Influence of selected factors on induced syneresis

• Published in: Journal of agricultural sciences (Belgrade, Serbia) Vol. 49; no. 2; pp. 205 - 217
• Main Authors: Jovanovic, Snezana, Macej, Ognjen, Denin-Djurdjevic, Jelena
• Format: Journal Article
• Language: English
• Published: University of Belgrade - Faculty of Agriculture, Belgrade 2004
• Subjects: casein gel; coagulation factors; induced syneresis; milk; sera
• ISSN: 1450-8109; 2406-0968
• DOI: 10.2298/JAS0402205J

Syneresis is the process of whey separation induced by gel contraction resulting in rearranging or restructuring of casein matrix formed during enzymatic coagulation. Numerous factors can influence the process of syneresis. The influences of pH, calcium concentration, temperature of coagulation of milk and applied heat treatment on the syneresis induced by different intensity of centrifugal force have been investigated. Coagulated samples were centrifuged at 1000, 2000 and 3000 rpm for 5 min, respectively. Reconstituted skim milk powder (control sample) and reconstituted non-fat milk heat treated at 87?C/10 min (experimental sample) are coagulated at temperatures of 30?C and 35?C, at pH value of 5.8 and 6.2, and with the addition of 100, 200 and 400 mg/l of CaCl2, respectively. Centrifugation at 1000 rpm of both control and experimental samples didn?t recover any sera, regardless of the applied coagulation conditions. This indicates that the intensity of centrifugal force wasn?t strong enough to disrupt gel structure and cause syneresis. When the intensity of centrifugal force was increased up to 2000 rpm, the syneresis was induced, but the degree of syneresis depended on the applied factors of coagulation, primary on the applied heat treatments and temperature of coagulation. The amount of added CaCl2 didn?t have a significant influence on the induced syneresis at 2000 rpm. The induced syneresis was very significant for both control and experimental samples when the intensity of centrifugal force of 3000 rpm was applied. It was also noted that curd produced from heat treated milk in which milk protein coaggregates were formed, released less sera regardless of the applied coagulation factors. Sinerezis je proces izdvajanje surutke usled kontrakcije grusa, pri cemu dolazi do rearanziranja, ili prestruktuiranja kazeinske mreze, koja je nastala tokom enzimske koagulacije, na koji utice veliki broj faktora. U ovom radu je ispitivan uticaj pH, koncentracije Ca2+, temperature koagulacije mleka i uticaj termickog tretmana na indukovani sinerezis pod uticajem razlicitog intenziteta centrifugalne sile. Koagulisani uzorci mleka centrifugirani su pri 1000, 2000 i 3000 o/min u vremenu od 5 minuta. Rekonstituisano obrano mleko u prahu (kontrolni uzorak) i rekonstituisano obrano mleko termicki tretirano na temperaturi 870C/10 minuta (ogledni uzorak) je koagulisalo pri razlicitim temperaturama 30?C i 35?C, pH vrednostima 5.8 i 6.2, kao i pri dodatku 100, 200 i 400 mg/l CaCl2. Centrifugiranjem kontrolnih i oglednih uzoraka pri 1000 o/min, bez obzira na uslove koagulacije nije dovelo do izdvajanja seruma iz gela, pa se moze zakljuciti da intenzitet primenjene centrifugalne sile nije bio dovoljno veliki da narusi strukturu gela i izazove sinerezis. Sa povecanjem intenziteta centrifugalne sile (2000 o/min), dolazi do veceg, ili manjeg stepena pojave indukovanog sinerezisa, a uocava se uticaj ispitivanih faktora koagulacije, pre svega primenjenih termickih tretmana, pH vrednosti temperature koagulacije, a u manjoj meri i kolicine dodatog CaCl2 na kolicinu izdvojenog seruma. Pri delovanju centrifugalne sile veceg intenziteta (3000 o/min), kod kontrolnih i kod oglednih uzoraka u znatno vecoj meri je uticalo na kolicinu izdvojenog seruma. Takodje je uoceno da gel dobijen od mleka u kojem su obrazovani koagregati, pri svim ispitivanim faktorima koagulacije, izdvaja manju kolicinu seruma u odnosu na kontrolne uzorke.