Effect of varying oxygen concentrations on the shelf-life of fresh pork sausages packaged in modified atmosphere

A total of 105 fresh pork sausages were packaged in atmospheres varying in oxygen concentration, using the following mixtures (%O₂/%CO₂/%N₂): 0/20/80, 0/20/80 + O₂ scavenger, 20/20/60, 40/20/40, 60/20/20, and 80/20/0. In addition, two batches were subjected to vacuum packaging or over-wrap with O₂-permeable film. They were stored for 20 days at 2 ± 1 °C in the dark. Values of pH, CIE L*, a* and b* color parameters, surface metmyoglobin percentage, TBA-reactive substances, psychrotroph aerobe bacterial numbers and sensory discoloration and off-odor were assessed throughout storage. Packaging in the absence of O₂, either under vacuum or in atmosphere with O₂ scavenger, led to extension of shelf-life in terms of both color and odor stability due to low oxidation rates. Increase of O₂ caused a significant enhancement of oxidation, decrease of shelf-life due to discoloration and off-odor development. The highest O₂ concentration gave rise to a significant color improvement, though only for a limited period of 8 days.     

Packaging-specific influence of chitosan on color stability and lipid oxidation in refrigerated ground beef

We examined the influence of chitosan on lipid oxidation and color stability of ground beef stored in different modified atmosphere packaging (MAP) systems. Ground beef patties with chitosan (1%) or without chitosan (control) were packaged either in high-oxygen MAP (HIOX; 80% O₂ + 20% CO₂), carbon monoxide MAP (CO; 0.4% CO + 19.6% CO₂ + 80% N₂), vacuum (VP), or aerobic packaging (PVC) and stored at 1 °C. Chitosan increased (P < 0.05) redness of patties stored in PVC and CO, whereas it had no effect (P > 0.05) in HIOX. Chitosan patties demonstrated lower (P < 0.05) lipid oxidation than controls in all packaging. Control patties in PVC and HIOX exhibited greater (P < 0.05) lipid oxidation than those in VP and CO, whereas chitosan patties in different packaging systems were not different (P > 0.05) from each other. Our findings suggested that antioxidant effects of chitosan on ground beef are packaging-specific.     

Quality and microbial stability of partially baked bread during refrigerated storage

Partially baked bread was prepared and stored at 1 °C or 7 °C for 28 days. Periodically, this product was subjected to moisture, hardness, and microbiological analyses. After storage, the baking process of part-baked bread was completed and product evaluated according to microbiological, physical, and sensorial tests, as well as hardness analysis. Part-baked breads stored at 7 °C showed mold growth at day ninth, while the product stored at 1 °C did not show mold growth through 28 days. The full-baked bread obtained from part-baked samples stored at 1 °C showed higher values of hardness and change in crumb hardness, and lower sensorial quality than bread from part-baked samples stored at 7 °C. Moisture content, specific volume, and width/height ratio in the full-baked bread were not affected by storage time and temperature.     

翡翠贻贝气调保鲜包装研究

采用涂布聚偏二氯乙烯的聚酯与聚乙烯复合薄膜袋(KPET/PE)气调包装翡翠贻贝,混合气体包括:CO2、O2和N2。选用5组气体配比(A:V(75%O2)/V(25%N2);B:V(50%O2)/V(50%N2);C:V(20%O2)/V(30%CO2)/V(50%N2);D:V(10%O2)/V(50%CO2)/V(40%N2);E:空气)进行包装并贮藏在5℃以下。在贮藏期间测定包装袋内气体浓度变化、需氧菌总数、TVBN和pH值,研究在不同气调比例包装条件下,翡翠贻贝的品质变化。实验结果表明:在贮藏温度为5℃条件下采用气调包装的样品,其需氧菌总数和TVBN等指标明显优于空气对照组。在5组气体比例中,以V(O2)∶V(CO2)∶V(N2)=10%∶50%∶40%的配气比例包装的保鲜效果最佳,其贮藏期比对照组空气包装延长3￣8d。     

Colour stability of beef from different Spanish native cattle breeds stored under vacuum and modified atmosphere

Beef steaks from five Spanish cattle breeds were submitted to three packaging conditions: (a) 15 days under vacuum, (b) 15 days under modified atmosphere (MAP) (60% O₂, 30% CO₂ and 10% N₂), and (c) 10 days under vacuum plus 5 days more under MAP. CIE L^*a^*b^* coordinates, chroma (C^*) and hue (H^*), relative concentration of myoglobin, oxymyoglobin and metmyoglobin at the meat surface and sensory evaluation of colour were determined 0, 5, 10 and 15 days after packaging. Beef under MAP showed higher lightness (L^*) and hue (H^*) and lower redness (a^*) and chroma (C^*) than beef under vacuum. Colour of beef under MAP was not acceptable after 15 days of storage, due to the high metmyoglobin concentration. Yellowness (b^*) was the indicator of differences due to ageing and differences in colour between breeds were related to L^*, a^* and H^* values. Packaging conditions had a greater effect on beef colour than breed, but breed differences might change with packaging atmosphere. Both packaging and breed are major factors in packaged beef quality.     

Effect of modified atmospheres on microbiological, color and sensory properties of refrigerated pork

Pork loin samples were stored (4 °C) in nylon polyethylene plastic bags using different modified atmospheres packaging (MAP): vacuum, 100% CO₂ 99% CO₂ + 1% CO, 100% O₂ or 100% CO followed by vacuum. Throughout the storage period Pseudomonas growth was limited in loins packaged in all MAPs evaluated, except for 100% O₂. Psychrotrophs reached 10⁷ CFU g⁻¹ after 20 days of storage except for the loin samples in 100% O₂ MAP that present count above 10⁸ CFU g⁻¹. The 1% CO/99% CO₂ atmosphere was best for preserving the desirable pork loin color and the L* and a* values remained similar to the fresh meat values using this MAP. Pork loins in 99% CO₂/1% CO MAP obtained the highest consumer acceptance scores after 24 h of storage. These samples and those treated with CO and then vacuum packaged received the greatest acceptance scores even after 20 days of storage.     

陈列方式对立式冷藏陈列柜食品温度的影响

目的与方法：降低冷藏陈列柜内冷藏食品的温度及提高食品冷藏品质；将超市里一般平行摆放食品的方式改为阶梯型，通过比较采用这2种陈列方式后是否能够降低食品内部温度以及降低幅度，来决定其试验的可行性和实用价值；结果：与水平型陈列方式相比，采用阶梯型陈列方式后，总体来说，各层搁板前后排食品温差均有所降低，第1、2层冷藏空间的食品温度下降幅度较大，具用一定的可行性；而对第3、4层冷藏空间来说，其效果不如前2层理想，有待于采用其它方式进行强化传热。     

The performance of several oxygen scavengers in varying oxygen environments at refrigerated temperatures: implications for low-oxygen modified atmosphere packaging of meat

The oxygen scavenging capacity of four commercially available iron-based oxygen scavengers was studied. Individual oxygen scavenger sachets were placed in pouches and filled with 1%, 2%, 6%, 12% or 22% oxygen, 40% carbon dioxide and balance nitrogen, and stored at 3 °C or 10 °C, with or without a drip pad infused with water and monitored over 24 h. The four scavengers all reduced oxygen from the packs at the oxygen concentrations and temperatures tested. However, for all of the conditions measured, the scavengers did not absorb their nominal capacity in the 24-h period. In anoxic modified atmosphere packaging of beef steaks, it is essential to reduce residual oxygen levels to below 0.05% as quickly as possible to minimise the formation of metmyoglobin. While the scavengers tested were effective in removing oxygen, the rate of removal would appear not to be fast enough to create the anoxic conditions required to prevent metmyoglobin formation in beef steaks, particularly in those cuts, which are highly susceptible to metmyoglobin formation. Reproducibility was also a critical issue for the scavengers, particularly at low oxygen concentrations. None of the scavengers had a coefficient of variation of less than 20% at the low oxygen concentrations. Therefore, to obtain consistent results, it is recommended that multiple scavengers be used.     

Potential mechanisms of carbon monoxide and high oxygen packaging in maintaining color stability of different bovine muscles

The objectives were to compare the effects of packaging methods on color stability, metmyoglobin-reducing-activity (MRA), total-reducing-activity and NADH concentration of different bovine muscles and to explore potential mechanisms in the enhanced color stability by carbon monoxide modified atmosphere packaging (CO-MAP, 0.4% CO/30% CO₂/69.6% N₂). Steaks from longissimus lumborum (LL), psoas major (PM) and longissimus thoracis (LT) packaged in CO-MAP, high-oxygen modified atmosphere packaging (HiOx-MAP, 80% O₂/20% CO₂) or vacuum packaging were stored for 0 day, 4 days, 9 days, and 14 days or stored for 9 days then displayed in air for 0 day, 1 day, or 3 days. The CO-MAP significantly increased red color stability of all muscles, and especially for PM. The PM and LT were more red than LL in CO-MAP, whereas PM had lowest redness in HiOx-MAP. The content of MetMb in CO-MAP was lower than in HiOx-MAP. Steaks in CO-MAP maintained a higher MRA compared with those in HiOx-MAP during storage. After opening packages, the red color of steaks in CO-MAP deteriorated more slowly compared with that of steaks in HiOx-MAP.     

Trace metal concentrations in Mediterranean blue mussel and surface sediments and evaluation of the mussels quality and possible risks of high human consumption

The concentrations of trace metals (Fe, Zn, Mn, Ni, Cu, Co and Cr) were determined for the first time in Mediterranean blue mussels (Mytilus galloprovincialis) and surface sediments. The mussel and sediment samples were collected from five sites on the Montenegrin coastal area (southeastern Adriatic Sea) in the fall of 2005 and 2006. The collected samples were digested with a microwave digestion system. The maximum Fe, Zn, Mn, Ni, Cu, Co and Cr mean concentrations in the mussel samples were 603.0, 345.0, 85.0, 18.9, 17.2, 9.1 and 4.2 mg/kg of sample dry weight, respectively. The maximum Fe, Mn, Cr, Ni, Zn, Cu and Co concentrations in the sediment samples were 40867, 943.0, 382.0, 336.0, 67.2, 24.8 and 16.9 mg/kg of sample dry weight, respectively. A correlation between the metal levels found in the mussel soft tissues with those found in sediments, for both 2005 and 2006, could be established, except for the levels of Zn observed.     

Effect of refrigerated storage time on the viability of probiotic bacteria in fermented probiotic milk drinks

The viability of Lactobacillus acidophilus and Bifidobacterium lactis in fermented milks A, B and AB, containing respectively these strains separately and mixed, was studied over 21 days of storage at 5°C. Samples were analysed for titratable acidity and viable cell counts of probiotics. Milks A and AB showed post-acidification mainly due to the β-galactosidase activity of L. acidophilus . Generally, the viability of the probiotics decreased during storage, whereas, in some cases, the proteoletic activity of L. acidophilus resulted in a higher survival rate of the probiotics even with the adverse effects of low temperature and organic acids.     

Effect of initial headspace oxygen level on growth and volatile metabolite production by the specific spoilage microorganisms of fresh-cut pineapple

The effect of initial headspace (IH) O₂ level on the shelf-life of fresh-cut pineapple was evaluated in this study. The results showed that although the IH O₂ level had a minor effect on the growth of Candida argentea, Candida sake and Meyerozyma caribbica on pineapple agar, the quantities of the volatile organic metabolites produced by these yeasts was generally smaller the lower the IH O₂ level. The only exception was the production of ethyl acetate by C. argentea, which was higher at low IH O₂ levels. In triangle tests performed with trained panellists, pineapple cubes packaged in an IH of 5% O₂ were determined to be significantly different (P < 0.05) to those packaged in 21% O₂ from day 5 of storage. Preference was shown for the pineapple cubes packaged in an IH of 5% O₂. The results imply that packaging in an IH O₂ level of 5% could be used to extend the shelf-life of fresh-cut pineapple.     

Effect of natural antioxidant combinations on lipid oxidation in cooked chicken meat during refrigerated storage

The effect of combinations of sage, oregano and honey on lipid oxidation in cooked chicken meat during refrigeration at 4°C for 96h was determined. Chicken samples (thigh and breast) were then separated into five groups: control; butylated hydroxytoluene; oregano+sage; oregano+sage+5%honey and oregano+sage+10%honey. Quantitative measurements of thiobarbituric acid reactive substances, conjugated dienes, hexanal, fatty acids, cholesterol and cholesterol oxides were used as indicators of lipid oxidation. Acceptability and preference were also evaluated. The effectiveness of the natural antioxidants for reducing the velocity of lipid oxidation in cooked chicken thigh and breast was demonstrated after 48 and 96h of refrigeration at 4°C. The treatments that presented the lowest hexanal values after 96h of refrigeration were oregano+sage+5%honey and oregano+sage+10%honey. Only traces of free cholesterol oxides were found (25-OH, 7-k, 7α-OH and 7β-OH). The natural antioxidants protected cooked chicken meat from oxidation processes and resulted in great acceptability.     

Impact of minimal processing on orange bioactive compounds during refrigerated storage

The effect of minimal processing on the health-related attributes of orange fruit was investigated. Oranges were prepared as whole fruits, hand-peeled fruits and manually separated segments, packed under air atmosphere and stored at 4 °C for 12 days. The stability of main bioactive compounds (carotenoids, flavanones and vitamin C) and antioxidant activity was evaluated. The total carotenoid content showed a significant increase for the whole samples during refrigerated storage, whereas no significant changes were observed for segments or peeled samples. A similar trend was found for vitamin A. With regard to vitamin C, at the end of refrigerated storage, some losses were observed although no significant differences were found among the different processed samples. The flavanone content showed a significant increase throughout refrigerated storage as response to cold stress. In general, the antioxidant activity remained stable in relation to the initial values. Hence, the health-related characteristics of minimally processed oranges were retained during refrigerated storage.     

Combined effect of oregano essential oil and modified atmosphere packaging on shelf-life extension of fresh chicken breast meat, stored at 4 degrees C

The combined effect of oregano essential oil (0.1% and 1% w/w) and modified atmosphere packaging (MAP) (30% CO2/70% N2 and 70% CO2/30% N2) on shelf-life extension of fresh chicken meat stored at 4 degrees C was investigated. The parameters that were monitored were: microbiological (TVC, Pseudomonas spp., lactic acid bacteria (LAB), yeasts, Brochothrix thermosphacta and Enterobacteriaceae), physico-chemical (pH, TBA, color) and sensory (odor and taste) attributes. Microbial populations were reduced by 1-5 log cfu/g for a given sampling day, with the more pronounced effect being achieved by the combination of MAP and oregano essential oil. TBA values for all treatments remained lower than 1 mg malondialdehyde (MDA) kg(-1) throughout the 25-day storage period. pH values varied between 6.4 (day 0) and 5.9 (day 25). The values of the color parameters L*, a* and b* were not considerably affected by oregano oil or by MAP. Finally, sensory analysis showed that oregano oil at a concentration of 1% imparted a very strong taste to the product for which reason these lots of samples were not scored. On the basis of sensory evaluation a shelf-life extension of breast chicken meat by ca. 3-4 days for samples containing 0.1% oregano oil, 2-3 days for samples under MAP and 5-6 days for samples under MAP containing 0.1% of oregano oil was attained. Thus oregano oil and MAP exhibited an additive preservation effect.     

The influence of headspace and dissolved oxygen level on growth and haemolytic BL enterotoxin production of a psychrotolerant Bacillus weihenstephanensis isolate on potato based ready-to-eat food products

The major objective of this study was to determine the influence of the initial headspace and dissolved O₂ level and vacuum packaging on growth and diarrhoeal enterotoxin production by Bacillus weihenstephanensis on potato based ready-to-eat food products. In general, the lower the initial headspace or dissolved O₂ level the slower the maximum growth rate (μ_max, log₁₀ CFU g⁻¹ d⁻¹), the longer the lag phase duration (λ, d) and the smaller the maximum population density (N_max, log₁₀ CFU g⁻¹) became. The slowest μ_max, the longest λ and the smallest N_max were generally found for growth under vacuum packaging. This implies shorter shelf-lives will occur at higher initial headspace or dissolved O₂ levels as the growth of B. weihenstephanensis to the infective dose of 10⁵ CFU g⁻¹ in such atmospheres takes a shorter time. Significant consumption of dissolved O₂ only occurred when growth shifted from the lag to the exponential phase and growth generally transitioned from the exponential to the stationary phase when the dissolved O₂ levels fell below ca. 75 ppb. Diarrhoeal enterotoxin production (determined via detection of the L2 component of haemolytic BL) was similar for growth under initial headspace O₂ levels of 1-20.9%, and was only reduced when growth took place under vacuum packaging. The reduction in L2 production when growth took place under vacuum was most probably related to the low final cell densities observed under this condition. Both growth and L2 production were inhibited over a 32-day incubation period at 7 °C by 40% CO₂ irrespective of the headspace or dissolved O₂ levels. The results illustrate the importance of residual O₂ and CO₂ on the shelf-stability and safety of modified atmosphere packaged potato based ready-to-eat food products with regards to B. weihenstephanensis.     

The effect of dietary oregano essential oil on microbial growth of rabbit carcasses during refrigerated storage

The effect of dietary supplementation with oregano essential oil on microbial growth of rabbit carcasses during refrigerated storage was investigated. A total of 45 weaned rabbits were separated into three equal groups with three subgroups each. One group was given the basal diet and served as control and the other two groups were administered diets supplemented with oregano essential oil at levels of 100 and 200 mg/kg diet, respectively (OR100 and OR200 groups). Total viable counts, Pseudomonas spp., lactic acid bacteria, Brochothrix thermosphacta, Enterobacteriaceae and yeast and mould counts, as well as off-odours and appearance of slime were all assessed on rabbit carcasses stored at 3 ± 1 °C for 12 days. The results showed that performance parameters were not affected (p > 0.05) whereas the dietary supplementation with oregano essential oil resulted in lower (p < 0.05) average microbial counts on the carcasses, compared to controls, throughout storage. Dietary supplementation with oregano essential oil at 200 mg/kg was more effective in inhibiting microbial growth compared with 100 mg/kg. Sensory evaluation scores indicated that the carcasses obtained from OR100 and OR200 groups gave a noticeable putrid odour after days 8 and 10, respectively, whereas the control carcasses developed off-odours after the 6th day of storage. Slime formation in the controls was observed after day 6, while the OR100 and OR200 groups were just beginning to show slime after days 8 and 10, respectively.     

硅窗气调包装保鲜贮藏茶树菇呼吸特性与贮藏品质的研究

以乙醇作为厌氧呼吸的指标，评估气调包装贮藏茶树菇时厌氧呼吸产生的条件，探讨硅窗对茶树菇的呼吸特性与贮藏品质变化的影响。结果表明：与普通气调相比较，硅窗气调能明显改善茶树菇贮藏的气体环境。贮藏温度为3℃，硅窗面积0．9cm。以上和贮藏温度为7℃，硅窗面积1．2cm。以上，都能避免厌氧呼吸的发生，茶树菇有更好的贮藏品质。     

Physiological and behavioral effects of different concentrations of diatomaceous earth on common stored product pest Callosobruchus maculatus

The presented research focuses on the assessment of the changes in the behavioral and physiological parameters of Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae), treated with amorphous diatomaceous earth (DE) (Perma- Guard™). During the experiments, parameters such as stimulated and spontaneous locomotor activity, oxygen consumption and fecundity were tested. Increasing DE concentration caused significant inhibition in both oxygen consumption and locomotor activity. Moreover, the treated insects had significantly lower fecundity, due to decreased egg laying, lower number of infested beans as well as lowered hatchability. By limiting the progeny number, DE possibly prevents or at least reduces the size of the C. maculatus outbreak. Additionally, scanning electron microscope (SEM) micrographs revealed that DE particles accumulate especially in joints or hairy regions of the insect body close to the sensilla. This, along with data on locomotor activity, indicates a possible presence of additional, previously undescribed, mode of DE action - as an irritant. In conclusion, the presented results contribute to the understanding of the insecticidal activity of DE and provide novel data on the potential application of oxygen consumption as a pesticide efficiency marker.     

Effect of ageing prior to freezing on colour stability of ovine longissimus muscle

The effect of different ageing periods (0, 2 and 3 weeks at -1.5°C) of lamb loins (n=24) prior to freezing (9, 7 and 6 weeks at -18°C, respectively) compared to the aged-only (never frozen) lamb for 9 weeks postmortem on colour stability during display was assessed under high-oxygen modified atmosphere (HiOx-MAP; 80% O(2)) and oxygen permeable overwrap packaging conditions. The aged/frozen loins and aged-only loins in HiOx-MAP had similar (P>0.05) surface redness, colour intensity, and discolouration. Further, no significant difference found in shear force between the loins aged 3 weeks/frozen 6 weeks and the aged-only loins. However, more lipid oxidation (P<0.05) was found in the aged-only compared to the aged/frozen loins in HiOx-MAP throughout display. These results suggest that ageing loins prior to freezing would provide equivalent tenderness and colour stability, and better lipid oxidation stability compared to the aged-only loins under HiOx-MAP.