Dynamic Changes of Headspace Gases in CO2 and N2 Packaged Fresh Beef

Two independent experiments were conducted to examine the effects of initial packaging/product conditions and storage conditions on in-package headspace pressure changes for modified atmosphere packaged beef during 12 hr storage. Headspace-to-meat volume ratio 1.8 to 5.9, surface area 200--800 cm², sample volume 0.22–0.75L, storage at 3–13°C and initial gas composition 20–100% CO₂ balanced with N₂ were studied. Headspace-to-meat volume ratio was the most important packaging parameter, but surface area and meat volume also affected headspace CO₂ changes. Decreased storage temperature reduced CO₂ concentration remaining in headspace. Higher initial CO₂ concentration resulted in greater concentration changes.     

METHOD FOR MEASURING CO2 ABSORPTION IN CO2 and N2 PACKAGED FRESH MEAT1

Headspace gas composition of meat stored in modified atmosphere packaging (MAP) undergoes dynamic changes as a result of packaging film permeability, postmortem metabolic activity, CO₂ absorption in water and lipid, and bacteria growth and respiration. A combined analytical and experimental method was developed to investigate CO₂ absorption by packaged fresh meat in a gas-impermeable environment and during isothermal storage. the ideal gas law was used as a theoretical basis and a gas-impermeable and constant-volume chamber was constructed to evaluate the theoretical derivation. Changes in headspace pressure caused by dynamic interactions between beef and MAP atmospheres were monitored to predict concentration changes of CO₂ within the chamber. the proposed methodology for measuring CO₂ concentration changes was confirmed by gas analysis and proved valid for prediction of headspace CO₂ concentration changes in MAP gas-impermeable systems within the range of initial gas composition 20% to 100% CO₂ balanced with N₂, at temperatures ranging from 3 to 13C, and an initial headspace pressure of 155 kPa.     

Modified atmosphere packaging as a means to alleviate package expansion of Korean fermented red pepper paste

Summary Korean fermented red pepper paste was packaged under a modified atmosphere (MA) of 30% CO₂/70% N₂ and 100% CO₂. A plain air package was also prepared as a control for comparison. The MA conditions were applied with a high gas barrier film and subsequently with a gas permeable film. Throughout the storage period at 13 °C, package volume, headspace gas composition, microbial flora, surface colour, pH and acidity were measured. An MA of 100% CO₂ suppressed the growth of aerobic bacteria and yeasts, and reduced the CO₂ production from the paste without any adverse effect on product quality, and thus alleviated the volume expansion of flexible packages stored at 13 °C. However, the reduced volume expansion for the package of high‐barrier film was not sufficient in prolonged storage. An MA package of 100% CO₂ using plastic film of appropriate gas permeability could be stored at 13 °C for 150 days without volume expansion or any adverse quality changes, and was also tolerant to temperature abuse conditions at 25 °C.     

Evaluation of CO2 absorption and desorption rate in oysters (Cassostrea gigas) using the soluble gas stabilisation method

Soluble gas stabilisation (SGS) is a recently proposed method to extend the shelf life of food. However, no studies have determined the amount of carbon dioxide absorbed in food and particularly in oysters. Thus, the aim of this study was to determine CO₂ absorption and desorption rates in oysters during the solubilisation process. Cooked oysters were placed in the apparatus's chamber, CO₂ was injected into the chamber, and the SGS process started at different pressures, temperatures and gas/product (g/p) ratios. CO₂ absorption and desorption rates were obtained from data of CO₂ concentration in the chamber headspace and calculated by mathematical models. The results showed higher absorption rates under higher pressure, higher g/p ratio and lower temperature (0 °C). The concentration of CO₂ dissolved in the oysters was 21008.45 mg CO₂ kg product^?1. On the other hand, lower desorption rates occurred for the lowest pressure (200 kPa) and lowest gas/product ratio (1:1). For CO₂ desorption from oysters, it was observed that 10 min was enough to desorb a large amount of CO₂ under normal atmosphere.     

Optimization of Temperature,Relative Humidity and Storage Time before and after Packaging of Baby Spinach Leaves Using Response Surface Methodology

Second-order polynomial models were used to relate the independent variables, temperature, relative humidity and storage time, to the quality attributes (electrolyte leakage, chlorophylls, weight loss, humidity and headspace gas composition inside packages before and after packaging) of ready-to-eat spinach leaves. Results show that while waiting for processing the best conditions to assure high quality spinach leaves before packaging were 4 °C, 83 % RH and 4 h. The weight loss of spinach leaves was time-dependent: increasing the exposure time under these conditions decreased the amount of wet leaves before packaging. Under the same conditions, the electrolyte leakage was lower (4.63 %) and the chlorophyll content (45.44) was higher. After packaging and while waiting for dispatch, temperature most affected the package headspace atmosphere. Indeed, an increase in storage temperature from 3 to 7 °C led to a significant increase in respiration. The best combination of conditions in the high-care room was 3 °C, 74 % relative humidity for a maximum of 1 day before dispatch. In this case, the moisture content (0.46 %) and electrolyte leakage (4.16 %) were lower and the chlorophyll content (43.37) and oxygen concentration inside the packages of ready-to-eat spinach leaves (19.55 kPa) were higher.     

Determination of Gas Partial Pressures in Closed Respirometers using Gas Chromatography

In a closed respirometer, important pressure changes can result from the difference between O₂ and CO₂ solubilities in water and gas sampling. Several mathematical equations were developed to estimate pressure changes by nitrogen changes in the headspace. The importance of headspace volume, liquid volume, sampled gas volumes, temperature, solubility of the gases, and method of sampling was evaluated. Respiration and nitrogen evolution in a 250-mL closed respirometer, containing 90 g of blueberries, were followed by measuring the relative headspace composition (O₂, CO₂, and N₂) by gas chromatography. Changes in partial pressure of N₂ associated with gas taken were important, resulting in a decrease of the estimated total pressures. Nitrogen released from the solution and the method of sampling had limited effect. Methods to estimate the errors associated with the experimental conditions and methods for their elimination were proposed.     

Evaluation of parameters affecting modified atmosphere packaging engineering design for pomegranate arils

This study evaluated the effects of passive modified atmosphere packaging design parameters as a function of the amount of product (g), temperature (°C) and time (days) on two pomegranate cultivars. Arils (75, 100 and 125 g) were packed in trays, heat sealed with polylid film and stored at 5, 10 and 15 °C for 14 days, and analysed for physicochemical parameters viz headspace gas composition, weight loss, total soluble solids, titratable acidity, pH, anthocyanin, aerobic‐mesophilic bacterial and fungal load (log CFU g^?1). At the highest temperature and weight, O₂ concentration continuously decreased below the critical limit (2%) after 4 days, while at 5 °C, this lower limit was not reached. Shelf life of arils was limited to 10, 7 and 3 days by fungal growth ≥2 log CFU g^?1 at 5, 10 and 15 °C, respectively. Using unsteady‐state equation, a good agreement was found between simulated and experimental gas composition data.     

Effect of muscle,ageing time and modified atmosphere packaging conditions on the colour,oxidative and microbiological stability of packed beef

The objective of this study was to evaluate the influence of two different vacuum ageing times (7 and 14 days) and the impact of the modified atmosphere packaging (MAP) configuration (gas/product ratios: 0.5 and 1 and gas composition: 70% O₂ + 30% CO₂ and 40% O₂ + 30% CO₂ + 30% N₂) on the quality of fresh beef during subsequent storage at 4 °C. For this purpose, three separate experiments were performed. For each experiment, two different muscles (Longissimus dorsi and Biceps femoris) were sampled from four double‐muscled Belgian Blue beef carcasses. Next to colour, also the evolution in microbial load, pH, O₂ and CO₂ in the headspace and lipid oxidation at the meat surface were evaluated. A vacuum ageing for 14 days compared with 7 days resulted in a higher initial microbial load on the day of MAP packaging, which resulted finally in a significantly shorter shelf life. This ageing effect was less pronounced on the colour stability and lipid oxidation of the meat samples. No significant influence of the packaging configuration on any of the analysed parameters (colour, microbial load, pH and lipid oxidation at the meat surface) was observed.     

Ethylene production,respiration and gas exchange modelling in modified atmosphere packaging for banana fruits

A mathematical model was developed from experimental measurements to describe the evolution of the O₂, CO₂ and ethylene in a modified atmosphere packaging system for Cavendish bananas. The respiration and ethylene production in the fruits were experimentally obtained from a closed system method and then represented by Michaelis–Menten equations of enzyme kinetics. The gas transfer through the packaging was described by a Fick's diffusion equation, and the temperature dependence was represented based on the Arrhenius law. The model was validated by packaging the fruit in perforated bags of polypropylene and low density polyethylene at 12 °C for a period of 8 days. With the developed model it was possible to satisfactorily describe the experimental evolution of the gas content in the headspace of the packages, obtaining coefficients of determination (R²) of 0.93 for the O₂ levels, 0.90–0.91 for the CO₂ levels, and 0.89–0.93 for the ethylene levels.     

A dissolving CO2 headspace combined with organic acids prolongs the shelf-life of fresh pork

The aim of this paper was to evaluate the effect of a novel CO₂ packaging method in combination with organic acids on the microbial growth in fresh pork meat. Fresh pork fillet was packed with a small amount of 100% CO₂ (initial gas/product ratio 0.2/1.0) and a brine solution containing citric acid (3% w/w, pH 5), acetic acid (1% w/w, pH 5) or a combination of both. Microbial counts and composition in the product were determined. CO₂, citric acid and acetic acid each reduced total growth after four weeks of storage and delayed the onset of microbial growth. Combinations of treatments increased the effects and microbial growth in samples packed with a combination of CO₂ and both acids was negligible even after 35 days. However, the addition of citric acid to the packages led to significant precipitation in the brine. Analysis of the bacterial flora showed that lactic-acid bacteria dominated the flora in samples packed with CO₂ while vacuum-packed samples contained high numbers of Pseudomonas sp. and yeast. As all CO₂ dissolved in the product within hours after packaging, the outer appearance of the package was that of a vacuum-package. As a result, this novel packaging method combined the advantages of modified atmosphere packaging (antimicrobial effect of CO₂) and vacuum packaging (low space requirement).     

Effects of packaging type, gas atmosphere and storage temperature on survival and growth of Listeria spp. in shredded dry coleslaw and its components

The survival and growth of Listeria populations inoculated on to dry coleslaw mix and its components were investigated, focusing on effects of storage temperatures and gas atmospheres within packaging films or storage chambers. There were few significant effects of packaging film at 3 °C, but at 8 °C the elevated CO₂/low O₂ atmospheres generated within orientated polypropylene (OPP) packages and used in controlled atmosphere chambers were inhibitory. Although two strains of Listeria monocytogenes had survival characteristics comparable with Listeria innocua, L. monocytogenes ATCC 19114 survived better at 3 °C and also in the elevated CO₂/low O₂ atmospheres within OPP at 8 °C. The effects of product components on the survival of L. innocua were linked to storage temperature. Shredded carrot reduced initial counts and at 8 °C inhibited survival of L. innocua in comparison with shredded cabbage.     

Potential for improving the carbon footprint of butter and blend products

To reduce the environmental impact of a product efficiently, it is crucial to consider the entire value chain of the product; that is, to apply life cycle thinking, to avoid suboptimization and identify the areas where the largest potential improvements can be made. This study analyzed the carbon footprint (CF) of butter and dairy blend products, with the focus on fat content and size and type of packaging (including product waste at the consumer level). The products analyzed were butter with 80% fat in 250-g wrap, 250-g tub, and 10-g mini tub, and blends with 80% and 60% fat in 250-g tubs. Life cycle assessment was used to account for all greenhouse gas emissions from cow to consumer. A critical aspect when calculating the CF is how emissions are allocated between different products. Here, allocation of raw milk between products was based on a weighted fat and protein content (1:1.7), based on the price paid for raw milk to dairy farmers. The CF (expressed as carbon dioxide equivalents, CO₂e) for 1 kg of butter or blend (assuming no product waste at consumer) ranged from 5.2 kg (blend with 60% fat content) to 9.3 kg of CO₂e (butter in 250-g tub). When including product waste at the consumer level, the CF ranged from 5.5 kg of CO₂e (blend with 60% fat content) to 14.7 kg of CO₂e (butter in mini tub). Fat content and the proportion of vegetable oil in products had the greatest effect on CF of the products, with lower fat content and a higher proportion of vegetable oil resulting in lower CF. Hence, if the same functionality as butter could be retained while shifting to lower fat and higher proportions of vegetable oil, the CF of the product would be decreased. Size and type of packaging were less important, but it is crucial to have the correct size and type of packaging to avoid product losses at the consumer. The greatest share of greenhouse gas emissions associated with butter production occurred at the farm level; thus, minimizing product losses in the whole value chain—from cow to consumer—is essential for efficient production.     

Effects of extrusion with CO<Subscript>2</Subscript> injection on physical and antioxidant properties of cornmeal-based extrudates with carrot powder

Carrot powder and cornmeal were extruded at ratios of 0:100, 10:90, and 20:80 with and without CO₂ injection at die temperatures of 80, 100, and 120 °C. The effects of the composition of the extrudate, die temperature, and CO₂ injection on physicochemical and antioxidant properties of extruded products were studied. The results showed that die temperature had a significant effect on expansion ratio (ER), specific length, piece density, color, water absorption index (WAI), and water solubility index (WSI) (p < 0.05). The injection of CO₂ significantly affected the ER, WAI, WSI, lightness, redness, microstructure, total phenolic content, and the 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity of extrudates (p < 0.05). Increasing the proportion of carrot powder in extrudates resulted in better antioxidant properties and higher levels of crude ash, crude fat, crude protein, and redness; however, it resulted in lower WAI, lightness, and yellowness (p < 0.05). The study demonstrated that extrusion with CO₂ injection and addition of carrot powder may improve the nutritional quality and structure-forming ability of extrudates.     

The combined effect of superchilling and modified atmosphere packaging using CO2 emitter on quality during chilled storage of pre‐rigor salmon fillets (Salmo salar)

BACKGROUND: Pre‐rigor fillets of Atlantic salmon were either superchilled or chilled prior to packaging in air or in modified atmosphere (MAP, 60% CO₂/40% N₂) with a CO₂ emitter, in 5.3 L high‐density polyethylene trays with three to four layers of fillets (3.0–3.7 kg). All samples were stored at 0.1 °C for 28 days. RESULTS: Fillets stored in MAP had significantly lower bacterial growth compared to fillets stored in air, and MAP superchilled bottom fillets had lower bacterial counts compared to the corresponding chilled fillets. Samples superchilled prior to refrigerated storage in air had similar bacterial growth to ordinary chilled samples. Faster fillet softening during storage and higher liquid loss were observed in superchilled MAP samples. CONCLUSION: Combining short‐term superchilling and MAP with a CO₂ emitter prolonged the shelf‐life of pre‐rigor salmon fillets, which can improve sustainability throughout the value chain. The superchilling method needs to be optimized to avoid negative effects on texture and liquid loss. Copyright © 2009 Society of Chemical Industry     

Effect of combined application of high pressure treatment and modified atmospheres on the shelf life of fresh Atlantic salmon

High pressure (HP) processing at low temperatures combined with modified atmosphere packaging (MA) was used for the preservation of salmon. A shelf life extension of 2 days was obtained after a HP treatment of 150 MPa for 10 min at 5°C compared to unpressurised, vacuum-packed salmon. MA storage (50% O₂+50% CO₂) alone extended the shelf life of salmon for 4 days at 5°C. When salmon had been subjected to HP treatment in the presence of 50% O₂+50% CO_2, the threshold value for microbial spoilage of salmon (7.0–7.2 log CFU/g) was not reached for at least 18 days at 5°C. Spoilage microorganisms (lactic acid bacteria, Shewanella putrefaciens) as well as pathogens (Listeria monocytogenes Scott A, Salmonella typhimurium) spiked on salmon prior to the treatment, were more susceptible to HP in the presence of 50% O₂+50% CO₂. The mode of action of compressed gases is probably related to intracellular formation of reactive oxygen species as well as to phase transition phenomena. Although microbial growth on salmon was retarded, the combined HP and MA treatments, at the settings used in this study, promoted a detrimental effect on colour and changes in the balance of oxidative rancidity.     

Method of Measurement of CO2 Adsorbed into α-Cyclodextrin by Infra-Red CO2 Probe

A simple CO₂ probe system for quantifying CO₂ gas adsorbed in solid matrix of α-cyclodextrin powder (α-CD) by measuring the gas concentration in the headspace was developed and validated. The essential components of this system are an infrared CO₂ probe and an air tight chamber equipped with a two-fan system to uniformly mix the relatively high density CO₂ gas. First, a known weight of dry ice (considered as pure CO₂) was used to create different amounts of CO₂ in the headspace of the chamber, and the resultant gas concentrations were measured by the probe and gas chromatography. The gas concentrations measured by both methods were quite similar (R² = 0.9950), and the calculated amount of dry-ice in the headspace using the probe was highly comparable to the amount of dry ice initially added in the chamber (R² = 0.9970). This system was then tested to measure adsorbed CO₂ content in CO₂-α-CD complexed powder by using water injection to release CO₂ from the complexed powder into the headspace. The measured results using this system were quite similar (R² = 0.9972) to those determined by a conventional acid-base titration method.     

Determination of Total Acid Content in Vinegars by Reaction-Based Headspace Gas Chromatography

This work reports on a simple and efficient method for the determination of total acid content in vinegars by reaction-based headspace gas chromatography. The method is based on the neutralization reaction between the acids in vinegar and carbonate solution in a closed headspace sample vial, from which the carbon dioxide generated from the reaction is analyzed by gas chromatograph equipped with a thermal conductivity detector. The results showed that the headspace equilibration of CO₂ generated from the reaction was achieved in 15 min at 60 °C. The method has a good precision and accuracy, in which the relative standard deviation in the repeatability measurement was 1.73 %, and the relative differences between the data obtained by the headspace gas chromatographic method and the reference titration method were within 4.81 %. The present method is particularly suitable to be used for determining the total acid content of vinegar not only in the process control but also the quality check of point-of-sale samples from commercial markets.     

Effect of Shear Rate on Crystallisation Phenomena in Olive Oil-Based Organogels

The aim of the present work was the rheological and microstructural analysis of olive oil/mono- and diglycerides/cocoa butter organogels as a potential oil phase of structured food emulsions. Step temperature ramp tests at different shear rates and controlled cooling conditions (5 °C/min) were adopted to evaluate the onset of crystallisation temperature (T _co) and viscosity of different samples. In order to study the crystallisation phenomena potentially occurring in adopted raw materials, a preliminary characterisation was carried out on pure and blended fats (olive oil and/or cocoa butter), evidencing a relevant effect of adopted shear rate on T _co. Afterwards, the influence of mono- and diglycerides on organogelation of either pure or blended fats was investigated, increasing the organogelator from 0.5% (w/w) up to 60% (w/w) and observing the increase of T _co with its concentration from 17.7?±?2.7 °C up to 64.5?±?1.0 °C. Experimental results showed that T _co is only determined by the organogelator concentration, and it does not depend on the shear rate and fat source. On the other hand, sample viscosity depends on both the amount of organogelator and the oil phase composition, increasing with saturated fat concentration. Finally, the obtained results allow the fat to be designed with the desired properties: its crystallisation point and rheology can be predicted on the basis of the amounts of the organogelator and the saturated fats, respectively.     

Effect of Crystalline Structure on Oxidation of Fish Oil in Stearin:Fish Oil Mixtures

Effects of incorporation of stearin fraction into fish oil on crystallisation behaviour and oxidative stability of fish oil were examined. The stearin fraction (S₂₅) was obtained from step-wise dry fractionation of anhydrous milk fat at 25 °C. Analysis of fatty acid composition by gas chromatography showed that unsaturated fatty acids (89.3 %) were enriched in the fish oil whereas the S₂₅ typically comprises of saturated fatty acids (79.4 %). A series of S₂₅:fish oil mixtures (0:100, 25:75, 50:50, 75:25; 90:10 and 100:0) was prepared by mixing the S₂₅ and fish oil at 50 °C under flushing of nitrogen gas. Crystallisation and thermal properties and crystal structures of the mixtures were investigated by differential scanning calorimetry and small- and wide-angle X-ray scattering, respectively. The crystallisation/melting temperatures and crystallisation/melting enthalpies of the mixtures increased with increasing ratios of S₂₅ blended into fish oil. All mixtures showed similar crystal structures (double- and triple-chain length) and crystal polymorphs (α, β’ and β) at 4 °C. A decrease in S₂₅ fraction in the mixtures caused a higher proportion of triple-chain length crystal packing and β polymorph. Measurement of peroxide values of the mixtures upon storage at 8 °C for 42 days showed that blending as low as 25 % S₂₅ sufficiently delayed the lipid oxidation of fish oil by about two-fold and the rancidity threshold to 16 days instead of 9 days for fish oil only. This study demonstrates that mobility of oxygen and triacylglycerol (TAG) molecules in fish oil can be restricted by crystalline state of milk fat, in turn, limiting the propagation of oxidative reaction in fish oil.     

Predicting the headspace oxygen level due to oxygen permeation across multilayer polymer packaging materials: A practical software simulation tool

The shelf life of a food product is largely determined by its chemical and microbiological stability. In this respect, the gas composition surrounding a packaged product plays a major role. Modified Atmosphere Packaging (MAP) is a packaging technique that usually reduces the headspace oxygen to a preferable minimum for most food products. Besides the residual oxygen, the O₂-permeability of the packaging material is also important, as it determines the amount of oxygen permeating into the package during storage. This paper describes the development of a practical software simulation tool to predict the amount of oxygen permeating into the headspace during storage for a variety of multilayer packaging configurations. The simulation tool gives access to simulation models for mono- and multilayer films, trays covered with top foils and bottles with caps. The user can compose his/her own (multilayer) packaging material and check the oxygen ingress over time for different temperature conditions for all packaging configurations.Industrial relevanceThe software simulation tool is of industrial relevance to food companies, as they can use it to select or compare different films, but also to underpin their choice for a certain packaging material with regard to the sensitivity of the food product to oxygen and the desirable shelf life. The simulation program also provides food companies with information about the influence of storage conditions, like time and temperature, on the ingress of oxygen in their food package throughout the storage-distribution chain. On the other hand, it can also be used by packaging suppliers to predict the oxygen permeability in the optimization process of new films and as a client support tool.