Texture modification in acid milk gels produced at low temperature
Special Symposium - Innovations in Food Technology (LMC Congress)
Innovations in Food Technology - Poster Session (LMC/Food - P1)
Keywords: protein, acid milk gels
Milk is a complex biological system and it has some of the interesting properties which make it important in formulation of many delicious food products. One peculiar property of milk is that its protein’s (Protein system) gets disturbed in presence of acid, heat or both. This property of milk proteins is desired in one product while it is not in another. The magnitude of such physico-chemical changes in protein system and thus in the final quality of product differs with different physical and chemical conditions and history of milk handling. Our aim in this research project was to examine changes induced by in situ acidification at temperature lower than 5°C in a model fat free milk system and to know how addition and different degree of complexation of whey proteins with colloidal system yields different types of acid milk gels.
In our study we tried to increase the protein content by addition of whey proteins to four different levels (0, 0.44, 0.88 and 1.32% by wt) corresponding to its natural level of 0.44%, followed by formation of four different protein systems based on literature reports. This includes; 1. Heating (90°C for 10 min) at pH 6.55 to produce coating of casein micelles by whey proteins . 2. Heating (90°C for 10 min) at natural milk pH of 6.7 to produce Partial coating of casein micelles with whey proteins and partial formation of whey protein aggregates1 3. In situ formation of whey protein aggregates (>90%) by heating at (90°C for 10 min) at pH of 7.1 4. Addition of pre formed whey protein aggregates (heating of whey protein solution to 90°C for 10 min) in the heated milk system
The pH of gelation was monitored in all above systems and gelled systems were physically characterised by the textural analysis at uniform acidification time with same amount of acidulant added. Sensoric analysis was also carried out using trained panel. Findings of this study has revealed that pH and heat treatment along with addition of whey proteins to milk leads to early gelation and produces gels with more hardness. In fact as a general rule we observed that increase in whey protein addition level by three times leads to increase in gel hardness by three times showing a clear contribution of whey protein in acid gelation of milk in these systems. However, in contrast to the aforementioned result we found some interesting observation in texture profile when whey protein aggregates were added to heated milk at 0.44%. This system was having very different texture profile then the remaining samples. Also in sensory testing gel made with 0.44% whey protein aggregates was found to be two times less clumpy than normal milk gel. Mixed protein system (as in Normal heated milk) with partial whey protein coating on casein and partial whey protein aggregates formation gives highest gel hardness, suggesting that the two gel systems may be incorporated in one another. This study shows new ways to modify texture of set yoghurt type products to meet different consumer demands without addition of non-milk ingredients.
Presented Wednesday 19, 13:30 to 15:00, in session Innovations in Food Technology - Poster Session (LMC/Food - P1).
