions.
PloS one, 2019Co-Authors: Zi Teng, Bin Zhou, Ellen R Turner, Shihchi Weng, Bryan T. Vinyard, Yaguang LuoAbstract:Organic materials in Fresh-Cut Produce wash water deplete free chlorine that is required to prevent pathogen survival and cross-contamination. This research evaluated water quality parameters frequently used to describe organic load for their fitness to predict chlorine demand (CLD) and chemical oxygen demand (COD), which are major needs identified by the industry-led Produce food safety taskforce. Batches of romaine lettuce, iceberg lettuce, or carrot of different cut sizes and shapes were washed in 40 liters of water. Physicochemical properties of wash water including CLD, COD, total organic carbon (TOC), total suspended solids (TSS), total dissolved solids (TDS), turbidity, total sugar content, and pH, were monitored. Results indicate that pH is primarily commodity dependent, while organic load is additionally impacted by cutting and washing conditions. Significant linear increases in COD, TOC, CLD, TDS, and turbidity resulted from increasing product-to-water ratio, and decreasing cut size. Physicochemical parameters, excluding pH, showed significant positive correlation across different cut sizes within a commodity. High correlations were obtained between CLD and COD and between COD and TOC for pooled products. The convenient measurement of TDS, along with its strong correlation with COD and CLD, suggests the potential of TDS for predicting organic load and chlorine reactivity. Finally, the potential application and limitation of the proposed models in practical Produce processing procedures are discussed extensively.
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association between bacterial survival and free chlorine concentration during commercial fresh cut Produce wash operation
Food Microbiology, 2018Co-Authors: Yaguang Luo, Bin Zhou, Sam Van Haute, Xiangwu Nou, Boce Zhang, Zi Teng, Ellen R Turner, Qin Wang, Patricia D MillnerAbstract:Determining the minimal effective free chlorine (FC) concentration for preventing pathogen survival and cross-contamination during Produce washing is critical for developing science- and risk-based food safety practices. The correlation between dynamic FC concentrations and bacterial survival was investigated during commercial washing of chopped Romaine lettuce, shredded Iceberg lettuce, and diced cabbage as pathogen inoculation study during commercial operation is not feasible. Wash water was sampled every 30 min and assayed for organic loading, FC, and total aerobic mesophilic bacteria after chlorine neutralization. Water turbidity, chemical oxygen demand, and total dissolved solids increased significantly over time, with more rapid increases in diced cabbage water. Combined chlorine increased consistently while FC fluctuated in response to rates of chlorine dosing, product loading, and water replenishment. Total bacterial survival showed a strong correlation with real-time FC concentration. Under approximately 10 mg/L, increasing FC significantly reduced the frequency and population of surviving bacteria detected. Increasing FC further resulted in the reduction of the aerobic plate count to below the detection limit (50 CFU/100 mL), except for a few sporadic positive samples with low cell counts. This study confirms that maintaining at least 10 mg/L FC in wash water strongly reduced the likelihood of bacterial survival and thus potential cross contamination of washed Produce.
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Can UV absorbance rapidly estimate the chlorine demand in wash water during Fresh-Cut Produce washing processes?
Postharvest Biology and Technology, 2018Co-Authors: Sam Van Haute, Yaguang Luo, Bin Zhou, Zi Teng, Qin Wang, Imca Sampers, L. Mei, Ellen R. Bornhorst, Patricia D MillnerAbstract:Abstract Free chlorine is used in industrial Fresh-Cut Produce washing to avoid cross-contamination from pathogenic and spoilage microorganisms, although chlorine dosing typically depends on feedback control. Control of free chlorine levels in Fresh-Cut Produce wash water could be improved if chlorine demand (CLD) could be determined real-time, during processing. Previous research has shown that the CLD of non-chlorinated fresh Produce wash water (CLDmax) correlates with UV absorbance (UVA) at 254 nm (UVA254). The goal of this study was to estimate CLD for Produce wash conditions that are in-progress, i.e., when the chlorine concentration in water partially meets the CLD, as is the case during industrial, continuous Produce washing. This was done for cabbage, carrot, green leaf lettuce and onion. UVA changed with both CLDmax and remaining CLD. Two wavelengths were necessary to predict the CLD:UVAmin, which changed minimally due to chlorination and had maximum correlation with CLDmax and UVAmax. The CLDmax and UVAmax changed maximally with chlorination and had maximum correlation with the fraction of the remaining CLD. Results showed that UVAmin and UVAmax were between 240–290 nm, and the exact wavelength depended on the vegetable. However, free chlorine itself influences UVA, and at a residual above 25 mg/L the chlorine interfered with the estimation of CLD. A case study on green leaf lettuce showed that CLD can be predicted by a model of the form f(UVAmin) x g(UVAmax /UVAmin). Using external validation data, optimal predictability of the model was obtained when both f and g were expressed as quadratic equations (SD/RMSE = 3.55; R² = 0.93). The described UVA method for predicting CLD shows promise for online application. Further studies should incorporate the possible variability in crop composition as well as other possible interferences with the UVA signal.
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Immersion-free, single-pass, commercial Fresh-Cut Produce washing system: An alternative to flume processing
Postharvest Biology and Technology, 2018Co-Authors: Ellen R. Bornhorst, Yaguang Luo, Bin Zhou, Xiangwu Nou, Ellen R Turner, Bryan T. Vinyard, Eunhee Park, Patricia D MillnerAbstract:Abstract Fresh-Cut vegetable processing in the USA typically involves submerging Produce in chlorinated water that is often reused and re-circulated. However, this washing practice is water and chemical intensive and subject to rapid decreases in free chlorine concentration, which may increase the probability of water mediated microbial cross-contamination. An immersion-free, single-pass Produce washing system was recently developed to address these challenges by over-head spraying clean (retreated) water, rather than spent wash water. The objective of this study was to compare single-pass and flume systems during commercial processing of Fresh-Cut vegetables in terms of wash water physicochemical and microbiological quality and cut Produce microbiological and sensorial quality. Two products, shredded iceberg lettuce and diced cabbage, were selected; processes were evaluated for each product on three separate days. Wash water and Produce were sampled every 30 min during production for 2.7 h. Water that was used to wash the Produce was collected from representative locations in the single-pass (input water, pre-wash, cutter, incline wash, vibra-wash) and flume (flume A, flume A catch tank, flume B, flume B catch tank) systems. Physicochemical (free chlorine, total chlorine, pH, total dissolved solids (TDS), chemical oxygen demand (COD), turbidity) and microbial analyses (aerobic plate count (APC)) were conducted on the wash water samples. Produce samples collected after cutting and after washing were analyzed onsite for APC immediately after collection. Final packaged products were analyzed weekly for sensorial quality (visual, olfactory, overall acceptability) during three weeks of storage at 1 °C by a trained panel using a 9-point hedonic scale. Results show that the organic load indicators in wash water samples from the single-pass system were consistent over time for most sampling locations, with no statistically significant increases in turbidity, TDS, or COD during production. In contrast, the organic load indicators in wash water samples from the flume system increased significantly during production by 13–45 NTU h−1 for turbidity, 382–1094 mg L−1 h−1 for TDS, and 597–2772 mg L−1 h−1 for COD. For the single-pass system, the wash water from the cutter had the largest APC of 3.8–4.2 log CFU/100 mL and the highest values of organic load indicators (152–186 NTU for turbidity, 623–904 mg L−1 for TDS, and 4420–4673 mg L−1 for COD) compared to the wash water from all the other processing stages (input water, pre-wash, incline, vibra-wash), which ranged from 0.05) in APC between the single-pass and flume washed product samples; APC on the final product samples ranged from 3.2 to 3.4 log CFU g−1 for lettuce and 3.9–4.1 log CFU g−1 for cabbage. Panelists rated the quality of the products washed using the single-pass system as comparable to those washed using the flume system within the first two weeks and slightly better after three weeks of storage. Results from this study could be used by the Produce industry to further optimize the single-pass system and develop additional processing innovations to improve the safety, efficacy, economics, and environmental impacts of Produce washing systems.
Pramod V. Mahajan - One of the best experts on this subject based on the ideXlab platform.
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Modelling the effect of time and temperature on respiration rate of selected Fresh-Cut Produce
Postharvest Biology and Technology, 2013Co-Authors: Roji B. Waghmare, Pramod V. Mahajan, Uday S. AnnapureAbstract:Abstract For the design of modified atmosphere packaging (MAP) it is necessary to know the influence of time and temperature on the respiration rate (RR) of Fresh-Cut Produce. Mathematical modelling is used for prediction of RR as a function of both time and temperature. In this work, RR of three Fresh-Cut products viz. coriander, cluster beans and beetroot, were quantified and a mathematical model was developed for prediction of RR as a function of both time and temperature. RR ( R O 2 and R CO 2 ) of each Fresh-Cut Produce was measured at 10, 20 and 30 °C for storage times of 1–5 d under aerobic conditions using a closed system. R O 2 of coriander, cluster beans and beetroot ranged from 54.0 to 228.6, 40.5 to 143.9 and 11.5 to 130.5 mg kg−1 h−1 respectively and R CO 2 ranged from 81.2 to 301.7, 52.7 to 199.7 and 33.5 to 195.2 mg kg−1 h−1 respectively over the three storage temperatures tested. Temperature and the interaction of time and temperature had significant effects on RR. The dependence of respiration rate of Fresh-Cut Produce on temperature and time was well described by Arrhenius and first order decay models.
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Modified Atmosphere Packaging Technology of Fresh and Fresh-Cut Produce and the Microbial Consequences—A Review
Food and Bioprocess Technology, 2013Co-Authors: Oluwafemi James Caleb, Fahad Al-julanda Al-said, Pramod V. Mahajan, Umezuruike Linus OparaAbstract:Modified atmosphere packaging (MAP) technology offers the possibility to retard the respiration rate and extend the shelf life of fresh Produce, and is increasingly used globally as value adding in the fresh and Fresh-Cut food industry. However, the outbreaks of foodborne diseases and emergence of resistant foodborne pathogens in MAP have heightened public interest on the effects of MAP technology on the survival and growth of pathogenic organisms. This paper critically reviews the effects of MAP on the microbiological safety of fresh or Fresh-Cut Produce, including the role of innovative tools such as the use of pressurised inert/noble gases, predictive microbiology and intelligent packaging in the advancement of MAP safety. The integration of Hazard Analysis and Critical Control Points-based programs to ensure fresh food quality and microbial safety in packaging technology is highlighted.
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modified atmosphere packaging technology of fresh and fresh cut Produce and the microbial consequences a review
Food and Bioprocess Technology, 2013Co-Authors: Oluwafemi James Caleb, Pramod V. Mahajan, F A Alsaid, Umezuruike Linus OparaAbstract:Modified atmosphere packaging (MAP) technology offers the possibility to retard the respiration rate and extend the shelf life of fresh Produce, and is increasingly used globally as value adding in the fresh and Fresh-Cut food industry. However, the outbreaks of foodborne diseases and emergence of resistant foodborne pathogens in MAP have heightened public interest on the effects of MAP technology on the survival and growth of pathogenic organisms. This paper critically reviews the effects of MAP on the microbiological safety of fresh or Fresh-Cut Produce, including the role of innovative tools such as the use of pressurised inert/noble gases, predictive microbiology and intelligent packaging in the advancement of MAP safety. The integration of Hazard Analysis and Critical Control Points-based programs to ensure fresh food quality and microbial safety in packaging technology is highlighted.
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mathematical modelling of modified atmosphere package an engineering approach to design packaging systems for fresh cut Produce
2009Co-Authors: Elena Torrieri, Pramod V. Mahajan, Fernanda A R Oliveira, Silvana Cavella, Maria De Sousa Gallagher, P MasiAbstract:Consumer demand for freshness and for convenience food has led to the evolution and increased production of Fresh-Cut fruits and vegetables. Moreover, this may represent a way to increase the consumption of fresh fruits and vegetables and therefore be a benefit for the crops-sector economy. Because the increase in convenience for the consumer has a detrimental effect on product quality, attention must be focused on extending shelf-life while maintaining quality. Modified atmosphere packaging (MAP) is a packaging technology that, by making qualitative or quantitative changes to the atmosphere composition around the product, can improve product preservation. However, MAP must be carefully designed, as a poorly designed system may be ineffective or even shorten product shelf-life. Thus, whereas in the past a trial-and-error approach to packaging of food was predominant, nowadays the need has emerged for an engineering approach to properly design a package to improve product shelf-life. Therefore, to ensure an appropriate gas composition during the product’s shelf-life, a model should take into account all the variables that play a critical role, such as product respiration and its mass; packaging material and its geometry; and environmental conditions such as temperature, relative humidity, and gas composition.
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development of user friendly software for design of modified atmosphere packaging for fresh and fresh cut Produce
Innovative Food Science and Emerging Technologies, 2007Co-Authors: Pramod V. Mahajan, Fernanda A R Oliveira, Julio C Montanez, Jesus M FriasAbstract:Abstract There is a wealth of published information on modified atmosphere packaging (MAP) but a lack of systematic treatment of the data in order to develop knowledge management systems that can provide information to users on which films to use for particular purposes and targets. This paper reports the development of user-friendly software for MAP design of fresh and Fresh-Cut Produce. The software can select suitable packaging materials and define the amount of product to be packed or the area of the film that should be available for gas exchange. Two databases have been built in the software, which include recommended gas composition for 38 products, 75 respiration rate models, and permeability data for 27 polymeric films. This software was successfully tested for some products and an example for mango and Galega kale is described. Industrial relevance The PACKinMAP software selects the best possible film type for the given type of fresh or fresh cut fruit/vegetable. A manufacturer can type in a specific food product, such as a golden delicious apple, and the software will tell him the ideal type of packaging material according to the supplier or the retailer's needs. The software has also been found to simulate the package for any type of real-life distribution temperature history thus testing the ability of the package to withstand abuse.
Eleftherios H Drosinos - One of the best experts on this subject based on the ideXlab platform.
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A ‘best practice score’ for the assessment of food quality and safety management systems in Fresh-Cut Produce sector
Food Control, 2016Co-Authors: Periklis Tzamalis, Demosthenes B. Panagiotakos, Eleftherios H DrosinosAbstract:Abstract The purpose of the present work was to develop a tool for the assessment of the Food Safety and Quality Management Systems (FSQMSs) applied in 75 (68% participation rate) micro, small and medium-sized enterprises (SMEs) of the Fresh-Cut Produce sector. Initially, a diagnostic quantitative questionnaire was constructed. The design and the implementation of this questionnaire were influenced by the SMEs business environment. The most common certified FSQMS was according to ISO 22000:2005 (N = 54). Twenty-eight SMEs had primary production in their process. Using factor analysis with the principal components method, six factors (PCF) were extracted that explained 67% of the total information of the FSQMSs performance. The six factors were ‘shelf life validation’, ‘prerequisites’, ‘product labeling’, ‘sanitation facilities’, ‘packaging’ and ‘deviation control’. The quartiles of the PCF scores may be used as cut-offs for a simple SMEs classification (poor, moderate, good and excellent). The proposed tool and overall methodology can be used by an SME to provide the ‘Best Practice Score’ for the FSQMSs. It will also be an input in management review for deciding opportunities of FSQMS improvement.
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a best practice score for the assessment of food quality and safety management systems in fresh cut Produce sector
Food Control, 2016Co-Authors: Periklis Tzamalis, Demosthenes B. Panagiotakos, Eleftherios H DrosinosAbstract:Abstract The purpose of the present work was to develop a tool for the assessment of the Food Safety and Quality Management Systems (FSQMSs) applied in 75 (68% participation rate) micro, small and medium-sized enterprises (SMEs) of the Fresh-Cut Produce sector. Initially, a diagnostic quantitative questionnaire was constructed. The design and the implementation of this questionnaire were influenced by the SMEs business environment. The most common certified FSQMS was according to ISO 22000:2005 ( N = 54). Twenty-eight SMEs had primary production in their process. Using factor analysis with the principal components method, six factors (PCF) were extracted that explained 67% of the total information of the FSQMSs performance. The six factors were ‘shelf life validation’, ‘prerequisites’, ‘product labeling’, ‘sanitation facilities’, ‘packaging’ and ‘deviation control’. The quartiles of the PCF scores may be used as cut-offs for a simple SMEs classification (poor, moderate, good and excellent). The proposed tool and overall methodology can be used by an SME to provide the ‘Best Practice Score’ for the FSQMSs. It will also be an input in management review for deciding opportunities of FSQMS improvement.
Lucia Guidi - One of the best experts on this subject based on the ideXlab platform.
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Suitability of Hydroponically-Grown Rumex acetosa L. as Fresh-Cut Produce
Horticulturae, 2020Co-Authors: Costanza Ceccanti, Marco Landi, Luca Incrocci, Alberto Pardossi, Lucia GuidiAbstract:Sorrel (Rumex acetosa L.) is a perennial wild herb appreciated as a folk medicine and for use in folk-traditional cuisines, and its nutraceutical properties are increasingly known and studied. Nowadays, there is a lack of knowledge about the possibility of using this species as Fresh-Cut Produce, and no reports have investigated the physiological/biochemical changes of sorrel leaves upon storage. To test the aforementioned, sorrel seedlings were cultivated in a floating system and two consecutive harvests took place: The first cut at 15 days (C1) and second cut at 30 days (C2) after sowing. Fresh-Cut sorrel leaves from C1 and C2 were stored in plastic boxes at 4 °C for 15 days and chlorophylls, carotenoids, total phenols, flavonoids, ascorbic acid, and antioxidant capacity were evaluated during the storage period. During storage, sorrel leaves from the same cut did not show significant changes in total phenolic content and antioxidant capacity, which represents a positive outcome for the maintenance of the nutraceutical value of this species. For this reason, sorrel may be a very promising species as a “new” Fresh-Cut leafy vegetable. However, some differences were observed between the two cuts, especially in the total flavonoid and the total ascorbic acid contents. While promising, further research will be necessary to standardize the yield and the nutraceutical content of this species in different cuts, which will be necessary to introduce and promote sorrel to consumers.
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Hydroponically Grown Sanguisorba minor Scop.: Effects of Cut and Storage on Fresh-Cut Produce.
Antioxidants (Basel Switzerland), 2019Co-Authors: Costanza Ceccanti, Marco Landi, Luca Incrocci, Alberto Pardossi, Gabriele Rocchetti, Maria Begoña Miras Moreno, Luigi Lucini, Lucia GuidiAbstract:Wild edible plants have been used in cooking since ancient times. Recently, their value has improved as a result of the scientific evidence for their nutraceutical properties. Sanguisorba minor Scop. (salad burnet) plants were hydroponically grown and two consecutive cuts took place at 15 (C1) and 30 (C2) days after sowing. An untargeted metabolomics approach was utilized to fingerprint phenolics and other health-related compounds in this species; this approach revealed the different effects of the two cuts on the plant. S. minor showed a different and complex secondary metabolite profile, which was influenced by the cut. In fact, flavonoids increased in leaves obtained from C2, especially flavones. However, other secondary metabolites were downregulated in leaves from C2 compared to those detected in leaves from C1, as evidenced by the combination of the variable important in projections (VIP score > 1.3) and the fold-change (FC > 2). The storage of S. minor leaves for 15 days as Fresh-Cut products did not induce significant changes in the phenolic content and antioxidant capacity, which indicates that the nutraceutical value was maintained. The only difference evidenced during storage was that leaves obtained from C2 showed a lower constitutive content of nutraceutical compounds than leaves obtained from C1; except for chlorophylls and carotenoids. In conclusion, the cut was the main influence on the modulation of secondary metabolites in leaves, and the effects were independent of storage.
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Do sun- versus shade-grown kiwifruits perform differently upon storage? An overview of fruit maturity and nutraceutical properties of whole and Fresh-Cut Produce.
Journal of agricultural and food chemistry, 2014Co-Authors: Marco Landi, Francesca Tardelli, Damiano Remorini, Rossano Massai, Lucia GuidiAbstract:Fresh-Cut Produce represents a good method to save about 25% of the kiwifruit not useful to meet the fresh fruit-marketing standard due to improper size and shape. For that reason, Fresh-Cut kiwifruit has been extensively studied. However, the comprehension of the influence of some aspects of cultivation might further increase the shelf life as well as the nutritional values of that fruit. This study explored the hypothesis that kiwifruits grown fully exposed to sunlight or partially shaded differently perform upon storage as whole fruit and as minimally processed Produce. Flesh firmness (FF), total solids soluble (SSC), ascorbate (AAT), flavonoids (TFO), and phenols (TF) contents were evaluated in sliced and whole fruit upon 3 days of storage at 4 °C after 75 days of cold chamber storage at 0 °C. The activities of two enzymes related to the softening process, polygalacturonase (PG) and pectinmethylesterase (PME), were evaluated as well. FF and SSC were constitutively higher in sun-exposed fruit, and those characteristics remained higher during the storage as whole fruit. Greater constitutive content of AAT, TFO, and TP was found in sun-exposed whole fruit, although after cutting the reduction in their content was significantly lower in shaded fruits. PME and PG activities were higher only in whole shaded fruits, whereas no relevant differences occurred after cutting. In summary, sun-exposed fruits were more suitable for the fresh-fruit market, whereas the shaded counterpart displayed a good predisposition for use as Fresh-Cut Produce, maintaining similar fruit maturity properties but higher nutraceutical values when sliced than fruit grown under full sun.
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role of ascorbic acid in the inhibition of polyphenol oxidase and the prevention of browning in different browning sensitive lactuca sativa var capitata l and eruca sativa mill stored as fresh cut Produce
Journal of the Science of Food and Agriculture, 2013Co-Authors: Marco Landi, E Deglinnocenti, Lorenzo Guglielminetti, Lucia GuidiAbstract:BACKGROUND: Polyphenol oxidase (PPO) and, to a minor extent, peroxidase (POD) represent the key enzymes involved in enzymatic browning, a negative process induced by cutting Fresh-Cut Produce such as lettuce (Lactuca sativa) and rocket salad (Eruca sativa). Although ascorbic acid is frequently utilised as an anti-browning agent, its mechanism in the prevention of the browning phenomenon is not clearly understood. RESULTS: The activity of PPO and POD and their isoforms in lettuce (a high-browning and low-ascorbic acid species) and rocket salad (a low-browning and high-ascorbic species) was characterised. The kinetic parameters of PPO and in vitro ascorbic acid-PPO inhibition were also investigated. In rocket salad, PPO activity was much lower than that in lettuce and cutting induced an increase in PPO activity only in lettuce. Exogenous ascorbic acid (5 mmol L(-1)) reduced PPO activity by about 90% in lettuce. POD did not appear to be closely related to browning in lettuce. CONCLUSION: PPO is the main enzyme involved in the browning phenomenon; POD appears to play a minor role. The concentration of endogenous ascorbic acid in rocket salad was related to its low-browning sensitivity after cutting. In lettuce, the addition of ascorbic acid directly inhibited PPO activity. The results suggest that the high ascorbic acid content found in rocket salad plays an effective role in reducing PPO activity.
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Role of ascorbic acid in the inhibition of polyphenol oxidase and the prevention of browning in different browning-sensitive Lactuca sativa var. capitata (L.) and Eruca sativa (Mill.) stored as Fresh-Cut Produce.
Journal of the science of food and agriculture, 2012Co-Authors: Marco Landi, Lorenzo Guglielminetti, Elena Degl’innocenti, Lucia GuidiAbstract:BACKGROUND Polyphenol oxidase (PPO) and, to a minor extent, peroxidase (POD) represent the key enzymes involved in enzymatic browning, a negative process induced by cutting Fresh-Cut Produce such as lettuce (Lactuca sativa) and rocket salad (Eruca sativa). Although ascorbic acid is frequently utilised as an anti-browning agent, its mechanism in the prevention of the browning phenomenon is not clearly understood. RESULTS The activity of PPO and POD and their isoforms in lettuce (a high-browning and low-ascorbic acid species) and rocket salad (a low-browning and high-ascorbic species) was characterised. The kinetic parameters of PPO and in vitro ascorbic acid–PPO inhibition were also investigated. In rocket salad, PPO activity was much lower than that in lettuce and cutting induced an increase in PPO activity only in lettuce. Exogenous ascorbic acid (5 mmol L−1) reduced PPO activity by about 90% in lettuce. POD did not appear to be closely related to browning in lettuce. CONCLUSION PPO is the main enzyme involved in the browning phenomenon; POD appears to play a minor role. The concentration of endogenous ascorbic acid in rocket salad was related to its low-browning sensitivity after cutting. In lettuce, the addition of ascorbic acid directly inhibited PPO activity. The results suggest that the high ascorbic acid content found in rocket salad plays an effective role in reducing PPO activity. © 2012 Society of Chemical Industry
Johan Debevere - One of the best experts on this subject based on the ideXlab platform.
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Relation between microbiological quality, metabolite production and sensory quality of equilibrium modified atmosphere packaged Fresh-Cut Produce
International Journal of Food Microbiology, 2003Co-Authors: Liesbeth Jacxsens, Frank Devlieghere, Peter Ragaert, E Vanneste, Johan DebevereAbstract:Abstract The quality of four types of Fresh-Cut Produce, packaged in consumer-sized packages under an equilibrium modified atmosphere and stored at 7 °C, was assessed by establishing the relation between the microbial outgrowth and the corresponding production of nonvolatile compounds and related sensory disorders. In vitro experiments, performed on a lettuce-juice-agar, demonstrated the production of nonvolatile compounds by spoilage causing lactic acid bacteria and Enterobacteriaceae. Pseudomonas fluorescens and yeasts, however, were not able to Produce detectable amounts of nonvolatile metabolites. The type of spoilage and quality deterioration in vivo depended on the type of vegetable. Mixed lettuce and chicory endives, leafy tissues, containing naturally low concentrations of sugars, showed a spoilage dominated by Gram-negative microorganisms, which are not producing nonvolatile compounds. Sensory problems were associated with visual properties and the metabolic activity of the plant tissue. Mixed bell peppers and grated celeriac, on the other hand, demonstrated a fast and intense growth of spoilage microorganisms, dominated by lactic acid bacteria and yeasts. This proliferation resulted in detectable levels of organic acids and the rejection by the trained sensory panel was based on the negative perception of the organoleptical properties (off-flavour, odour and taste). The applied microbiological criteria corresponded well with detectable changes in sensory properties and measurable concentrations of nonvolatile compounds, surely in the cases where lactic acid bacteria and yeasts were provoking spoilage. Consequently, the freshness of minimally processed vegetables, sensitive for outgrowth of lactic acid bacteria and yeasts (e.g., carrots, celeriac, bell peppers, mixtures with non-leafy vegetables) can be evaluated via analysis of the Produced nonvolatile compounds.
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Relation between microbiological quality, metabolite production and sensory quality of equilibrium modified atmosphere packaged Fresh-Cut Produce
International journal of food microbiology, 2003Co-Authors: Liesbeth Jacxsens, Frank Devlieghere, Peter Ragaert, E Vanneste, Johan DebevereAbstract:Abstract The quality of four types of Fresh-Cut Produce, packaged in consumer-sized packages under an equilibrium modified atmosphere and stored at 7 °C, was assessed by establishing the relation between the microbial outgrowth and the corresponding production of nonvolatile compounds and related sensory disorders. In vitro experiments, performed on a lettuce-juice-agar, demonstrated the production of nonvolatile compounds by spoilage causing lactic acid bacteria and Enterobacteriaceae. Pseudomonas fluorescens and yeasts, however, were not able to Produce detectable amounts of nonvolatile metabolites. The type of spoilage and quality deterioration in vivo depended on the type of vegetable. Mixed lettuce and chicory endives, leafy tissues, containing naturally low concentrations of sugars, showed a spoilage dominated by Gram-negative microorganisms, which are not producing nonvolatile compounds. Sensory problems were associated with visual properties and the metabolic activity of the plant tissue. Mixed bell peppers and grated celeriac, on the other hand, demonstrated a fast and intense growth of spoilage microorganisms, dominated by lactic acid bacteria and yeasts. This proliferation resulted in detectable levels of organic acids and the rejection by the trained sensory panel was based on the negative perception of the organoleptical properties (off-flavour, odour and taste). The applied microbiological criteria corresponded well with detectable changes in sensory properties and measurable concentrations of nonvolatile compounds, surely in the cases where lactic acid bacteria and yeasts were provoking spoilage. Consequently, the freshness of minimally processed vegetables, sensitive for outgrowth of lactic acid bacteria and yeasts (e.g., carrots, celeriac, bell peppers, mixtures with non-leafy vegetables) can be evaluated via analysis of the Produced nonvolatile compounds.
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High oxygen concentration in combination with elevated carbon dioxide to affect growth of Fresh-Cut Produce micro-organisms
Acta Horticulturae, 2003Co-Authors: Caroline Van Der Steen, Frank Devlieghere, Johan DebevereAbstract:High oxygen atmospheres (> 70 %) can be used as an alternative for the nowadays applied low O-2/elevated CO2 modifled atmosphere, to prolong shelf life of respiring Fresh-Cut vegetables and fruit. The effect of high oxygen atmosphere, applied alone or in combination with elevated CO2 concentrations, on the growth of spoilage micro-organisms (14 species) and pathogens (Listeria monocytogenes and Aeromonas caviae (HG4)), isolated from Fresh-Cut Produce, has been studied. Of each species only one strain was considered, except for Candida lambica, from which 5 different strains were analyzed to check possible differences in sensitivity for high O-2 concentrations between strains of the same species. Lag phase (lambda), maximum specific growth rate (mu(max)), initial count (N-0) and maximum count (N-max) were determined applying the Baranyi model. The maximum specific growth rate of G(-) spoilage bacteria was slightly reduced by high O-2. Growth rate of the two tested pathogens was rather stimulated by high O-2. Lactic acid bacteria were much more sensitive to high O-2 concentrations, but no additive or synergistic effect was found when high O-2 was combined with high CO2. In most of the cases, growth of yeast strains was strongly inhibited by high O-2, and this effect was even more pronounced when applying 80 % O-2 + 20 % CO2 (additive effect). Only one strain of Candida lambica was not at all affected by high O-2 concentrations and/or elevated CO2. Growth of Candida humicola and of another strain of Candida lambica was significantly stimulated by high O-2. So although yeast are generally inhibited during storage experiments with Fresh-Cut Produce under high O-2 atmosphere, this inhibitory effect is not true for every individual yeast strain in in vitro experiments.
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effect of high oxygen modified atmosphere packaging on microbial growth and sensorial qualities of fresh cut Produce
International Journal of Food Microbiology, 2001Co-Authors: Liesbeth Jacxsens, Frank Devlieghere, Caroline Van Der Steen, Johan DebevereAbstract:Abstract The application of High Oxygen Atmospheres (HOA) (i.e. >70% O 2 ) for packaging ready-to-eat vegetables was evaluated as an alternative technique for low O 2 Equilibrium Modified Atmosphere (EMA) packaging (3% O 2 –5% CO 2 –balance N 2 ) for respiring products. Comparative experiments between both techniques were performed in-vitro and in-vivo. Typical spoilage causing microorganisms ( Pseudomonas fluorescens , Candida lambica ), the moulds Botrytis cinerea , Aspergillus flavus and the opportunistic psychrotrophic human pathogenic microorganism associated with refrigerated minimally processed vegetables, Aeromonas caviae (HG4), showed a retarded growth during the conducted in-vitro studies at 4 °C in 70%, 80% and 95% O 2 as examples of HOA compared to the in-vitro experiments in 5% O 2 (as example of EMA packaging) and the effect was more pronounced in 95% O 2 . The effect of the high O 2 -concentrations on the human pathogen Listeria monocytogenes resulted in an extended lag phase (95% O 2 ). The plant pathogen Erwinia carotovora was increasingly stimulated by increasing high O 2 -concentrations. During a storage experiment of three types of ready-to-eat vegetables (mushroom slices, grated celeriac and shredded chicory endive), which are sensitive to enzymatic browning and microbial spoilage, the effect of EMA and HOA (95% O 2 –5% N 2 ) on their quality and shelf life was compared. High O 2 atmospheres were found to be particularly effective in inhibiting enzymatic browning of the tested vegetables. Also, the microbial quality was better as a reduction in yeast growth was observed. The HOA can be applied as an alternative for low O 2 modified atmospheres for some specific types of ready-to-eat vegetables, sensitive to enzymatic browning and spoilage by yeasts.
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effect of high oxygen modified atmosphere packaging on microbial growth and sensorial qualities of fresh cut Produce
International Journal of Food Microbiology, 2001Co-Authors: Liesbeth Jacxsens, Frank Devlieghere, Caroline Van Der Steen, Johan DebevereAbstract:The application of High Oxygen Atmospheres (HOA) (i.e. > 70% O2) for packaging ready-to-eat vegetables was evaluated as an alternative technique for low O2 Equilibrium Modified Atmosphere (EMA) packaging (3% O2-5% CO2-balance N2) for respiring products. Comparative experiments between both techniques were performed in-vitro and in-vivo. Typical spoilage causing microorganisms (Pseudomonas fluorescens, Candida lambica), the moulds Botrytis cinerea, Aspergillus flavus and the opportunistic psychrotrophic human pathogenic microorganism associated with refrigerated minimally processed vegetables. Aeromonas caviae (HG4), showed a retarded growth during the conducted in-vitro studies at 4 degrees C in 70%, 80% and 95% O2 as examples of HOA compared to the in-vitro experiments in 5% O2 (as example of EMA packaging) and the effect was more pronounced in 95% O2. The effect of the high O2-concentrations on the human pathogen Listeria monocytogenes resulted in an extended lag phase (95% O2). The plant pathogen Erwinia carotovora was increasingly stimulated by increasing high O2-concentrations. During a storage experiment of three types of ready-to-eat vegetables (mushroom slices, grated celeriac and shredded chicory endive), which are sensitive to enzymatic browning and microbial spoilage, the effect of EMA and HOA (95% O2-5% N2) on their quality and shelf life was compared. High O2 atmospheres were found to be particularly effective in inhibiting enzymatic browning of the tested vegetables. Also, the microbial quality was better as a reduction in yeast growth was observed. The HOA can be applied as an alternative for low O2 modified atmospheres for some specific types of ready-to-eat vegetables, sensitive to enzymatic browning and spoilage by yeasts.
