Modelling O2 and CO2 exchange for development of perforation-mediated modified atmosphere packaging

Potential Applications of Thermoresponsive Poly(N-Isoproplacrylamide)-Grafted Nylon Membranes: Effect of Grafting Yield and Architecture on Gating Performance

This study illustrated the potential applications of thermoresponsive poly(N-isopropylacrylamide) (PNIPAm) grafted nylon membranes with different grafting yields and grafting architecture. The thermoresponsive gating performance at temperatures below and above the lower critical solution temperature (LCST) of PNIPAm (32 °C) were demonstrated. The linear PNIPAm-grafted nylon membrane exhibited a sharp response over the temperature range 20-40 °C. The grafting yield of 25.5% and 21.9%, for linear and crosslinked PNIPAm respectively, exhibited highest thermoresponsive gating function for water flux and had a stable and repeatable "open-closed" switching function over 5 cycle operations. An excellent oil/water separation was obtained at T < 32 °C, at which the hydrophilic behavior was observed. The linear PNIPAm-grafted nylon membrane with 35% grafting yield had the highest separation efficiency of 99.7%, while PNIPAm structures were found to be independent of the separation efficiency. In addition, the membranes with thermoresponsive gas permeability were successfully achieved. The O₂ and CO₂ transmission rates through the PNIPAm-grafted nylon membranes decreased when the grafting yield increased, showing the better gas barrier property. The permeability ratio of CO₂ to O₂ transmission rates of both PNIPAm architectures at 25 °C and 35 °C were around 0.85 for low grafting yields, and approximately 1 for high grafting yields. Ultimately, this study demonstrated the possibility of using these thermoresponsive smart membranes in various applications.

Effect of ozone and antimicrobial treatments on the shelf life of cauliflower under modified atmosphere packaging

The study focuses on development of modified atmosphere packaging for fresh-cut minimally processed cauliflower to increase its shelf-life and enhancing the on-farm value addition by utilizing perforated packaging films along with pretreatments with ozonated water and antimicrobials. The samples were treated with ozonated water, oregano essential oil (antimicrobial), and cinnamon essential oil (antimicrobial). Based on preliminary treatments, the number of perforations made by specially prepared tool was kept as 6 and 12, which represented 5.1 × 10-5 and 1.02 × 10-4% of the total surface area of packages. These perforated packaged samples were stored in cold room at 4 °C temperature for 28 days. The shelf life and quality of treated cauliflower samples were compared with untreated samples. The quality analysis of the samples was carried up to 28 days at 7 days intervals based on their weight loss, headspace gas composition, texture, pH, total soluble solids, ascorbic acid, total phenolics, total microbial count, and sensory characteristics. The quality analysis revealed that ozonated water-treated samples at 12 perforations and stored at 4 °C for 28 days were most efficient in keeping it fresh without any significant reduction in quality as compared to the cauliflower stored for one week at normal conditions.

Development of a Controlled-Ventilation Box for Modified-Atmosphere Storage of Fresh Produce

Adjusting beneficial gas concentrations in real time in response to changing storage conditions is important for fresh produce, especially throughout the supply chain when temperature abuse occurs frequently. In this study, a controlled-ventilated box for bulk transportation of fresh produce was demonstrated and tested under variable temperatures. The presented system comprised a rigid container with a miniature blower installed in the opening of its wall for facilitating the gas exchange and an additional wall opening with a metal tube protruding into the inner container's space. The in-package atmosphere was formed by the balance between the respiratory activity of the produce and the influx of fresh air through the wall openings, regulated by switching the blower ON or OFF. The mass transfer coefficient for metal tubes of different dimensions was measured under modified atmosphere featuring 15% CO₂ and 5% O₂ at 10 °C. The addition of an air blower increased the mass transfer coefficient by at least 100 times. A further storage trial with cherries was successfully performed at 10 °C and 20 °C. The demonstrated trial featured some significant inputs to increase the knowledge about better storage of fresh produce throughout the supply chain and storage.

AI-based soft-sensor for shelf life prediction of ‘Kesar’ mango

This paper presents prediction of shelf-life of ‘Kesar’ cultivar of mangoes stored under specified conditions based on their respiration rate and ripeness levels. A deep-CNN was fine-tuned on 1524 image data of mangoes stored under different conditions to classify the ripeness levels of mangoes as ‘unripe’, ‘early-ripe’, ‘partially-ripe’ and ‘ideally-ripe’. CO2 respiration rate (RRCO2) was further calculated using principle of enzyme kinetics to establish a correlation between RRCO2 and ripeness levels. A Support Vector Regression model was employed to predict the shelf life and ripeness levels of mangoes under different storage conditions, thereby creating an AI based soft-sensor. The developed methodology can be used for other climacteric fruits besides mangoes. This solution can be used by producers and distributors for post-harvest handling of climacteric fruits like mango. It will also aid retailers in taking dynamic decisions with respect to pricing, logistics and storage conditions to be maintained to get the desired ripening rate, thus, contributing to reduction of wastage of fruits and subsequent economic losses.

Article highlights

Shelf life enhancement of guava (Psidium guajava cv. Baruipur) stored under pilot scale modified atmosphere storage system

PRACTICAL APPLICATION

The developed modified atmosphere storage (MAS) system has increased the shelf life of Guava up to 20 and 9 days at 10 °C and 25 °C, respectively. This extended period will be very much effective for providing the buffer period to the fresh Guava and facilitate extra time to the farmers for its marketing. The uniquely developed MAS system is helpful for the farmers for on-farm storage of fresh Guava at a large scale and will provide smooth handling and transportation for retailing and marketing.

Effects of Passive- and Active-Modified Atmosphere Packaging on Physio-Chemical and Quality Attributes of Fresh In-Hull Pistachios (Pistacia vera L. cv. Badami)

The effects of passive- and active-modified atmosphere packaging (passive- and active-MAP) were investigated on the physio-chemical and quality attributes of fresh in-hull pistachios stored at 4 ± 1 °C and 90 ± 5% R.H. Fresh pistachios were packaged under each of the following gas combinations: active-MAP1 (AMA1) (5% O2 + 5% CO2), AMA2 (5% O2 + 25% CO2), AMA3 (5% O2 + 45% CO2), AMA4 (2.5% O2 + 5% CO2), AMA5 (2.5% O2 + 25% CO2), and AMA6 (2.5% O2 + 45% CO2), all balanced with N2, as well as passive-MAP (PMA) with ambient air (21% O2 + 0.03% CO2 + 78% N2). Changes in quality parameters were evaluated after 0, 15, 30 and 45 days of storage. Results demonstrated that AMA6 and PMA had significantly lower (7.96 Log CFU g-1) and higher (9.81 Log CFU g-1) aerobic mesophilic bacteria counts than the other treatments. However, the AMA6 treatment decreased, kernel chlorophyll and carotenoid content, hull antioxidant capacity, and anthocyanin content. The PMA treatment produced a significant weight loss, 0.18%, relative to the other treatments. The active-MAP treatments were more effective than the passive-MAP in decreasing weight loss, microbial counts, kernel total chlorophyll (Kernel TCL), and kernel carotenoid content (Kernel CAC). The postharvest quality of fresh in-hull pistachios was maintained best by the AMA3 (5% O2 + 45% CO2 + 50% N2) treatment.

Quality, storability, and essential oil content of Ligularia fischeri during modified atmosphere packaging storage

Modified atmosphere packaging (MAP) enhanced the quality and storability of Ligularia fischeri. Oxygen transmission rate (OTR) films were used as a MAP. MAP storage displayed lower fresh weight loss than perforated film. The oxygen, carbon dioxide, and ethylene concentration were properly maintained by a 10,000 cc OTR packaging film at 8 °C and 30,000 cc OTR packaging film at 24 °C. On the last day of storage, the off-odor, such as the acetaldehyde and ethanol concentration, was the lowest in the 10,000 cc OTR film at 8 °C and 30,000 cc OTR film at 24 °C treatments. The 10,000 cc OTR film treatment at 8 °C and 30,000 cc OTR film treatments at 24 °C had the highest chlorophyll content, total phenolic content, leaf toughness, antioxidant activity, vitamin C, and less off-flavor. The shelf life of 10,000 cc OTR film was 13 days, at 8 °C storage temperature. At 24 °C storage temperature, the shelf life of 30,000 cc OTR film was 4 days. The MAP storage of the Ligularia treated with 10,000 cc OTR film at 8 °C and 30,000 cc OTR film at 24 °C had the highest essential oil content. These results suggest that the best MAP film for cold-chain distribution was the 10,000 cc OTR film, and the 30,000 cc OTR film was a more suitable MAP film for local distribution without the cold-chain system of L. fischeri.

Design and development of modified atmosphere packaging system for guava (cv. Baruipur)

Modified atmosphere packaging (MAP) is a dynamic system during which respiration and permeation occur simultaneously. Hence factors affecting both respiration and permeation were considered for designing a package. In the design of MA packages for guava (cv. Baruipur) a total of 13 variables were considered. The independent variables includes: weight of fruits, surface area of packaging film, free volume of the package, thickness of the film and permeabilities of film to O2 and CO2 gas. The fixed variables considered were: the surrounding gas composition and temperature, the respiration rates for O2 consumption and CO2 evolution, and the equilibrium gas compositions to be attained in the package so that the fruit's shelf-life is extended. Two types of MA packages, having package size of 19 cm × 19 cm for a fill weight of 1,000 ± 100 g were developed. Packages were designed to accommodate a fill weight range of 0.90-1.10 kg. Various package parameters were optimized to facilitate establishment of dynamic equilibrium at target levels of O2 and CO2 concentration in the package. The storage study of MA packages was performed at 10, 15, 20 and 25 °C temperatures. The performance of film packages was evaluated for their ability to establish equilibrium at target levels and to extend the shelf life of the packaged fruit. The MA packaging system increased the shelf life of guava by 128-200 % compared to the unpacked fruits at various storage temperatures with a quality comparable with the freshly harvested commodity.

Respiratory dynamics of fresh baby corn (Zea mays L.) under modified atmospheres based on enzyme kinetics

The respiratory behaviour of baby corn - whole and end-cut, under different temperatures and gas conditions was evaluated to study its respiratory dynamics based upon enzyme kinetics. The dependence of respiration rate on the O2 and CO2 concentrations has been described assuming the enzyme kinetics model for combined type of inhibition caused by CO2. Various respiratory parameters viz. maximal O2 consumption rate Michaelis-Menten constants, Inhibition constants under the specified environmental conditions of 5, 12.5, 20°C and 75% relative humidity (RH) were estimated using non-linear regression technique. The enzyme kinetics parameters were analyzed according to Arrhenius law to study their temperature dependence. Based upon the overall analysis, it was found that storage temperature had substantial affect on the partial pressures within the closed containers and subsequently the respiration rates. The concentration of O2 inside the container and surrounding temperature had synergistic effect on the rate of respiration and respiratory parameters. Though the inhibition by evolved CO2 was observed to be of combined type, it changed from predominantly competitive at 5°C to predominantly uncompetitive at 12.5 and 20°C. This study can be utilized for design of modified atmosphere packages for storage of fresh and minimally processed baby corn.