Florent Remeuf

The Relative Effect of Milk Base, Starter, and Process on Yogurt Texture: A Review

Yogurt is a milk curd produced all over the world, obtained by a lactic fermentation of a milk base enriched with milk proteins, and sometimes sugars and thickeners. One of the most important sensorial attributes for yogurt is texture, which could be assessed by sensory or instrumental analysis. A lot of work has been published in studying the contribution of milk base, starter, and process on yogurt texture in order to develop new textures, or simply to reduce fat content, or the level of addition of protein and thickener in milk. However, these studies are limited to only a few factors. The topic of this review was to synthesize the data of literature, with the aim of extracting and classifying factors on the basis of their influence on yogurt texture. Three factors, milk base heating, starter, and yogurt shearing after fermentation, respectively, play a key role in the elaboration of texture. The control of these three parameters allows the improvement of the textural attributes of yogurts by 2 to 15 times.

Preliminary observations on the effects of milk fortification and heating on microstructure and physical properties of stirred yogurt

The aim of this work was to study how milk fortification and heating affect yogurt microstructure (micellar characteristics, protein network) and physical properties (viscosity, water-holding capacity (WHC), and graininess). Milk was fortified with skim milk powder (control), whey protein concentrate (WPC), caseinate, or a mixture of caseinate and whey protein. Two heat treatments were applied, giving average whey protein denaturation levels of 58% and 77%. For caseinate-enriched yogurts, the heating effect was negligible. When milk was enriched with WPC, heating led to a high level of cross-linking within the gel network. Heating increased yogurt viscosity and WHC, but also graininess. When milk was fortified with a blend of WPC and caseinate giving a whey protein-to-casein ratio of 0.20, the yogurt viscosity was greatly improved, while graininess was kept low. The results show a relationship between micelle solvation and yogurt microstructure, as well as micelle size in milk base and yogurt graininess.

Technological adjustment of goat milk containing low synthesis-rate αs1-casein variants

Abstract In the present work, we studied the effect of calcium addition, pH adjustment, and ultrafiltration on the physico-chemical characteristics and cheesemaking properties of goat milk that contained low synthesis-rate α s1 -casein variants. Calcium addition resulted in an increase in the colloidal calcium content of milk but had no major effect on its renneting properties. Milk acidification caused a major modification of calcium equilibria, a decrease of rennet clotting time and an increase of gel firmness. Milk protein enrichment by ultrafiltration led to an increase in the curd firming rate and its maximum strength. This treatment also improved the dry matter recovery during cheese manufacture, proportionally to milk solids enrichment. The three treatments had cumulative effects (no interaction) and it is concluded that an adequate combination of acidification and protein concentration can improve the cheesemaking properties of deficient milk to make them equivalent to those of milk that contain favourable variants.