The influence of whey protein concentrate on the viscosity of yoghurt, acidophilus and acidophilus yoghurt

U raduje istražen utjecaj koncentrata proteina sirutke (KPS) sa 16,3% suhe tvari i 10,2% proteina dodanog u mlijeko na viskoznost jogurta (3% jogurtne kulture), acidofila (3% kulture Lactobacillus acidophilus) te acidofilnog jogurta (2% kulture, L. acidophilus i 1% jogurtne kulture). Fermentacija uzoraka mlijeka (sa i bez KPS) provedena je pri 4CPC do pojave koaguluma, pH vrijednosti oko 4,6. Tijekom deset dana čuvanja fermentiranih napitaka u hladnjaku pri 4°C, praćene su promjene pH vrijednosti te promjene senzorskih svojstava. Viskoznost fermentiranih napitaka izmjerena je (prvi i deseti dan čuvanja) rotacijskim viskozimetrom (HAAKE, VT 500) pri 20PC i primjenom brzine smicanja od 0 do 500 s\u27K Kemijski sastav i kiselost uzoraka mlijeka i mješavine mlijeka sa KPS (4:1) korištenih za proizvodnju fermentiranih napitaka određen je standardnim analitičkim metodama. Dodatak KPS u mlijeko uzrokovao je nešto smanjenu viskoznost svih fermentiranih napitaka za sličnu vrijednost. Nakon 10 dana čuvanja zabilježena je promjena viskoznosti jedino acidofilnog jogurta (sa i bez KPS) i jogurta. Pri senzorskoj ocjeni, razlika u konzistenciji i okusu između proizvedenih napitaka (sa i bez KPS) također nije bila znatno izražena, čak ni nakon deset dana čuvanja (+4°C).In this paper the influence of whey protein concentrates (WPS) with 16.3% of total solids and 10.2% of proteins, added to milk on the viscosity of yoghurt (3% of yoghurt culture); acidophilus (3% culture Lactobacillus acidophilus) and acidophilus yoghurt (2% culture L acidophilus and 1% yoghurt culture) was determined. Fermentation of milk samples (with and without WPC) was performed at 40PC until coagulum formed at pH value about 4.6. During 10 days of storage in refrigerator at 4°C, changes of pH value and sensory properties of fermented beverages, were determined. Viscosity of fermented beverages was measured (the first and the tenth day of storage) using rotatory viscosymeter (HAAKE, VT 500) at 2CPC and applying the shear rate from 0 to 500 ®"^ Chemical composition and acidity of milk samples and mixture of milk with WPC (4:1) used in fermented beverages production, were determined using standard analytical methods. Addition of WPC to milk brought about nearly the same viscosity decrease in all fermented beverages values being similar. After 10 days of storage viscosity change was noticed only in acidophilus yoghurt and yoghurt. However during sensory evaluation the consistency and flavour differences were as well not significant between fermented beverages (with and without WPC), even after 10 days\u27 storage (+4°C)