Predictive modelling and selection of Time Temperature Integrators for monitoring the shelf life of modified atmosphere packed gilthead seabream fillets

The objective of the present study was to validate a kinetic model for growth of spoilage bacteria in modified atmosphere packed (MAP) gilthead seabream fillets and to select a Time Temperature Integrator (TTI). The temperature and CO₂ dependence of the growth of lactic acid bacteria in MAP gilthead seabream fillets was expressed by an Arrhenius-type model for the range of 0-15 °C and 20-80% CO₂, which was validated at isothermal, variable and chill chain conditions. A new UV activatable photochemical TTI, was kinetically studied and the influence of the level of activation on the response of the TTI was modelled. Applying the developed models, the required charging levels were estimated so that the TTI response was tailored to monitor the shelf life of fish fillets at selected MAP conditions, during the chill chain storage. A simulation experiment of the product distribution and storage in various chill chain conditions showed the applicability of the TTIs as shelf life monitors.     

Quality assessment of whole and gutted sardines (Sardina pilchardus) stored in ice

The quality and shelf life of whole ungutted and gutted sardines ( Sardina pilchardus ) stored in ice were studied. The changes in the fish were investigated by sensory assessments, chemical analyses and microbiological analyses. The sensory scores of uneviscerated and gutted sardines stored in ice at +4 °C were 7 days. The chemical indicators of spoilage, total volatile basic nitrogen and trimethylamine values of gutted sardine increased very slowly, whereas for whole ungutted samples higher values were obtained reaching a final value of 15.03–29.23 mg per 100 g and 2.36–4.16 mg per 100 g, respectively (day 9). Peroxide and thiobarbituric acid values remained lower for whole ungutted sardine samples until day 9 of storage, whereas for gutted fish were higher. The level of histamine exceeded the legal limit in whole ungutted sardine after 7 days of storage in ice, during which sardines were rejected by the sensory panel. Mesophilic aerobic bacteria count, H₂S-producing bacteria, sulphide reducing anaerobe Clostridias, Enterobacteriaceae count of whole ungutted sardine samples are higher than gutted sardine samples during the storage. Psychrotrophic bacteria counts of the two groups were not different. The limits of microbiological data were not exceeded throughout the storage in both the groups' samples.     

Shelf life of Turkish whey cheese (Lor) under modified atmosphere packaging

In this study, the shelf life of Lor cheese stored under different atmosphere compositions was assessed and compared. Lor cheeses were held in four different atmospheres containing: vacuum packaging (VP), 40% CO₂/60% N₂, 60% CO₂/40% N₂ and 70% CO₂/30% N₂ (modified atmosphere packaging). Control cheeses were stored in air. All cheese samples were kept in the refrigerator at 4°C for 45 days and investigated for physicochemical, microbiological and sensory properties. The acidity index value was significantly higher ( P  < 0.05) in the control and vacuum packaged samples than in those stored for the same period under CO₂. Microbiological results showed that modified atmosphere packaging delayed microbial growth compared with air and VP samples. Of the three modified atmospheres, gas mixtures 60% and 70% CO₂ were the most effective for inhibition of growth of micro-organisms. Sensory evaluation (odour and taste) results showed that Lor cheese packaged under modified atmosphere packaging (60% CO₂/40% N₂ and 70% CO₂/30% N₂ ) retained good characteristics for 45 days of storage, while vacuum and control samples were sensorily unacceptable after 10 days of storage.     

Minimally processed butternut squash shelf life

The effects of dipping in antimicrobial solution and efficacy of proper film and modified atmosphere packaging conditions (MAP) on the quality decay of packaged fresh-cut butternut squash were investigated. The work was divided into three subsequent experimental trials: the first two were aimed to select the optimal packaging film mass transport properties, being micro-perforated and no-perforated films been tested. In the third experimental step, the best film (i.e., no-perforated oriented polypropylene, OPP40) was used to package sliced butternut squash under passive and active MAP. Each slice of product was dipped in aqueous solution of potassium sorbate, while no dipped samples were stored as the controls. During storage at refrigerated temperature (4 ± 1 °C) headspace gas concentrations, mass loss, microbiological and sensory quality were monitored. Results obtained from the preliminary pre-screening showed that micro-perforated films did not match fresh-cut butternut squash respiratory requirements. In these films a high proliferation of moulds occurred, probably due to elevated oxygen levels. Among the no-perforated films with different thickness, the OPP40 showed better performances. In the third trial samples dipped in potassium sorbate and packaged in OPP40 under active MAP recorded a shelf-life of about 22 days respect to the no-dipped samples packaged under both passive and active MAP that reached a shelf life of about 2 weeks.     

Storage behaviour of minimally processed pumpkin (Cucurbita maxima) under modified atmosphere packaging conditions

 Minimally processed vegetables in fresh, ready-to-cook form are gaining the confidence of both the trader and the consumer. This has led to a need to develop technology for increasing shelf life while maintaining the microbial, nutritional and sensory quality of minimally processed vegetables. This investigation was carried out on pumpkin in minimally processed form, packed in different polymeric film bags of varying permeabilities, creating an active equilibrium modified atmosphere within the package for the extention of storage life. It was observed that minimally processed pumpkin, which has a high respiratory rate at room temperature (155.7 mg CO₂/kg/h) could be stored for a period of 25 days at 5±2  °C under modified atmosphere packaging conditions with a minimum physiological loss in weight of 0.06% and marginally low changes in biochemical constituents, such as vitamin C, total soluble solids, moisture, carotenoids and titrable acidity, enabling the retention of near-fresh quality. The microbial loads of mesophilic aerobes and coliforms, which were log 5.5 and log 4.3 were less than threshold level. There was no growth of yeasts and moulds or mesophilic spore formers at the end of the storage period. Received: 24 January 2000 / Revised version: 4 April 2000     

Effectiveness of active and modified atmosphere packaging on shelf life extension of a cheese tart

This study evaluated the shelf life extension of a cheese cake subjected to modified atmosphere (MAP) and active packaging (AP). Cheese cakes were packaged under different N₂/CO₂ ratios (70/30 and 20/80) (MAP batches), by placing a sachet of an iron oxide-based oxygen absorber inside trays (AP batch) and with air (air batch). Changes in microbial growth, in-package gas composition, chemical–physical parameters including texture and sensory attributes were monitored for 48 days at 20 °C. AP allowed a mould-free cheese cake shelf life of 48 days, MAP extended the shelf life of samples packaged under 30% and 80% CO₂ up to 14 and 34 days, respectively, whereas tarts stored with air spoiled after 7 days. MAP resulted in a significant increase in hardness after 14 days of storage, whereas AP tarts recovered the initial texture after 48 days. Panellists judged AP tarts over the acceptability threshold during the whole shelf life of cheese tarts.     

Effects of modified atmosphere packaging (MAP) on the microbiological quality and shelf life of ostrich meat

Effects of various concentrations of O₂/CO₂ in modified atmosphere packaging on the microbiological quality and shelf-life of ostrich meat was investigated. Nine–12 months old ostriches were used. The iliofibularis muscle was cut into small cubes that were divided into five groups and then separately packaged under various gas mixes: air and O₂:CO₂:N₂ ratios of 80:20:0, 60:20:20, 60:40:0, and 40:40:20, using 2 different headspace ratios (1:1 and 3:1). The packaged meats were kept at 4 °C for 10 days and were analysed microbiologically, physico-chemically and sensorially. As a result, the meat quality and shelf-life of ostrich meat under various gas compositions were improved; microbial growth was delayed due to high CO₂ usage and shelf-life was increased by 5–7 days. However, an undesired loss of red colour of the ostrich meat may affect consumer acceptance.     

Effects of novel modified atmosphere packaging on lipid quality and stability of sardine (Sardina pilchardus) fillets

Modified atmosphere packaging (MAP) is an efficient method to increase shelf-life of fishery products by inhibiting bacterial growth and oxidative reactions. Beside the traditional gases used for MAP, novel gases such as argon (Ar) and nitrous oxide (N₂O) were approved for food use in the European Union. The present research investigates the effect of MAP with unconventional gas mixtures, that previously positively affected microbial shelf-life, on colour, lipid oxidation and sensorial characteristics of sardine fillets during storage. Four atmosphere conditions were tested: Air (20.8% O₂/79.2% N₂), N₂ (30% CO₂/70% N₂), N₂O (30% CO₂/70% N₂O) and Ar (30% CO₂/70% Ar). Samples were stored for 12 days at 3 °C. Results showed that the removal of oxygen significantly inhibited the oxidation process; however, most of the investigated parameters related to fat oxidation did not show any improvement, except for a slight decrease in lipid hydrolysis and improvement in sensory properties in the packaging containing Ar.     

Effects of passive and active modified atmosphere packaging conditions on ready-to-eat table grape

The effects of passive and active modified atmosphere packaging conditions (MAP) on quality of packaged table grape were investigated. To this aim, three films made up of oriented polypropylene and characterized by a different thickness (20, 40 and 80 μm, respectively) were used to package the grape in air (passive MAP) and under three different initial headspace gas compositions (active MAP). As controls, grape samples were also stored without packaging. During a prolonged storage period at refrigerated temperature (5 °C) the headspace gas concentrations, the mass loss, the microbiological stability and the sensory acceptability were monitored. Results obtained highlight that all selected packaging films significantly prevent product decay, thus promoting a substantial shelf life prolongation, if compared to the unpackaged product. In particular, the best results were recorded with the thickest polymeric matrix sealed in air, that assured a shelf life more than 70 days. The active MAPs were not found significant for a shelf life prolongation, due to the fast equilibrium of gas reached in the bags and due to a more pronounced product dehydration.     

Combined effect of chitosan and modified atmosphere packaging for shelf life extension of chicken breast fillets

The combined effect of dipping in a chitosan solution (1 g/100 ml) and packaging under modified atmosphere (MAP, 70% CO₂, 30% N₂) on shelf life extension of refrigerated chicken fillets was investigated. Microbiological (Total Viable Counts, Pseudomonas spp., Lactic Acid Bacteria and Enterobacteriaceae), physicochemical (headspace gas composition, pH, color and Thiobarbituric Acid test) and sensory (odor and taste) parameters were monitored for up to 14 days. TVC were 3.9–4.9 log cfu/g lower on day 6 of storage in treated vs. untreated air-packaged samples with the strongest effect being shown by the combination of chitosan plus MAP. A similar reduction in LAB, Pseudomonads and Enterobacteriaceae was recorded during storage. pH values varied between 5.73 (day 8, for acetic acid treated samples) and 6.28 (day 6, for air-packaged samples). Malondialdehyde (MDA) values ranged between 0.19 and 0.80 mg/kg indicating negligible oxidation of lipids. The color parameter L* decreased with time in the air-packaged samples but remained unaffected in all other treatments. Parameters a* and b* were not significantly affected by the chitosan or the MAP treatments. Based on the microbiological and sensory data, shelf life of air-packaged, chitosan-treated, MAP-treated and chitosan/MAP treated samples was 5, 11, 12 and 14 days, respectively.     

Influence of chilling methods on the quality of sardines (Sardina pilchardus)

The aim of this study was to determine for sardines (Sardina pilchardus) the effect of (i) chilling in ice and water in small expanded polystyrene boxes during distribution and in ice thereafter and (ii) chilling in ice and water for the entire storage period. These storage methods were compared with storage of the fish in ice in wooden boxes or in expanded polystyrene boxes. Three storage experiments were performed to take into account the variability in handling conditions and seasonality. There were significant (P < 0.05) differences in the results of some of the sensory, physical, chemical, and microbiological analyses performed that showed that the fish were of better quality when preserved in water and ice than when preserved in ice alone. The effects of dewatering of the fish after transport and subsequent storage in ice were also significantly different (P < 0.05) from those of storage in ice, with the former storage method resulting in better sensory and microbial indices. However, oxidative rancidity, as measured by thiobarbituric acid-reactive substances, was higher for the dewatered fish than for fish preserved in water and ice throughout the storage period. It is concluded that for sardines, storage in water and ice, either only during transport or throughout the storage period, can be useful as an alternative preservation method during distribution and retail sale.     

Effect of dietary supplementation of vitamin E on characteristics of lamb meat packed under modified atmosphere

The effect of dietary vitamin E supplementation on modified-atmosphere packed lamb meat during storage was studied. Thirty-six weaned male Manchego breed lambs were fed diets supplemented with three different vitamin E concentrations (0, 250, 500 and 1000 mg/kg feed) for an average of 37 days, in the 13–26 kg live weight growth range. Slices of m. longissimus dorsi were packaged under modified atmosphere (70% O₂ and 30% CO₂), stored at 2 ± 1 °C in darkness for 14 and 28 days. Meat quality parameters after both storage periods were assessed. Dietary vitamin E supplementation significantly increased -tocopherol concentration in muscle. Initially, lipid oxidation (TBARS), meat colour and bacterial load were similar in all groups. Lipid and colour oxidation of meat increased significantly (P < 0.001) throughout storage. The increase was greater in non-supplemented lambs than in supplemented ones. The bacterial counts after 28 days of storage reached the limit for microbiological shelf life (7 log₁₀cfu/cm²). Dietary vitamin E supplementation increased the shelf life of meat packaged under modified atmosphere to 14 days. TBARS, pigment oxidation and bacterial load were inside the acceptable limit. The meat maintained its quality for 28 days of storage only when lambs were fed with the 1000 mg/kg dietary supplement, though the bacterial load was at the limit of acceptability.     

Sensory shelf life of butterhead lettuce leaves in active and passive modified atmosphere packages

The objective of the present work was to study the influence of both passive and active modified atmosphere packaging on sensory shelf life of butterhead lettuce leaves, stored at 5 and 10 °C. Results showed that the efficacy of active modified atmosphere with respect to passive modified atmosphere depended on the storage temperature considered. When stored at 10 °C, despite being subjected to different package atmosphere composition, lettuce leaves in active and passive modified atmosphere showed the same sensory deterioration rate and sensory shelf life. On the contrary, when stored at 5 °C, lettuce leaves in active modified atmosphere packages showed lower deterioration rate and higher sensory shelf life than those in passive modified atmosphere. Sensory shelf life of lettuce in modified atmosphere packages was estimated using criteria determined according to consumers' rejection to purchase percentage, which consisted on an improvement over more arbitrary criteria presented in most studies.     

Effects of chitosan-based coating and modified atmosphere packaging (MAP) on browning and shelf life of fresh-cut lotus root (Nelumbo nucifera Gaerth)

The present study investigated the effect of chitosan coating containing antibrowning agents and modified atmosphere packaging (MAP) on the browning and shelf life of fresh-cut lotus root stored at 4 °C for 10 days. The atmosphere in the packages was evaluated for O₂ and CO₂ concentrations. The browning on the surface of lotus root slices was prevented by chitosan-based coating and MAP treatment. L* values of coated + MAP and control samples were 68.8 and 48.9 after 8 days storage, respectively. For a^? and b^? values, samples of coated + MAP treatment had the slowest increasing trends among all the treatments. At the end of storage, the coated + MAP samples exhibited the lowest polyphenol oxidase (PPO) activity and malondialdehyde (MDA) content. Its highest overall visual quality (OVQ) scores (> 7) demonstrated that chitosan-based coating + MAP treatment could provide a better inhibitory effect on the browning and extend the shelf life of fresh-cut lotus root.Industrial relevance: Fresh-cut vegetables have drawn the attention of industry as a novel lightly processed product. Both edible coating and MAP treatment cause changes in atmosphere composition and respiration rate of lotus root slices. This combined treatment could be used to control the browning and improve the storage life of this fresh-cut vegetable. This information could be useful for the development of novel application to edible coating and MAP design for lightly processed lotus root.     

Influence of sodium replacement and packaging on quality and shelf life of smoked sea bass (Dicentrarchus labrax L.)

The aim of this work was to study the effect of sodium chloride replacement by potassium chloride on the quality of smoked sea bass, as well as the effect of different types of packaging. Samples were salted with 100% NaCl or 50% NaCl-50% KCl, then smoked, and packaged in air, vacuum, or modified atmosphere. Chemical, microbial, and sensory analyses were periodically carried out during cold storage. In general, partial sodium replacement did not affect total volatile basic nitrogen, trimethylamine nitrogen, thiobarbituric acid, microbial counts, or sensory scores. However, the formation of histamine, putrescine, and cadaverine was delayed by using the mixture of salts. Vacuum and modified atmosphere packaging increased samples shelf life compared with air.     

Extension of the shelf life of beef steaks packaged in a modified atmosphere by treatment with rosemary and displayed under UV-free lighting

Fresh beef steaks, either sprayed on the surface with a solution of rosemary and vitamin C or not sprayed, were packaged in 70%O₂₊20%CO₂₊10%N₂ and displayed at 1±1 °C without illumination or illuminated by a standard fluorescent lamp, a low-UV, colour-balanced lamp (Promolux®), or the fluorescent lamp with a UV filter. Metmyoglobin formation, lipid oxidation (2-thiobarbituric acid reactive substances), instrumental colour (CIE L*, a*, b*), psychrotrophic bacterial counts (PCA) and sensory discolouration and off-odour were determined. Results showed that the use of the antioxidant mixture of rosemary and vitamin C together with the absence of UV radiation significantly reduced the rates of metmyoglobin formation and lipid oxidation, as well as microbial growth, and extended the display life from about 10 to about 20 days.     

Quality changes in sardines (Sardina pilchardus) stored in ice and at ambient temperature

The keeping times of sardines were 21–27 h (average 23 h) at ambient temperature (T_amb) and 8–11 days (average 9.5 days) in ice. The muscle pH increased from 6.15 to 6.85 atT_amband from 6.24 to 6.55 in ice. Trimethylamine–nitrogen (TMA-N) and total volatile basic nitrogen (TVB-N) accumulated rapidly atT_ambto reach 11.2 mg 100 g⁻¹of fish and 57.3 mg 100 g⁻¹of fish, respectively at spoilage. In ice, the rate was rapid for two trials (2.72 mg TMA-N 100 g⁻¹of fish per day and 5.20 mg TVB-N 100 g⁻¹of fish per day) and slow for three trials (0.21 mg TMA-N 100 g⁻¹of fish per day and 3.7 mg TVB-N 100 g⁻¹of fish per day). Likewise, the histamine development rate was rapid during one trial (5.4 per day atT_amband 0.313 per day in ice), slow (average rate 3.503 per day during four trials atT_amb, 0.305 per day during one trial in ice) and zero during the other three ice-trials. Bacteria multiplied rapidly atT_amb; psychrotrophs multiplied slowly, and represented 10–68% of mesophiles at rejection point.In ice, bacteria multiplied slowly after lag phases of up to 120 h, but reached levels of rejection similar to those observed forT_ambstorage, H₂S-producing bacteria represented 0.5–7% of the initial fish flora and 3–10.1% at rejection point. They grew with a shorter lag phase as was the situation with the total flora.     

Extending the shelf life of fresh ewe’s cheese by modified atmosphere packaging

This study evaluated the effect of modified atmosphere packaging (MAP) in extending the shelf life of a fresh ewe’s cheese stored at 4 °C for 21 days. Three batches were prepared with 20, 30 or 50% CO₂ with N₂ as filler gas. MAP controlled well the microbial growth, and the best result was obtained with 50% CO₂. Pathogens were not detected in any sample. Softening of cheese was best reduced by 30% or 50% CO₂. The sensory characteristics of the cheeses markedly decreased during storage. Only the sample stored with 50% CO₂ obtained an overall score above the acceptability at 14 days.     

Effect of previous slurry ice treatment on the quality of cooked sardine (Sardina pilchardus)

The use of slurry ice was evaluated as a technological treatment prior to cooking processing of fish. Thus, sardine (Sardina pilchardus) was stored in slurry ice for 2, 5 and 8 days. At such times, sardine specimens were taken and subjected to steam cooking, and the results were compared with those from a parallel control batch previously stored in flake ice. Quality assessment of lipid damage in cooked fish was performed by measuring the formation of free fatty acids, peroxides, thiobarbituric acid-reactive substances and interaction compounds. The volatile amines–total and trimethylamine–assessment was also carried out. A significant (p<0.05) inhibition of lipid damage–peroxides and fluorescent compounds assessment–and trimethylamine formation was observed in cooked sardine as a consequence of the preliminary treatment in slurry ice. This work opens the way to the use of slurry ice as a preliminary treatment of fish material prior to its thermal processing.