Effects of Cholesterol Extraction Process and Fat and Whey Protein Additions on Ice Cream Mixes.

The aim of this work was to evaluate the cholesterol extraction process in ice cream mixes (ICMs) by using ß-cyclodextrin (ßCD) and to analyze the effect of this extraction on the ICM rheological, stability, and sensory characteristics. The effects of fat and whey protein (WP) additions on ICM stability were also evaluated. The maximum percentage obtained for cholesterol extraction was 93.6%. The flow curves indicated that ICM showed a thixotropic behavior before and after cholesterol extraction, which was enhanced when the fat content and/or percentage of ßCD increased. The stability of ICM with cholesterol-reduced content (RCho-ICM) was influenced by the fat content and/or the presence of WP. The RCho-ICM with the highest fat and/or WP addition showed less tendency to melt and had the smallest amount of accumulated molten liquid. These latter ICMs presented the slowest melting rates. Also, RCho-ICMs proved to be more stable than ICMs. RCho-ICM samples obtained with a ratio of ßCD/fat content of 1% w/w were evaluated by a trained sensory panel. In addition, an acceptability test of the sample with better sensory attributes was conducted. PRACTICAL APPLICATION: The effects of a cholesterol extraction process and fat and whey protein additions on the rheological and stability characteristics of ice cream mixes were evaluated. The extraction of cholesterol from an ice cream mix is interesting from a nutritional point of view and the extraction process of cholesterol itself may also help to improve the mix stability by controlling the fat and/or whey protein contents. These findings may prove useful as a starting point for the rational design of new functional ice cream mixes.

A study on bovine kappa-casein aggregation after the enzymatic action of chymosin.

Kappa-casein (kappa-CN) is a milk phospho-glycoprotein that plays an important role in the electrostatic and steric stabilization of casein micelles suspensions. kappa-CN characteristics such as its aminoacidic composition and its high denaturalization temperature make this protein an excellent nutrient. The enzymatic destabilization of kappa-CN is the basis of cheese and yoghurt manufacture. In this paper, modifications on the kappa-CN aggregation process by hydrolysis with chymosin derived from the initial protein state and the presence of sucrose and lactose were studied. Our study shows that, during its self-association, kappa-CN opens its conformation by raising the exposition of hydrophobic regions to the medium. Hence, the initial polymerization or association state of kappa-CN affects on the aggregation stage after the enzymatic action of chymosin. The inhibition of aggregation when the protein was previously associated suggests that the region which participates in the aggregation of p-kappa-CN particles, would be the one involved in the self-association during the heating of kappa-CN samples. Sucrose and lactose also affect the aggregation of proteolized particles of kappa-CN. Furthermore, the nature and the concentration of the added sugars had significant influence on the protein aggregation process.