Meat shelf-life and extension using collagen/gelatin coatings: a review.

Different factors lead to the end of shelf-life for fresh meat products. The factors depend upon the animal including breed difference and muscle fiber type, external influences such as diet and stress, and post-harvest storage conditions including time, temperature, and packaging atmosphere. The characteristics that indicate the end of shelf-life for fresh meat products include water loss/purge accumulation, color deterioration due to myoglobin oxidation, rancidity due to lipid oxidation, and microbial spoilage. The characteristics can be measured and studied in the laboratory. Meat shelf-life is extended with the application of a surface coating because it provides a water and oxygen barrier. Collagen and gelatin coatings are used as a barrier on meat products to reduce purge, color deterioration, aroma deterioration, and spoilage, improve sensory scores, and act as an antioxidant.

Effect of relative humidity on coating efficiency in nonelectrostatic and electrostatic coating.

Fifteen food powders were coated on aluminum targets at 0, +25, and -25 kV using corona electrostatic coating at 20% to 80% relative humidity (RH). The effect of RH on 3 losses, that is, targeting loss, coating loss, and transportation loss, which contribute to coating efficiency, was studied. RH had no effect on targeting loss in either nonelectrostatic or electrostatic coating. In nonelectrostatic coating, increasing RH increased coating loss for powders with particle size > or =297 microm, but had no effect on powders < or =227 microm. Large powders were free-flowing and clumped with increasing RH, and then rolled off the targets, resulting in high coating loss. RH had no effect on nonelectrostatic transportation loss for all powders, except for very high absolute humidity when capillary forces dominated. Electrostatic charging efficiency and powder resistivity decreased with increasing RH. Electrostatic coating loss for salts increased with increasing RH. At high RH, powder resistivity decreases, increasing the charge decay rate, which decreases electrostatic adhesion. Electrostatic coating loss for powders other than salts, whose resistivities are much higher than salts, was not affected by RH until 80% RH. Electrostatic transportation loss for powders other than proteins was not affected by RH. There was no significant difference between positive and negative electrostatic transfer efficiency and adhesion, except for transfer efficiency of soy protein and pork gelatin, whose high positive tribocharging values cause higher positive electrostatic transfer efficiency. A 20% to 60% RH is recommended for both nonelectrostatic and electrostatic coating.

Increased aflatoxin contamination of dried figs in a drought year.

Dried figs (4917 samples) destined for export from Turkey to the European Union were collected between September and December during the very dry crop year of 2007 and tested for aflatoxins B(1), B(2), G(1) and G(2) by immunoaffinity column clean-up and reverse-phase high-performance liquid chromatography (RP-HPLC). While 32% of the samples contained detectable levels of total aflatoxins, 9.8% of them exceeded the European Union limits. Aflatoxin levels were in the range of 0.2-259.46 microg kg(-1) and 2.04-259.46 microg kg(-1) for all samples and samples that exceeded the limits, respectively. A substantial increase in the incidence of aflatoxins was observed in 2007 compared with previous years, most likely due to the drought stress, high temperatures and low relative humidity encountered during the period from January to September of that year. In 2007, the mean temperature was 1-2 degrees C higher, there was 300 mm less total rain, and the mean relative humidity was 10-15% lower than in 2002-06. The average concentration of individual aflatoxins present in the samples was quantified to determine whether the drought conditions promoted certain types of aflatoxins. Among the contaminated samples, aflatoxin B(1) occurred in 97% of the contaminated samples, followed by G(1) in 47%, B(2) in 24%, and G(2) in 6% of samples. Concentrations of individual aflatoxins exhibited great variability among the samples but were not significantly different from those reported in previous studies, which were conducted under conditions without drought and high temperatures.

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

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% O(2) and 20% CO(2) modified atmosphere and stored under fluorescent light at 4 degrees 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.

Factors dominating adhesion of NaCl onto potato chips.

In this study, the adhesion factors examined were time between frying and coating, surface oil content, chip temperature, oil composition, NaCl size, NaCl shape, and electrostatic coating. Three different surface oil content potato chips, high, low, and no, were produced. Oils used were soybean, olive, corn, peanut, and coconut. After frying, chips were coated immediately, after 1 d, and after 1 mo. NaCl crystals of 5 different particle sizes (24.7, 123, 259, 291, and 388 microm) were coated both electrostatically and nonelectrostatically. Adhesion of cubic, dendritic, and flake crystals was examined. Chips were coated at different temperatures. Chips with high surface oil had the highest adhesion of salt, making surface oil content the most important factor. Decreasing chip temperature decreased surface oil and adhesion. Increasing time between frying and coating reduced adhesion for low surface oil chips, but did not affect high and no surface oil chips. Changing oil composition did not affect adhesion. Increasing salt size decreased adhesion. Salt size had a greater effect on chips with lower surface oil content. When there were significant differences, cubic crystals gave the best adhesion followed by flake crystals then dendritic crystals. For high and low surface oil chips, electrostatic coating did not change adhesion of small size crystals but decreased adhesion of large salts. For no surface oil content chips, electrostatic coating improved adhesion for small salt sizes but did not affect adhesion of large crystals.

The dielectric properties of meats as a function of temperature and composition.

The dielectric properties of cod, perch, salmon, chicken breast, chicken thigh and beef were measured at 15 to 65 degrees C at 2450 MHz. The samples covered a moisture range of 68.9-81.2% and ash range of 0.96-1.20%. Equations were developed as a function of temperature, moisture, and ash, and compared to literature equations. The dielectric constant decreased with temperature and increased with moisture content. It was not affected by ash content. The dielectric loss factor increased with moisture content for moisture contents lower than 74.9%, then decreased for higher moisture contents. The dielectric-loss factor was quadratically related to temperature, decreasing to 30.2 degrees C then increasing. The dielectric loss factor increased with ash content. The effect of moisture content and temperature on the dielectric loss factor in the literature is reviewed to explain these results.

Use of dielectric properties to detect egg protein denaturation.

Changes in water and ion binding that occur during egg protein denaturation can be detected by measuring the dielectric properties. The dielectric properties of egg yolk, egg white and egg ovalbumin were tested from 25 to 105 degrees C at 11 frequencies from 300-2450 MHz. DSC was used to determine the temperature of protein denaturation. Both the dielectric constant and loss factor of egg yolk decreased due to denaturation of the protein lipovitellin. The dielectric constant increased at the initial denaturation and decreased after the complete denaturation and aggregation of egg ovalbumin in both egg white and ovalbumin.

Use of dielectric properties to detect whey protein denaturation.

Denaturation of whey proteins can be detected by the dielectric properties. The dielectric properties of 20% whey protein with 0, 5 or 15% sugar, 2% salt, at pH 4 and isolated whey proteins were measured from room temperature to 100 degrees C at 300-2450 MHz. The temperature at which a decrease in the dielectric loss factor, or increase in the dielectric constant, occurred was compared to the temperature of denaturation as determined by DSC and found to match. The change in the dielectric properties is likely caused by binding of water and/or ions that occurs during protein denaturation. For most of the samples, the dielectric loss factor showed the protein denaturation, but when ions were present due to salt or low pH, the dielectric constant showed the denaturation.

In vitro shoot proliferation and propagation of guava (Psidium guajava L.) from germinated seedlings.

Guava seeds were germinated on Murashige and Skoog (MS) medium with or without 8.8 µM benzyladenine (BA). BA increased the rate of germination and the number of lateral shoots (3.4 vs 1.2 per seedling). Stem nodes from these lateral shoots were cultured on proliferation media with 4.4 µM BA, and multiple shoots (3.5) were formed within 4 weeks of culture. Increasing the concentration of BA or the addition of naphthaleneacetic acid (NAA) did not affect shoot formation. Shoots produced from explants and lateral shoots from germinated seedlings were rooted in media containing activated charcoal (AC) or 9.8 µM indolebutyric acid (IBA). Shoots rooted with IBA had a higher rooting percentage (100% vs 75%) and a greater number of roots (5.5 vs 3.2) but the shoots were shorter (2.6 vs 3.4 cm) than when rooted in AC, and they required an additional 4 weeks of culture in media with AC to achieve shoot elongation. About 80% of the shoots with roots survived in the glasshouse and produced normal phenotypic plants.