Impact of transglutaminase reaction on the immunoreactive and sensory quality of yoghurt starter

Abstract

Cross-linking reaction with transglutaminase (m-TG) was used to obtain yoghurt produced with YO-MIX TM 511 yoghurt starter (Danisco). The use of two different temperatures (37 and 42°C), the presence of m-TG and the storage time (28 days) of the yoghurt were the factors that influenced the immunoreactive and sensory properties. The ELISA results obtained during the reaction of yoghurt proteins with a specific antibody against individual milk proteins (b-lactoglobulin, a-lactalbumin, a-casein, b-casein and j-casein) indicated differences on the level of immunoreactivity of individual proteins. The b-lg immunoreactivity of yoghurt produced at 37°C was not detectable in any of the samples whereas during the process conducted at 42°C the presence of this protein at low level was observed (1.00 and 3.33% without and with m-TG, respectively). The lack of j-casein was detected in the storage yogurt sample prepared during fermentation at 42°C. The samples were subjected to sensory evaluation using quantitative descriptive analysis (QDA). A trained personnel (n = 6) rated the yogurts for smell, taste and texture. The data obtained from QDA (16 attributes and 4 yoghurts) were subjected to a principal component analysis (PCA). The results (QDA and PCA) proved that the addition of the m-TG enzyme had significant impact on the sensory quality of the samples. Four principal components (PC1-PC4) determined 96.05% of the total variance of the samples.

Enzymatic modification of dairy product texture

“…Even though TGase activity is significantly reduced below pH 5 (Ando et al, 1989), it has been shown that residual activity led to increasing gel strength and viscosity during storage in set-type (Lorenzen et al, 2002;Y€ uksel and Erdem, 2010) and stirred yoghurts (Guyot and Kulozik, 2011;Ş anli et al, 2013;Wróblewska et al, 2011). In practice, treatment of yoghurt milk with TGase simultaneously with the fermentation is a more cost-and timeefficient method compared to pretreating the milk with TGase for a certain time followed by inactivation (by additional heat treatment) prior to fermentation.…”

Current enzymatic milk fermentation procedures

“…Interestingly, these encapsulation proceedings might also alter immunological characteristics of milk products. Wróblewska et al [65] could demonstrate that TGase reaction in yoghurt impacts the capability of starter bacteria to deplete antigenic milk proteins dependent on the storage temperature and duration. Further, the antigenic capacity of milk proteins, especially for a-casein, b-casein, j-casein and b-lactoglobulin cross-linked by TGase, was reduced [65].…”

“…Wróblewska et al [65] could demonstrate that TGase reaction in yoghurt impacts the capability of starter bacteria to deplete antigenic milk proteins dependent on the storage temperature and duration. Further, the antigenic capacity of milk proteins, especially for a-casein, b-casein, j-casein and b-lactoglobulin cross-linked by TGase, was reduced [65]. In conclusion, the hydrolysation or hiding of immunoreactive milk antigens by bacterial proteolysis and TGase protein cross-linking activities might support the development of hypo-immune milk products.…”

Textural properties of low-fat set-type yoghurt depending on mTG addition

“…The enzyme dosage is in most cases standardised according to the manufacturer's recommendation to 1 U/g protein concentration (Gauche et al, 2007;Wroblewska et al, 2010; yüksel and Erdem, 2010; Sanlı et al, 2010). Guyot and Kulozik (2011) analysed the effect of (0.5, 1, 3 and 10 U/g protein) mTG treated skim milk powder on the viscosity of stirred skim milk yoghurt, and find out that the addition of mTG treated skim milk powder (where mTG was inactivated by heat treatment and spray drying) did not influence on structural defects during the storage of final product.…”

“…According to the majority of articles in the literature, a temperature above 70 °C and up to 10 minutes holding time is needed to ensure total inactivation of the enzyme (Bönisch, et al, 2007a;Gauche et al, 2007;Iličić et al, 2008;Wroblewska et al, 2010) although this inactivation step seems to be too expensive for the dairy industry and therefore often neglected. While the possibility of negative structural effects due to mTG activity during storage period seems to be obvious, it is still a debatable topic whether active mTG may cause longer fermentation time due to a possible change of available amino acids for the growth of lactobacilli (Faergemand et al, 1999; L orenzen et al, 1998).…”