The grease resistance of corn zein coated paper was measured as related to coating level, plasticizer addition and time. Overall grease resistance ws normalized by time and expressed as percent area stained/hr (%AS * hr-I). For a 2.2 kg coating * ream-* of paper, %AS * hr-' was greater than both unplasticized and plasticized 4.4 and 6.6 kg -ream-' coating levels @
The yellowing rates of edible coatings were determined at 23, 40, and 55°C at 75% relative humidity (RH). Whey protein isolate (WPI) coatings had lower yellowing rates than whey protein concentrate (WPC) and the same rates as shellac coatings. Hydroxypropyl methylcellulose (HPMC) coatings had the lowest yellowing rates. Zein coatings became less yellow during storage; however, their color was still pronounced. Activation energies and Q 10 values for the yellowing of whey protein coatings were similar to those previously reported for the browning of whey powder. The results indicate that WPI coatings can be used in place of shellac coatings when low-color development is desired. WPC coatings can be used to tailor color development of a food.
Water-based whey protein isolate (WPI) coatings had the same gloss as shellac and zein coatings cast from ethanol solutions and water-based tapioca dextrin and hydroxypropyl methylcellulose (HPMC) coatings. For lipid dispersion coatings, the particle size of the dispersed phased influenced gloss values. WPI coatings had stable gloss values at 52%, 75%, and 95% relative humidity (RH). At 95% RH, shellac and zein coatings "blushed," and both dextrin and HPMC coatings became tacky. WPI and shellac films maintained a high gloss after 7.6 mo of storage at 23 °C and 75% RH and had higher gloss than whey protein concentrate (WPC) and HPMC coatings. The type and level of surfactant added to WPI coatings greatly influenced gloss.
Lipid oxidation is one of the leading causes of deterioration in peanuts. Oxygen concentration plays an important role in oxidation. Oxygen uptake can be impeded by specialized packaging systems or an edible coating, which in turn will decrease the rate of lipid oxidation. Four different formulations of whey-protein-based coatings were used to coat the peanuts. The peanut samples were stored in duplicate at 40 8C, 50 8C, and 60 8C, each for storage times of 0, 5, 15, and 45 d. Descriptive analysis results revealed that the rancidity was significantly lower for whey-protein-coated peanuts than for uncoated peanuts. This finding was also confirmed by static headspace GC analysis.
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