Pramod V. Mahajan

Modified atmosphere packaging technology of fresh and fresh-cut produce and the microbial consequences ? A review

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.

Postharvest treatments of fresh produce

Postharvest technologies have allowed horticultural industries to meet the global demands of local and large-scale production and intercontinental distribution of fresh produce that have high nutritional and sensory quality. Harvested products are metabolically active, undergoing ripening and senescence processes that must be controlled to prolong postharvest quality. Inadequate management of these processes can result in major losses in nutritional and quality attributes, outbreaks of foodborne pathogens and financial loss for all players along the supply chain, from growers to consumers. Optimal postharvest treatments for fresh produce seek to slow down physiological processes of senescence and maturation, reduce/inhibit development of physiological disorders and minimize the risk of microbial growth and contamination. In addition to basic postharvest technologies of temperature management, an array of others have been developed including various physical (heat, irradiation and edible coatings), chemical (antimicrobials, antioxidants and anti-browning) and gaseous treatments. This article examines the current status on postharvest treatments of fresh produce and emerging technologies, such as plasma and ozone, that can be used to maintain quality, reduce losses and waste of fresh produce. It also highlights further research needed to increase our understanding of the dynamic response of fresh produce to various postharvest treatments.

Effect of time, temperature, and slicing on respiration rate of mushrooms.

Respiration rate measurement considering the effects of cutting, temperature, and storage time are important for the shelf life study and modified atmosphere-packaging design of fresh-cut produce. This study investigates in the respiration rate of fresh whole and sliced mushrooms at 0, 4, 8, 12, 16, and 20 degrees C under ambient atmosphere and different storage times. The O(2) consumption rate increased with temperature and ranged from 22.13 to 102.41 mL/(kg.h) and 28.87 to 143.22 mL/(kg.h) for whole and sliced mushrooms, respectively, in the temperature range tested. Similar trend was observed for CO(2) production rate. Slicing of mushrooms increased the respiration rate by 30% at 0 degrees C and 40% at 20 degrees C indicating that the mushrooms are not as sensitive to the stress caused by cutting as other fresh produce. Storage time affected both respiration rate of whole and sliced mushrooms and this effect was prominent at higher temperatures. The respiration rates increased initially for some time, then decreased and reached steady state value at 12, 16, and 20 degrees C. A 2nd-order polynomial equation was used to fit the respiration rate data as a function of time at each temperature tested.

Transpiration rate and quality of pomegranate arils as affected by storage conditions

This study investigated the transpiration rate (TR) of pomegranate (Punica granatum L.) arils under various combinations of temperature (5, 10 and 15°C) and relative humidity (RH) (76, 86 and 96%) during storage. Transpiration rateTR ranged from 1.14 to 16.75 g/kg day across the various combinations of RH and temperature studied. Relative humidityRH had the most significant impact on TR (p < 0.05). Transpiration rateTR increased six-fold when RH was reduced from 96 to 76%, and correlated well with water vapour pressure deficit (WVPD) (R 2 = 96.1%). Aril weight loss increased at higher WVPD. After 8 days of storage, losses in quality attributes of arils were higher with increasing storage temperature and lowering RH. A mathematical model to predict TR as a function of temperature and RH was developed and successfully validated at 8°C. The target water vapour transmission rate of packaging materials for pomegranate arils was found to be 33 to 68 g/m2 day.

Effect of Minimal Processing Conditions on Respiration Rate of Carrots

Measurement, analysis, and modeling of respiration rate (RR) of fresh produce are fundamental for the engineering design of MAP. This study investigates the effect of type of cutting (sliced in circular shape, batons in rectangular shape, and shredded into thin strips) on the respiration rate of carrots at different temperatures (4, 8, 12, 16, and 20 degrees C) with ambient atmosphere. The higher respiration rates were found for shredded carrots and the lowest for whole carrots at all the temperatures tested. The RR increased from 9 +/- 1 to 26 +/- 3, 10 +/- 1 to 53 +/- 2, 11 +/- 1 to 55 +/- 2, and 18 +/- 1 to 75 +/- 3 mL of O(2) per kilogram hour for whole, sliced, baton, and shredded carrots, respectively, as the temperature increased from 4 to 20 degrees C. On an average, RO2 and RCO2 were increased by 85% and 64%, 100% and 72%, and 151% and 124% for sliced, baton, and shredded carrots, respectively, compared to the RR values of whole carrots. The temperature dependence of RR followed an Arrhenius-type relationship for all types of carrots, with activation energies in the range of 35 +/- 3 to 62 +/- 2 kJ/mol. Type of cut was the major factor for both RO2 and RCO2, with shredded carrots having the highest rates and whole carrots the lowest. RR of whole carrots did not vary during storage, whereas it increased for cut carrots and especially for shredded carrots. The respiratory quotient (RQ) increased with temperature and did not vary during storage in all types of carrots, except the RQ of whole carrots decreased significantly over time.

Development and validation of a comprehensive model for map of fruits based on enzyme kinetics theory and arrhenius relation

MAP is a dynamic system where respiration of the packaged product and gas permeation through the packaging film takes place simultaneously. The desired level of O2 and CO2 in a package is achieved by matching film permeation rates for O2 and CO2 with respiration rate of the packaged product. A mathematical model for MAP of fresh fruits applying enzyme kinetics based respiration equation coupled with the Arrhenious type model was developed. The model was solved numerically using MATLAB programme. The model was used to determine the time to reach to the equilibrium concentration inside the MA package and the level of O2 and CO2 concentration at equilibrium state. The developed model for prediction of equilibrium O2 and CO2 concentration was validated using experimental data for MA packaging of apple, guava and litchi.

Mathematical Modelling of Modified Atmosphere Package: An Engineering Approach to Design Packaging Systems for Fresh-Cut Produce

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.

Development of a small and flexible sensor-based respirometer for real-time determination of respiration rate, respiratory quotient and low O2 limit of fresh produce

We developed a small and flexible respirometer for non-invasive determination of real-time respiration rate.The gas sampling implied little manual handling.The respiratory quotient and the low O2 limit could be acquired.The respirometer was tested with fresh produce kept at varying temperature and O2 contents. Information on the respiration rate and the low O2 limit (LOL) is important for optimization of packaging and storage systems for fresh fruit and vegetables. In this study, a small and flexible sensor-based respirometer was developed for real-time determination of the respiration rate, respiratory quotient (RQ), and LOL of fresh produce. The respirometer consisted of a wide mouth 1-L glass jar with a screw-type metal lid and an electrochemical and an infra-red sensor mounted directly on the lid of the glass jar to take continuous and non-invasive measurements of the O2 and CO2 contents. Data from the respirometer was compared with data obtained from two fluorescence-based spot sensors (OpTech and PreSens) and a headspace gas analyzer (CheckMate). A test with strawberry showed that similar respiration rates (14.1-16.2mLO2kg-1h-1 and 13.4-16.4mLCO2kg-1h-1 at 10?C) were obtained with all instruments. Further on, a Savitzky-Golay smoothing filter was implemented on the data from the respirometer to estimate the real-time respiration rate. The result showed that the respiration rate could be acquired in 2-3h after filling of the respirometer or even after 1h if the produce was equilibrated to the target storage temperature before the measurements. Detailed information on the respiration rate of wild rocket, strawberry, and carrot showed that the respiration rate decreased with time as the O2 content decreased; however, the RQ remained almost constant throughout storage until the LOL was reached. Information on the RQ and the LOL value is rare in the literature; however, the RQ and the LOL could easily be determined by the use of the respirometer. The RQ was 1.0, 1.0-1.5, and 0.5 for wild rocket, strawberry, and carrot, respectively, during storage under an O2 content above >2.0kPa. As the O2 content dropped to 0.5, 1.0 and 2.0kPa O2, for wild rocket, strawberry, and carrot, respectively, the RQ values increased sharply. The described respirometer made it easy to analyze the impact of a dynamic temperature and O2 content on the respiration rate, the RQ, and the LOL as handling was limited and real-time data could be obtained. With such detailed information, a knowledge-intensive design of packaging and storage systems for fresh horticultural produce is enabled.

Effects of storage conditions on transpiration rate of pomegranate aril-sacs and arils

This study investigated the effects of temperature (5, 10, 15 and 22 °C) and relative humidity (RH) (76%, 86% and 96%) on the transpiration rate (TR) of pomegranate (Punica granatum L.) cv. Bhagwa fruit fractions, namely arils and aril-sac. Both temperature and RH had significant effects on the TR of fruit fractions. The TR increased with an increase in temperature and decrease in RH, with the fruit fraction stored at 5 °C and 96% RH showing the lowest TR in comparison to other storage conditions. Arils showed higher TR than the aril-sac under all storage conditions. The TR of the arils at 96% RH was in the range 1.42–15.23 g kg−1 d−1, whereas that for the aril-sac was 0.63–9.95 g kg−1 d−1, respectively. The higher TR of fruit arils may be attributed to the larger surface area as compared to the aril-sac whereby some of the arils are covered with the membrane, albedo and peel. A mathematical model was applied and the model adequately predicted the TR for arils and aril-sacs stored at 22 °C and RH 76%, 86% and 96%, with a good correlation between experimental and predicted data.

Modelling the effects of storage temperature on the respiration rate of different pomegra nate fractions

Temperature is one of the main factors that affects fresh produce respiration rate (RR). This study investigated the effects of storage temperature (5, 10, 15 and 22 °C) on the RRs of the pomegranate (Punica granatum L.) ‘Bhagwa’ whole fruit, aril-sacs and arils, and a mathematical model relating temperature to RR was applied. The aril-sacs had the highest RR at all storage temperatures in comparison to the whole fruit and arils. Overall, rates of carbon dioxide production (RCO2) and oxygen consumption (RO2) of the aril-sacs were in the range of 2.95–27.66 ml kg−1 h−1 and 5.49–48.44 ml kg−1 h−1, respectively, whereas those of the whole fruit ranged between 2.66 and 22.97 ml kg−1 h−1 and 3.71 and 33.3 ml kg−1 h−1, respectively, and those of arils were 1.96–18.64 ml kg−1 h−1 and 3.19–28.91 ml kg−1 h−1, respectively. Reducing storage temperature from 22 °C to 5 °C resulted in a reduction in RR of about 74.5% across all samples. Effect of temperature on RR of whole fruit, aril-sacs and arils were adequately predicted by an Arrhenius-type equation (R2 > 97.1%). The model validated RR for arils stored at 22 °C and a good correlation was found between experimental and predicted data.