A Simple Nondestructive Method for Determination of Air Content in Polymeric Packages

A new nondestructive method of estimating the residual air volume in food packages was developed and compared with the standard destructive technique. The nondestructive method involved enclosing the test package in a nonflexing, plexiglass container and placing this container into a vacuum chamber. Monitoring changes in volume at two vacuum levels and using Boyle's Law, the air content of more than fifty polymeric packages was computed. The difference between the destructive and nondestructive volumes was found to be statistically insignificant.     

Effect on Retortable Pouch Heat Transfer Coefficients of Different Thermal Processing Stages and Pouch Material

Apparent heat transfer coefficients (h) were determined for the come-up, heating, and cooling cycles of thermal processing for retortable pouches heated by circulating hot water under overriding air pressure. Values for h were converged on by a computer-based optimization method that incorporated process data, a finite difference model, and optimization criteria. For retortable pouches thermally processed in circulating water under overriding air pressure, h values for the come-up, heating, and cooling cycles were found not significantly different (95% confidence). This indicates that in mathematical models a constant h value may be assumed for the three thermal processing stages. Also, there was no significant difference between h values for aluminum foil/plastic laminate pouches and all-plastic pouches during the combined come-up and heating stages. Thus, the same h value for a given process is applicable to either pouch type.     

Effect of Thermal Process Time on Quality of "Shrimp Kuruma" in Retortable Pouches and Aluminum Cans

ABSTRACT:  The effect of processing time on biochemical, sensory characteristics, and instrumental texture profiles of "Shrimp Kuruma" in retortable pouches and aluminum cans with equal pack weight and lethality was studied. Processing in pouches resulted in a 35% reduction in processing time compared to cans for equal lethality ( F ₀ 8.0). Thermal processing resulted in a 14% loss of water in canned samples compared to 9% in pouched products. Thermal processing resulted in an increase in the volatile compounds and a decrease in the oxidation products in both canned and pouched samples. Products processed in pouches were rated as lighter in color, more succulent, and more desirable in firmness compared to products in cans. Chewiness and hardness showed a significant difference ( P < 0.05) between the 2 treatments.     

Effects of Packaging Conditions on the Flavor Stability of Dry Whole Milk

The flavor stability of dry whole milk packed with air, nitrogen, or a mixture of 92% nitrogen and 8% hydrogen (NH) in gas-impermeable pouches containing palladium as a catalyst was evaluated by measuring headspace volatile, oxygen, carbon dioxide contents using gas chromatography, brown color formation by reflective spectroscopy, and sensory scores. The headspace volatile and carbon dioxide contents of the dry whole milks packed with air or nitrogen were significantly higher (P <0.05) than the samples packed with NH. Brown color formation and sensory scores of products packed with air were significantly different (P <0.05) from the samples packed with 92% nitrogen and 8% hydrogen. The flavor stability of dry whole milk could be increased by packaging the products with NH in pouches containing palladium.     

Effect of residual oxygen on the colour, odour and taste of carbon dioxide-packaged beef, lamb and pork during short term storage at chill temperatures

Samples of boneless pork, lamb, beef (high and normal pH) were packaged in '100%' carbon dioxide atmospheres in foil laminate pouches. These pouches were fitted with a septum and a gas sampling port that allowed the introduction of air and removal of gas samples for analysis from the sealed packs. After sealing, measured volumes of air were introduced into test packs that had been gassed at a carbon dioxide volume to meat weight ratio of either 1 litre/kg or 2 litres/kg, to give initial atmospheres containing approximately 0·1, 0·2 and 1·0% oxygen. After 24 and 168 h storage at -1·5 ± 0·5°C, test packs were removed and compared with similarly treated control packs without added oxygen with respect to meat odour, taste and colour. No significant differences between the test and control packs in respect to odour or taste were evident with any meat type. The tendency to develop browning in response to the presence of residual oxygen within packs, increased in the order: pork, normal pH beef, normal pH lamb, high pH beef. Beef and lamb developed noticeable browning in packs containing more than 0·15% total oxygen while pork was able to tolerate 1% oxygen without obvious detrimental effects. For all meat types, the colour stability was greater in packs gassed to the higher gas volume to meat weight ratio.     

Effect of freezing time on the quality of Indian mackerel (Rastrelliger kanagurta) during frozen storage

The present study aims to find the effect of freezing methods on the quality of mackerel (Rastrelliger kanagurta) in commercial plate and air blast freezers during freezing and subsequent frozen storage (-18 degrees C). Total time for freezing was significantly different (P < 0.05) between the plate and air blast freezers (90 and 220 min, respectively). This difference in the freezing time could be attributed to the varied quality of the 2 samples. Upon freezing, the moisture content decreased in air blast frozen samples compared to plate freezer where protein content decreased in both the samples. Upon freezing and during frozen storage, lipid oxidation products (peroxide value, thiobarbutiric acid value, and free fatty acid value) and volatile bases (total volatile base nitrogen and trimethyl amine nitrogen) showed an increasing trend in both the samples with values slightly higher in air blast frozen samples compared to plate frozen samples. The total plate counts showed a significantly (P < 0.05) decreasing trend in both the samples. K value did not show any significant (P < 0.05) difference between the samples where as the histamine formation was significantly (P < 0.05) increased in air blast frozen samples compared to plate frozen samples. The taste and overall acceptability was significantly different (P < 0.05) in plate frozen samples compared to air blast frozen samples on 3rd month. Both samples were in acceptable condition up to 3 mo but the plate frozen samples quality was slightly better than the air blast frozen samples.     

EFFECTS OF MODIFIED ATMOSPHERE PACKAGING AND FILM ON SENSORY AND STORAGE PROPERTIES OF FROZEN HAM STRIPS

The effectiveness of modified atmosphere packaging and barrier properties of films upon the product attributes of frozen (IQF) ham strips, that are normally found at salad bars, was studied every 28 days over a period of 196 days. Three gases/mixture were used (CO₂, N₂ and ambient air) for flushing two pouches, one made from normal barrier film (861) and the other from a high barrier film (863). A triangle test and sensory evaluations were performed by a semi-trained panel (six members) for the following traits: freshness, structure, mouth feel, overall evaluation, aroma, appearance and off-flavors. Overall evaluation scores were acceptable up to 140 days of storage, regardless of the pouch used, but from 140 to 196 days, the product would be only marginally acceptable. Ham strips stored in N₂ or CO₂ atmospheres had a higher acceptance level than those stored frozen in ambient air. Panelists distinquished between fresh and stored product more frequently (75%) when the product was stored in ambient air pouches rather than CO₂ or N₂ atmospheres. Pouches made from the higher barrier film had lower (398/g) total aerobic plate counts than pouches (736/g) made from normal barrier film, but these counts are low and would be acceptable in industry.     

Heating Rates in Flexible Packages Containing Entrapped Air During Overpressure Processing

Experiments were performed in two steam/air retorts and one water immersion retort to test the influence of included air on heating rate index (f_h) values at the center of thin plastic bricks packaged in retort pouches and processed under various temperature and overpressure conditions. In general, high air overpressures (>80 kPa) allowed up to 30 mL air to be included with no detrimental effect on heating rates; however, even small amounts of entrapped air (<5 mL) degraded heat transfer when processed at low air overpressures (<40 kPa). Processing medium and retort type were important factors in the sensitivity of heating rate to increases of air volumes beyond a threshold value.     

Residual gas and storage conditions affect sensory quality of diced pears in flexible retortable pouches

Diced pears packed in flexible retortable pouches were manufactured to obtain packages with 10, 15, 20 and 30 cm³ residual gas, then stored at 4.4, 26.7 and 37.8 °C for six months. The 2-furaldehyde and 5-hydroxymethyl-2-furaldehyde values increased and pears turned darker, softer, more homogeneous in shape/size, less fruity in flavor and aroma, and less acceptable to consumers over time. Elevated temperatures and high residual gas levels were particularly detrimental to pear quality. Highest quality was maintained for 6 months when pears packaged at any residual gas level were stored at 4.4 °C. Acceptable quality was maintained for 6 months in pears packaged with less than 30 cm³ residual gas, stored at 26.7 °C. Pear quality declined most rapidly at 37.8 °C, 30 cm³ residual gas. Residual gas volume of 15 cm³ should not be exceeded to maintain highest quality and acceptability of diced pears packed in flexible retortable pouches.     

RESIDUAL GAS VOLUME EFFECT ON QUALITY OF RETORT POUCH WET-PACK PEARS

Wet pack pears in retort pouches were studied for six months. Four selected residual gas volumes [10, 15, 20 and 30 cubic centimeters (cc)] were used to determine the influence of residual gas volume on physicochemical and sensory attributes. Three storage temperatures (4.4, 26.7 and 37.8C) were used to carry out an accelerated shelf‐life study. Residual gas of 30 cc promoted faster darkening and higher ascorbic acid degradation than the rest of the volumes studied (α≤ 0.01). No significant effect of residual gas volume was found on any other attribute analyzed. Temperature accelerated the consumption of remaining oxygen in the pouches, degradation of ascorbic acid, formation of 5‐hydroxymethyl‐2‐furaldehyde (HMF) and 2‐furaldehyde, and softening of pears. Calculated activation energies (E_a) for HMF and 2‐furaldehyde formation, ascorbic acid, and color degradation were 35, 31.1, 29.8, and 10.4 kcal/mol, respectively. Residual gas volume of 20 cc was the maximum volume studied that accomplished the desired shelf‐life for this product.     

Shelf Life of Sunflower Kernels

One raw and two oil roasted samples of sunflower kernels packaged in paper bags and in two types of low oxygen atmosphere pouches were stored at 5, 21 and 38°C. Quality of the stored samples was monitored by an expert sensory panel, peroxide, hexanal, free fatty acids and moisture determinations. Liking ratings, obtained with 99 consumers after 24 wk storage, were used to select end points for expert sensory ratings. The shelf life for roasted sunflower kernels was greater than 12 month when stored in nitrogen flushed pouches and as low as 8 wks when exposed to air at 38°C. Hexanal was a better index for shelf life of roasted sunflower kernels than was peroxide. The shelf life of raw sunflower kernels was > 12 month in packages providing some moisture but no oxygen protection.     

Anthocyanin infused watermelon rind and its stability during storage

Anthocyanins from Garcinia indica Choisy was impregnated in watermelon rind (WMR) through osmotic dehydration. The impregnation of anthocyanin was enhanced by application of pretreatments like vacuum and sonication (from 24 to 32 mg/100 g). Application of pretreatment during impregnation changes the tissue architecture of the WMR which helps in retaining the infusate during candy making process. The developed product from WMR was highly acceptable w.r.t. texture, taste and appearance. Moisture sorption study indicated that the WMR product was quite stable at ambient temperature upto 75% RH. Storage of the sample in LDPE (low density polyethylene pouches) and PET/LDPE (Polyethylene terephthalate/low density polyethylene pouches) did not show any significant difference in moisture content, anthocyanin degradation, texture, taste and appearance of the product. The WMR product was stable for 90 days at ambient storage conditions.Industrial relevanceThe knowledge provided by this work may be useful the development of new product (watermelon candy) from watermelon rind impregnated with anthocyanin. The extent and rate of infusion of anthocyanin was enhanced by application of pretreatments like vacuum and sonication. The developed product had highly acceptable texture, taste and appearance. The product was quite stable at ambient temperature upto 75% RH in LDPE (low density polyethylene pouches) and PET/LDPE (Polyethylene therapthalate/low density polyethylene pouches) pouches without significant difference in moisture content, anthocyanin degradation, texture, taste and appearance of the product. The WMR product was stable for 90 days at ambient storage conditions. This technique may be helpful in producing foods with enriched bioactive compounds, besides providing diversified products in terms of taste and nutrition.     

Quality Enhancement of Sexually Mature Chum Salmon Oncorhynchus keta in Retort Pouches

Sexually mature or late-run chum salmon muscle was packaged in thin-profile retort pouches and in conventional 307 × 200 metal cans. After retort processing to equivalent lethality, samples were evaluated by sensory and instrumental methods. The pouch product was firmer, more fibrous, drier and chewier than the canned. Less late-run flavor and greater overall acceptability were reported for pouch-processed samples. More free liquid was found in pouches than in cans. Histological examination revealed a more compact structure in chum muscle processed in retort pouches, possibly due to air over-pressure applied to flexible pouches during processing.     

Sensory effects of hexanal vapor on fresh-cut slices of golden delicious apples

Hexanal is a natural antimicrobial molecule that characterizes apples aroma. In this paper, the sensory effects of hexanal, as a component of packaging atmosphere, on fresh sliced Golden Delicious apples after storage at 4 °C for 8 d were evaluated. In particular, a colorimetric analysis of slices treated with different concentrations of hexanal vapor (coming from 3.040 to 0.076 mmol of liquid aldehyde per liter of air) fixed at 0.076 mmol/L the amount of hexanal in evaluating sensory effects in the subsequent analysis. Color and texture evaluation of slices by Two-out-of-Five method did not highlight any significant difference between treatment and control. The results from olfactory evaluation showed instead that treated samples had an intense odor compared with those untreated (P < 0.001). A significant difference between treatment and control was also highlighted during the flavor evaluation (P < 0.01); however, from the panelists' observations it emerged that such an effect would work negatively. The positive effect of the tested dose of hexanal on the odor of Golden Delicious slices and its flavor acceptability were verified by using regular apple consumers. A significant preference (P < 0.001) for the odor of treated apple slices came out, so the small dose of hexanal intensifies the odor of apples pleasantly. The different flavor of treated samples was not identified by the consumers, who altogether expressed positive judgments about it. This suggests the nicety of this difference that in the absence of an untreated reference sample is very difficult to detect.     

Microbial quality of water supply to an urban community in Trinidad

A microbiological study was conducted to determine the quality of the water supply to an urban community in San Fernando proper in south Trinidad using total coliforms and thermotolerant coliforms as indicators of water pollution. The membrane filter technique was used to detect total coliforms and thermotolerant coliforms on endo agar and MFc agar, respectively. The residual chlorine levels in water from the reservoir, from standpipes along the distribution line, and from households were determined with a commercial test kit. Of a total of 104 drinking water samples obtained from households, 84 (80.8%), 56 (53.8%), and 70 (67.3%) tested positive for total coliforms, thermotolerant coliforms, and Escherichia coli, respectively. The difference was statistically significant (P < 0.05, chi2). Of the 81 water samples collected from the Water and Sewerage Authority (WASA) main supply to households, 38 (46.9%), 13 (16.0%), and 27 (33.3%) were contaminated by total coliforms, thermotolerant coliforms, and E. coli, respectively, and the difference was statistically significant (P < 0.05, chi2). Eight (20.5%) of 39 water samples from standpipes along the distribution line tested positive for total coliforms, compared with 4 (10.3%) samples testing positive for thermotolerant coliforms. All five samples of treated water obtained from the reservoir tested negative for coliforms. There was a significant difference (P = 0.004) in the mean residual chlorine levels in water from the reservoir, water from standpipes, and water from households. Similarly, as the level of residual chlorine decreased, there was a statistically significant (P = 0.004) increase in the prevalence of total coliforms in water from 0.0% (treated reservoir water) to 15.2% (standpipe) to 53.5% (household mains) to 80.0% (household drinking water). There was also a statistically significant difference (P < 0.001, chi2) in the prevalence of total coliforms in drinking water and in water from the WASA main supply to households. Of the 105 E. coli strains tested, 7 (6.7%), 16 (15.2%), and 22 (21.0%) were mucoid, hemolytic, and non-sorbitol fermenters, respectively. It was concluded that the high degree of contamination of drinking water in households poses a health hazard to consumers.     

Decoloration and Gel-forming Ability of Horse Mackerel Mince by Air-flotation Washing

ABSTRACT: The decoloration effects and gel-forming ability of horse mackerel mince by air-flotation washing (AFW) was investigated. The lowest residual myoglobin content (RMb) and relative fluorescence intensity (RFI), the highest metmyoglobin (metMb) content and best decoloration effects were recorded for the mince washed with AFW. AFW also effectively improved gel strength in heated surimi. No significant difference in RMb was found when mince was treated with flotation washing using nitrogen, air and ozone. Although the highest metMb content and the lowest RFI were found for the mince washed with ozone, significant differences in whiteness were observed only when the mince was treated with a different gas at 10 or 20 L/min for 5 to 10 min. The physical removal of myoglobin was suggested to be the main factor contributing to accelerated decoloration with AFW.     

不同预处理方式对冻藏草莓品质的影响

为了解决速冻草莓在贮藏过程中品质快速下降的问题,采用糖溶液和氯化钙溶液对其进行处理,以改善其冻藏品质。以VC、汁液流失率、电导率、硬度、可溶性固形物和总酸含量为评价指标,考察不同预处理后在－18 ℃条件下冻藏0.5、1.0、2.0、3.0、4.0、5.0 个月时草莓的品质变化情况。结果表明：20%糖溶液处理20 min的处理组VC损失率最小,可溶性固形物含量、电导率变化最小,总酸含量降低得慢,且与其他处理组相比差异显著（P＜0.05）;3%氯化钙溶液处理15 min的处理组汁液流失率最小,硬度变化最小,且与其他处理组相比差异极显著（P＜0.01）。     

Microbial and sensory quality of marinated and irradiated chicken

Chicken legs were subjected to two pretreatments (packaged in air or marinated in natural plant extracts and then packaged in air) followed by irradiation (0, 3, or 5 kGy). The control and irradiated chicken legs were stored at 4 degrees C and underwent microbial analysis (mesophilic aerobic plate counts and Salmonella detection) and sensory evaluation at predetermined intervals. Microbial analysis indicated that irradiation had a significant effect (P < or = 0.05) on the mesophilic aerobic plate counts of the poultry. For each treatment, the bacterial growth decreased with an increase of irradiation dose. The marinade had an additive effect with irradiation in reducing bacterial growth and controlling proliferation during storage at 4 +/- 1 degree C. No Salmonella was observed until day 12 in marinated chicken irradiated at 3 kGy and for all experiments with chicken legs stored under air or marinated at 5 kGy. However, Salmonella was found in chicken legs irradiated at 3 kGy in air and in nonirradiated samples. The sensory evaluation indicated a significant (P < or = 0.05) difference in odor and flavor intensities between the irradiated chicken at 5 kGy and the control. No significant difference was found (P > 0.05) between the marinated chicken irradiated at 5 kGy and the control.     

干制方式对腌腊草鱼脂肪氧化和挥发性风味成分的影响

以不同干制方式制得的腌腊鱼（水分质量分数40%）为对象,基于菌落总数、酸价（acid value,AV）、过氧化值（peroxide value,POV）、硫代巴比妥酸（thiobarbituric acid,TBA）含量、总脂含量与总脂肪酸组成、挥发性风味物质、感官评分等指标,探讨了光照和温度对腌腊鱼风味品质的影响。结果显示：冷风避光组腌腊鱼样品的菌落总数最高,而热风光照组最低,分别为4.42、2.91（lg（CFU/g））。光照组腌腊鱼的脂质氧化指标均高于避光组,两者总脂含量无显著差异（P＞0.05）;热风组腌腊鱼的POV和TBA含量均显著高于冷风组（P＜0.05）,AV和总脂含量显著低于冷风组（P＜0.05）。多不饱和脂肪酸含量占腌腊鱼总脂肪酸含量的40%左右。无论是温度还是光照均对以二十二碳六烯酸为代表的n-3系多不饱和脂肪酸有显著影响（P＜0.05）。感官评价结果表明,冷风组和光照组腌腊鱼样品香气得分均显著高于热风组和避光组（P＜0.05）。本研究共从4 种腌腊鱼样品中检出了82 种挥发性物质,筛选确定了2-壬烯醛等14 种气味活性物质。相同温度下,光照组样品的气味活性值总和显著高于避光组（P＜0.05）,表明光照更有利于香气物质的生成。本研究可为腌腊鱼生产企业改善产品品质提供理论依据。