Nitric oxide prevents wound-induced browning and delays senescence through inhibition of hydrogen peroxide accumulation in fresh-cut lettuce
Iakimova, E.T. ; Woltering, E.J. - \ 2015
Innovative Food Science and Emerging Technologies 30 (2015). - ISSN 1466-8564 - p. 157 - 169.
programmed cell-death - short-term exposure - lactuca-sativa l. - disease resistance response - processed romaine lettuce - ammonia-lyase activity - phenolic metabolism - iceberg lettuce - shelf-life - postharvest senescence
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.
Reusing salad from salad bars – simulating the effects on product loss, microbial safety and product quality
Tromp, S.O. ; Rijgersberg, H. ; Franz, E. - \ 2012
International Journal of Food Science and Technology 47 (2012)6. - ISSN 0950-5423 - p. 1144 - 1150.
listeria-monocytogenes - iceberg lettuce - risk-assessment - outbreak - restaurant - salmonella - growth - sustainability - contamination - challenges
The goal of this study is to model the effects of reusing salad from salad bars to reduce product loss, while keeping microbial safety and product quality at acceptable levels. We, therefore, expand our previously developed simulation model by incorporating reuse strategies and a quality decay model. The expanded model is used to simulate different salad reuse scenarios and to quantify the consequences to product loss, microbial safety and product quality. With this study, we show an application of a generic approach for the integrated modelling of product loss, microbial safety and product quality. The most cautious scenario consists of reusing salad for only 1 day after the first use and only if the salad originates from a package with a valid best-before date at the time of reuse (‘minimum reuse of salad with the best-before date criterion’). This scenario decreases product loss at the salad bar considerably from 37% to 29% ()21%). This considerable benefit occurs almost without causing product loss at the cold storage (increase from 0% to 1%), with only a minimal increase in the number of foetal mortality cases because of Listeria monocytogenes (increase from 11.9 to 12.2 cases per year (+3%)) and hardly any decline in product quality
Quantitative Microbial Risk Assessment for Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in Leafy Green Vegetables Consumed at Salad Bars, Based on Modeling Supply Chain Logistics
Tromp, S.O. ; Rijgersberg, H. ; Franz, E. - \ 2010
Journal of Food Protection 73 (2010)10. - ISSN 0362-028X - p. 1830 - 1840.
iceberg lettuce - dose-response - fresh produce - growth - outbreaks - foodborne - o157h7 - temperatures - restaurant - infection
Quantitative microbial risk assessments do not usually account for the planning and ordering mechanisms (logistics) of a food supply chain. These mechanisms and consumer demand determine the storage and delay times of products. The aim of this study was to quantitatively assess the difference between simulating supply chain logistics (MOD) and assuming fixed storage times (FIX) in microbial risk estimation for the supply chain of fresh-cut leafy green vegetables destined for working-canteen salad bars. The results of the FIX model were previously published (E. Franz, S. O. Tromp, H. Rijgersberg, and H. J. van der Fels-Klerx, J. Food Prot. 73:274-285, 2010). Pathogen growth was modeled using stochastic discrete-event simulation of the applied logistics concept. The public health effects were assessed by conducting an exposure assessment and risk characterization. The relative growths of Escherichia coli O157 (17%) and Salmonella enterica (15%) were identical in the MOD and FIX models. In contrast, the relative growth of Listeria monocytogenes was considerably higher in the MOD model (1,156%) than in the FIX model (194%). The probability of L. monocytogenes infection in The Netherlands was higher in the MOD model (5.18 × 10-8) than in the FIX model (1.23 × 10-8). The risk of listeriosis-induced fetal mortality in the perinatal population increased from 1.24 × 10-4 (FIX) to 1.66 × 10-4 (MOD). Modeling the probabilistic nature of supply chain logistics is of additional value for microbial risk assessments regarding psychrotrophic pathogens in food products for which time and temperature are the postharvest preventive measures in guaranteeing food safety.
Simulation modelling and risk assessment as tools to identify the impact of climate change on microbiological food safety – The case study of fresh produce supply chain
Jacxsens, L. ; Luning, P.A. ; Vorst, J.G.A.J. van der; Devlieghere, F. ; Leemans, R. ; Uyttendaele, M. - \ 2010
Food Research International 43 (2010)7. - ISSN 0963-9969 - p. 1925 - 1935.
minimally processed vegetables - escherichia-coli o157-h7 - agricultural land-use - time rt-pcr - ambient-temperature - iceberg lettuce - cryptosporidium oocysts - foodborne pathogens - contaminated water - future scenarios
The current quality assurance and control tools and methods to prevent and/or to control microbiological risks associated with fresh produce are challenged due to the following pressures upon the food supply chain, i.e. changing consumption patterns, globalization and climate change. It demonstrates the need for scientific research and development of new and/or improved tools, techniques and practices to adapt the current risk management systems. In this paper, a conceptual research approach is presented to analyse the complexity of the climate change and globalization challenge on the fresh produce supply chain taken as a case study. The factors which affect the vulnerability of the fresh produce chain demand a multidisciplinary research approach. The proposed knowledge-based modelling system is believed to be a most appropriate way to identify problems and to offer solutions to monitor and prevent microbiological food safety risks during all phases of food production and supply. To explore the potential impact of climate change and globalization, baseline information can be obtained by surveillance and performance measurement of implemented food safety management systems. Simulation of climate change scenarios and the logistic chain of fresh produce, along with mathematical models to optimize packaging technology to maintain quality and safety of fresh produce are tools to provide insights in the complex dynamic ecosystem. They are the basis for elaboration of risk assessment studies to scientifically support management options and decisions to new microbiological threats related to globalization and climate change in the fresh produce supply chain. This research concept as such will contribute to develop strategies in order to guarantee the (microbiological) food safety of fresh produce on the long term
Modeling Logistic Performance in Quantitative Microbial Risk Assessment
Rijgersberg, H. ; Tromp, S.O. ; Jacxsens, L. ; Uyttendaele, M. - \ 2010
Risk Analysis 30 (2010)1. - ISSN 0272-4332 - p. 20 - 31.
equilibrium-modified atmosphere - listeria-monocytogenes growth - fresh-cut produce - exposure assessment - iceberg lettuce - microbiological quality - deli meats - food - phase - vegetables
In quantitative microbial risk assessment (QMRA), food safety in the food chain is modeled and simulated. In general, prevalences, concentrations, and numbers of microorganisms in media are investigated in the different steps from farm to fork. The underlying rates and conditions (such as storage times, temperatures, gas conditions, and their distributions) are determined. However, the logistic chain with its queues (storages, shelves) and mechanisms for ordering products is usually not taken into account. As a consequence, storage times—mutually dependent in successive steps in the chain—cannot be described adequately. This may have a great impact on the tails of risk distributions. Because food safety risks are generally very small, it is crucial to model the tails of (underlying) distributions as accurately as possible. Logistic performance can be modeled by describing the underlying planning and scheduling mechanisms in discrete-event modeling. This is common practice in operations research, specifically in supply chain management. In this article, we present the application of discrete-event modeling in the context of a QMRA for Listeria monocytogenes in fresh-cut iceberg lettuce. We show the potential value of discrete-event modeling in QMRA by calculating logistic interventions (modifications in the logistic chain) and determining their significance with respect to food safety.