Manda sütü ve diğer süt karışımlarıyla üretilen kefirlerin reolojik özelliklerinin belirlenmesi
Yıl 2023,
Cilt: 60 Sayı: 1, 37 - 51, 01.04.2023
Cansu Kırmaz
,
Özer Kınık
,
Filiz İçier
Öz
Amaç: Bu çalışmada farklı ruminant sütlerinin çeşitli kombinasyonları ile kefir üretmek üzere ürün geliştirilmesi ve kefirin reolojik modellere uyumu ve duyusal özelliklerinin belirlenmesi amaçlanmıştır.
Materyal ve Yöntem: Farklı ruminant süt türleri ile üretilen kefirin reolojik özellikleri 15-20C'de ölçülen kayma hızı (γ), kayma gerilimi (τ), kıvam katsayısı (K), akış davranış indeksi (n), eşik kayma gerilimi (τ0) ve görünür viskozite (µapp) değerleri matematiksel modeller (Newton, Power law, Bingham) ile karakterize edilerek hesaplanmıştır. Yüz ifadeli duyusal değerlendirme formu ve puanlama yönteminde yararlanarak duyusal değerlendirme gerçekleştirilmiştir.
Araştırma Bulguları: Reolojik analizler sonucunda, yüksek korelasyon katsayısı (R2) değerleri ile gösterilen kefir türlerinin akış davranışlarını açıklamak için Power-law modelinin uygun olduğu belirlenmiştir. Farklı süt türleri ile işlenen kefirin akış diyagramları, Newtonian olmayan kayma incelmesi davranışı sergilemektedir. Duyusal analiz sonuçlarına göre, örneklerin duyusal olarak çok fazla takdir almadığı görülmektedir.
Sonuç: Raf ömrünün 28 gün olması gerektiği sonucuna varılmıştır. Bu sayede hem duyusal özellikler raf ömrünün sonuna kadar korunabilir hem de reolojik özellikleri raf ömrü boyunca birbirleriyle uyumlu kalabilir.
Destekleyen Kurum
Tez çalışmamdan üretilen bu çalışma Ege Üniversitesi Bilimsel Araştırma Projeleri Koordinatörlüğü tarafından desteklenmiştir.
Proje Numarası
FYL-2019-20613
Teşekkür
Ege Üniversitesi Bilimsel Araştırma Projeleri Koordinatörlüğü'ne ve emeği geçen hocalarıma teşekkür ederim.
Kaynakça
- Ahmed, J., S.T. Prabhu, G.S.V. Raghavan & M. Ngadi, 2007. Physicochemical, rheological, calorimetric and dielectric behavior of selected Indian honey. Journal of Food Engineering, 79:1207-1213.
- Altınayar, A., 1994. Geleneksel Fermente Süt Ürünlerimizin Raf Ömürlerini Arttırma Yolları. Ankara Üniversitesi, Ziraat Fakültesi, Süt Teknolojisi Bölümü, (Basilmamış) Seminer Notları, 34 s.
- AOAC, 2000. Official Methods of Analysis. The Association of Official Analytical Chemists, Gaithersburg, MD, USA. 17th ed. Methods 925.10,65.17,974.24,992.16, 771 pp.
- Assil, H.I., R. Sterling & P. Sporns, 1991. Crystal control in processed liquid honey. Journal of Food Science, 56: 1034-1041.
- Bensmira, M., C. Nsabimana & B. Jiang, 2010. Effects of fermentation conditions and homogenization pressure on the rheological properties of Kefir. Lebensmittel-Wissenschaft & Technologie Food Science and Technology, 43 (8): 1180-1184. https://doi.org/10.1016/j.lwt.2010.04.005.
- Diosma, G., D.E. Romanin, M.F. Rey-Burusco, A. Londero & G.L. Garrote, 2014. Yeasts from kefir grains: Isolation, identification, and probiotic characterization. World Journal of Microbiology and Biotechnology, 30 (1): 43-53.
- Dogan M., 2011. Rheological behaviour and physicochemical properties of kefir with honey. Journal fur Verbraucherschutz und Lebensmittelsicherheit, 6: 327-332. doi: 10.1007/s00003-010-0643-6.
- Duboc, P. & B. Mollet, 2001. Applications of exopolysaccharides in the dairy industry. International Dairy Journal, 11 (9): 759-768. https://doi.org/10.1016/S0958-6946(01)00119-4.
- Elzeini, H. M., 2006. Microstructure, rheological and geometrical properties of fat globules of milk from different animal species. Polish Journal of Food and Nutrition Science, 1556 (2): 147-154.
- Ergin, F., G. Öz, Ü. Özmen, Ş. Erdal, E. Çavana & A. Küçükçetin, 2017. Sütün homojenizasyonunun kefirin fizikokimyasal ve mikrobiyolojik özellikleri üzerine etkisi. Akademik Gıda, 15 (4): 368-376, DOI: 10.24323/akademik-gida.370105.
- Everett, D.W. & N.F. Olson, 2003. Free oil and rheology of Cheddar cheese containing fat globules stabilized with different proteins. Journal of Dairy Science, 86 (3): 55-63. DOI:10.3168/jds.S0022-0302(03)73656-X.
- Golowczyc, M.A., M.J. Gugliada, A. Hollmann, L. Delfederico, G.L. Garrote & A.G. Abraham, 2008. Characterization of homofermentative lactobacilli isolated from kefir grains: Potential use as probiotic. Journal of Dairy Research 75 (2): 211-217.
- Gomes, J.J.L., A.M. Duarte, A.S.M. Batista, R.M.F. De Figueiredo, E.P. De Sousa, E.L. De Sousa & R.D.C.R. Do Egypto, 2013. Physicochemical and sensory properties of fermented dairy beverages made with goat’s milk, cow’s milk and a mixture of the two milks. Lebensmittel-Wissenschaft & Technologie Food Science and Technology, 54 (1) 18-24.
- Gul, O., I. Atalar, M. Mortas & M. Dervisoglu, 2018. Rheological, textural, colour and sensorial properties of kefir produced with buffalo milk using kefir grains and starter culture: A comparison with cows’ milk kefir. International Journal of Dairy Technology, 71: 73-80. http://dx.doi.org/10.1111/1471-0307.12503.
- Gunasekaran, S. & K. Ding, 1999. Three-dimensional characteristics of fat globules in Cheddar cheese. Journal of Dairy Science, 82 (9): 1890-1896. https://doi.org/10.3168/jds.S0022-0302(99)75423-8.
- Gurbuz, S. & E. Sheifel, 2008. Bazı Gıdaların Akıcılık Özelliklerinin Belirlenmesi. Ege Üniversitesi Mühendislik Fakültesi Gıda Mühendisliği Bölümü, (Basilmamış) Bitirme Tezi, İzmir, 74 s.
- Hassan A.N., 2008. ADSA Foundation Scholar Award: Possibilities and challenges of exopolysaccharide-producing lactic cultures in dairy foods. Journal of Dairy Science 91: 1282-1298.
- Hussain, I., J. Yan, A.S. Grandison & A.E. Bell, 2012. Effects of gelation temperature on Mozzarella-type curd made from buffalo and cows’ milk: 2. Curd yield, overall quality and casein fractions. Food Chemistry 135 1404-1410.
- Icier, F., H. Bozkurt & S. Gurbuz, 2008. Kefir ve akıcı yoğurdun reolojik davranışlarının karakterizasyonu. Akademik Gıda, 6 (5): 6 -11.
- Karatas, M. 2014. Greyfurt Kabuğu Selülozu ve Karboksimetil Selülozunun Akış Davranışları. Fırat Üniversitesi Kimya Mühendisliği Bölümü, (Basilmamış) Yüksek Lisans Tezi, Elazığ, 118 s.
- Kayacier, A & M. Dogan, 2006. Rheological properties of some gums-salep mixed solution. Journal of Food Engineering, 72: 261-265.
- Kesenkas, H., N. Akbulut, O. Yerlikaya, A. Akpınar & M. Acu, 2013. Kefir dondurması üretiminde soya sütünün kullanım olanakları üzerine bir araştırma. Ege Üniversitesi Ziraat Fakültesi Dergisi, 50 (1): 1-12.
- Lopitz-Otsoa, F., A. Rementeria, N. Elguezabal & J. Garaziar, 2006. Kefir: A symbiotic yeasts-bacteria community with alleged healthy capabilities. Revista Iberoamericana de Micología, 23: 67-74.
- Lucey, J.A., M. Tamehana, H. Singh & P.A. Munro, 1998. A comparison of the formation, rheological properties and microstructure of acid skim milk gels made with a bacterial culture or glucono-d-lactone. Food Research International, 31 (2): 147-155.
- Ma, Y. & D.M. Barbano, 2000. Gravity separation of raw bovine milk: Fat globule size distribution and fat content of milk fractions. Journal of Dairy Science, 83 (8): 1719-1727. https://doi.org/10.3168/jds.S0022-0302(00)75041-7.
- Meilgaard, M.C., G.V. Civille & B.T. Carr, 1999. ‘’Descriptive Analysis Techniques, 161-170’’. In: Sensory Evaluation Techniques, 3rd ed.CRC Pres, Inc.Boca Raton,FL, 416 pp.
- Menard, O., S. Ahmad, F. Rousseau, V. Briard-Bion, F. Gaucheron & C. Lopez, 2010. Buffalo vs. cow milk fat globules: Size distribution, zeta-potential, compositions in total fatty acids and in polar lipids from the milk fat globule membrane. Food Chemistry, 120: 544-551.
- Metzger, M.E. & V.V. Mistry, 1995. A new approach using homogenization of cream in the manufacture of reduced fat Cheddar cheese. 2. microstructure, fat globule distribution, and free oil. Journal of Dairy Science, 78 (9): 1883-1895. https://doi.org/10.3168/jds.S0022-0302(95)76813-8.
- Michalski, M.C., F. Michel & C. Geneste, 2002. Appearance of submicronic particles in the milk fat globule size distribution upon mechanical treatments. Le Lait, 82 (2): 193-208.
- Nguyen, H.T.H., L. Ong, C. Lefevre, S.E. Kentish & S.L. Gras, 2014. The microstructure and physicochemical properties of probiotic buffalo yoghurt during fermentation and storage: A comparison with bovine yoghurt. Food and Bioprocess Technology, 7: 937-953.
- Otles, S. & O. Cagindi, 2003. Kefir: A probiotic dairy-composition, nutritional and therapeutic aspects. Pakistan Journal of Nutrition, 2 (2): 54-59.
- ParaskevopoulouaI A., I. Athanasiadisa, M. Kanellakib, A. Bekatoroua, G. Blekasa & V. Kiosseoglo, 2003. Functional properties of single cell protein produced by kefir microflora. Food Research International, 36 (5): 431-438. https://doi.org/10.1016/S0963-9969(02)00176-X.
- Ramchandran, L. & N.P. Shah, 2009. Effect of exopolysaccharides on the proteolytic and angiotensin-I converting enzyme-inhibitory activities and textural and rheological properties of low-fat yogurt during refrigerated storage. Journal of Dairy Science, 92: 895-906.
- Rimada, P.S. & A.G. Abraham, 2006. Kefiran improves rheological properties of glucono- δ-lactone induced skim milk gels. International Dairy Journal, 16 (1): 33-39. DOI:10.1016/j.idairyj.2005.02.002.
- Rosa, D.D., M.M.S. Dias, L.M. Grzeskowiak, S.A. Reis, L.L. Conceicao & M. Peluzio, 2017. Milk kefir: Nutritional, microbiological and health benefits. Nutrition Research Review, 30 (1): 82-96.
- Rowney, M.K., M.W. Hickey, P. Roupas & D.W. Everett, 2003. The effect of homogenization and milk fat fractions on the functionality of Mozzarella cheese. Journal of Dairy Science, 86 (3): 712-718. https://doi.org/10.3168/jds.S0022-0302(03)73651-0.
- Sabancı, S., O.F. Cokgezme, D. Tezcan, M. Çevik & F. Icier, 2016. Effects of temperature on time dependent rheological characteristics of koumiss. Turkish Journal of Agriculture-Food Science and Technology, 4 (4): 262-266.
- Saygılı, D., D. Doner, F. Icier & C. Karagozlu, 2022. Reological properties and microbiological characteristics of kefir produced from different milk types. Food Science and Technology, 42: e32520 (1-6) (DOI: https://doi.org/10.1590/fst.32520).
- Steffe, J.F., 1996. Rheological Methods in Food Process Engineering. 2nd ed. Michigan, 428 pp.
Tamime, A.Y. & R.K. Robinson, 2007. Tamime and Robinson’s Yoghurt - Science and Technology, 3rd ed. Cambridge, Woodhead Publishing Ltd. 808 pp.
- Walstra, P. & R. Jenness, 1984. Dairy Chemistry and Physics. New York, 467 pp.
- Walstra, P., 1995. ‘’Physical Chemistry of Milk Fat Globules, 131-178’’. In: Advanced Dairy Chemistry. 2nd ed. (Ed. P. F. Fox) Vol. 2. Lipids. Chapman & Hall, 826 pp.
- Wszolek, M., A.Y. Tamime, D.D. Muir & M.N.I. Barclay, 2001. Properties of kefir made in Scotland and Poland using bovine, caprine and ovine milk with different starter cultures. Lebensmittel-Wissenschaft und-Technologie. 34: 251-261.
- Zanirati, D.F., M. Abatemarco, S.H. de Cicco Sandes, J.R. Nicoli, Á.C. Nunes & E. Neumann, 2015. Selection of lactic acid bacteria from Brazilian kefir grains for potential use as starter or probiotic cultures. Anaerobe, 32: 70-76.
Determination of rheological properties of kefir produced with buffalo milk and other milk mixtures
Yıl 2023,
Cilt: 60 Sayı: 1, 37 - 51, 01.04.2023
Cansu Kırmaz
,
Özer Kınık
,
Filiz İçier
Öz
Objective: The objective of this study was to develop the product and to determine the rheological model and sensorial properties of kefir.
Material and Methods: The shear rate (γ) and shear stress (τ) values measured at 15-20C using the rheological properties of kefir produced with different types of ruminant milk are characterized by mathematical models (Newton, Power law, Bingham), consistency coefficient (K), flow behavior index (n), threshold shear stress (τ0) and apparent viscosity (µapp) values were calculated. Sensory assessment was carried out using facial expression sensory evaluation scale and scoring method.
Results: As a result of rheological analysis, the Power law model appears to be suitable for describing the flow behavior of kefir types as indicated by high correlation coefficient (R2) values in this study. The flow diagrams of kefir processed with different milk species exhibit shear-thinning non-Newtonian behavior. Sensory analysis showed that the samples did not receive a great deal of appreciation about organoleptic properties.
Conclusion: Shelf life should be 28 days. Hence, kefir preserves the sensory properties until end of shelf life and to keep rheological properties compatible with each other throughout shelf life.
Proje Numarası
FYL-2019-20613
Kaynakça
- Ahmed, J., S.T. Prabhu, G.S.V. Raghavan & M. Ngadi, 2007. Physicochemical, rheological, calorimetric and dielectric behavior of selected Indian honey. Journal of Food Engineering, 79:1207-1213.
- Altınayar, A., 1994. Geleneksel Fermente Süt Ürünlerimizin Raf Ömürlerini Arttırma Yolları. Ankara Üniversitesi, Ziraat Fakültesi, Süt Teknolojisi Bölümü, (Basilmamış) Seminer Notları, 34 s.
- AOAC, 2000. Official Methods of Analysis. The Association of Official Analytical Chemists, Gaithersburg, MD, USA. 17th ed. Methods 925.10,65.17,974.24,992.16, 771 pp.
- Assil, H.I., R. Sterling & P. Sporns, 1991. Crystal control in processed liquid honey. Journal of Food Science, 56: 1034-1041.
- Bensmira, M., C. Nsabimana & B. Jiang, 2010. Effects of fermentation conditions and homogenization pressure on the rheological properties of Kefir. Lebensmittel-Wissenschaft & Technologie Food Science and Technology, 43 (8): 1180-1184. https://doi.org/10.1016/j.lwt.2010.04.005.
- Diosma, G., D.E. Romanin, M.F. Rey-Burusco, A. Londero & G.L. Garrote, 2014. Yeasts from kefir grains: Isolation, identification, and probiotic characterization. World Journal of Microbiology and Biotechnology, 30 (1): 43-53.
- Dogan M., 2011. Rheological behaviour and physicochemical properties of kefir with honey. Journal fur Verbraucherschutz und Lebensmittelsicherheit, 6: 327-332. doi: 10.1007/s00003-010-0643-6.
- Duboc, P. & B. Mollet, 2001. Applications of exopolysaccharides in the dairy industry. International Dairy Journal, 11 (9): 759-768. https://doi.org/10.1016/S0958-6946(01)00119-4.
- Elzeini, H. M., 2006. Microstructure, rheological and geometrical properties of fat globules of milk from different animal species. Polish Journal of Food and Nutrition Science, 1556 (2): 147-154.
- Ergin, F., G. Öz, Ü. Özmen, Ş. Erdal, E. Çavana & A. Küçükçetin, 2017. Sütün homojenizasyonunun kefirin fizikokimyasal ve mikrobiyolojik özellikleri üzerine etkisi. Akademik Gıda, 15 (4): 368-376, DOI: 10.24323/akademik-gida.370105.
- Everett, D.W. & N.F. Olson, 2003. Free oil and rheology of Cheddar cheese containing fat globules stabilized with different proteins. Journal of Dairy Science, 86 (3): 55-63. DOI:10.3168/jds.S0022-0302(03)73656-X.
- Golowczyc, M.A., M.J. Gugliada, A. Hollmann, L. Delfederico, G.L. Garrote & A.G. Abraham, 2008. Characterization of homofermentative lactobacilli isolated from kefir grains: Potential use as probiotic. Journal of Dairy Research 75 (2): 211-217.
- Gomes, J.J.L., A.M. Duarte, A.S.M. Batista, R.M.F. De Figueiredo, E.P. De Sousa, E.L. De Sousa & R.D.C.R. Do Egypto, 2013. Physicochemical and sensory properties of fermented dairy beverages made with goat’s milk, cow’s milk and a mixture of the two milks. Lebensmittel-Wissenschaft & Technologie Food Science and Technology, 54 (1) 18-24.
- Gul, O., I. Atalar, M. Mortas & M. Dervisoglu, 2018. Rheological, textural, colour and sensorial properties of kefir produced with buffalo milk using kefir grains and starter culture: A comparison with cows’ milk kefir. International Journal of Dairy Technology, 71: 73-80. http://dx.doi.org/10.1111/1471-0307.12503.
- Gunasekaran, S. & K. Ding, 1999. Three-dimensional characteristics of fat globules in Cheddar cheese. Journal of Dairy Science, 82 (9): 1890-1896. https://doi.org/10.3168/jds.S0022-0302(99)75423-8.
- Gurbuz, S. & E. Sheifel, 2008. Bazı Gıdaların Akıcılık Özelliklerinin Belirlenmesi. Ege Üniversitesi Mühendislik Fakültesi Gıda Mühendisliği Bölümü, (Basilmamış) Bitirme Tezi, İzmir, 74 s.
- Hassan A.N., 2008. ADSA Foundation Scholar Award: Possibilities and challenges of exopolysaccharide-producing lactic cultures in dairy foods. Journal of Dairy Science 91: 1282-1298.
- Hussain, I., J. Yan, A.S. Grandison & A.E. Bell, 2012. Effects of gelation temperature on Mozzarella-type curd made from buffalo and cows’ milk: 2. Curd yield, overall quality and casein fractions. Food Chemistry 135 1404-1410.
- Icier, F., H. Bozkurt & S. Gurbuz, 2008. Kefir ve akıcı yoğurdun reolojik davranışlarının karakterizasyonu. Akademik Gıda, 6 (5): 6 -11.
- Karatas, M. 2014. Greyfurt Kabuğu Selülozu ve Karboksimetil Selülozunun Akış Davranışları. Fırat Üniversitesi Kimya Mühendisliği Bölümü, (Basilmamış) Yüksek Lisans Tezi, Elazığ, 118 s.
- Kayacier, A & M. Dogan, 2006. Rheological properties of some gums-salep mixed solution. Journal of Food Engineering, 72: 261-265.
- Kesenkas, H., N. Akbulut, O. Yerlikaya, A. Akpınar & M. Acu, 2013. Kefir dondurması üretiminde soya sütünün kullanım olanakları üzerine bir araştırma. Ege Üniversitesi Ziraat Fakültesi Dergisi, 50 (1): 1-12.
- Lopitz-Otsoa, F., A. Rementeria, N. Elguezabal & J. Garaziar, 2006. Kefir: A symbiotic yeasts-bacteria community with alleged healthy capabilities. Revista Iberoamericana de Micología, 23: 67-74.
- Lucey, J.A., M. Tamehana, H. Singh & P.A. Munro, 1998. A comparison of the formation, rheological properties and microstructure of acid skim milk gels made with a bacterial culture or glucono-d-lactone. Food Research International, 31 (2): 147-155.
- Ma, Y. & D.M. Barbano, 2000. Gravity separation of raw bovine milk: Fat globule size distribution and fat content of milk fractions. Journal of Dairy Science, 83 (8): 1719-1727. https://doi.org/10.3168/jds.S0022-0302(00)75041-7.
- Meilgaard, M.C., G.V. Civille & B.T. Carr, 1999. ‘’Descriptive Analysis Techniques, 161-170’’. In: Sensory Evaluation Techniques, 3rd ed.CRC Pres, Inc.Boca Raton,FL, 416 pp.
- Menard, O., S. Ahmad, F. Rousseau, V. Briard-Bion, F. Gaucheron & C. Lopez, 2010. Buffalo vs. cow milk fat globules: Size distribution, zeta-potential, compositions in total fatty acids and in polar lipids from the milk fat globule membrane. Food Chemistry, 120: 544-551.
- Metzger, M.E. & V.V. Mistry, 1995. A new approach using homogenization of cream in the manufacture of reduced fat Cheddar cheese. 2. microstructure, fat globule distribution, and free oil. Journal of Dairy Science, 78 (9): 1883-1895. https://doi.org/10.3168/jds.S0022-0302(95)76813-8.
- Michalski, M.C., F. Michel & C. Geneste, 2002. Appearance of submicronic particles in the milk fat globule size distribution upon mechanical treatments. Le Lait, 82 (2): 193-208.
- Nguyen, H.T.H., L. Ong, C. Lefevre, S.E. Kentish & S.L. Gras, 2014. The microstructure and physicochemical properties of probiotic buffalo yoghurt during fermentation and storage: A comparison with bovine yoghurt. Food and Bioprocess Technology, 7: 937-953.
- Otles, S. & O. Cagindi, 2003. Kefir: A probiotic dairy-composition, nutritional and therapeutic aspects. Pakistan Journal of Nutrition, 2 (2): 54-59.
- ParaskevopoulouaI A., I. Athanasiadisa, M. Kanellakib, A. Bekatoroua, G. Blekasa & V. Kiosseoglo, 2003. Functional properties of single cell protein produced by kefir microflora. Food Research International, 36 (5): 431-438. https://doi.org/10.1016/S0963-9969(02)00176-X.
- Ramchandran, L. & N.P. Shah, 2009. Effect of exopolysaccharides on the proteolytic and angiotensin-I converting enzyme-inhibitory activities and textural and rheological properties of low-fat yogurt during refrigerated storage. Journal of Dairy Science, 92: 895-906.
- Rimada, P.S. & A.G. Abraham, 2006. Kefiran improves rheological properties of glucono- δ-lactone induced skim milk gels. International Dairy Journal, 16 (1): 33-39. DOI:10.1016/j.idairyj.2005.02.002.
- Rosa, D.D., M.M.S. Dias, L.M. Grzeskowiak, S.A. Reis, L.L. Conceicao & M. Peluzio, 2017. Milk kefir: Nutritional, microbiological and health benefits. Nutrition Research Review, 30 (1): 82-96.
- Rowney, M.K., M.W. Hickey, P. Roupas & D.W. Everett, 2003. The effect of homogenization and milk fat fractions on the functionality of Mozzarella cheese. Journal of Dairy Science, 86 (3): 712-718. https://doi.org/10.3168/jds.S0022-0302(03)73651-0.
- Sabancı, S., O.F. Cokgezme, D. Tezcan, M. Çevik & F. Icier, 2016. Effects of temperature on time dependent rheological characteristics of koumiss. Turkish Journal of Agriculture-Food Science and Technology, 4 (4): 262-266.
- Saygılı, D., D. Doner, F. Icier & C. Karagozlu, 2022. Reological properties and microbiological characteristics of kefir produced from different milk types. Food Science and Technology, 42: e32520 (1-6) (DOI: https://doi.org/10.1590/fst.32520).
- Steffe, J.F., 1996. Rheological Methods in Food Process Engineering. 2nd ed. Michigan, 428 pp.
Tamime, A.Y. & R.K. Robinson, 2007. Tamime and Robinson’s Yoghurt - Science and Technology, 3rd ed. Cambridge, Woodhead Publishing Ltd. 808 pp.
- Walstra, P. & R. Jenness, 1984. Dairy Chemistry and Physics. New York, 467 pp.
- Walstra, P., 1995. ‘’Physical Chemistry of Milk Fat Globules, 131-178’’. In: Advanced Dairy Chemistry. 2nd ed. (Ed. P. F. Fox) Vol. 2. Lipids. Chapman & Hall, 826 pp.
- Wszolek, M., A.Y. Tamime, D.D. Muir & M.N.I. Barclay, 2001. Properties of kefir made in Scotland and Poland using bovine, caprine and ovine milk with different starter cultures. Lebensmittel-Wissenschaft und-Technologie. 34: 251-261.
- Zanirati, D.F., M. Abatemarco, S.H. de Cicco Sandes, J.R. Nicoli, Á.C. Nunes & E. Neumann, 2015. Selection of lactic acid bacteria from Brazilian kefir grains for potential use as starter or probiotic cultures. Anaerobe, 32: 70-76.