Preventing the loss of tensile, barrier and appearance properties caused by plasticiser crystallisation in whey protein films

Whey protein films plasticised with sucrose have excellent oxygen barrier properties and high gloss that are reduced with time as sucrose crystallises. Whey protein isolate (WPI) films plasticised with sucrose were stored in 53% relative humidity for up to 60 days. The oxygen permeability, tensile properties and gloss of the films were measured periodically following ASTM (American Society for Testing Materials) methodology. Changes in properties were compared with changes in WPI films plasticised with glycerol (no crystallisation) or plasticised with sucrose (crystallisation) plus a crystallisation inhibitor. The two inhibitors studied were lactose and raffinose. Crystallisation in WPI/sucrose films decreased tensile strength and elongation at break. However, the inhibitors hindered sucrose crystallisation, and the desired film properties were maintained for a longer period of time. Raffinose was the more effective inhibitor, maintaining the film flexibility and barrier properties for over 28 days and maintaining gloss at almost 90% of the initial value for 60 days of storage.     

Gloss Stability of Whey-Protein/Plasticizer Coating Formulations on Chocolate Surface

ABSTRACT: :
Four different whey-protein-isolate (WPI)/plasticizer formulations were compared to determine which provided the most gloss and which was most stable with time when applied on chocolates. The 4 plasticizers studied were glycerol, polyethylene glycol 400 (PEG 400), propylene glycol (PG), and sucrose, all in a 1:1 ratio with WPI. Gloss stability was determined by measuring gloss fade over time using the Tricor Gloss Analysis System. WPI/sucrose coatings provided the highest and most stable gloss. With optimization, water-based WPI/sucrose coatings could be an alternative source of glaze to alcohol-based shellac coatings in the confectionery industry.     

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.     

Consumer Acceptance of Whey-protein-coated as Compared with Shellac-coated Chocolate

ABSTRACT: Four formulations of whey-protein-isolate (WPI) coatings were used to coat chocolate-covered almonds. Two formulations were without lipid and two were with lipid. The 2 WPI formulations without lipid varied in native- as compared with the heat-denatured WPI amount. The 2 WPI formulations with lipid varied in the lipid amount. The shellac formulation consisted of 30% solids, of which 90% was shellac and 10% was propylene glycol. A central location consumer test was carried out for attributes such as overall degree of liking. The results strongly indicate that water-based WPI-lipid coatings can be used as an alternative glaze, with higher consumer acceptance than alcohol-based shellac.     

The Effect of Protein Particle Size Reduction on the Physical Properties of CO2-Precipitated Casein Films

ABSTRACT:  Casein precipitated with high pressure-CO₂ (CO₂CAS) has unique properties compared to commercial acid-precipitated casein. CO₂CAS is less water-soluble and films made from it are less susceptible to high humidity environments; however, the films are also opaque and hazy. The appearance of CO₂CAS films is important especially if applied as a food coating. To improve the appearance properties, the particle size of CO₂CAS film plasticized with glycerol was reduced. The effect of protein particle size reduction on tensile properties, water vapor permeability (WVP), and gloss was studied using ASTM methodology. As particle size of the CO₂CAS was reduced from 126 μm to 111 μm, tensile strength and modulus of the films increased, while WVP decreased. With the same particle reduction, gloss increased from 55.3 gloss units on average to 73 gloss units, but films were still hazy. With a particle size less than 86 μm, CO₂CAS films were glossy and transparent, however, tensile strength decreased and WVP increased. Depending on desired application, the properties of CO₂CAS films can be optimized by changing particle size.     

Protein‐transition metal ion networks

Proteins obtained from agricultural sources were blended with divalent metal ions to see if binding reactions occurred between protein chains. Feather keratin, egg albumin, and wheat gluten showed elastic modulus increases of 2–3 times with addition of divalent transition metal ions Cu²⁺ and Zn²⁺. Increasing concentrations of ions resulted in increased stiffness. Birefringence experiments performed concurrently with tensile experiments showed refractive index changes indicative of network formation. Binding divalent alkaline earth metal Ca²⁺ ions did not result in an elastic modulus increase. Addition of Zn²⁺ to egg albumin resulted in a 34% decrease in water permeability but no change in oxygen permeability. FTIR spectroscopy showed that the directed valence of the transition metals was primarily binding glycerol and amide sites on the protein and secondarily carbonyl sites on the protein. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007