The Influence of Ultrafiltration on Hydrophobic Interactions of Milk Proteins in the Presence of Fat Globules on the Course of Renneting (Turkish with English Abstract)

Year 2006, Volume: 31 Issue: 6, - , 01.12.2006

Yaşar K. Erdem Zerrin Yüksel

Abstract

In this study the skim milk and whole milk samples were concentrated for 2-fold by ultrafiltration (UF). Then the skim milk retentates were recombined with cream as such and 2-times protein / fat ratio of whole milk retentate. The modification of the milk proteins and fat globules was explained as the variation of protein surface hydrophobicity, and UF performance was explained as a result of collected permeat volume in giving time intervals during the ultrafiltration. It was also studied on renneting properties of these samples and their retentates. It was found that the number of hydrophobic sites of the whole milk 's protein system lower than that of skim milk and it was observed at minimum in the whole milk 's retentate. It is suggested that the renneting process accelerated due to the modification of protein structure resulted by UF and protein/ fat ratio.

Keywords

Milk, poteins, ft, utrafiltration, surfacehdrophobicity, casein, renneting. 

Rennetlenmede Yağ Globüllerinin Varlığında Süt Proteinlerinin Hidrofobik Etkileşimleri Üzerine Ultrafiltrasyonun Etkisi

Abstract

Bu çalışmada yağsız ve yağlı süt örnekleri ultrafiltrasyon (UF) ile 2 kat konsantre edilmiştir. Sonra yağsız süt retentatları krema ile yağlı süt retentatının protein/yağ oranı ile aynı ve 2 katı olacak şekilde rekombine edilmiştir. Süt proteinleri ve yağ globüllerindeki modifikasyon protein yüzey hidrofobisitesindeki değişim ile açıklanırken UF performansı ultrafiltrasyon boyunca belli sürelerde toplanan permeat hacmi ile açıklanmıştır. Ayrıca bu örneklerin ve retentatlarının rennetlenme özellikleri üzerine çalışılmıştır. Yağlı sütlerin protein sistemindeki hidrofobik kısımların sayısı, yağsız sütünkinden daha düşük bulunmuş ve yağlı süt retentatında minumuma ulaşmıştır. UF 'den kaynaklanan protein yapısındaki modifikasyona ve protein/yağ oranına bağlı olarak rennetlenme sürecinin hızlandığı öne sürülmektedir.

Keywords

Süt, proteinler, yağ, ultrafiltrasyon, yüzey hidrofobisitesi, kazein, rennetleme. 

References

• Green ML, Turvey A, Hobbs DG. 1981. Development of structure and texture in Cheddar cheese. J Dairy Res, 48: 343-355.
• Leievre J, Lawrence RC. 1988. Manufacture of cheese from milk concentrated by ultrafiltration. J Dairy Res, 55: 465-477.
• Hao DV, Renner E. 1988. Studies on the application of ultratiltrationfor the manufacture of Cheddar cheese. 2. Effect of heating UF whole milk concentrate on composition and yield. Miichwiss, 43: 708-711.
• Fox PF. 1987. Cheese manufacture: chemical, biochemical and physical aspects. Dairy Industry Int, 52: 11-130.
• Grandison, AS, Glover FA. 1994. Membrane processes of milk. In Modern Dairy Technology, RK Robinson (ed), vol 1. UK: Chapman & Hall, 485 p.
• Erdem, YK. 2000. Influence of ultrafiltration on modification of surface hydrophobic sites of the milk protein system in the course of renneting. J Food Eng, 44: 63-70.
• Dalgleish, DG, Banks JM. 1991. The formation of complexes between serum proteins and fat globules during heating of whole milk. Milchwiss, 46: 2, 75-78.
• B. Rodriguez, J, Requeana, T. Fontecha .J. Goudedranche H, Juarez, M. 1999. Effect of different membrane seperation technologies (ultrafiltration and microfiltration) on the texture ad microstructure of semihard low-fat cheeses. J Agric and Food Chem, 47: 558—565.
• Fox, PF, Mc Sweeney PLH. 1998. Dairy Chemistry and Biochemismz, Chapman and Hall, London, 478p.
• Bradford, MM. 1976. A rapid and sensitive method for quantitation of microgramquantities of protein utilizing the principle of protein-dye binding. Anal Biochem, 72: 248-254.
• Bonomi, F, iaemetti S, Pagliarini. E, Peri. C. 1988. A spectrofluorimetric approach to the estimation ofthe surface hydrophobicity modifications in milk proteins upon thermal treatment. Milchwiss, 43: 281-285.
• Erdem, YK, Yuksel, Z. 2001. lnfluece of heat treatment of milk before ultrafiltration on the membrane performance. Proc. on 4th WISA-MTD Symposium Membrane; Science & Engineering, Stellenbosch, RSA, p.58.
• Walstra. P, Jennes. R. 1984. Dairy Chemistry and Physics, John Willey and Sons Inc, NY, 407 p.