Effect of initial oxygen concentration and film oxygen transmission rate on the quality of fresh‐cut romaine lettuce

Modified atmosphere packaging (MAP) is widely used to maintain the quality of fresh‐cut produce by matching the oxygen transmission rate (OTR) of the packaging film to the respiration rate of the packaged product. The effect of the interaction between film OTR and the initial headspace O₂ on quality of fresh‐cut vegetables has not previously been reported. Romaine lettuce leaves were sliced, washed, dried and packaged with film OTRs of 8.0 and 16.6 pmol s^?1 m^?2 Pa^?1, and with initial headspace O₂ of 0, 1, 2.5, 10 and 21 kPa. Packages were hermetically sealed and stored at 5 °C for up to 14 days. For samples packaged in 16.6 OTR film, increasing the initial headspace O₂ concentration delayed O₂ depletion within the packages, hastened the onset and increased the intensity of discoloration, and inhibited the development of CO₂ injury, acetaldehyde and ethanol accumulation, off‐odors and electrolyte leakage. With 8.0 OTR‐packaged lettuce pieces, ≤1 kPa initial headspace O₂ treatments induced an essentially anaerobic environment within the packages and increased acetaldehyde and ethanol accumulation and off‐odor development. Increasing the initial O₂ concentration above 1 kPa in 8.0 OTR packages transiently increased O₂ concentrations and reduced fermentative volatile production, off‐odors, electrolyte leakage and CO₂ injury. Regardless of initial headspace O₂ concentration, all 16.6 OTR‐packaged samples had severe discoloration after 14 days of storage. Quality was better maintained in 8.0 OTR‐packaged lettuce pieces as the initial headspace O₂ concentration was increased. A 21 kPa initial O₂ treatment of 8.0 OTR‐packaged lettuce maintained good quality throughout storage and had the best overall quality score. Copyright © 2005 Society of Chemical Industry     

Effects of type of packaging material on shelf-life of fresh broccoli by means of changes in weight,colour and texture

Five polymeric films were studied to determine their ability to retain the colour, weight and texture of broccoli (Brassica oleracea L. var. Italica Monterey). The materials were oriented polypropylene (OPP), polyvinyl chloride (PVC) and two different low-density polyethylenes (LDPE), one of which contained a sachet reported to absorb ethylene. The broccoli was packaged and stored at 4 and 10 °C for 4 weeks. The weight, colour, chlorophyll content and texture were monitored during storage as well as O₂ and CO₂ concentrations inside the packages. Packaging prolonged the broccoli shelf-life by up to 14 days. The shelf-life varied depending on the packaging material and quality parameter considered. The atmosphere was modified inside the packages; however, no package provided the recommended atmosphere (O₂ 1–2% and CO₂ 5–10%) for broccoli. Packaging in OPP resulted in the highest CO₂ concentration, 6%, while the lowest O₂ concentration, 9%, was created in the LDPE package without a sachet for ethylene absorption. Storage in LDPE without ethylene absorber resulted in the overall longest shelf-life. Broccoli stored in PVC deteriorated faster than broccoli packaged in the other materials. The influence of packaging material was greater at the higher temperature.     

Modified Atmosphere Packaging Protects Market Quality in Broccoli Spears Under Ambient Temperature Storage

Broccoli spears were packaged using a semipermeable polymeric film and stored 96 hr at 20°C. CO₂ and O₂ concentrations within the packages equilibrated to about 9 and 3%, respectively. Relative to non-packaged spears, ascorbic acid, chlorophyll and moisture retention were greater; and peroxidase activity was lower in packaged broccoli. No differences were found in total aerobic microbial population growth or Instron shear values between packaged and control spears.     

Effect of modified atmosphere packaging on visual quality and glucosinolates of broccoli florets

Broccoli (Brassica oleracea var. italica) florets were packaged in polyethylene bags with no holes (M₀), two microholes (M₁), and four macroholes (M₂), and then stored at 4 or 20 °C. The effects of modified atmosphere packaging (MAP) treatments on visual quality and glucosinolate contents were determined by comparing with non-wrapped florets. The results showed that MAP treatments, especially with M₀ and M₁, extended the shelf life and reduced the postharvest deterioration of broccoli florets stored at 4 and 20 °C. All three MAP treatments reduced the decreasing concentration rates of individual, total aliphatic and indole glucosinolates in broccoli florets when compared to those in the control, with M₀ being the most significant, followed by M₁ and M₂ during 23 days of storage at 4 °C or 5 days of storage at 20 °C. Broccoli florets with M₀ treatment maintained the visual quality and glucosinolate contents for 13 days at 4 °C and 3 days at 20 °C.     

QUALITY OF MINIMALLY PROCESSED LETTUCE AS INFLUENCED BY PACKAGING AND CHEMICAL TREATMENT

Shredded lettuce was packaged in sealed bags of monooriented polypropylene (OPP) film and also in polyethylene (PE) trays overwrapped with a multilayer polyolefin (RD106) or plasticized polyvinyl chloride (PVC) film; and stored at 4C in a refrigerated case during 8 days. Chemical treatment by dipping in a 0.3% ascorbic acid /0.3% citric acid solution did not significantly affect changes in microbial populations or visual sensory attributes. Type of package was not a significant factor for microorganism populations, but was significant (p<0.001) for changes in gas composition and visual sensory attributes. The modified atmosphere within the packages changed from normal air composition to about 1.5% O₂/12% CO₂ for OPP bags and to about 17–18% O₂/1–2% CO₂ for PVC-PE trays and RD106-PE trays after 8 days of storage. The visual sensory quality of the product was retained better in OPP bags than in the other ones.     

Influence of the modified atmosphere packaging on shelf life and quality of Navalinda sweet cherry

The benefits of different wrap-films for Navalinda sweet cherry, packaged in small-format (consumer packages), were analysed. A storage and distribution process entailing eight days at 4 °C plus four days at 20 °C was simulated. The cherries were packed in punnets and film-wrapped with one macroperforated film and two microperforated films of 0.30 (MAP.30) and 0.55 (MAP.55) µmol cm/cm² atm day of CO₂ permeability at 0 °C. Packing in MAP at 0 °C did not alter the subsequent respiratory intensity of the fruits at 20 °C; however, the respiratory intensity at 20 °C did increase when the storage temperature was raised to 4 °C. The concentration of CO₂ (%) inside the packets at 20 °C was proportional to the permeability of the films: MAP.30 (21%) and MAP.55 (15%). The microperforated films preserved fruit acidity and firmness while slowing down the darkening of colour, loss of quality and decay. Shelf life was most effectively prolonged with MAP.30 film. However, in view of the levels of hypoxia reached at 20 °C, its use is recommended only in the distribution and marketing processes with failsafe cold chains. The recommendations of use of the films, for the different markets, are expressed in light of the obtained results.     

ANTIOXIDANT CONTENT AND MARKET QUALITY OF JALAPENO PEPPER RINGS AS AFFECTED BY MINIMAL PROCESSING AND MODIFIED ATMOSPHERE PACKAGING

Retention of β-carotene in jalapeno pepper rings after 12 days' storage at 4.4C, and an additional 3 days at 13C was 87% in modified atmosphere packages (MAP, 5% O₂, 4% CO₂) and 68% in air. Retention of α-carotene was 92% in MAP and 52 % in air after 15 days, while ascorbic acid retention after 15 days was 83% in MAP and 56% in air. MAP retarded the conversion of L-ascorbic acid to dehydroascorbic that occurred in air stored peppers. Most antioxidant losses occurred within 3 days after minimal processing. MAP treatment resulted in greater preservation of quality attributes (texture, color and moisture content) and antioxidants than air stored peppers.     

Keeping quality and safety of minimally fresh processed melon

Fresh-cut Amarillo melon was stored under passive modified atmosphere packaging (MAP) for 14 days at 5 °C. Three commercial films were tested: microperforated polypropylene (MPP), bioriented PP (BPP), and oriented PP (OPP). As a control, a macroperforated PP film was used. The effect of a citric acid dip treatment (0.52 mM) on the quality of the melon pieces packaged in OPP film was also evaluated. A similar final gas composition (4 kPa O2 plus 12–13 kPa CO2) within packages was achieved by using the three tested films. This atmosphere was effective for maintaining sensorial quality and microbial safety and for avoiding weight loss and translucency. When citric acid dip was applied, a reduction of microbial counts, a low discoloration, an increase of lightness, and a general improvement of visual appearance were found. However, after 14 days of storage, neither MAP treatments nor citric acid dip were enough to avoid softening of at least 23%, although the highest value (32%) was found in control pieces. Taking into account safety, quality attributes and consumer acceptance, shelf life of fresh processed melon stored under the studied MAP conditions could be stabilised for 10 days.     

EFFECT of MODIFIED ATMOSPHERE PACKAGING ON GLUTATHIONE and ASCORBIC ACID CONTENT of ASPARAGUS SPEARS

Asparagus (Asparagus Officinalis L.) spears were packaged in ordinary and microperforated oriented polypropylene (OPP) films and were stored at 15C and 75% RH for up to 10 days. CO₂ concentrations ranged from 15.5 to 23% at 10 days of storage. Weight loss was less than 1.2% in microperforated film packages compared with 15% in air storage under similar conditions. Ascorbic acid content was found to be adversely affected at all the O₂ levels (1–6%) prevailing in microperforated film packages, but it was retained to the extent of 45–55% of its original concentration in ordinary OPP film packaged asparagus. the O₂ concentrations in microperforated film packages were also associated with higher glutathione concentrations in packed asparagus spears. Results of the study indicated that to preserve ascorbic acid and glutathione simultaneously in stored asparagus through MAP under high CO₂ and low O₂ conditions, O₂ concentration levels must be selected between 1 and 6% in such a way so as to get acceptable retention levels of ascorbic acid and glutathione.     

PROLONGING THE SHELF-LIFE OF FRESH GREEN CHILE PEPPERS THROUGH MODIFIED ATMOSPHERE PACKAGING AND LOW TEMPERATURE STORAGE

The postharvest quality of green chile fruit was compared after storage in 3 types of packages at 2 temperatures (24C and 8C). Package types were corrugated cardboard boxes, pressed cardboard trays overwrapped with VF-71 polyethylene, or low-density polyethylene (LDPE) bags. Fruit packaged in boxes or overwrapped trays had 24.8% and 10.1% weight loss, respectively, after 1 week of storage at 24C. Fruit packaged in polyethylene bags lost 0.3% weight and remained green. After 1 week at 8C, the weight losses were 3.8%, 1.8% and 0% for the boxed, overwrapped and bagged treatments, respectively. Postharvest quality was maintained up to 4 weeks when fruit were packaged in LDPE bags and stored at 8C. In a second study, steady state O₂ and CO₂ levels were determined inside the LDPE packages as fruit weight and temperature were varied. Storage temperatures were 24C, 16C and 8C. At 8C, steady state O₂ levels ranged from 12.0 kPa to 0.9 kPa, and CO₂ levels ranged from 2.0 kPa to 4.6 kPa as fruit weight was increased from 120 to 480 g. At 24C and 16C, fruit packaged in 480 g units had slower ripening rates than fruit packaged in smaller units; however, fruit stored at 8C remained green the longest, regardless of fruit weight.     

Effect of modified atmosphere packaging and vacuum packaging on the shelf-life of refrigerated chub mackerel (<Emphasis Type="Italic">Scomber japonicus</Emphasis>): biochemical and sensory attributes

The effect of modified atmosphere packaging (MAP 1: 70% CO₂/30% N₂ and MAP 2: 50% CO₂/30% N₂/20% O₂) and vacuum packaging (VP), on the shelf-life of chub mackerel (Scomber japonicus) fillets stored under refrigeration was studied. Quality assessment was based on sensory analysis and biochemical indices determination. Increase in total volatile basic nitrogen (TVBN) and trimethylamine nitrogen (TMAN) followed the order: MAP 1 < MAP 2 < VP < air (control samples). The presence of oxygen into the fish package (air or MAP) resulted in an increase in the 2-thiobarbituric acid (TBA) values in comparison with samples packaged in the absence of oxygen. The most effective MAP used was MAP 1 which contributed to a considerably slower rate of fish spoilage. Based primarily on odour scores it was observed that raw chub mackerel fillets stored in the presence of air remained acceptable up to ca. 11 days, VP and MAP 2 samples up to ca. 15–16 days, while MAP 1 samples up to ca. 20–21 days of storage. On the other hand, flesh texture and flesh colour of all packaged samples received scores above or equal than the acceptability limit up to ca. 13–14 days of storage.     

Postharvest performance of fresh‐cut ‘Big Top’ nectarine as affected by dipping in chemical preservatives and packaging in modified atmosphere

Fresh‐cut ‘Big Top’ nectarines were dipped in 2% (w/v) ascorbic acid–1% (w/v) calcium lactate and stored at 4 °C for up to 12 days in 10 kPa O₂‐ and 10 kPa CO₂‐modified atmosphere packaging (MAP). The used microperforated plastic film allowed O₂ and CO₂ concentrations to reach steady values from the fifth day in storage onwards. Samples stored in MAP after chemical dipping showed the highest visual quality score, slight browning symptoms, increment in firmness and very low ethanol and acetaldehyde content. The chemical dipping also increased antioxidant capacity, probably due to the effect of ascorbic acid. The results suggested that the control of yeasts was mainly exerted by MAP, whereas only a slight effect was achieved by the chemical dipping. Therefore, MAP plus ascorbic acid/calcium lactate dipping was the best combination to preserve phytochemical content, antioxidant capacity and microbiological safety of fresh‐cut nectarines during storage.     

Modified Atmosphere Packaging Affects Ascorbic Acid, Enzyme Activity and Market Quality of Broccoli

Reduced ascorbic acid (RAA) content, total chlorophyll and green color retention, enzyme activities and texture changes were followed in broccoli spears packaged in polymeric film and nonpackaged during 96 hr storage (10°C). Concentrations within packages monitored by gas chromatography were (CO₂,) 8% and (0²) 10%. RAA retention, moisture content, total chlorophyll and color retention were greater in packaged broccoli. No differences were found between packaged and nonpackaged broccoli for ascorbate oxidase and peroxidase activities, or texture.     

Survival of hepatitis A virus on modified atmosphere-packaged (MAP) lettuce

Experiments were designed to study the effect of various modified atmospheres (MA) on the survival rate of hepatitis A virus (HAV) on lettuce. Pieces of lettuce inoculated with HAV were incubated at room temperature (RT) and 4°C for 12 days in ambient air and under various modified atmospheres (CO₂:N₂at 30:70, 50:50, 70:30 and 100% CO₂) inside plastic bags of low O₂permeability. Samples were removed on days 1, 3, 6, 9 and 12 and the virus was recovered and plaque-assayed to determine residual titer. Incubation for 12 days at 4°C showed that the lowest HAV survival rate (47·5%) was on lettuce stored in a petri-dish (atmospheric air), whereas the greatest survival rates (83·6%) was on lettuce stored under 70% CO₂. Statistical analysis of virus survival at 4°C indicated that HAV titers decreased for all packages, but without a significant (P>0·05) difference between the package types. At RT, however, a significantly (P<0·05) lower HAV survival rate (0·01%) was evident on lettuce stored in a petri dish, whereas survival rates as high as 42·8% were observed on lettuce stored under 70% CO₂; much lower survival rates (≤8·6%) were obtained on lettuce stored under other MAP environments at RT. Statistical analysis of the RT data indicated that there was a highly significant (P<0·05) decrease in HAV titre with increasing storage time and between package types, except for lettuce stored under 70% CO₂. These data indicate that MAP does not influence HAV survival when present on the surface of produce incubated at 4°C. A slight improvement in virus survival on lettuce was seen in the presence of high CO₂levels at RT. This may have been attributed to the inhibition of spoilage-causing enzymatic activities in the lettuce, which may have reduced exposure of the virus to potential toxic by-products.     

Effect of Modified Atmosphere Pakaging on the Shelf-life of Common Carp (Cyprinus carpio) Steaks

The effect of modified atmosphere packaging (MAP 1: 40%CO₂+60%N₂ and MAP 2: 100%CO₂) on the shelf-life of carp steaks was studied. Carp steaks were stored at +3±0.5˚C and on days 1, 3, 6, 9, 13 and 15, microbiological, chemical and sensory testing was performed. Based primarily on odour scores it was observed that carp steaks packaged in MAP1 remained acceptable up to 13 days of storage, while carp steaks packaged in MAP2 remained unchanged until the end of the study. By using MAP, especially 100% CO₂, products shelf-life can be significantly prolonged.     

Maintaining quality of wild vegetables (Aster glehni and Aruncus dioicus var. kamtschaticus) from Ulleungdo(Island), Korea by modified atmosphere packaging

Wild vegetables, Aster glehni and Aruncus dioicus var. kamtschaticus, produced from Ulleungdo (Island), Korea were packaged with 30 μm polypropylene (PP), 30 μm antifogging oriented polypropylene (A-OPP), 30 μm microperforated antifogging oriented polypropylene (MiA-OPP), 30 μm macroperforated low density polyethylene (Ma-LDPE), and 20 μm macroperforated high density polyethylene (Ma-HDPE), stored at 4, 10, and 20°C. Concentrations of O₂ and CO₂ in the packages were not modified by Ma-LDPE and Ma-HDPE. Weight loss was retarded by PP, A-OPP, MiA-OPP, especially as storage temperature decreased. Soluble solids were not affected by packaging materials. pH slightly decreased in LDPE and Ma-HDPE. Appearance, color, and overall acceptability of both vegetables stored at 4°C in PP or MiA-OPP showed the highest sensory score. These results suggest that packaging with PP or MiA-OPP films and storage at 4°C could be a useful method to maintain quality of the wild vegetables.     

STORAGE OF MINIMALLY PROCESSED ROMAINE LETTUCE UNDER CONTROLLED ATMOSPHERE

The effects of CO₂ and O₂ concentration on the preservation of minimally processed Romaine lettuce (Lactuca sativa, L.) under controlled atmosphere were studied. The lettuce was stored at 4C for 16 days under a continuous stream of nitrogen containing 0.5 to 2% O₂ and 2 to 15% CO₂. Increasing the CO₂ content in the atmosphere to 10% or more reduced enzymatic browning due to wounding and improved lettuce visual quality. However, 15% CO₂ caused brown lesions (brown stain, BS) after 8 days of storage. Decreasing the O₂ content to 1% in the presence of 10% CO₂ reduced tissue browning slightly without lowering the content of phenols, but 0.5% O₂ increased browning and anaerobiosis. Among the atmospheres tested, 10% CO₂ and 1% O₂ were beneficial for maintenance of the quality of minimally processed Romaine lettuce.     

Volatile compounds of modified atmosphere packaged cut iceberg lettuce: Effect of extremely low O2, season,cultivar and storage time

This study investigates the changes in volatile compounds in minimally processed iceberg lettuce as a function of season, cultivar, packaging and time. In order to achieve this, iceberg lettuce cultivars Platinas, Diamantinas and Morinas were harvested from June to September 2009. Lettuces were minimally processed and stored under three different treatments: two passive modified atmosphere packagings using films of different permeabilities, F1 (OPALEN 65 AF) and F2 (OPP/PE-L 2040 AF), and storage in air. All packages were stored at 5 °C. Gas composition and volatile compounds were assessed at 1, 5, 8 and 11 days of storage in packaged lettuce, whereas in air stored samples volatiles were analyzed only at 1 and 5 days of storage. Twenty one potent odorants were identified by GC–O. Among the months, August presented a notary increase of elemene, β-selinene and 2,3-butanedione, which likely contribute to off-odor of packaged cut lettuce. The content of O₂ and CO₂ was demonstrated to influence the formation of odorants as storage time increased. Higher amount of cis-3-hexenol was related to aerobic conditions found in the modified atmosphere packages and air stored samples after 1 day of storage, whereas levels of odorants such as 2,3-butanedione, elemene and β-selinene were significantly enhanced under anaerobic conditions after 11 days of storage. Film F2 seems to be the most promising because it kept the concentration of elemene and β-selinene lower than film F1. No clear differences were seen between the cultivars Morinas, Diamantinas and Platinas with regard to production of objectionable odorants under anaerobic conditions.     

The effects of packaging film and storage temperature on the quality of a dry coleslaw mix packaged in a modified atmosphere

Summary The effects of six packaging treatments on the quality of dry coleslaw packaged in modified atmospheres and stored at 4 and 8 °C for 9 days were determined. The coleslaw was packaged within either oriented polypropylene (OPP) or one of four microperforated OPP films, PA‐120, PA‐160, PA‐190, and PA‐210. It was also stored within punctured OPP (i.e. in air). Packaging within OPP resulted in an atmosphere with very low O₂ (<1%) and extremely high CO₂ (25–35%) levels. These storage conditions had detrimental effects on the quality of coleslaw: loss of firmness, falling pH, high cell permeability and exudate, high surface moisture and poor acceptability of aroma. By contrast, the microperforated films generated less atmosphere modification; in some cases this was insufficiently modified to be technically useful. The relatively high O₂ levels in these microperforated packs resulted in lower appearance and colour scores, increased surface dryness and higher firmness values. Increasing storage temperature from 4 to 8 °C resulted in a reduction in shelf‐life for all film types. While still not optimal, packaging within microperforated films allowed better preservation of quality and reduced cell membrane damage.