Whey Protein-Sucrose Coating Gloss and Integrity Stabilization by Crystallization Inhibitors

ABSTRACT: Whey protein coatings protect foods from change and deterioration and can extend product shelf life. However, because they are also made from food materials, whey protein coatings may also change over time if not properly formulated. Whey protein isolate (WPI)-sucrose high-gloss coatings, with and without crystallization inhibitors, were formed on chocolate-covered peanuts. The objective was to determine the effectiveness of crystallization inhibitors on preventing cracking of coatings and loss of coating gloss caused by sucrose crystallization during product storage. The 4 inhibitors tested were lactose, modified starch, polyvinylpyrrolidone, and raffinose. The WPI-coated chocolate-covered peanuts were stored for 119 d in 23%, 33%, and 44% relative humidity (RH) at 25°C. Gloss of the WPI coatings was measured periodically with a gloss-analysis system. It was found that raffinose is the most effective inhibitor of sucrose crystallization in whey protein-sucrose coatings. WPI coatings containing raffinose had significantly higher gloss values than all other coatings. For raffinose-containing samples stored in 23% and 33% RH environments, less than 3% of gloss was lost during storage. In 44% RH, the raffinose coating system had significantly less gloss fade than other WPI-sucrose coatings. This information can be used to improve the effectiveness of water-based high-gloss edible coatings.     

Rheological Properties of Chymosin-Induced Skim Milk Gels as Affected by Milk Storage Time and Temperature

Fundamental dynamic rheological tests were used to measure the rigidity (|G*|) and viscoelasticity (tan δ) of gels made from skim milk samples that were (1) never cooled, (2) stored at 4°C, or 3) stored at 4°C and then rewarmed to 25°C. Milk cooled and held at 4°C prior to gel formation produced gels with lower |G*| and higher tan(δ) than fresh milk gels. Chilled milk samples that were rewarmed to 25°C for 16h prior to gel formation produced gels with rheological properties similar to fresh milk gels. The solubilization of β-casein during cold storage was hypothesized to be the cause of observed differences in gel rheology.