Shelf life of fresh‐cut green beans as affected by packaging systems

To reduce quality loss of fresh‐cut green beans, different packaging systems were studied. In particular, samples were packaged in micro‐perforated and no‐perforated films and stored at 5 °C; unpackaged fresh‐cut green beans were also stored at the same temperature as the control. Headspace gas concentrations, mass loss, sensory quality and microbial proliferation were monitored for about 3 weeks. Results confirmed that selection of proper packaging is of crucial importance to create conditions able to guarantee the maintenance of product quality. Shelf life of fresh‐cut green beans packaged in the no‐perforated film (polyethylene, 25 μm) and in two micro‐perforated films (polypropylene films with 7 and 4 micro‐holes per package) was higher (19.2, 18.13 and 17.7 days, respectively) than that of the control or samples packaged in the micro‐perforated film with 12 micro‐holes per package (16.5 days).     

Original article: Incorporations of blueberry extracts into soybean‐protein‐isolate film preserve qualities of packaged lard

The effect of blueberry‐extract incorporation into soybean‐protein‐isolate edible film on the quality of packaged lard was compared with vitamin E or butylated hydroxyl anisole (BHA) incorporations individually during the storage at 36 °C and relative humidity of 40% for 5 weeks. Blueberry‐extract incorporations into soybean‐protein‐isolate film showed a greater tensile strength, lower water vapour permeability and lower oxygen permeability than vitamin E or BHA incorporations individually. On the other hand, the antioxidant capacity of soybean‐protein‐isolate film incorporated with the blueberry extract was greater than that incorporated with vitamin E and similar to that incorporated with BHA. Moreover, soybean‐protein‐isolate film incorporated with the blueberry extract showed a greater capacity to delay the lard hydrolysis than that incorporated with BHA, and a similar capacity to that incorporated with vitamin E. Consequently, blueberry‐extract incorporations into soybean‐protein‐isolate film not only improved mechanical and barrier properties, but also delayed the oxidation and hydrolysis of packaged lard. Therefore, blueberry‐extract incorporations into soybean‐protein‐isolate films have potential as a packaging material which will preserve the qualities of stored lard.     

Rinse Treatment and Oxygen Barrier Properties of Films for Improving Quality Retention in Vacuum-Skin Packaged Fresh Chicken

Fresh chicken drumsticks rinsed with water or salt solution (28% NaCl) were vacuum‐skin packaged in films differing in oxygen transmission rate (OTR) (< 10, 3000, ≥ 7000 cm³/m²/24 h). Salt rinsing decreased surface lightness (CIE L*). Higher OTR films maintained surface redness (CIE a*) better than oxygen barrier film. Neither rinse nor film OTR had any effect on yellowness (CIE b*). Salt rinsing drumsticks also reduced drip loss. Counts of aerobic and coliform bacteria increased during storage for product in all films. Within each film, salt‐rinsed drumsticks had lower counts at 3 and 6 d of storage (through 12 d) for total aerobic and coliform bacteria, respectively. Product in low OTR (barrier) film generally had lower bacteria counts than product in higher OTR films.     

Preservation of fatty duck liver by high pressure treatment

Fatty liver samples from duck were treated with high pressures and packaged in multilayer films. Microbiological analysis, permeability of the films to oxygen and fat loss, caused by melting, were assessed after pressure or thermal treatment. Microbiological analysis showed a noteworthy reduction in the total aerobic mesophilic flora and eradication of the coliform flora, whichever film or treatment was used. Nevertheless, a significant bacterial flora was observed during storage at 4 °C from 42 days with a polyethylene/polyamide/polyethylene film and a sample which had been treated with pressure. But, treatment at 550 MPa for 55 °C and 20 min, in combination with two low oxygen permeability films (ethylene and vinyl alcohol copolymer) gave a product with long storage life (90 days) at 4 °C and a significant reduction in the melting of lipids.     

Mango film coated for fresh‐cut mango in modified atmosphere packaging

Mango puree is known to have good oxygen barrier properties. Therefore, mango film on its own might be useful to extend the shelf life of fresh‐cut mango. In this study, fresh‐cut mango was wrapped with mango film and packed in modified atmosphere packaging (MAP). Each package was stored at 30 °C or 5 °C and sensory evaluation was performed to determine its quality and shelf life. The shelf life of uncoated and coated fresh‐cut mango pieces was 6 days for each at 5 °C and was 3 and 4 days, respectively, at 30 °C. The sensory evaluation indicated that coated fresh‐cut mango was slower to produce an off‐flavour and maintained better visual quality than uncoated mango at 30 °C. Nonetheless, coated fresh‐cut mango was softer than uncoated mango because of the hydrophilic nature of the mango film. No significant difference in the oxygen and carbon dioxide concentrations was observed between coated and uncoated fresh‐cut mango. Coating fresh‐cut mango with mango film showed a similar effect to MAP in prolonging the shelf life of the fresh produce. The use of the coating will enhance fruit quality and lead to better acceptance by consumers.     

CAP@GO/PVC薄膜对生鲜牛肉糜的保鲜作用

以氧化石墨烯(graphene oxide,GO)为载体吸附辣椒素(capsaicin,CAP),负载率达95％以上,采用喷涂成膜的方式制备CAP@GO/聚氯乙烯(polyvinyl chloride,PVC)释放型抑菌抗氧化包装薄膜,协同气调包装和低温等离子体技术探究其在包装生鲜牛肉糜贮藏期内的保鲜作用.结果表明:低...     

Heat resistance of Escherichia coli O157:H7 in cook‐in‐bag ground beef as affected by pH and acidulant†

Summary The heat resistance of a four‐strain mixture of Escherichia coli O157:H7 was tested. The temperature range was 55–62.5 °C and the substrate was beef at pH 4.5 or 5.5, adjusted with either acetic or lactic acid. Inoculated meat, packaged in bags, was completely immersed in a circulating water bath and cooked to an internal temperature of 55, 58, 60, or 62.5 °C in 1 h, and then held for pre‐determined lengths of time. The surviving cell population was enumerated by spiral plating meat samples on tryptic soy agar overlaid with Sorbitol MacConkey agar. Regardless of the acidulant used to modify the pH, the D ‐values at all temperatures were significantly lower (P < 0.05) in ground beef at pH 4.5 as compared with the beef at pH 5.5. At the same pH levels, acetic acid rendered E. coli O157:H7 more sensitive to the lethal effect of heat. The analysis of covariance showed evidence of a significant acidulant and pH interaction on the slopes of the survivor curves at 55 °C. Based on the thermal‐death–time values, contaminated ground beef (pH 5.5/lactic acid) should be heated to an internal temperature of 55 °C for at least 116.3 min and beef (pH 4.5/acetic acid) for 64.8 min to achieve a 4‐log reduction of the pathogen. The heating time at 62.5 °C, to achieve the same level of reduction, was 4.4 and 2.6 min, respectively. Thermal‐death–time values from this study will assist the retail food processors in designing acceptance limits on critical control points that ensure safety of beef originally contaminated with E. coli O157:H7.     

Inactivation of microorganisms naturally present in raw bovine milk by high‐pressure carbon dioxide

This study assessed the inactivation of microorganisms naturally present in raw bovine milk by high‐pressure carbon dioxide (HPCD) at 10–30 MPa and 20–50 °C for 20–70 min. The log reduction of microorganisms increased as raw bovine milk was exposed to higher pressures and temperatures and longer treatment times. The maximum reduction of aerobic bacteria (AB) was 4.96‐log at 25 MPa and 50 °C for 70 min. At lower temperatures and treatment times, a complete inactivation of yeasts and moulds (Y&M) and coliform bacteria (CB) was obtained at 25 MPa. Changes in microorganisms naturally present in raw bovine milk during storage were also assessed. There were 1.83‐log survival of AB, 0.65‐log survival of Y&M and a complete inactivation of CB in raw bovine milk when subjected to HPCD at 25 MPa and 40 °C for 50 min. Moreover, the AB, Y&M and the CB in raw bovine milk exhibited insignificant alterations during storage at 4 °C for 15 days, indicating a potential capability of HPCD to extend the shelf life of milk.     

Microbial inactivation and quality improvement of tomatoes treated by package film with allyl isothiocyanate vapour

In‐package sanitisation was developed using polylactic acid (PLA) films with allyl isothiocyanate (AIT) vapour. Tomatoes were artificially inoculated with Escherichia coli, Geotrichum candidum and Fusarium oxysporum and stored in clamshell boxes with the film fixed to the underside of the lid. The changes in bacterial and fungal populations and the quality of tomatoes during storage at 4 and 10 °C were evaluated. The results revealed that the film treatment (4 × 8 cm² film in 1 L box) reduced the populations of inoculated bacteria and fungi on tomatoes by 2–3 log CFU g^?1, and then significantly (P < 0.05) inhibited their growth during the 21‐day storage period at both temperatures. Tomatoes subject to film treatment had fewer changes in quality (colour, firmness, contents of total soluble solid, titratable acids and vitamin C) than the control samples during storage. The antimicrobial PLA film can be used for in‐package sanitisation to extend the shelf‐life of packaged tomatoes or similar perishable vegetables.     

Moisture Loss and Lipid Oxidation for Precooked Ground-Beef Patties Packaged in Edible Starch-Alginate-Based Composite Films

Edible films of starch‐alginate (SA), starch‐alginate‐stearic acid (SAS), SA‐tocopherol, SAS‐tocopherol, tocopherol‐coated SA film, and tocopherol‐coated SAS film were evaluated for their effectiveness in maintaining quality of precooked beef patties stored at 4 °C. Patty weight loss, moisture loss, 2‐thiobarbituric acid‐reactive substances value, the formation of hexanal, pentane, and total volatiles of samples differed with film composition. SAS‐based films were more effective (P < 0.05) in controlling moisture loss than lipid oxidation. Tocopherol‐treated films were more effective (P < 0.05) in inhibiting lipid oxidation than were nontocopherol films. Most of the tested edible films were not as effective as polyester vacuum bags in retarding moisture loss and lipid oxidation.     

Antioxidant activity and properties of gelatin films incorporated with tea polyphenol‐loaded chitosan nanoparticles

BACKGROUND: Gelatin film is widely used for the protection of food quality. In order to improve its antioxidant activity, natural antioxidant tea polyphenol‐loaded chitosan nanoparticles (TPCN) were prepared and incorporated into gelatin film. The antioxidant effect of TPCN against the oxidation of fish oil was investigated, as well as the release of TP from nanoparticles in the film. RESULTS: The incorporation of TPCN greatly decreased the tensile strength and oxygen permeability but increased the water vapour permeability and affected the transparency of gelatin film. Scanning electron microscopy images indicated that extensive interference was embedded with TPCN in the film microstructure. The peroxide value of fish oil packaged with films incorporated with TPCN was lower than that of fish oil packaged with control films during the incubation period. The radical‐scavenging activity of films incorporated with TPCN was higher than that of control films, and increasing radical‐scavenging activity of the former was observed during the storage period. CONCLUSION: The antioxidant activity and properties of gelatin film were affected by TPCN incorporation and storage time. Also, the oxidation of fish oil was retarded. The addition of TPCN could improve the antioxidant activity of gelatin film, and the release of TP from nanoparticles in the film was achieved during the storage period. Copyright © 2009 Society of Chemical Industry     

Effects of Metmyoglobin Reducing Activity and Thermal Stability of NADH‐Dependent Reductase and Lactate Dehydrogenase on Premature Browning in Ground Beef

Premature browning is a condition wherein ground beef exhibits a well‐done appearance before reaching the USDA recommended internal cooked meat temperature of 71.1 °C; however, the mechanism is unclear. The objectives of this study were: (1) to determine the effects of packaging and temperature on metmyoglobin reducing activity (MRA) of cooked ground beef patties and (2) to assess the effects of temperature and pH on thermal stability of NADH‐dependent reductase, lactate dehydrogenase (LDH), and oxymyoglobin (OxyMb) in‐vitro. Beef patties (lean: fat = 85:15) were packaged in high‐oxygen modified atmosphere (HiOX‐MAP) or vacuum (VP) and cooked to either 65 or 71 °C. Internal meat color and MRA of both raw and cooked patties were determined. Purified NADH‐dependent reductase and LDH were used to determine the effects of pH and temperature on enzyme activity. MRA of cooked patties was temperature and packaging dependent (P < 0.05). Vacuum packaged patties cooked to 71 °C had greater (P < 0.05) MRA than HiOX‐MAP counterparts. Thermal stability of OxyMb, NADH‐dependent reductase, and LDH were different and pH‐dependent. LDH was able to generate NADH at 84 °C; whereas NADH‐dependent reductase was least stable to heat. The results suggest that patties have MRA at cooking temperatures, which can influence cooked meat color.     

Application of electron‐beam irradiation pasteurization of ground beef,from steers fed vitamin E fortified diets: microbial and chemical effects

The effects of vitamin E supplementation of diets and electron‐beam irradiation (EBI) processing of ground beef patties on microbial and chemical qualities were investigated during 21 days of storage at 4 °C. Oxidative damage to lipids induced by EBI in ground beef patties containing different fat contents was first determined at 3 day intervals throughout a 7 day storage period at 4 °C. Significantly (P ≤ 0.05) higher values for thiobarbituric acid reactive substances (TBARS) were detected in beef patties of higher fat content (ie at 17 and 30%), which was further enhanced by irradiation at 5 kGy. Since lipid oxidation proceeded to a greater extent in beef patties with higher fat levels, ground beef patties of 30% fat were prepared from steers fed basal (diet I) or basal + 500 IU (diet II) of the antioxidant (vitamin E) supplemented diets. Plasma vitamin E concentrations in cattle fed diets I and II were 1.58 ± 0.42 µg ml^?1 and 2.49 ± 0.40 µg ml^?1 respectively. Patties were processed with three doses (2, 5, or 10 kGy) of EBI and compared with non‐irradiated patties. Microbial indices monitored at 3 day intervals included total aerobic plate count, psychrotrophic counts, and total coliform and Escherichia coli counts. Bacterial growth in ground beef patties stored at 4 °C was significantly (P ≤ 0.05) reduced by EBI at 2 kGy dose. Complete inhibition of bacteria occurred at 5 kGy or higher (P ≤ 0.05) dosage of EBI over 21 days of storage at 4 °C. Quality indices monitored at 3 day intervals throughout a 21 day storage (4 °C) study involving 30% fat ground beef patties made from steers fed vitamin E supplemented diets I and II included TBARS and colour. Results indicated that irradiation at the highest dosages was associated with higher (P ≤ 0.05) TBARS values, which in turn corresponded to lower linoleic acid content. With all three levels of irradiation, Hunter a values of beef patties decreased (P ≤ 0.05) significantly. Lipid oxidation was significantly (P ≤ 0.05) retarded in stored beef patties derived from cattle fed vitamin E (diet II). Copyright © 2003 Society of Chemical Industry     

Modified Atmosphere Packaging of Fresh, "Ready-to-use" Grated Carrots in Polymeric Films

“Ready-to-use” grated carrots were packaged in different films (oxygen permeability from 950 to 22,000 cc/m²/day/atm at 25°C) and stored at 2, 6 or 10°C for 10 days. Gaseous atmosphere in packs and the following were monitored: lactic acid bacteria, yeast counts, exudate and potassium ion released, sugars, carotene, ethanol and lactic acid. The respiration rate of the packaged carrots was measured. Films with very low oxygen permeability resulted in anaerobic respiration, high leakage of potassium, and high lactic acid bacteria. With high-permeability films (between 10,000 and 20,000 cc/m²/day/atm at 25°C), grated carrots showed aerobic respiration and retained good quality. At 10°C, in carrots packed in the most permeable film, sucrose decreased markedly during storage. The gas permeabilities required for packaging grated carrots were evaluated in relation to storage temperature.     

Potassium Sorbate Inhibition of Microorganisms Growing on Refrigerated Packaged Beef

The influence of potassium sorbate concentration (27–1325 ppm of sorbic acid) on the growth of natural flora in raw beef samples wrapped in plastic films of different oxygen permeability was studied at 0° and 4°C. Changes in aerobic plate counts, Pseudomonas spp., Brochothrix thermosphacta, Lactobacillus spp., Enterobacteriaceae and yeasts were monitored. Sorbate treatment effect on percentage increment of lag phase and reduction of growth rate during exponential phase for the different microorganisms were analyzed and antimicrobial action was evaluated by the Inhibition Index. A significant increase in the time to reach aerobic counts of 10^6.5 CFU/cm² was observed at low storage temperatures and pH values in vacuum packaged treated samples.     

Gas‐producing and spoilage potential of Enterobacteriaceae and lactic acid bacteria isolated from chilled vacuum‐packaged beef

This study aimed to enumerate and identify lactic acid bacteria and Enterobacteriaceae from spoiled and nonspoiled chilled vacuum‐packaged beef and determine their potential to cause blown pack spoilage. These microbial groups were also enumerated in nonspoiled samples and detected in abattoir samples. The potential of isolates to cause ‘blown pack’ spoilage of vacuum‐packaged beef stored at chilled temperature (4 °C) and abuse temperature (15 °C) was investigated. Populations of lactic acid bacteria in exudate of spoiled and nonspoiled samples were not significantly different (P > 0.05), whereas the number of lactic acid bacteria on the surface was significantly higher (P < 0.05) in spoiled samples as compared to nonspoiled samples. The population of Enterobacteriaceae species in exudate and on the surface of samples were significantly higher (P < 0.05) in spoiled packs in comparison with nonspoiled packs. Results of the deterioration potential showed that ‘blown pack’ spoilage was noticeable after 7 days at 15 °C and after 6 weeks at 4 °C for samples inoculated with Hafnia alvei.     

Antioxidant ability of BHT‐ and α‐tocopherol‐impregnated LDPE film in packaging of oatmeal

Cereals in general, and particularly oatmeals, are considered rather sensitive to oxidation owing to their relatively high fat content. The addition of antioxidants can sometimes prolong the shelf‐life of products. The aim of the present study was to investigate how the rate of lipid oxidation of a packaged oatmeal product was affected by the nature and level of antioxidants incorporated in an LDPE film structure. The stability of the product, which was determined by hexanal analysis using GC–MS and by electronic nose analysis, showed very small variations over the chosen storage period. No oxidation, as determined by hexanal levels in the oatmeal, was initiated during storage, but small variations in volatile profile were seen among the samples analysed by the electronic nose. The product stored in the BHT‐impregnated LDPE film had undergone the least change during 10 weeks of storage at 20 °C. α‐Tocopherol‐impregnated LDPE film did not appear to prolong the shelf‐life of the oatmeal at all. © 2000 Society of Chemical Industry     

Postharvest Quality of Fresh-Cut Carrots Packaged in Plastic Films Containing Silver Nanoparticles

Active food packaging containing antimicrobial additive goes beyond traditional functions of packaging, once it can extend food shelf life maintaining its quality, safety and reducing postharvest losses by controlling food spoilage. Among several antimicrobial additives employed in polymeric films for packaging, metallic nanoparticles outstand due to its facility for synthesis, low-cost of production, and intense antimicrobial properties. In this work, extruded plain films of low-density polyethylene (LDPE) containing silver nanoparticles (AgNPs) embedded in SiO₂ and TiO₂ carriers (namely MS and MT, respectively) were produced and used as active packaging for maintaining the physicochemical and microbiological quality of carrots (Daucus Carota L. cv. Brasília). The neat (LDPE) and composite films containing MS and MT were characterized by scanning electron microscopy and permeability to oxygen and used for packaging fresh-cut sliced carrots stored at 10 °C for 10 days. After the storage time, the physicochemical properties of carrots were characterized, while the antimicrobial properties of films and AgNP migration were investigated. Our results revealed that both MT and MS packages showed antimicrobial activity even for films containing low concentration of AgNP. In addition, AgNP antimicrobial activity demonstrated to be carrier-dependent, once MT-LDPE showed improved performance compared to MS-LDPE. Regarding the physicochemical properties of packaged carrot, lower soluble solids and weight loss and higher levels of ascorbic acid were observed for carrots packaged with MT-LDPE films (compared to MS-LDPE), leading to a better postharvest quality conservation. Such differences observed in physicochemical properties of carrots are related to the distinct antimicrobial and film permeability properties for each composite film. In addition, under the conditions employed in this study, AgNP migration from the packages to fresh-cut carrot was not observed, which is highly desirable for food packaging safety, indicating the potential of such active packages for food preservation application.     

Composite starch‐based coatings applied to strawberries (Fragaria ananassa)

Starch‐based coatings were used to the extend storage life of strawberries (Fragaria ananassa) stored at 0°C and 84.8% relative humidity. Effects of coating formulation (including starch type, plasticizer, lipid and antimicrobial agent) were analysed with respect to fruit quality. Plasticizer addition was necessary for film and coating integrity to avoid pores and cracks. Plasticizer presence reduced weight losses and maintained surface colour of fruits. Amylomaize coatings showed lower water vapour and gas permeabilities and decreased weight losses for longer periods than corn starch ones. Coatings with sorbitol showed lower permeabilities than glycerol ones. Coatings with antimicrobial agents decreased microbial counts, extending storage life of coated fruits by 10 to 14 days in comparison to the control. The addition of 2 g/l sunflower oil to the formulations decreased the water vapour permeability of starch‐based films, maintained the surface colour of coated fruits and controlled effectively fruit weight losses during storage. Lipid addition minimized the effects of starch and plasticizer types. Composite starch‐based coatings showed selective gas permeability (CO₂ higher than O₂) which helps to delay senescence of fruits.     

Bacteriological Quality of Hot-Boned Primal Cuts from Electrically Stimulated Beef Carcasses

The objective of this study was to determine bacterial numbers on primal cuts from hot and cold-boned beef carcass sides, and to determine the influence of U.S. Grade and electrical stimulation of the cracass on the incidence of bacteria. Ten boneless primal cuts were removed from each of ten beef carcass sides either 1 or 48 hr after animal slaughter. The primal cuts included the brisket, clod, chuck roll, ribeye, striploin, tenderloin, top sirloin, knuckle, inside round, and gooseneck. The primal cuts were sampled for aerobic (APC 5°C, 20°, 35°C) and coliform bacteria at time of removal from the side and after 20 days' vacuum packaged storage at 2°C. The psychrotrophic bacteria enumerated at 5°C were more numerous (P<0.05) on the primals from the hot-boned sides than from the cold-boned sides before storage, but not after 20 days' storage at 2°C. The mesotrophic and psychrotrophic bacteria enumerated at 20°C, and the mesotrophic bacteria enumerated at 35°C, were more numerous on the hot-boned primals than on the cold boned primals both before and after storage (P<0.05). The magnitude of the difference, on some primals, was greater than one logarithm. Coliform bacteria were not influenced (P<0.05) by hot boning before or after storage. Storage of the primal cuts resulted in some profuse growth of the coliforms. Neither U.S. grade nor electrical stimulation had any apparent influence on the incidence or growth of aerobic bacteria.