Effect of a gelatin coating on the shelf life of fresh meat

ABSTRACT:  The end of shelf life for fresh meat is determined by unacceptable aroma, appearance, and color, which appear before unacceptable microbial counts. Addition of a bovine gelatin coating to fresh meat may extend its shelf life. This study utilized a 20% bovine gelatin solution that was spray-coated onto beef tenderloins, pork loins, salmon fillets, and chicken breasts which were packaged in an 80% O₂ and 20% CO₂ modified atmosphere and stored under fluorescent light at 4 °C for 2 wk. All of the gelatin-coated fresh meat products showed a reduction in purge. The gelatin reduced purge by acting as a barrier to water loss. There was a reduction in color deterioration for gelatin-coated beef, a slight reduction of color deterioration for gelatin-coated pork, and no reduction in color deterioration for salmon and chicken. The gelatin coat reduced color deterioration by acting as a barrier to oxygen, but also had a negative effect on color due to its own color deterioration. No change in lipid oxidation was seen with any of the gelatin-coated meat products. The gelatin coat was not an effective barrier for lipid oxidation at refrigeration temperatures. Sensory analysis of beef tenderloins confirmed that color deterioration was reduced, and flavor was not affected by the application of a gelatin coat. The gelatin coat was equally effective during light and dark storage. It was more effective on vacuum packaged products than on modified atmosphere packaged products.     

Development of edible bioactive coating based on modified chitosan for increasing the shelf life of strawberries

For increasing the shelf life of strawberries during storage, bioactive coatings were applied using modified polysaccharides of chitosan. First, antimicrobial tests were performed with selected essential oils to evaluate their antimicrobial capacities against moulds and total flora isolated from strawberries. Red thyme (RT) and oregano extract (OR) were found as strong bioactive agents against moulds and total flora isolated from strawberries, whereas limonene (LIM) and peppermint (PM) had lower antimicrobial properties. These essential oils were also used as bioactive compounds which were sprayed onto strawberries and evaluated for their potential to increase shelf life during storage at 4 °C. RT, PM and LIM were found to be more efficient preservative agents for strawberries during 14 days of storage. Finally, chitosan was functionalized by acylation with palmitoyl chloride to increase its hydrophobicity, to ensure a controlled release and improve its stability and adhesion to the fruit product. LIM and PM were incorporated into the modified chitosan to create bioactive edible coatings and these were tested for their ability to extend the shelf life of fresh strawberries during storage. Formulations based on modified chitosan containing LIM and Tween®80 were shown to perform better than other formulations.     

Effects of chitosan coating and storage position on quality and shelf life of eggs

Effects of chitosan coating and storage positions (small-end down, small-end up or horizontal) on internal quality and shelf life of eggs were evaluated during 5 weeks of storage at 25 °C. Compared with noncoated eggs, all chitosan-coated eggs, irrespective of storage positions, had significantly lesser weight loss, higher Haugh units and higher yolk index throughout the storage. Chitosan coating, irrespective of storage positions, extended the egg shelf life by at least 3 weeks at 25 °C compared with noncoated eggs. Noncoated and chitosan-coated eggs placed small-end down tentatively showed better quality than eggs placed small-end up after 3 and 4 weeks of storage. After 5 weeks of storage, storage positions did not significantly affect quality of noncoated and chitosan-coated eggs. There were no notable differences in total amino acid content of the albumen and fatty acid composition of the yolk between noncoated and chitosan-coated eggs after 5 weeks of storage.     

Antimicrobial silver-montmorillonite nanoparticles to prolong the shelf life of fresh fruit salad

In this work, silver-montmorillonite (Ag-MMT) antimicrobial nanoparticles have been obtained by allowing silver ions from nitrate solutions to replace the Na⁺ of natural montmorillonite and then to be reduced by a thermal treatment. Ag-MMT were used as active antimicrobial compounds to improve the shelf life of fresh fruit salad. In order to assess their influence on product shelf life, sensorial and microbiological quality has been monitored during the storage. The microbiological quality was determined by monitoring the principal spoilage microorganisms (mesophilic and psychrotrophic bacteria, coliforms, lactic acid bacteria, yeasts and molds). Additionally, the evolution of sensorial quality was assessed by monitoring color, odor, firmness and product overall quality. The Ag-MMT nanoparticles seemed to be effective in inhibiting microbial growth, above all at the highest tested concentration. Consequently, the sensorial quality of samples stored in the active packaging appeared to be better preserved. Thus, experimental results showed that a significant shelf life prolongation of fresh fruit salad can be obtained by a straightforward new packaging system.     

Effect of high pressure on fresh cheese shelf-life

The effect of high pressure (HP; 300 and 400 MPa for 5 min at 6 °C) on physico-chemical, microbial, color, texture and sensorial characteristics of starter-free fresh cheeses stored at 4 and 8 °C was studied. Physico-chemical parameters considered were total solids, fat, total protein, pH, whey loss and water activity. The microbiological quality was studied, on cheeses stored at 4 and 8 °C, by enumerating aerobic mesophilic bacteria, lactococci, psychrotrophic bacteria, Enterobacteriaceae, Escherichia coli, molds and yeasts. Cheeses treated at 300 and 400 MPa, stored at 4 °C, presented a shelf-life of 14 and 21 days, respectively, compared to untreated control cheese, which presented a shelf life of 7 days. On the other hand, HP treatments modified the texture (more firm) and color (more yellow) compared to control cheeses. These changes were detected by instrumental and sensory analysis.     

Edible coatings for enhancing microbial safety and extending shelf life of hard-boiled eggs

ABSTRACT:  Hard-boiled eggs were coated with chitosan–lysozyme (CL), whey protein isolate (WPI), or Bake sheen (BS), inoculated with Listeria monocytogenes or Salmonella enterica Ser. Enteritidis at 10⁴ CFU/g, and stored for 4 wk at 10 °C. Microbial populations were enumerated weekly. Two nonchallenge studies were also conducted with hard-boiled eggs: coated shell-on eggs packaged in plastic containers or peeled eggs coated and vacuum-packaged. Total plate counts (TPC), coliforms, yeasts, molds, weight loss, pH, and color of eggs were determined during the 10-wk storage at 10 °C. Uncoated eggs served as controls. All the coatings were not effective in inhibiting the growth of L. monocytogenes, but CL coating controlled the growth of S. Enteritidis. At the end of 4-wk storage, the numbers of S. enteritidis on CL-coated eggs were about 4-log₁₀ CFU/g less than that of the controls. Coatings reduced ( P < 0.05) the populations of coliforms and TPC, and completely inhibited mold growth during the 10-wk storage. Coatings also reduced ( P < 0.05) the weight loss of eggs, 4.1% to 4.8% on coated eggs compared with 7.5% in uncoated ones at the end of 10-wk storage. The pH of CL-coated eggs remained stable throughout the storage period, while the control eggs increased from 7.6 to 8.6. Color changes in CL- and WPI-coated eggshells were less ( P < 0.05) than those of BS-coated and the control. The CL coating effectively suppressed the numbers of TPC, coliforms, yeasts, and molds on peeled eggs during the 6-wk storage ( P < 0.05). The results suggest that CL coating on hard-boiled eggs can control the growth of S. Enteritidis and reduce undesirable changes in the interior quality of eggs.     

Plasticizer types and coating methods affect quality and shelf life of eggs coated with chitosan

ABSTRACT:  Effects of different plasticizer types (glycerol, propylene glycol, and sorbitol) and coating methods (brushing, dipping, and spraying) on the internal quality and shelf life of chitosan-coated eggs were evaluated during 5 wk of storage at 25 °C. The Haugh unit and yolk index values suggested that chitosan coating, irrespective of the plasticizer types, extended the shelf life of eggs by almost 3 wk at 25 °C compared with noncoated eggs. After 5 wk of storage, plasticizer types did not significantly affect the quality (weight loss, Haugh unit, and yolk index) of chitosan-coated eggs. However, there was an observable trend indicating that use of sorbitol rather than propylene glycol and glycerol as a plasticizer was better in reducing weight loss (whole egg) of chitosan-coated eggs during a 5-wk storage. After a 5-wk storage, there were no significant differences in weight loss and weight of albumen and yolk among chitosan-coated eggs, regardless of the coating methods. However, both brushing and dipping methods yielded chitosan-coated eggs with better yolk (higher yolk index values) and albumen (lower pH) qualities than did the spraying method. During 3 to 5 wk of storage, the Haugh unit values of chitosan-coated eggs by the brushing method were higher than or comparable to those by dipping or spraying. Therefore, coating of eggs with chitosan using sorbitol as a plasticizer and by the brushing method may offer a protective barrier in preserving the internal quality and thus extending shelf life of eggs.     

影响冷藏荔枝货架期因素的研究

状元红荔枝果实经保鲜剂处理，在低温2－4℃下贮藏60d后，然后采用出库复色剂处理和出库复色并加固色剂处理2种出库方式。结果表明，贮藏期间荔枝果实呼吸强度明显下降，但出库后呼吸强度显著上升；冷藏期荔枝果皮PPO酶活性下降，出库后稍微上升，其b处理60d后好果率为90．1％，采用抗氧化剂出库的果实货架期常温72h后好果率为85．7％。     

Effectiveness of chitosan‐based coating in improving shelf‐life of eggs

Despite eggs having a natural packaging—shell—they are perishable and can lose their quality during storage. Chitosan‐based coatings were applied to shell eggs to examine potential effects on egg quality properties (weight loss, Haugh unit, yolk index) during 4 weeks of storage. Mineral amounts in yolks were also evaluated after 4 weeks of storage. Three chitosan‐based coatings produced with organic acids (acetic‐(C‐AA), lactic‐(C‐LA), and propionic (C‐PA)) were evaluated on shelf‐life enhancements of fresh egg quality. All chitosan‐coated eggs showed greater interior quality than the non‐coated eggs. The coatings significantly maintained weight loss compared to the control specimen (4.96%). Lower weight loss (3.45% for C‐PA, 3.53% for C‐LA) was observed in the coated eggs. Eggshell chitosan coat containing lactic and propionic acids maintained higher Haugh unit and yolk index than eggs coated with acetic acid. Uncoated (UC) eggs changed from grade ‘A’ to ‘B’ after 1 week of storage. Chitosan‐based coating containing lactic and propionic acids maintained eggs in grade ‘A’ for 4 weeks. Haugh unit showed that C‐LA and C‐PA effectively maintained eggs at grade ‘A’ quality for at least 3 weeks more than control and 1 week more than C‐AA. Results also indicated that the chitosan coating maintained mineral amounts at nutritional values (especially calcium, iron and magnesium concentration) in yolks after 4 weeks storage. Copyright © 2006 Society of Chemical Industry     

Effects of antimicrobial coating from catfish skin gelatin on quality and shelf life of fresh white shrimp (Penaeus vannamei)

Abstract: The present study was conducted to evaluate the effect of fish skin gelatin‐based antimicrobial coating on the shelf life of fresh white shrimp (Penaeus vannamei). Antimicrobial coating was prepared by incorporating potassium sorbate, sodium tripolyphosphate, or both ingredients in coating solution made from catfish skin gelatin. Shrimp samples were untreated, rinsed with water, or coated with the antimicrobial films, and then they were stored in ice under aerobic conditions. Samples were taken periodically and evaluated for total aerobic plate count, psychrotrophic bacteria count, near‐infrared spectrum (NIR), springiness, pH value, and color measurement. The results showed that the antimicrobial coating could retard microbial growth and prolong shelf life for up to 10 d. Partial least square analysis produced an acceptable model fitting between the NIR and the changes of microbial count in shrimp samples. The springiness and pH value of shrimp muscle were not affected by the coating treatments. Color parameter a* value increased linearly for all the treatments during the whole ice‐storage period. Practical Application: One of the most important technical and economic problems facing the shrimp industry is the relatively short shelf life of fresh shrimp products. Catfish skin gelatin‐based antibacterial edible films/coatings provide an ideal technique to solve this problem. The shrimp industry will be the immediate beneficiary of the study, and the information provided by this research will be expended to other seafood.     

Quality and shelf life assessment of Pacific white shrimp (Litopenaeus vannamei) freshly harvested and stored on ice

Pacific white shrimps (Litopenaeus vannamei) are an important shrimp aquaculture species worldwide. To quantify the quality and shelf life of untreated shrimp is imperative prior to the application of preservative treatments. In this paper, the quality and shelf life of Pacific white shrimp freshly harvested from three different farms and stored on ice for up to 12 days was investigated. The titratable acidity (TA) of shrimp specimens exhibited significant decreases (P < 0.05) whereas the metric chroma (C), total colour difference (TCD), aerobic plate count (APC), trimethylamine (TMA-N) and total volatile basic – nitrogen (TVB-N), peroxide value (PV) and p-anisidine value (AnV) exhibited significant increases during iced storage (P < 0.05). The TMA-N and TVB-N were significantly correlated whereas temporal TMA-N/TVB-N ratio increased considerably (P < 0.05). While the PV and AnV significantly correlated (P < 0.05), the temporal PV/AnV ratio depicted how primary and secondary lipid oxidation of Pacific white shrimp could relate during iced storage of 12 days. The shelf life of ice stored Pacific white shrimps was determined to be 8 days. The information gained by this study could serve as baseline for preservative treatments applied to fresh shrimps.     

含茶多酚的壳聚糖涂膜对鸡蛋保鲜效果的影响

用茶多酚和壳聚糖制成的复合涂膜液对鸡蛋进行涂膜处理,以感官指标、失重率、蛋黄指数、蛋清pH值、哈夫单位为质量指标定期取样分析测定,研究所制成的涂膜液在室温条件下对鸡蛋的保鲜效果。结果表明,和对照相比,含茶多酚的壳聚糖涂膜液能较好地保持鸡蛋的新鲜度和品质,尤其以1.5%的壳聚糖溶液联合200mg/kg茶多酚制得的涂膜液保鲜效果最好,经此涂膜液处理后的鸡蛋室温下贮存35d,失重率为1.89%,蛋黄指数为0.26,哈夫单位为60.109,蛋清pH值为8.20。     

Effect of electron beam irradiation on the shelf life of mozzarella cheese

The effectiveness of electron beam irradiation on the shelf life of mozzarella cheese was evaluated using five different irradiation doses and a control cheese. Shelf life tests were run at 10 °C by determining the cell load of spoilage micro‐organisms monitored on the consecutive days during storage. By fitting the experimental data through a modified version of the Gompertz equation, the shelf life of samples irradiated to the different doses was calculated. Results show significant increases in the shelf life of the investigated cheese. There were slight differences in the functional properties such as stretching, oiling off, melting between irradiated and unirradiated cheeses at 260 °C in oven. Our results indicated that the electron irradiation at the dose of 2.0 kGy may inhibit the growth of spoilage micro‐organisms such as coliforms and Pseudomonas sp. without affecting the sensorial characteristics of the product.     

Whey protein isolate coating and concentration effects on egg shelf life

The influences of three different concentrations (6, 12 and 18%) of whey protein isolate (WPI) coatings on shelf‐life enhancements of the fresh egg quality (weight loss, pH, Haugh unit, yolk index and colors) and the shelf life were evaluated at room temperature. All coated eggs showed lower weight loss than uncoated eggs. Less weight loss (2.46 for 12% WPI and 2.38 for 18% WPI) was observed in WPI‐coated eggs. Haugh units (HU) indicated that coated eggs remained in grade ‘A’ during 3 weeks storage period, whereas uncoated (UC) changed from grade ‘A’ to ‘B’ after 1 week of storage. The HU and yolk‐index (YI) values of all WPI‐coated eggs were significantly higher than those of UC. Among the coated eggs, there were no significant differences in HU, but 12 and 18% WPI coated had higher YI than WPI 6% coated and UC. The albumen pH of the UC eggs was significantly higher than that of coated eggs. Yolk lightness (L*) and (b*); shell (a*) and (b*) of coated eggs were not different from UC after 4 weeks. Performance of WPI coatings depended on the concentration up to 12% but not between 12 and 18%. Results also indicated that WPI coatings served as protective barrier for shelf life of the eggs. Copyright © 2005 Society of Chemical Industry     

Effects of Different Whey Protein Concentrate Coating on Selected Properties of Rainbow Trout (Oncorhynchus mykiss) During Cold Storage (4°C)

In this study, the effect of different whey protein concentrate coating formulations (with or without glycerol) on the storage of fillets over a period of 15 days at 4ºC was investigated. Fillets were conducted to microbiological, chemical, and sensory analyses. Difference in microbiological and chemical changes between samples was found to be significant (p < 0.05) during storage period. The Y and Z were preferred more by the panellists, while C samples received the lowest scores. According to the results of microbiological analyses, shelf life of fillets was estimated at 6, 9, 12, and 15 days for C, X, Y, and Z samples, respectively.     

Internal quality and shelf life of eggs coated with oils from different sources

Selected internal quality and shelf life of eggs coated with oils from differences sources (mineral oil, canola oil, corn oil, grape seed oil, olive oil, soybean oil, and sunflower oil) were evaluated during 5 wk of storage at 25 °C. As the storage time increased, weight loss increased whereas Haugh unit and yolk index values decreased. Throughout the 5 wk of storage, eggs coated with oils, regardless of oil sources, possessed better albumen and yolk quality than the control noncoated eggs. Oil coating minimized weight loss of eggs (<0.8%) compared with that (7.26%) of the noncoated eggs after 5 wk of storage at 25 °C. No significant differences in internal quality (weight loss, Haugh unit, yolk index, and albumen pH) were generally observed among oil-coated eggs during 5 wk of storage. Based on the Haugh unit, the grade of noncoated eggs changed from AA at 0 wk to A at 1 wk and to B after 3 wk whereas that of oil-coated eggs from AA at 0 wk to A at 4 wk and maintained A grade until 5 wk. This study demonstrated that oil coating, irrespective of oil sources, preserved the internal quality, minimized weight loss (<0.8%), and extended the shelf life of eggs by at least 3 wk longer than observed for the noncoated eggs at 25 °C storage. Soybean oil was a more practical option as a coating material for eggs due to its low cost. PRACTICAL APPLICATION: Eggs are highly perishable and susceptible to internal quality deterioration when stored above 7 °C. Refrigeration of eggs may be seldom practiced in some developing regions of the world. Therefore, an alternative method, that is inexpensive yet effective, to preserve the internal quality of eggs and to prevent microbial contamination is needed. Oil coating has been proven to preserve the internal quality, prolong shelf life, and minimize weight loss of eggs. This study demonstrated that, compared with other vegetable oils, soybean oil was a more practical option as a coating material for eggs during 5 wk of storage at 25 °C due to its low cost.     

Effect of cellulose ethers on the microstructure of fried wheat flour-based batters

The effect of type, molecular weight, and concentration of cellulose ethers on the microstructure of fried batter-coated potatoes in two batter systems: controlled viscosity batters (CVB) at 1200 cP and controlled initial moisture content batters (CIMB) at 134 g/100 g flour, were studied by coating cylindrical potatoes (10 mm diameter and 50 mm long) with treatment batters and fried at 160 °C for 3 min. The coatings were separated and their structures were viewed by scanning electron microscopy technique. The micrographs of fried batters showed that different types of cellulose ethers with the same molecular weight and concentration did not affect the microstructures of batters. The viscosity and water content of batters as well as the molecular weight and concentration of cellulose ethers altered the microstructure of fried batters. For CVB, the structure of fried batter containing methylcellulose of higher molecular weight and concentration with simultaneous higher moisture content showed greater hole-size which allowed higher amount of oil penetration through the batter into the food substrate. In contrast, the structure of CIMB with a higher molecular weight and concentration of methylcellulose was relatively more continuous; therefore, it might help in preventing oil penetration into the food substrate.     

Estimating packaging atmosphere–temperature effects on the shelf life of cod fillets

The behaviour of the natural microflora (total bacterial count, psychrotrophic bacteria, total coliforms, and lactic acid bacteria) of fresh cod fillets packaged in air, under vacuum, in a modified atmosphere with low oxygen concentration (5%) and in a modified atmosphere with high oxygen concentration (80%) was monitored during storage at different isothermal conditions from 4 to 12 °C. The growth data of the total bacterial count and total coliforms were used to model kinetically the shelf life of the samples in order to check the effects of storage temperature and packaging atmosphere. The acceptability times were compared with the stability times to establish if the shelf lives predicted were correlated. At 4 °C, cod fillets packaged under vacuum and in a modified atmosphere with low oxygen concentration had a higher shelf life (6.00 and 5.42 days), calculated from the growth of the total bacterial count, than the samples packaged in other atmospheres (1.96 and 2.62). Kinetic modelling could be valuable for the prediction of microbial fish quality loss.