Instrumental Texture, Syneresis, and Microstructure of Yoghurts Prepared from Ultrafiltrated Goat Milk: Effect of Degree of Concentration

Abstract

The objective of this study was to determine the effect of concentration degree (1.5-fold, 2-fold, and 2.5-fold [v/v]) of ultrafiltrated goat milk on instrumental texture, syneresis, and microstructure of set-yoghurt. The milk for control yoghurt was non-concentrated. The concentration of goat milk by ultrafiltration caused an increase in the hardness, the adhesiveness, the extrusion force of yoghurt, and a reduction in the syneresis. The microstructure of yoghurts from ultrafiltrated milk showed a compact protein matrix, a small amount of void spaces, and large casein micelles in comparison to the microstructure of yoghurts from non-concentrated milk. The best texture and the smallest syneresis of goat milk yoghurts could be obtained at 1.5-or 2-fold [v/v] goat milk concentration. Yoghurt from 2.5-fold concentrated milk was characterized by a too hard and compact structure with a consistency typical for cream cheese, not yoghurt.

Gelation properties of partially renneted milk

“…Syneresis is also an important parameter in the processing of milk. As syneresis is not expected to occur in yogurt production, [58] this finding on HHT milk supports the use of pre-heated milk for yogurt production. However, for cheese-or curd-making, syneresis is desirable.…”

“…3b) milk was around 10 g, which was in the range of gel hardness reported in another study. [58] The hardness values of the gels made from renneted LHT and HHT milk ranged from 20 to 35 g and 10 to 20 g, respectively. In LHT milk, the highest gel hardness was obtained with the higher pre-rennet concentration, which was up to 3 times higher than that of control LHT milk.…”

Physicochemical, Nutritional, and Organoleptic Characterization of a Skimmed Goat Milk Fermented with the Probiotic Strain Lactobacillus plantarum C4

“…In this regard, distinct rheology properties have been described for fermented milks concentrated by different methods [ 37 ]. These differences may be attributable to casein alteration by the spray-drying process or to the increase of all milk compounds in the same proportion with the addition of powdered skimmed milk, whereas ultrafiltration of milk mainly concentrates caseins, which are responsible for formation of the yoghurt coagula [ 17 , 38 ]. Syneresis in fermented milks may be dependent on the pH because the isoelectric point of caprin caseins (at which they start to aggregate) is reached at pH 4.2, forming the gel network.…”

Microstructural and textural properties of rennet-induced milk protein gel: Effect of guar gum

“…The final texture of dairy products as well as their susceptibility to syneresis are closely related to the microstructure, especially the structure of the protein matrix. [7,8] CM plays a major role in imparting structure to dairy products. During CM coagulation, the CM network initially formed in the aggregation step undergoes structural changes, leading to the shrinkage of the gel by rearrangement of the interparticle interactions in the following step of the process.…”