Oxygen Transmission Rate Of Film Research Articles

Pilot Scale Assessment of High-Pressure Processing (HPP) to Enhance Microbiological Quality and Shelf Life of Fresh Ready-to-Eat (RTE) Blue Crab Meat.

Blue crab (Callinectes sapidus) is a highly valuable wild fishery species of crab native to the waters of the western Atlantic Ocean and the Gulf of Mexico. The annual commercial production of live blue crabs is approximately 50,000 metric tons with a dockside value of USD 200 million. Presently the US blue crab processing industry sells crab meat in three basic forms: fresh crab meat, pasteurized crab meat, and frozen crab meat. By far "Fresh" is the most desirable form of crab meat. However, fresh crab meat has a limited shelf life. This study evaluated the effects of high-pressure processing (HPP) on enhancing the microbiological quality and shelf life of blue crab meat. Live blue crabs were pressure-cooked in a retort (≥115 °C for 4-6 min). The crab meat was handpicked, packed in plastic containers with seals, subjected to HPP treatment, and stored at 4 °C. Container integrity and water leakage issues were examined by observation in addition to weight comparison before and after HPP treatment; the shelf life of crab meat with and without HPP treatments was examined via microbiological tests and sensory evaluations. Results show that polypropylene containers sealed with 10K OTR (oxygen transmission rate) film could withstand high pressure without water leakage issues; HPP treatment at 600 MPa for 3 min could extend the shelf life of fresh, cooked, and handpicked crab meat from 6 days to 18 days based on the strictest APC (aerobic plate account) limit (APC ≤ 100,000 CFU/g). The sensory quality of the HPP-treated crab meat was well accepted throughout the 3-week storage period. The results support the use of HPP as an effective non-thermal processing technology to enhance the microbiological quality and extend the shelf life of fresh RTE blue crab meat.

Shelf Life of Aquaponically-grown Finstar Lettuce in Different Oxygen Transmission Rate Films

The effects of oxygen transmission rate of packaging material on the shelf life of aquaponically-grown Finstar lettuce was studied. Parameters of packaging headspace gas composition (oxygen and carbon dioxide concentrations), lettuce pH, percentage weight loss, total aerobic microorganisms, and color were analyzed every ten days for sixty days. Finstar lettuce was stored at 4○C in four different types of packages (treatments), including a clamshell package and three film bags with oxygen transmission rates (OTR) of 3.0-6.0 cc/(m2/24 hr/1 atm), 80-90 cc/(m2/24 hr/1 atm), and >225 cc/(m2/24 hr/1 atm). The percentage weight loss of the 3.0-6.0 OTR package (-0.76-1.05%) was lowest while the percentage weight loss of the clamshell package was highest (0.81-7.72%) among packaging treatments. Nearly ½ of the panelists rated lettuce as fresh enough to eat as is after 50 days of storage in 80-90 cc/(m2/24 hr/1 atm) films while lettuce packaged in the other treatments had less that 1/3 of the panelists judging the lettuce fresh enogh to eat as is. The long shelf-life may be attributed to Finstar having resilient genetic properties along with being greenhouse-grown which lessens the possibility of contamination compared to field-grown lettuces.

Morphological and performance characteristics of nanocomposite films based on poly(lactic acid) compounded with nanocrystalline cellulose and chitin whiskers using melt extrusion

The purpose of this work was to evaluate the morphological, mechanical, barrier and phase-transition properties of poly(lactic acid) (PLA) films with nanofillers such as nanocrystalline cellulose (NCC, 1–5%) and chitin whiskers (CHW, 3%). Nanofiller addition using melt extrusion led to decrease in heat capacity change at glass transition as observed from differential scanning calorimetry data. Transmission electron microscopy and x-ray diffraction studies showed that the nanofillers were dispersed in the polymer matrix. This indicated confinement of the motion of polymer chains between layers of nanofillers. Tensile strength (TS) of PLA-based nanocomposite films increased from 50.2 to 70.9 MPa with addition of 5% NCC to PLA. However, addition of CHW did not significantly improve TS. Addition of 3% NCC reduced oxygen transmission rate of films from 209.9 to 180.8 cm3/m2/day, which further reduced to 109.3 cm3/m2/day by adding compatibilizer, methylene diphenyl diisocyanate (MDI, 4%). Water vapor transmission rate of PLA reduced from 44.4 to 28.6 g/m2/day with 3% NCC and 4% MDI addition. This research suggested the promising application of NCC as a nanofiller in PLA films with enhanced thermal, mechanical and barrier properties, and potential application in bio-based food packaging.

Natural color pigments: oxidative stability and degradation kinetics during storage in thermally pasteurized vegetable purees.

Package oxygen transmission rate (OTR) can affect the stability of natural color pigments such as anthocyanins, betalains and chlorophylls in foods during storage. In the present study, we investigated the oxygen sensitivity of selected pigments in thermally pasteurized vegetable purees held at a refrigeration temperature. We modulated the oxygen ingress in packaging using multilayer films with OTRs of 1, 30 and 81 cm3 m-2 day-1 . Red cabbage, beetroot and pea purees were vacuum packed, pasteurized to achieve a cumulative lethality of = 12.8-13.4min and stored at 7°C for 80 days. Anthocyanins were relatively stable (< 4% losses), regardless of the film OTR. Betalains showed the highest sensitivity to different OTRs, with total losses varying from 4% to 49% at the end of storage and showing significant differences (P < 0.05) among the three films. Chlorophylls showed no significant difference (P > 0.05) in sensitivity to film OTRs. However, continuous degradation of chlorophylls was observed for all film types, with total chlorophyll losses ranging from 33% to 35%. Overall color differences (ΔE) at the end of storage for cabbage, beet and pea puree were between 0.50-1.70, 1.00-4.55 and 7.41-8.08, respectively. Betalains and chlorophylls degradation followed first-order and fractional conversion kinetics, whereas ΔE followed zero-order and fractional conversion kinetics during storage. All three pigments behaved differently to oxygen ingress during storage. Low to medium barrier films are suitable for products containing red cabbage anthocyanins. High barrier films are must for betalains, whereas medium to high barrier films are suitable for chlorophyll-containing products. © 2019 Society of Chemical Industry.

Stability of color, β‐carotene, and ascorbic acid in thermally pasteurized carrot puree to the storage temperature and gas barrier properties of selected packaging films

AbstractQuality of pasteurized products can be affected by the combination of temperature abuse and gas barrier properties, especially oxygen transmission rate (OTR), of packaging films. Carrot puree was thermally pasteurized (90 °C, 14 min) and stored in three different types of pouches (OTR—0.99 ± 0.05 [F‐1], 29.8 ± 1.38 [F‐30], and 80.9 ± 2.15 [F‐81] cm3 m−2 day−1) at different temperatures (4, 8, and 13 °C). Weight loss, pH, instrumental color, β‐carotene, and ascorbic acid were evaluated over a 100‐day storage period. Results show that film OTR and temperature had a significant (p &lt; 0.05) effect on food quality and nutritional attributes. High‐barrier film (F‐1) retained quality, while low‐barrier film (F‐81) increased losses during processing and storage for all parameters tested. High‐barrier film demonstrated stable color values (a* and b*) and significantly (p &lt; 0.05) higher retention of β‐carotene during storage period. Ascorbic acid retention varied from 0 to 89%, depending upon packaging type. Based on ascorbic acid degradation kinetics, activation energy and Q10 values ranged from 20.3–72.3 kJ/mol and 1.36–2.96, respectively.Practical applicationsPasteurized food products have limited shelf life under refrigerated conditions. The shelf life of these products can be reduced by the combined effect of temperature abuse and gas barrier properties of packaging films. There is scarce information in the literature focusing on the shelf life studies of in‐pack thermally pasteurized products as a function of gas barrier properties. The selection criteria of films for pasteurized products are complex. Generally, higher the barrier properties needed higher is the cost of packaging. This study demonstrated the suitability of medium‐barrier films for in‐pack pasteurization; and combined effect of temperature abuse and gas barrier properties on the nutrient retention.

포장 필름과 저장 온도 조건에 따른 양송이버섯의 품질 변화

This study was conducted to investigate the effects of temperature and packing film with varying oxygen transmission rate (OTR) on the quality of Agaricus bisporus (mushrooms) to determine the optimum modified atmosphere package. Mushrooms were packed using 10 µm polyvinyl chloride (PVC), and 30 µm oriented polypropylene (OPP) films with the OTR ranging from 1,000 to 20,000 mL/m2/day/atm (OPP1000, OPP6000, OPP10000, and OPP20000). The quality parameters including weight loss, gas composition, cap opening rate, stipe elongation, firmness, and color of mushrooms were monitored at the following temperatures: 4℃, 8℃, 12℃, and 20℃. Overall, the mushrooms packed in OPP films showed less change in weight loss, cap opening rate, stipe elongation, and firmness than those of the control, however, these effects differed with the temperature and film OTR. Among the OPP films, OPP20000 did not exhibit any effect with respect to tissue growth inhibition. OPP1000 and OPP6000 were the most effective in suppressing the cap opening rate and stipe elongation but induced tissue damage and water soaking in the internal section. In contrast, the mushrooms packed in PVC film showed less change in weight loss, cap opening rate, and stipe elongation than those of the control, and browning of inside and outside of mushroom was less than that mushroom packed in OPP film.

Effect of biaxial‐simultaneous stretching conditions on OTR and CO2 permeation of CO2 laser perforated poly(lactic acid) film

The biaxially oriented poly(lactic acid) films prepared using simultaneous biaxial stretching were perforated by CO2 laser with the power of 60 W. The focal spot diameter was fixed at 103 μm. Pulse durations were varied from 1 to 30 μs, which corresponds to the fluence from 1.4 to 42.6 J/cm2. The perforated microhole size increased with increasing laser energy. The shape of microholes was circular for the films of equi‐biaxial stretching, whereas elliptical microholes were formed with its long and short axes corresponding to the directions of higher and lower stretch ratios, respectively. Comparing the laser perforation behavior of the as‐drawn films and annealed films, the opening of a microhole in the annealed films started at higher laser fluence, and at the same fluence the size of microhole was smaller. Gas transmission rates of the biaxially oriented poly(lactic acid) films with different thicknesses were examined. The oxygen transmission rates (OTR) of film improved with increased microhole diameter. The OTR of films containing 1 microhole/103 cm2 (hole diameter of ~110 μm) was 184, 150, and 98 cm3/d in comparison with the OTR for the original films without microhole of only 16, 10, and 8 cm3/d, respectively. Packaging films with OTR higher than 100 cm3/d (equivalent to the 9700 cm3/m2/d) are required to create a modified atmosphere inside the package of fresh produce for shelf‐life extension. Measured OTR and CO2TR values of the 3 different shapes of microhole were compared and discussed.

산소투과도를 달리한 MA 필름으로 포장한 딸기 ‘매향’의 모의 수출 조건에서 품질 고찰

This study was conducted to determine types of oxygen transmission rate (OTR) films suitable for modified atmosphere (MA) storage treatment of strawberries (cv. ‘Maehyang’) for export and examination related changes in quality of strawberries during simulated shipping distribution conditions (2oC for 10 days~8oC for 11 days). Strawberries were packed by 1,300, 10,000, 20,000, and 30,000 cc/m2·day·atm OTR films for MA storage treatment and perforated film as the control for MAP. Fresh weight loss rate was less than 0.5% in OTR films except for the perforated film. Carbon dioxide and oxygen content in packages prevailed in permissible range for strawberries under recommended CA/MA conditions (i.e., CO2: 15~20%, O2: 5~10%) at 10,000 cc, 20,000 cc, and 30,000 cc OTR films. Ethylene content in OTR films did not reveal significant differences during storage. The 1,300 cc OTR film revealed highest off-flavor and lowest fungal incidence rate by sensory evaluation. The firmness, soluble solids, and visual quality were preserved the highest at 10,000 cc OTR film. In conclusion, 10,000 cc OTR film preserved the highest quality and extended shelf-life by 13 days if compared with conventional distribution conditions.

Different Oxygen Transmission Rate Packing Films During Modified Atmosphere Storage: Effects on Asparagus Spear Quality

The aim of this study was to determine suitable oxygen transmission rate (OTR) films for modified atmosphere (MA) storage of asparagus spears (Asparagus officinalis L.), and to examine the related changes in asparagus spear quality. Asparagus spears were packed with 10,000, 20,000, 40,000, 70,000, and 100,000 cc/m2·day·atm OTR film treatments for MA storage, and perforated film (conventional storage) was used as the control. The fresh weight loss rate was less than 1% in all OTR film treatments but not in the control. In all OTR film treatments, ethylene content rapidly increased on the first day of storage, and gradually decreased thereafter to 2.0 μL·L-1 by the final storage day. In the 10,000 cc and 20,000 cc OTR film treatments, carbon dioxide content was maintained within the permissible range for asparagus spears under recommended controlled atmosphere (CA) and MA conditions (5-12%). The oxygen content was maintained between 12% and 20% in all OTR film treatments. Hue angles and total chlorophyll content were highest in the 10,000 cc OTR film treatment in both tips and stems. Visual quality was maintained at a saleable level only in the 10,000 cc OTR film treatment until the final storage day (25 days). Based on sensory evaluation, the least off-odor was detected in the 10,000 cc OTR film treatment, and the most in the control treatment. While the soluble solids content decreased with all film treatments, it was maintained at the highest level in the 10,000 cc OTR film treatment. Vitamin C content decreased with all film treatments during storage, but was maintained at higher levels in the 10,000, 20,000, and 40,000 cc OTR film treatments. The firmness of tips and stems increased with storage duration in all film treatments, stems were firmer under the perforated film, 10,000, and 20,000 cc OTR film treatments. Given these results, the 10,000 cc OTR film treatment is considered the most appropriate for MA asparagus spear storage since visual quality and soluble solids content were maintained, and fresh weight loss, vitamin C content, off-odor, and yellowing were suppressed during storage.

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 10,000cc OTR packaging film at 8°C and 30,000cc 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 10,000cc OTR film at 8°C and 30,000cc OTR film at 24°C treatments. The 10,000cc OTR film treatment at 8°C and 30,000cc 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 10,000cc OTR film was 13days, at 8°C storage temperature. At 24°C storage temperature, the shelf life of 30,000cc OTR film was 4days. The MAP storage of the Ligularia treated with 10,000cc OTR film at 8°C and 30,000cc 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 10,000cc OTR film, and the 30,000cc OTR film was a more suitable MAP film for local distribution without the cold-chain system of L. fischeri.

Effect of Package Film on the Quality of Postharvest Chinese Toon Tender Shoots Storage

The young leaves and shoots of the Toona sinensis (A. Juss.) Roem. tree, called Chinese toon, are commonly eaten as a vegetable in China. This study was conducted to develop a modified atmosphere packaging (MAP) system for Chinese toon tender shoots and to evaluate the effect of film oxygen transmission rate (OTR) on package atmospheres and consequent product quality changes during storage. Fresh precooled Chinese toon tender shoots (25±0.5 g each) were packaged in sealed 10 cm × 15 cm polyethylene bags prepared with films of OTRs of 8.0, 11.6, 16.6, 21.4, or 29.5 pmol s−1 m−2 Pa−1 and stored at 4±0.5°C for 25 days. Evaluations included package atmospheres, tissue electrolyte leakage, color, and sensory attributes (overall visual quality, off-odor, texture, and marketability). Results indicated that the OTR of the package film significantly (P&lt;0.05) affected package headspace gas composition, a⁎, hue angles, product quality, and shelf-life, under the tested package configurations and storage conditions. Packages with film OTR of 21.4 pmol s−1 m−2 Pa−1 attained stable O2 (8.4–10.0 kPa) and CO2 (2.2–3.0 kPa) levels by day 10, which were maintained through the end of storage; products stored in these packages maintained freshness with high overall quality scores.

Oxidation-reduction potential and lipid oxidation in ready-to-eat blue mussels in red sauce: criteria for package design.

Ready-to-eat in-package pasteurized blue mussels in red sauce requires refrigerated storage or in combination with an aerobic environment to prevent the growth of anaerobes. A low barrier packaging may create an aerobic environment; however, it causes lipid oxidation in mussels. Thus, evaluation of the oxidation-reduction potential (Eh) (aerobic/anaerobic nature of food) and lipid oxidation is essential. Three packaging materials with oxygen transmission rate (OTR) of 62 (F-62), 40 (F-40) and 3 (F-3) cm3 m-2 day-1 were selected for this study. Lipid oxidation was measured by color changes in thiobarbituric acid reactive substances (TBARS) at 532 nm (TBARS@532) and 450 nm (TBARS@450). Significantly higher (P < 0.05) TBARS@532 was found in mussels packaged in higher OTR film. TBARS@450 in mussels packaged with F-62 and F-40 gradually increased during refrigerated storage (3.5 ± 0.5 °C), but remained constant after 20 days of storage for mussels packaged with F-3. The Eh of pasteurized sauce was not significantly affected (P > 0.05) by OTR and remained negative (< -80 mV) during storage. Negative Eh values can support the growth of anaerobes such as Clostridium botulinum. The headspace oxygen concentration was reduced by about 50% from its initial value during pasteurization, and then further declined during storage. The headspace oxygen concentration was higher in trays packaged with higher OTR film. Mussels packed with high OTR film showed higher lipid oxidation, indicating that high barrier film is required for packaging of mussels. Pasteurized mussels must be kept in refrigerated storage to prevent growth of anaerobic proteolytic C. botulinum spores under temperature abuse. © 2016 Society of Chemical Industry.

Clostridium botulinum Toxin Production in Relation to Spoilage of Atlantic Salmon (Salmo salar) Packaged in Films of Varying Oxygen Permeabilities and with Different Atmospheres

Shelf life of fish packaged under modified atmosphere (MA) is extended, but within the United States, commercial application of MA with impermeable packaging films is restricted due to concerns that botulinum toxin production would precede spoilage when contaminated fish are held at abusive storage temperatures. Use of semipermeable packaging films has been advocated; however, previous studies are inconclusive in determining the oxygen transmission rate (OTR) of a film that is needed to achieve an acceptable margin of safety (i.e., toxin production occurs only after spoilage). This study was conducted to determine the influence of OTR (target OTRs of 3 to 15,000) on the development of spoilage volatiles and toxin in salmon inoculated with type E Clostridium botulinum and subjected to air, vacuum, or 75:25 CO2:N2 MA and storage temperatures of 4, 8,12, or 16°C. The most dominant headspace volatile peak that was produced during spoilage of samples at 4, 8 or 12°C was a peak, having a Kovats retention index (KI) of 753, and at which external standards of 2- or 3-methyl 1-butanol also eluted. Under anaerobic conditions, both the aerobic microbial populations and the size of the KI 753 spoilage peak were less in inoculated samples compared with uninoculated samples. C. botulinum-inoculated samples that were stored at 12 or 16°C under conditions favorable for anaerobic growth were also characterized by a KI 688 peak. Using a previously developed model that related the percentage of elderly consumers who would prepare a sample having the KI 753 spoilage peak of a specific size, it was determined that for salmon packaged with 3 or 3,000 OTR films under any atmosphere and stored at 12 or 16°C, 2 to 61% of the consumers could potentially prepare toxin-contaminated samples. Hence, when abusive storage conditions are suspected, the fish should not be consumed.

Evaluation of packaging films to extend storage life of indigenous Australian vegetables and herbs

A study undertaken in Hervey Bay, Queensland, investigated the potential of creating an indigenous agribusiness opportunity based on the cultivation of indigenous Australian vegetables and herbs. Included were warrigal greens (WG) (Tetragonia tetragonioides), a green leafy vegetable and the herb sea celery (SC) (Apium prostratum); both traditional foods of the indigenous population and highly desirable to chefs wishing to add a unique, indigenous flavour to modern dishes. Packaging is important for shelf life extension and minimisation of postharvest losses in horticultural products. The ability of two packaging films to extend WG and SC shelf life was investigated. These were Antimisted Biaxial Oriented Polypropylene packaging film (BOPP) without perforations and Antifog BOPP Film with microperforations. Weight loss, packaging headspace composition, colour changes, sensory differences and microbial loads of packed WG and SC leaves were monitored to determine the impact of film oxygen transmission rate (OTR) and film water vapour transmission (WVT) on stored product quality. WG and SC were harvested, sanitised, packed and stored at 4°C for 16 days. Results indicated that the OTR and WVT rates of the package film significantly (PKLEINERDAN0.05) influenced the package headspace and weight loss, but did not affect product colour, total bacteria, yeast and mould populations during storage. There was no significant difference (PGROTERDAN0.05) in aroma, appearance, texture and flavour for WG and SC during storage. It was therefore concluded that a shelf life of 16 days at 4°C, where acceptable sensory properties were retained, was achievable for WG and SC in both packaging films.

Effect of Packaging Films on the Quality of Canola Oil under Photooxidation Conditions

The objective of this study was to evaluate the influence of packaging films on the quality of canola oil which contains high concentration of fat under photooxidation condition and get the oxidation kinetics based on measuring the oxidation intensities including peroxide value, hexanal, and photosensitizer (chlorophyll). The canola oil was packaged by PET/CPP; KPET/PE was used for experiments. The change of light and oxygen transmission rate (OTR) of PET/CPP which was considered as the typical fatty foods packaging film under different light intensities was also tested. The results show that the peroxide value increased rapidly under light conditions and fitted the zero order kinetics; also the oxygen transmission rate had great impact on it; hexanal fitted the zero order kinetic in oil whose package of low OTR generated a lot; however package in high OTR films changed very slowly that might be dependent on the performance of hexanal through plastic films. The degradation of chlorophyll fitted the first order kinetic and decreased quickly under light but was almost independent of OTR of transparent packaging material. Light reduced the oxygen barrier properties of the films, which should be considered as the photooxidation condition (and the photooxidation condition thus should be considered).

Effect of Modified Atmosphere Packaging (MAP) on the Quality of Sea Buckthorn Berry Fruits during Postharvest Storage

AbstractThe effect of modified atmosphere packaging (MAP) on the quality of the berry fruits of sea buckthorn (SBT) during refrigerated storage was investigated. SBT berries were packaged in 160 and 525 oxygen transmission rate (OTR) films or in vented clamshell containers (air control) and stored at 10C for 10 days. Changes in the quality of the berries were determined by the evaluation of their headspace composition, moisture content, dry weight, pH level, color, total soluble solids, texture and antioxidant activity. The results indicated that the 160 OTR film presented good competency to maintain a proper atmosphere for storage. Both the 160 and 525 OTR films showed better capability for retaining the firm and springy texture of the berries, as well as their weight. The total soluble solids of 160 OTR packed fruits remained a stable value. The pH of SBT berries packed in different films and control samples increased in general during storage compared with the initial pH of fruits. The antioxidant activity of the berries was higher in MAP samples, especially those in the 160 OTR packages.Practical ApplicationsThis is the first study on the storage characteristics of berry fruit of sea buckthorn (SBT) under modified atmosphere packaging conditions. Film of 160 oxygen transmission rate (OTR) effectively maintained the initial quality parameters and antioxidant activity of berries by slowing down the respiration intensity. It may be because 160 OTR provided excellent CO2/O2 exchange performance to supply a desired gaseous environment of berry fruit. Thus, 160 OTR could be used as a potential packaging film for SBT berry on maintaining fruit quality and antioxidant activity. Furthermore, 160 OTR to different food systems of vegetables, mushrooms and juicy fruits can greatly maintain the nutritional value, product quality and fresh supply. The results of the present study can also serve as an assistive technology combined with other preservation techniques such as ice temperature, controlled atmosphere storage and so on to achieve desirable storage performance.

Effect of Modified Atmosphere Packaging on Postharvest Quality of Kohlrabi

Abstract: The effect of modified atmosphere packaging (MAP) on kohlrabi (Brassica olerace L. gongulodes group)’s quality and antioxidant molecule during storage was examined to determine the optimal film package for maintaining freshness. To extend shelf life, MAP was tested using PE 50 μm and oriented polypropylene (OPP) films with oxygen transmission rate (OTR) at 3,000, 10,000, 15,000 mL/m 2 /day/atm. The OPP film packaging with modified oxygen transmission rate showed a delay in a weight loss and extended storage period. The package with OTR 3000 attained the desired gas composition of O 2 3.2-6.7 kPa and CO 2 13.1-19.8 kPa, in storage at room temperature. Kohlrabi stored in this package showed the lowest weight loss and the highest visual quality. Deterioration and off-odor were developed more rapidly in PE 50 μm towards the end of the storage at room temperature. However, there are no differences among OTR films in visual quality and off-odor until 60 days at cold storage. Vitamin C content of kohlrabi was reduced rapidly in OTR 15000 with high transmission rate and showed less loss in PE 50 μm and OTR 3000 in both room temperatures and cold storage. Results revealed that an OPP film with OTR 3000 extended the shelf life of kohlrabi in storage with maintained quality and vitamin C.Additional key words:

Postharvest quality and shelf life of radish microgreens as impacted by storage temperature, packaging film, and chlorine wash treatment

Microgreens are new and emerging products, which are young seedlings of vegetables and herbs. A recent study showed that microgreens contain higher nutrients compared to their mature counterparts. However, they typically have a short shelf life (1–2 days) at ambient temperature. The objective of this study was to optimize postharvest handling conditions to reduce the quality loss and extend the shelf life of daikon radish (Raphanus sativus L. var. longipinnatus) microgreens. Storage temperature, packaging film, and wash treatment were investigated. Changes in headspace composition, quality index, chlorophyll concentration, tissue electrolyte leakage, and aerobic mesophilic bacteria (AMB) and yeast & mold (Y&M) counts were monitored periodically during storage. Results indicated that (1) storage temperature significantly (P < 0.05) affected package atmosphere, product quality and shelf life. One degree Celsius was the optimal temperature for storage of radish microgreens with no chilling injury observed; (2) film oxygen transmission rate (OTR) significantly (P < 0.05) affected O2 and CO2 composition, but OTR did not significantly affect quality attributes during 28 days of storage at 1 °C; (3) Chlorine wash treatment (100 mg/L) significantly reduced initial microbial populations by 0.5 log cfu g−1, including AMB and Y& M. However, microbial populations rebounded after day 7.

Postharvest biology, quality and shelf life of buckwheat microgreens

Buckwheat microgreens have short shelf life which limits their commercial use. The effects of storage temperature, modified atmosphere packaging (MAP), and wash conditions on quality and shelf life of buckwheat microgreens were assessed. Temperature significantly (P < 0.0001) affected package atmospheres and product quality. At the end of storage, microgreens stored at 1, 5 and 10 °C had smaller microbial populations and less tissue electrolyte leakage than those stored at 15, and 20 °C. Package film oxygen transmission rate (OTR) significantly (P < 0.05) affected package atmospheres. However, differences in quality and shelf life of microgreens packaged in different OTR films were slight and not evident until day 21 of storage. On day 21, buckwheat microgreens packaged in 16.6 pmol/(m2 s Pa) oxygen transmission rate package films were observed to have the freshest appearance with lowest tissue electrolyte leakage. Chlorine (100 mg/L) wash significantly (P < 0.05) reduced microbial populations, initially; however, after 7 days of storage, all washed microgreens experienced accelerated microbial populations. Our findings suggest that buckwheat microgreens should be stored at 5 °C with moderately high O2 (14.0–16.5 kPa) and moderately low CO2 (1.0–1.5 kPa) content to maintain optimal quality and maximal shelf life.

Freshness and sensory quality of packaged wild rocket

Sensory descriptive analysis was used to evaluate visual and overall freshness and the underlying attributes of freshness of packaged wild rocket (Diplotaxis tenuifolia L.) quality. Variation was induced by differences in package atmosphere, temperature and storage time. The leaves were packaged in trays wrapped in film with a low oxygen transmission rate (OTR) (low OTR; 0.65pmols−1m−2kPa−1) or high OTR (high OTR; 17.4pmols−1m−2kPa−1). To create packages with variation in O2 and CO2 concentrations in the package atmosphere, and in the sensory quality, the packages were stored at 2°C for 6 or 7 d or at elevated temperatures (10, and 20°C) for various times (2, 3, 4, and 6 d). At low OTR, the O2 concentration decreased to ≤0.5kPa, and the leaves developed a ‘smoked odor’, lost leaf integrity and texture, and turned olive-brown. At high OTR, the O2 concentrations inside the package remained at 10–18kPa, and leaves showed signs of senescence, i.e. light-green to yellow leaves and a heterogeneous appearance of leaves in the tray. Freshness of the leaves was evaluated by sensory analysis without prior consensus. ‘Visual freshness’ was evaluated at first sight before opening the packages, while ‘overall freshness’ was evaluated after opening and careful inspection by looking, smelling and touching the product. ‘Visual freshness’ was highly correlated to green leaf color (r=0.98), whereas ‘overall freshness’ was described by color, odor and texture as found by interval PLS. The high OTR packages had similar scores for ‘freshness’ before and after opening (P>0.05), while the low OTR packages had significantly different scores (P≤0.05). As appearance is an indication of freshness at purchase, wild rocket must be MAP packaged in an OTR film that permits sufficient levels of O2 for aerobic respiration when storage temperature cannot be controlled and kept low during distribution and retail.