Factors affecting migration of vanillin from chitosan/methyl cellulose films.

The diffusion kinetics and factors affecting the migration of vanillin from chitosan/methyl cellulose (Chi/MC) films into water, cantaloupe juice (CJ), pineapple juice (PJ), and citrate buffer adjusted to pH values of 3.5, 5, and 6.5 were studied. Vanillin was incorporated into the Chi/MC films to provide an inhibitory effect against microorganisms. Initial vanillin concentration in the films, temperature, and pH of extracting solvent impacted the migration behavior of vanillin. The diffusion coefficients (D) followed the Arrhenius equation and increased as temperature increased for all the solvents. As temperature rose, the rate increment of the diffusion of vanillin into pineapple juice was higher than that into water and cantaloupe juice. Films containing lower vanillin content had a higher diffusion coefficient than those containing high vanillin content. Migration of vanillin was affected by pH rather than acid concentration. Lower pH resulted in a higher migration rate.

Development of a gas-phase oxygen biosensor using a blue copper-containing oxidase.

A gas-phase oxygen biosensor based on blue copper-containing oxidases was developed. Blue-oxidase enzymes, including laccase and ascorbate oxidase, have a blue chromophore prosthetic group, type 1 Cu+2, which can be reduced and decolorized with reducing substrates. When the enzyme is reoxidized with molecular oxygen, there is a concomitant return of the blue color. The oxygen biosensor consisted of the Rhus vernicifera laccase and ascorbate as substrate enclosed in pouches of low-density polyethylene under nitrogen gas. Operational stability of the biosensor was established by exposing it to different oxygen/nitrogen gas mixtures at 5 degrees C. Gas-phase oxygen concentrations were measured by keeping it under nitrogen gas and subsequently recording the rate of reappearance of the enzyme blue color, both visually and spectrophotometrically at 610 nm. The oxygen biosensor was able to detect a wide range of oxygen concentrations. The time required to recover the blue color, namely the biosensor response time, at the optimized assay conditions of 5 degrees C and a high-water activity level, was determined. This research describes the development of an oxygen biosensor with adequate activity and stability to measure gas-phase oxygen concentrations at 5 degrees C and high-water activity levels. The oxygen biosensor could be used to indicate oxygen concentrations above acceptable levels in headspace oxygen concentration which could affect the quality and safety of products packaged under initial low levels of oxygen concentration.

Physical Damage of Yogurt. The Role of Secondary Packaging on Stability of Yogurt.

Vibratory motions are common to packaged products in the shipping and distribution environment. Using an MTS vibration table, low-fat plain yogurt (packaged in various shipping containers) was vibrated and then evaluated for phase separation (whey-off) during storage. Three types of damage were apparent: (a) slight or definite whey-off, (b) cracked or broken coagulum and (c) completely disrupted coagulum. After 10 d of storage, whey-off was quantitated. Slight and definite whey-off corresponded to 0.2 to 0.6% (wt/wt) and 0.6 to 1.8% (wt/wt), respectively. Most damage was observed in the top layers of vibrated stacks (10 high). Stretch overwrapping the shippers proved most effective in reducing syneresis, with less than 1% of the primary containers evaluated showing phase separation.