The effect of oxygen absorbent packaging on the shelf life of the liquid composition of military operational daily rations

Abstract

Oxygen inside food packaging can improve the quality of liquid food products with high oil content, such as hot-filled meal-ready-to-eat (MRE), which is one of the parts of daily operational rations. is to reduce the military. The main objective of this study is to test a new oxygen absorber containing a coating material or laminate along with its ability to maintain or increase the shelf life of a hot ready-to-eat meal or MRE filled with cheese. A moisture-activated iron-based oxygen absorber (ABSO2RB R) was incorporated into the laminate and used to package hot cheese-filled MREs. The kinetics of the oxygen absorption process due to humidity and temperature were determined and peeling tests were performed to ensure the integrity of the bag closure. Accelerated shelf-life tests of ABSO2RB and conventional MRE bags without O2 absorbers for 3 months at 51.7°C (125°F), and 6 months at 37.8°C (100°F) to A device for measuring oxygen concentration (Mocon O2-analyzer) and physicochemical quality characteristics (depending on the physical and chemical properties of objects) and microbiological, which include color, texture, moisture, free fatty acids, pH value, water activity and vitamins, etc. They could have been done. Bags stored at 26.7°C (80°F) for 12 months served as calibrated controls. Consumer trials and tests were conducted at home and a confirmatory sensory test was conducted in Natick by a trained panel using a 9-point scale of pleasure and enjoyment. The ABSO2RB laminates exhibited similar chamber closure strength and integrity as those of the control samples. Oxygen concentrations in the upper empty space of the chamber in these packages are as high as (P < 0.05) < 0.5% was reached during 11 days of storage at 26.7 °C (80 °F) and remained below this level throughout the storage period (1 y). No microbiological growth (aerobic, coliform, yeast and molds) was observed for both packages (P < 0.05). Overall, ABSO2RB bags showed better oxygen reduction and vitamin C retention compared to MRE controls and maintained product quality (physicochemical and organoleptic). ABSO2RB laminates met the accelerated shelf life requirements of 1 month at 51.7°C (125°F), and 6 months at 37.8°C (100°F). This study has clearly discussed the benefits of using active packaging technology to preserve nutrients and increase the shelf life of liquid contents of high-fat MRE items.

Introduction

High levels of oxygen in food packaging may facilitate the growth of yeasts, molds and aerobic bacteria, the development of off-flavors due to the oxidation of unsaturated fatty acids, discoloration and loss of nutrients, thereby causing a significant reduction in Food shelf life. Therefore, controlling oxygen levels in food packaging in order to limit the rate of these destructive reactions and food spoilage is of particular importance. The rancidity process occurs when oxygen combines with unsaturated fatty acids. Additionally, several wet food ingredients in MREs are subject to non-enzymatic browning reactions. This type of spoilage and quality deterioration is facilitated by the presence of oxygen inside the packaging and can be reduced by packaging sensitive food items in packaging materials. Active packaging technologies, using methods designed to capture and contain oxygen and most widely used in the food industry, provide a means to address this problem (Charles and others 2006).

Oxygen absorption systems provide a suitable alternative to the vacuum method and gas injection packaging in order to improve product quality and shelf life. In addition, they are economically very suitable and affordable and play an effective role in reducing packaging costs and increasing profitability (Ozdemir and Floros 2004). Such new technology has been successfully applied to a wide variety of food products, including meat products, fresh pasta, fruits, dairy products, and similar products (Rooney 1995; Vermeeren et al. 1999; Koma 2008). The purpose of the oxygen absorber is to create an atmosphere containing a low concentration of oxygen in the airtight packages that contain the product, thereby slowing down or preventing the spoilage process through oxidation or the growth of microorganisms. By reducing the oxygen concentration, the oxygen absorber allows the detection value to be reduced to below 0.01%, and since it simplifies the process and reduces the cost of the equipment, it can be compared to modified atmosphere packaging or MAP for short, which includes The vacuum method can also be more economical and useful (Alvarez 2000).

Most oxygen scavengers in commercial use today are iron-based systems, but they can also be catechol, ascorbic acid, or the like, or even include unsaturated hydrocarbons and polyamides, most of which are in the form of sachets. are within packaging (Smith et al. 1990; Vermeeren et al. 1999, 2003; Brady et al. 2001). Inclusion and placement of absorbents Packaging film, is a better way to solve problems related to sachets. Oxygen absorbent sachets are commonly used in dry bakery products but are impractical in liquid suspensions where the sachet may be submerged in the food product. This complexity is modified and eliminated by placing the oxygen absorbing material inside the structure of the packaging film formulation. By placing an oxygen absorbing material in the contact layer of the product, contamination of the product by leakage from a sachet will not occur. This approach also eliminates the risk of ingestion by the customer (Graff 1998). However, it is possible for the active agent to penetrate the plastic sheet into the product. Oxygen absorbent plastic films also offer potential cost savings due to increased production efficiency and convenience. Absorbents may be either embedded in a solid material, dispersed in plastic, or embedded in various packaging layers, including layers of adhesive, varnish, or enamel (Rooney 1995; De Kruijf and others 2002). Shelf-life stability and shelf life are critical because the military requires MRE foods to be stable and usable for at least 3 years without refrigeration at 26.7°C (80°F). The requirement of unitized group ration (UGR) is at least 18 months at a temperature of 26.7 degrees Celsius. When there is a change in food formulation or in packaging, more studies should be done on durability and stability. In fact , these changes can affect the chemical, physical, and nutritional characteristics of the food product under consideration. Therefore, the following study was conducted to determine the effect of oxygen absorbing laminate on the shelf life of spread cheese MRE from a microbiological, physical, and chemical point of view. and to measure and evaluate the sensory characteristics (detectable by the five senses) during the storage period. Spread cheese is especially sensitive to this type of spoilage and was chosen as the food item to test this preservation technique. Was.

materials and methods

Foodstuffs

Cheese spread MREs were packaged using a PortionPac machine in Stone Mountain, USA with samples in ABSO2RB⃝R laminates and controls in plain MRE wrappers. The dimensions of the bag were 15.24 x 35.56 cm (or 6 x 14 inches) with an area of 542 square centimeters. This product was hot filled at a temperature of 76.7 to 82.2 degrees Celsius. A number of 600 samples (each equal to 42.5 grams) were transported to Texas A&M University.

For testing based on performance requirements and following the technical specifications required for packaging and quality assurance documents for plain cheese distribution, the Performance-Based Contract Requirements or PCRs were as follows: Number (1): shelf life 6 months (UGRs and MRES) at 26.7°C (80°F) (PCR-C-039) and (2) palatability and general acceptability shall meet the requirements and characteristics of the approved product standard (PCR- C-039).

Oxygen absorbent packaging material

Laminate was purchased from Cadillac Products Packaging Co. (Troy, Michigan), who then produced the bags for packaging the MREs. The structure consisted of 48 gauge PET/ten pounds per team PE/0.35 mil-inch aluminum foil per 3 micron ABSO2RB sealant. ABSO2RB sealant is a combination of low-density polyethylene (LDPE and linear LLDPE) (polyolefins) along with an iron-based oxygen absorber activated with water. Water reacts with oxygen to produce hydroxide ions, which then react with ferrous ions to produce iron. (II) is hydroxide. In the presence of oxygen, iron (II) hydroxide quickly forms iron (III) Oxide-hydroxide is transformed and oxidized (Vermeeren et al. 1999). In short, it is a three-layer coextractor containing both polyethylene PE and an iron-based oxygen absorber. However, the food contact layer consists entirely of PE. The structure of the laminate sheet is shown in figure 1. The laminate or coating was opaque and non-transparent.

A series of investigations were conducted on the new oxygen absorbent material in tablet form and its effect on the physicochemical and microbial quality to confirm that the material in question could definitely help maintain the shelf life of MRE spread cheese.

Optical microscope examination of laminate materials

Transmitted optical microscopy (TOM) was used to determine the characteristics of the laminate structure related to the oxygen-absorbing packaging sheets. The mentioned sheet was cut, cleaned and embedded in an epoxy resin. After storage and processing at room temperature, the epoxy block with the sheets embedded in the middle was cut using an Ultracut E microtome and a Microstar diamond knife. A thin section (about 40 µm thick) was collected in an oil-immersed medium and fixed between two glass slides. The thin section was examined using an Olympus BX60 light microscope (Details: Olympus America Inc., Center Valley, Pa., U.S.A.) in transmission mode.

Bag peeling test

The peeling test was performed on the gap of the reference bag and the bags containing the oxygen absorber, which were stored at room temperature and at 51.7 degrees Celsius (125 degrees Fahrenheit) for 60 hours, respectively. A storage time of 60 hours at high temperature was chosen to evaluate the integrity of the bag sheets. It has been shown that the oxygen absorber will complete its reaction within 60 hours. Experiments were performed using an Instron (model 4411) device at room temperature. The test rate was 5.08 mm/min. The layer resistance was obtained based on at least 4 models for each sample. T-peel tests were performed on actual (physical) bags having a typical closed thickness and width of 0.254 cm (0.1 inch). As a result, testing was performed on a 2.54 x 0.254 cm (1 x 0.1 in) closed enclosure. The rest of the test conditions and preparation were done according to ASTM F-88 standard (ASTM 2007). Mean detector values and standard deviations are reported.

Studies related to durability or shelf life

The content of each sample unit (1 bag) for the physical appearance, aroma, taste, texture, integrity and correctness of the sheet, chemical, microbiological properties and overall quality (sensory or perceptible with the five senses) for the duration of the studies with 3 types of storage and storage with Different conditions, including (1) 3 months at 51.7 °C (125 °F), (2) 6 months at 37.8 °C (100 °F), and (3) 12 months at 26.7 °C (80°F) with constant relative humidity (65% to 75%) was evaluated. Sampling intervals include 1) 4, 3, 2, 1, and 6 weeks at 51.7 °C (125 °F), (2) 3, 1, and 6 months at 37.8 °C (100 °F) and ( 3) 6, 1 and 12 months at 26.7 degrees Celsius (80 degrees Fahrenheit). Each test performed included 3 repetitions of the test along with 3 test results (which are storage temperature and time).

Analysis and examination of the upper empty space. The oxygen concentration inside the bags was measured using a Mocon Toray oxygen analyzer model LC700F (Toray Engineering Co., Chuo-ku, Tokyo, Japan) during the storage period. Bags were centrifuged at 1000 × g for 10 min (Allegra 25R centrifuge, Beckman Coulter Inc., Fullerton, Calif., U.S.A.). Then, internal gases were expelled across a rubber septum placed on one side of the bag using a 1 mL syringe. Exhaled gases (1 ml) were immediately injected into an O2 analyzer. Before sample injection, the O2 analyzer was calibrated using samples containing air. Determinations were performed in five replicates. From the day the bags arrived until oxygen concentrations were stable, headspace gas samples were collected from the new bags on a daily basis. After that, the data points related to the useful life study were collected monthly.

Microbial analysis. Total aerobic count, coliform count, Escherichia coli, yeast, fungus and mold and Lactobacilli spp were counted using standard methods (AOAC 1998c, d, e, f, g, h).

Figure number 1. An analogy of the laminate structure related to the oxygen absorbing packaging material

Briefly, the contents of 3 bags filled with cheese spreads for each of the test methods were placed in sterile stomacher bags and mixed throughout. 10 grams of the sample was transferred to a new sterile bag (stomacher) and 90 ml of buffered peptone water was added. The desired composition was homogenized for 1 minute. Serial solutions were made using buffered peptone water. Counting the number of total aerobic microorganisms, total form and Escherichia coli, and the number of yeast and fungus and mold population using aerobic counting plates, yeast and mold counting plates, E. coli / coliform counting plates and petrifilm plates (3M Petrifilm, 3M Products Microbiology, St. Paul, Maine, USA) were determined in the order mentioned in duplicate. To count the number of aerobic colonies, the plates were incubated for 48 hours, for 24 hours for coliforms, for 48 hours for E. coli at 35°C and at 25°C for 5 days for yeast and fungal molds. The population of Lactobacillus spp. Using the procedures suggested in the abstract section of APHA (Smittle and Cirigliano 1992) and using MRS agar plates, selected Lactobacillus Lactobacillus (Man, Rogosa, and Sharp) was determined and then at a temperature of 25 degrees Celsius and in an atmosphere enriched with CO2 They were incubated in two copies for 7 days. The population of Lactobacillus spp. Microbial counts were expressed as viable bacterial colonies per gram (CFU/g).

Product quality features

Color. Changes in the color of the spread cheese using a Labscan XE (16437) colorimeter (HunterLab, Inc., Reston, Va., U.S.A.) coupled to a CIELAB system measuring 36 mm aperture diameter and illumination angle (in calorimeters) It was evaluated as D65/10. The calorimeter was calibrated using standard black and white plates. Three bags were used for each test method and 3 readings were done on the contents of each bag. Average values were used to determine the color coordinates L∗ (lightness – darkness), a∗ (redness or redness – greenness) and b∗ (yellowness – blueness or bruise).

texture (distributable). Diffusibility was measured using a texture analyzer (TA.XT2i, Texture Technologies Corp., Scardale, N.Y., U.S.A.) equipped with a diffusible rig (TA-425 TTC) containing a set of male and female acrylic cones. 90◦ were exactly matched, measured and determined. Spread cheese was filled inside the bottom cones, smoothed with a spatula, and then placed in the holder base for testing. This test involves moving 24 mm from a fixed position and 25 mm from the end of the lower cone. The final empty space (gap) between the two cones was exactly equal to 1 mm. The test speed was equal to 3 mm/second. The texture related software program recorded and recorded the maximum force (N) for playing the samples. 15 measurements were performed for each test method (ABSORB bags and conventional MRE at different temperatures). The samples were allowed to equilibrate to room temperature (about 21°C) before testing.

Product weight. The average net weight of cheese samples distributed throughout the shelf life (total shelf life) study was measured to ensure that the samples met product weight requirements. No single bag should have a net weight of less than 39.69 grams (PCR-C-039 2006). The bags containing the spread cheese in each test method (ABSO2RB and conventional MRE bags) were weighed on an analytical balance (Sartorius analytical AC 210S, Sartorius Corp., N.Y., U.S.A., ± 0.0001 g). The average weight of the packaging sheet alone was subtracted to obtain the net weight of the bags. The readings were done in five copies.

Moisture content and water activity. In order to meet the requirements and technical specifications, the moisture content of spread cheese cannot be less than 38% and more than 42% (PCR-C-039 2006). Approximately 5 g of samples were weighed and dried at 60–65 °C (≤ 13.3 kPa) at constant weight (for about 10–12 h) in a vacuum oven (Squared Lab Line Instruments, Melrose Park, Ill. , U.S.A.) were dried according to AOAC method 930.04 (AOAC 1990a). After comparison and standardization with the AOAC method (standard), the moisture content was determined by microwave drying using a CEM SMART TRACTM System 5 moisture analyzer (CEM Corp., Matthews, N.C., USA). Since the oxygen absorbing compounds or O2 are activated by the moisture present in the upper empty space of the package, the monitoring of water activity is of particular importance. Water activity was measured using a Rotronic Hygroskop DT (model DT-2, Rotronic Instruments Corp., Huntington, NY, USA) connected to a water bath (Haake F3 Fisons, Thermo Fisher Scientific, New-ington, N.H. , U.S.A.) was connected, controlled and monitored at 20°C temperature. The samples were placed in a plastic sample holder and then loaded into the equipment. After the system reached equilibrium (about 30 minutes), the readings were recorded. Measurements were prepared in three copies.

Fat content. Fat content (%) of spread cheese samples by microwave drying using a CEM SMART TRACTM System 5 moisture analyzer (CEM Corp., Matthews, N.C., U.S.A.) followed by NMR readings of the dried samples (Smart System 5 Analyzer ProFat M, CEM Corp.) were determined. Three bags containing spread cheese per test method were analyzed and evaluated throughout the storage time.

Check the pH. AOAC method 981.12 (AOAC 1998a) was followed to measure pH using a registered digital pH meter (Corning model 350 pH/ion analyzer Corning, Inc., N.Y., U.S.A.) and a pH meter with two solutions with buffer pHs of 4.7 and 10 were calibrated. Samples included the contents of 1 bag of spreadable cheese. Three measurements were performed for each test method (ABSO2RB bags and conventional MRE at different temperatures) and analysis was performed throughout the storage time in triplicate.

Free fatty acid (FFA). This value (factor) was used as an indicator of fat rancidity, although other factors are responsible for the occurrence of the rancidity process in cheese, which include the activity of enzymes. FFA was measured according to AOAC official method 940.28 (AOAC 1990b). Fat was extracted from spread cheese samples by first drying them under vacuum method. The content of one bag is distributed in an aluminum cup (approximately 5 grams per cup), weighed and placed at a temperature of 60 to 65 degrees Celsius (≤ 13.3 kPa) for about 10 to 12 hours in a vacuum oven. Squared Lab Line Instruments, Melrose Park, Ill., U.S.A.) was dried. After drying, the samples were transferred to 250 ml of Erlenmeyer and 50 ml of ether or petroleum ether was added. The samples were kept at room temperature and in the dark for 6 hours. Ether was removed using a rotavapor (Hydolph Laborta 4001; Methrom U.S.A., Inc., Riverview, Fla., U.S.A.) at 40°C. Subsequently, the weight of the extracted fat was measured (about 3.5 g) and 50 ml of ethanol (which was previously neutralized) was added and the resulting solution was thoroughly mixed. Then the obtained mixture was titrated with 1% normal alcohol along with phenolphthalein reagent to reach a pale pink color with a stable color (for more than 1 minute).

The results obtained were reported as the percentage of free fatty acids expressed on the basis of oleic acid, since this is the predominant fatty acid in cheese (Pearson 1971).

Vitamin C content (ascorbic acid). Vitamin C content was monitored according to AOAC official method 985.33 (AOAC 1998b). Twenty grams (20 g) of the spread cheese was immersed with a blender (400 W Immersion Blender—Kitchen Choices, Lenexa, Kans, USA) for 1 min with 100 mL of extraction solution. (metaphosphoric acid – acetic acid solution) was homogenized (or homogenized). The homogenate was vacuum filtered (vacuum pump – KNF Neuberger, Trenton, N.J., USA) using qualitative paper (Whatman Nr 4; Whatman, Inc., Clifton, N.J., U.S.A.) and 10 mL of The purified or filtered solution was titrated with the standard solution of 6,2-dichloroindophenol. The titration volume was recorded and used to quantify the vitamin C content of the sample. Indophenol solution was standardized by titrating a standard solution of ascorbic acid (1 mg/mL) and a blank sample. Vitamin C content was expressed as milligrams of ascorbic acid per gram of sample based on moisture content. Three replications, each prepared in duplicate, were performed throughout the shelf life study.

Vitamin A content. Vitamin A content was determined according to the standard methods for examining dairy products method 15.160 (Hooi and others 2004). Briefly, 2 to 3 grams of cheese sample was spread, weighed and transferred to test tubes. After the samples were dissolved in ethanol with 5 mL (w/v) of 1% pyrogloll (Sigma-Aldrich, St. Louis, MO, USA), 2 mL of 50% (w/v) KOH (Sigma-Aldrich ) was added in water, the tubes were closed and mixed vigorously. Subsequently, the test tubes were placed in a water bath (S/P water bath, Baxter Healthcare Corp. Miami, Florida, USA) at a temperature of 80°C for 20 minutes with continuous agitation to enable saponification. Saponified samples were placed in a tub of ice water to cool quickly (about 30 minutes). Twenty milliliters of diethyl ether: Ether (petroleum ether) (1: 1) It was added to the test tubes and mixed vigorously after adding 15 ml of cold distilled water.

In order to complete the extraction of vitamin A, the samples were centrifuged at 1000 × g for 10 minutes (Allegra 25R centrifuge, Beckman Coulter Inc.). An amount of 10 ml was collected from the upper organic layer and transferred to conical flasks. Solvents were evaporated to dryness using a rotavapor (Heidolph Laborata 4001, Brinkmann) and redissolved in 5 mL of methanol suitable for HPLC and filtered through a 0.2 μm PTFE filter (13 mm Acrodisc CR syringe filter, Pall Life Sci, East Hill, New York, USA) were filtered. A quantity equal to 100 microliters of this solution was injected into the HPLC system. The HPLC system and HPLC conditions included a high-performance liquid chromatograph (Dionex, Germering, Germany) equipped with a P680 pump, a PDA-100 photodiode array detector set at 325 nm, an ASI-100 automated sample injector, and a Chromeleon software. 6.5 (Dionex). The column consisted of a 4.6 × 250 mm Supelcosil LC-18, C18, 5 μm particle size (Supelco, Bellefonte, Pa., U.S.A.) along with a C18, 5 μm, 4 × 20 mm, LC guard column. -18 would be SupelGuard (Supelco). The mobile phase consisted of methanol:water (95:5), isocratic washing with a flow rate of 1 ml/min. All-trans retinol (Sigma) was used as a standard (2 μg injected into the column, retention time: 7.30 min) following the same procedures used for sample preparation. Throughout the entire procedure, the samples were protected from contact and exposure to light. The analysis was done along with two tests with three repetitions.

Statistical analysis

Data analysis using SPSS software for Windows version v. 11.5.1 (SPSS 2002), was performed. The effect of the type of packaging, the length of the storage period (durability), and their interaction were evaluated. Differences between variables were tested for significance by one-way analysis of variance (ANOVA). Mean significant differences (P ≤ 0.05) were separated by Tukey’s test.

Discussion

Ability to absorb oxygen by the film

Before testing the ABSO2RB film’s ability to absorb oxygen, the kinetics of oxygen absorption related to the substance containing the oxygen absorber in pellet form in the temperature range of 25 to 65 degrees Celsius (77 to 149 degrees Fahrenheit) and relative humidity. RH) from 75% to 100% was characterized (described) for the first time. The results showed that both temperature and relative humidity can significantly affect the oxygen absorption rates. In the temperature range from 25 to 45 °C (77 to 113 °F), oxygen uptake rates increased with increasing temperature at constant RH (0.184% O2/h for 25 °C, 0.534% O2/h for 35°C, and 0.948% O2/h for 45°C under 100% relative humidity, 0.711% O2/h for 25°C, 0.890% O2/h for 35°C, and 0.990 % O2/hour for 45°C under 75% relative humidity or RH). In the RH range from 75% to 100%, oxygen uptake rates decreased and decreased when RH increased at a constant temperature. Further increases in temperature up to 65°C (149°F) will dramatically inhibit oxygen uptake rates. It is hypothesized that high temperature leads to high vapor pressure, thus limiting the oxygen absorption reaction. The activation energy for oxygen absorption was also estimated using the Arrhenius equation at different RH (the Arrhenius equation is as follows:

where k is the oxygen absorption rate, ka is the pre-exponential factor or probability factor of the shape of the molecule and the factors involved in collisions and molecular attractions, Ea is the activation energy, R is the gas constant, and T is the absolute temperature). The results showed that for 75% and 100% RH, Ea values are equal to 13.1 and 64.8 J per mole, respectively. The above data clearly show that lower RH values lead to lower activation energy and higher adsorption rate. Therefore, the oxygen absorbers selected in this study will perform better at lower temperature and lower relative humidity or RH. Optimum conditions were found at 45 degrees Celsius (113 degrees Fahrenheit) and 75% RH. The above findings are useful as a guide to better understand and design ABSO2RB for applications of laminated layers in packaging films.

Figure 2 shows the changes in O2 concentration for 2 types of packaging, ABSO2RB bags and regular MRE. Both types of packaging materials have their own expiration dates for oxygen concentration over time. Major changes in headspace gas composition in bags containing O2 sorbent or (ABSO2RB) occurred during the first days of storage at room temperature with bags equilibrating with the atmosphere at a faster rate. During 11 days of storage and storage, the oxygen concentration in the upper void space of the ABSO2RB laminate was below 1% and remained below this level throughout the entire storage period (1 year). The oxygen concentration in conventional MRE bags decreased by 50% during the first 15-day period and remained stable at a concentration of 5%. Oxygen was reduced in conventional packaging as the oxygen reacted with the food. Therefore, the purpose of oxygen absorbent packaging is to remove oxygen before destructive reactions occur. This finding supports the effectiveness of the laminated O2-absorber evaluated in this study because we had data showing that oxygen depletion occurred significantly faster in ABSO2RB bags than in conventional bags. That is solid evidence that the laminate effectively absorbed oxygen. A similar trend was observed with other food (namely fish) packaged with an O2 absorbent with an iron-based system (Mohan et al. 2008).

Film properties

Laminate structure. A TOM image of the cross section of the sheet containing the oxygen absorber is shown in Figure 3. A total of 6 layers can be clearly distinguished (polyethylene or PE, sealant containing oxygen absorber, tie-layer or oxygen absorber layer, aluminum foil, pigment layer, and PET). The dark particles scattered in the sealing layer are oxygen absorbers.

Bag skin test. T-peel testing reveals that the ablation process at 51.7°C (125°F) does not degrade (worse) the integrity of the bag containing the oxygen absorbers. Samples stored at room temperature and aged at 51.7 degrees Celsius for 60 hours had almost similar T-peel strength detector values (16 ± 0.6 and 16 ± 0.8, respectively). These T-peel strength detector values are similar to the reference sample that does not contain any oxygen absorbers.

Studies related to shelf life (maintenance)

Microbial analysis. Results from microbial tests confirmed that all tested samples were commercially sterilized. Neither bacterial growth nor yeast and mold growth was observed throughout the shelf life studies. The number of colonies was below the detection limit with EPC (estimated plate counts) less than 10 (data not shown). As a result, the spread cheese packaged using ABSO2RB laminates met the requirements and commercial sterility requirements for operational rations (PCR-C-039 2006).

Weight, moisture content, water activity, fat content, and pH of the product. Both packaging materials (conventional MRE and ABSO2RB) met the weight requirement during the storage period with an average of 45.5 grams. Similarly, both packaging materials provided moisture content characteristics throughout the storage period. In fact, no difference (P > 0.05) was not observed in moisture content between packages for all shelf-life studies (mean detector values were 40.53% and 40.27%, respectively). In the samples kept at 51.7 degrees Celsius, probably due to being exposed to high temperature, their water detector values slightly increased with time (the final detector values were 0.925±0.93 and 0.68±0. 92 for normal and ABSO2RB bags, respectively), although there were no significant differences (P > 0.05) did not exist between the above 2 types of packaging. Water activity of bags stored at 37.8°C for 6 months for normal MRE equals 0.925 ± 0.95 and for ABSO2RB bags equals 0.922 ± 0.93 and for samples stored at 80°F for 1 year was 0.9687 ± 0.93 for regular MRE and 0.9623 ± 0.98 for ABSO2RB bags, respectively.

Throughout the entire shelf-life study period for each of the two packaging materials (conventional MRE and ABSO2RB), the fat content of the spread cheese samples did not show any significant evolution and did not change significantly (P > 0.05). In addition, the average fat content of the spread cheese samples (40.84 ± 0.17%) complied with the requirements of product fat content not less than 38% and not greater than 43% (PCR-C-039 2006). There were changes in pH values during the storage period without any clear trend, which is probably due to the effect of temperature relative to the type of packaging. In general, the final pH values for the bags stored at 51.7 degrees Celsius ranged from 5.66 to 5.518 ± 0.03 until the end of shelf life and from 5.62 to 5.57 ± 0.02 respectively for Conventional bags and ABSO2RB changed, detector values for bags stored at 37.8°C for 6 months ranged from 5.62 to 5.45 ± 0.05 for conventional MRE and 5.64 to 5.52 ± 0.05. 03 were variable for ABSO2RB bags.

Figure number 2. Changes in headspace oxygen concentration in control and ABSO2RB⃝R spread cheese bags stored at room temperature.

Figure number 3. Optical microscope image (TOM model) related to the cross section of the sheet containing the oxygen absorber.

For the samples stored at 26.7°C for 1 year, the pH values ranged from 5.66 to 5.57 ± 0.03 for regular MRE and from 5.66 to 5.59 ± 0.01 for the bags, respectively. ABSO2RB was variable. All samples were in compliance with the requirements and requirements of the product during the entire storage period, where the value of the pH detector should not be less than 5.5 and more than 5.9 (PCR-C-039 2006) (mean values 5.57 and 5.59 for control and ABSO2RB, respectively).

Color. The effect of packaging type and storage temperature on the color parameters (L∗, a∗, b∗) of spread cheese is shown in Table No. 1. For samples stored at 51.7°C, changes in color due to packaging were minimal, with the result that storage time and temperature had the most significant effect. The L∗ detector values decreased significantly throughout the storage period (darker samples) for both packages. A similar trend was observed for the samples stored at 37.8 degrees Celsius, where the changes due to temperature and time were more than the type of packaging. The values of detector a∗ showed the greatest change (P < 0.05), although these changes were not noticeable at the end of 6 months. After 1 year of storage at 26.7°C, samples in bags containing oxygen scavenger or O2 were darker and more yellowish than those packed in conventional MRE bags (P < 0.05) were (the average values of detector L∗: equal to 66.07 and 68.00, a∗: equal to 11.43 and 12.41, b∗: were 35.97 and 38.02 for ordinary MRE and ABSORB laminates, respectively). The differences may be attributed to the inherent and natural variability of the samples during processing and packaging and were not perceived by the consumer panel members who gave the samples acceptable scores. In general, the color detector values are in good agreement with consumer preferences (see the Sensory Analysis and Evaluation section).

Texture. Changes in diffusibility and dispersibility due to packaging type and storage temperature are shown in Table 2. Overall, the maximum force required to expand and spread the sample decreased throughout the storage period for both types of packaging. However, differences between packaged samples were only expressed in bags stored at 51.7°C (P < 0.05). During 1 year of storage at 26.7°C, the spreadability of cheese spread packaged in two types of conventional MRE packaging and ABSO2RB laminate did not change (P ​​> 0.05). Therefore, storage temperature had a stronger effect on cheese spreadability, as expected. These results are in good agreement with consumer preferences (see sensory analysis section).

Free fatty acid. For bags stored at 51.7 and 38.8 degrees Celsius, free fatty acids increased linearly (R2 range from 0.971 to 0.985) with storage time (Figure 4). We can say that samples packaged in control MRE bags had higher FFA detector values than those packaged in ABSO2RB laminates (P ​​< 0.05) After 1 year at 26.7°C, the FFA content was approximately 0. .70, which is still at the lowest level perceived by consumers (objectionable odor or taste) and is approximately equal to 0.5% to 1.5% (Pearson 1971). This result was confirmed by the sensory evaluation scores (see sensory analysis section) and indicated that oxidation, a well-established and common spoilage problem in fatty foods, could be somehow controlled by using O2-absorbing laminate.

Vitamin C content (ascorbic acid). For all storage temperatures, the vitamin C content of the samples packaged in the O2-absorbing laminate was higher than the controls throughout the storage time (Figure 5). As expected, the lower the storage temperature, the slower the spoilage rate. At the end of 1 year of storage at 26.7°C, and 6 months of storage at 37.8°C, samples packaged in ABSO2RB laminates had approximately 1.5 times (47%) more vitamin C than the control group, respectively. It once again showed the effectiveness of the oxygen absorbing laminate or O2. It should be noted that at the end of the storage period (week 4) at a temperature of 51.7 degrees Celsius, the vitamin C content in the samples packed in ABSO2RB laminates was still much higher. Samples were tested two weeks later (week 6), at which time spoilage occurred with a similar concentration to that in conventional MRE pouches. This can be attributed to prolonged exposure to very high (or maximum) storage temperatures.

Table number 1. Effect of packaging type on color parameters (L∗, a∗, b∗) of MRE spread cheese packaged in control MRE and ABSO2RB⃝R pouches during accelerated shelf life studies (125°F {51.7°C} for for a period of 6 weeks and 100 degrees Fahrenheit {37.8 degrees Celsius} for a period of 6 months). Controls calibrated at 80°F (26.7°C) for 1 year.

Vitamin A content. Vitamin A content in control MRE and O2-absorbing laminates was well preserved during the storage period, only the samples stored at 26.7°C showed decreases at the end of the 1-year storage period for both types of packaging. (from 6.16 ± 0.69 μg/g to 3.07 ± 0.46 μg/g for control MRE bags and from 5.68 ± 0.86 μg/g to 3.58 ± 0.08 mg/g for absorbent bags – O2). However, no differences in vitamin A content were found between packages throughout the entire storage period for all temperatures tested.

Sensory analysis

Consumer testing. Color scores changed little throughout storage for samples stored at 26.7 and 37.8°C, and this change was associated with samples from both packages showing high acceptance levels (scores ≥ 5). (Figure number 6). When considering color measurements as a method to assess diet quality during storage, these results are similar to the study conducted by Ross and others (1997). They found that continuous color parameters were variable (different) for spread cheese samples under different storage conditions and that L∗ detector values showed the highest correlation with consumer ratings.

Scent scores had high acceptance levels throughout the storage period and no differences (P > 0.05) was not found between packages and storage temperature throughout the shelf life study (Figure 6). This result shows that the consumers were not able to distinguish the differences in the smell of diffused cheese among the different test methods. For texture scores, a slight decrease in acceptability was observed for samples stored at 37.8°C during storage for both packaging types, although acceptability was much higher than 5 for the control and ABSO2RB samples. (Figure number 6). The results are in good agreement with the emissivity measurements, although with no significant difference in acceptability and acceptability between the test methods at 26.7 and 37.8°C and a slight decrease (P > 0.05) in time acceptance for samples kept at 37.8 degrees Celsius. After the end of storage for the samples at 26.7 and 37.8°C it was still according to specifications (soft, homogeneous and easily spreadable) (PCR-C-039 2006).

When the taste was scored, all methods were highly acceptable and only slight changes were observed over time. No significant difference (P > 0.05) was not detected in the taste by the members of the consumer panel. A similar trend was observed for the overall quality scores (Figure 6). For samples stored at 26.7°C, aroma, flavor and overall quality sensory attributes did not show significant changes between methods (control and ABSO2RB) throughout the 12-month storage period (P > 0.05). These consumer acceptability results indicate that cheese spreads packaged in ABSO2RB pouches were rated on par with those packaged in control MRE pouches, and for most of the study, consumers were unable to discern significant differences between test methods.

Table number 2. Effect of packaging type on texture (spreadable force in Newtons) of MRE spread cheese packaged in control MRE and ABSO2RB⃝R pouches during accelerated shelf life studies (125°F [51.7°C] for 6 weeks and 100 degrees Fahrenheit [37.8 degrees Celsius] for 6 months [24 weeks]). Controls calibrated at 80°F (26.7°C) for 1 year (24 months)

Figure number 4. Effect of packaging type on the extent of rancidity (free fatty acid as percentage of oleic acid) of MRE spread cheese packaged in control MRE and ABSO2RB⃝R pouches during accelerated shelf-life studies (51.7°C [125°F] for 6 weeks MRE black circle, ABSO2RB white circle, 37.8°C [100°F] for 6 months: MRE black triangle, ABSORB white triangle, controls calibrated at 26.7°C [80°F] for 1 year: MRE black rhombus, ABSORB white rhombus)

Sensory testing using a trained panel. Results of analysis and review

The sense of accomplishment and leadership at the US Army Natick Soldier Center are summarized in Figure 7. These results confirmed the acceptance of products packaged in ABSO2RB bags with all samples with high acceptability scores (> 5) and with only slight differences between methods throughout the storage period.

Figure 5. Effect of packaging type on vitamin C retention (mg ascorbic acid/g) of cheese spread MRE packaged in control MRE and ABSO2RB⃝R pouches during accelerated shelf life studies (51.7°C [125°F] For 6 weeks: MRE black circle, ABSORBER white circle, 37.8°C [100°F] for 6 months: MRE black triangle, ABSORBER white triangle, controls calibrated at 26.7°C [80°F] for 1 year: MRE black rhombus, ABSORBER white rhombus).

Figure number 6. Sensory test results for MRE cheese spread kept and stored at 26.7°C (80°F) and 37.8°C (100°F) for 6 months. A total of 30 members of the consumer board were present. Points were given based on a 9-point hedonic scale. Error bars represent standard deviation. Controls calibrated at 26.7°C (80°F) for 1 year. Means a, bMeans with different capital letters are significantly different (P < 0.05).

Figure number 7. Results of sensory analysis testing for cheese spread MREs after 1 year of storage at 26.7°C (80°F) conducted at US Army Natick Soldier Center. A total of 12 members of the trained board were present. Points were given based on a 9-point scale related to happiness and pleasure. Means with superscript letters a, b were significantly different. with probability P smaller than five hundredths (P < 0.05).

Conclusion

This study showed that the proposed oxygen absorbing laminate was effective in reducing the oxygen concentration of the upper headspace to 67.44% (from 20.4% to 68.2%) within 24 hours. This active packaging material significantly reduced rancidity in spread cheese samples. In addition, the said laminate helped to delay the spoilage process of vitamin C, the samples had high acceptable sensory characteristics throughout the shelf life study and when in cases higher than the standard sample with respect to sensory, physical, chemical and microbiological characteristics. were not, they had equal rank. The samples also met the 6-month shelf life requirement at 37.8 degrees Celsius (100 degrees Fahrenheit). Therefore, bags containing oxygen absorbers in laminate can help preserve nutrients and increase the shelf life of liquid and high-fat products. Further research is suggested in other types of food products where oxygen can produce harmful properties on the food. This study may be extended to include cases of MRE and UGR including similar products.

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