- Email: [email protected]
Liquid Milk Products | Liquid Milk Products: Membrane-Processed Liquid Milk
Liquid Milk Products: Membrane-Processed Liquid Milk J-L Maubois, INRA Dairy Research Laboratory, Rennes, France ª 2011 Elsevier Ltd. All rights reserved.
Introduction
Bacteria Removal by MF
Laboratory curiosities until the late 1960s, membrane technologies started to become an industrial reality with the pioneering work of Loeb and Sourirajan (1963) who have developed the first anisotropic membranes, made from cellulose acetate, able to deliver reasonable fluxes and permeabilities for sea water desalination by reverse osmosis. Then, remarkable progress was also accomplished in the development of more robust membranes and better designed equipment as in the applications of this ubiquitous family of technologies which include separation of molecules or particles based on size differences: reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF); separation based on ionic charge: electrodialysis (ED); and separation based on chemical potential difference (pervaporation). Among the food industries, dairying is undoubtedly that which has known the largest introduction of most of the membrane technologies, MF, UF, NF, and RO (the total installed area was in 2007 more than 500 000 m2 according to Gezan-Guiziou, 2007), except for pervaporation which has, to our knowledge, no application in milk treatment. There are numerous reasons for this success: deep knowledge of the biochemical characteristics of milk and of the co-products (mostly whey) which helped greatly the optimization of the desired differential separation; the dynamism of several research teams; the operating temperature which did not cause irreversible damage to the biological properties of milk components; the high unacceptable environmental pollution caused by the discharge of cheese whey, etc. The presence of membrane equipment in dairy plants is nowadays as common as the presence of a cream separator in many countries worldwide. Concerning drinking liquid milks, the main applications are bacteria removal by MF, which has known worldwide success and adjustment of the protein content by UF. There has also been some use of RO for the concentration of milk for the production of yogurts or powders and some recent studies have been devoted to the specific separation of somatic cells (SC), described below, and to the separation of milk fat globules according to their size which has not yet been applied industrially.
Decontamination of collected milk is generally achieved through heat treatments: thermization, pasteurization, or sterilization by autoclaving or ultra-high temperature (UHT) treatment, using various combinations of time– temperature parameters to obtain the desired bactericidal effect. While these heat treatments ensure the safety of milk and dairy products, they almost always induce irreversible modifications of milk components, alter calcium salts– protein equilibrium, and also adversely affect the organoleptic quality of fluid milk and dairy products as well as the cheesemaking ability. Moreover, the cells of dead bacteria remain in heated milk with their potentially active enzymes which, with the metabolic activity of remaining thermoduric bacteria, will cause alterations of liquid milk during storage, thus reducing commercial shelf life. Tangential membrane microfiltration offers an interesting alternative to heat treatments. Initially proposed in 1984, it has led to the technology and equipment called ‘Bactocatch’ by the Tetra Laval Company. Numerous studies, done in Sweden and in France and summarized by Saboya and Maubois (2000), have optimized the original parameters described in the patent of Holm et al. (1984). Nowadays, skim milk heated to 50 C is circulated at a velocity of 7.2 m s 1 along a ceramic membrane made of porous alumina and having an average pore size of 1.4 mm (Sterilox or equivalent) supported by a thick porous layer also of alumina. The process is carried out according to the hydraulic concept of a uniform transmembrane pressure (UTP), approximately 0.5 bar, obtained either by recirculation of the permeate or by specially designed MF membrane with a continuous variation in the porosity of its support (Membralox GP) or continuous variation of the thickness of the membrane layer (Isoflux). All the somatic cells and most of the residual fat and contaminating microorganisms present in the incoming milk are concentrated 20 times in the MF retentate. In MF industrial equipment, this retentate is then concentrated 10-fold more in a second MF apparatus, thus leading to a volume concentration factor (VCF) of 200. Fluxes obtained industrially for the microfilterated skim milk are in the order of 500 l h 1 m 2 during 10 h. For VCFs 20 and 200, the observed permeation rates are, respectively, for proteins 99.0 and 99.4% and for total solids 99.5 and 99.9%. Average observed decimal reduction (DR) of bacteria is above 3.5 for milk collected in most developed dairy countries (initial total count (TC) <200 000 cfu ml 1);
307
308 Liquid Milk Products | Liquid Milk Products: Membrane-Processed Liquid Milk
it can be higher than 6.0 in milk of poor bacteriological quality collected in some developing countries. Sporeforming bacteria, which represent the main surviving species to pasteurization, are highly retained by MF membrane (DR > 4.5) because of their large apparent cellular volume when they are in milk. Synthesis of the different studies done by Pasteur Institute and INRA have shown for Listeria monocytogenes, Brucella abortus, Salmonella typhimurium, and Mycobacterium tuberculosis respective DR of 3.4, 4.0, 3.5, and 3.7. Considering the usually described contamination of milk at farm level, such results will assure that skim milk microfiltered through 1.4 mm membranes will contain less than 1 cfu l 1 of these pathogenic bacteria which means 1.4 mm MF milk can be considered as safe as pasteurized milk. France is the only country which has officially allowed the commercialization of extended shelf life (ESL) MF raw milk. The MF raw skim milk is mixed with an amount of heated cream (95 C for 20 s) required for fat standardization; the mixture is homogenized and aseptically filled. The authorized shelf life of the packed milk, legally raw, because it has a positive phosphatase reaction, at 4–6 C is 3 weeks. The annual volume of this MF milk, to our knowledge, produced by only one dairy company under the trade mark ‘Marguerite’ (see Figure 1) reached more than 10 million liters in 2008. Other plants as in many countries in the world homogenize the mixture, before a high temperature short time (HTST) (72 C for 20 s) pasteurization step leading to a claimed shelf life of 5 weeks. The commercial success experienced by MF milk is great in many countries because of its improved flavor (no cooked taste) and because it is long storable. In some plants, MF through 1.4 mm membranes has been used as a pretreatment in the production of UHT milk in order to reduce the intensity of heat treatment (reduced to 140 C for 4 s or less instead of 150 C for 5 s)
Figure 1 Microfilterated raw milk.
with consequently less cooked taste and improved storage arising from the removal by MF of thermostable enzymes present in dead bacterial cells and in somatic cells. Use of MF membranes with a smaller pore diameter (0.8 mm instead of 1.4 mm) originally proposed by Lindquist (1998) was studied in Sweden, France (AFSSA, 2002), and Canada. At 50 C, the flux obtained was approximately 400 l h 1 m 2 and the observed DR with this MF 0.8 mm membrane was higher than 13 on Clostridium botulinum, a value which means sterility of the product. After mixing with UHT (142 C to 4 s) cream for fat standardization, followed by homogenization at 80 C, a heat treatment at 95 C for 6 s is applied with the only purpose of inactivating endogenous milk enzymes; then aseptic packaging is done at 20 C. The resulting milk called ‘Ultima’ milk by the Tetra Laval Company was recognized as commercially sterile and was allowed to be commercialized. Indeed, it is stable at 40 C for 62 days and for more than 8 months at room temperature. Its organoleptic quality was judged to be similar to that of a HTST pasteurized milk. Its lactulose content was reduced by 71% compared to commercial UHT milk. But until now, to our knowledge, the ‘Ultima’ process has not been developed commercially by the Tetra Pak Co, for unknown reasons. Nevertheless, nowadays, in some dairy plants, the 1.4 mm MF membrane is substituted by a 0.8 mm membrane for the production of ESL MF pasteurized milk in order to extend storage ability to more than 5 weeks.
Protein Standardization by UF Ultrafiltration offers the possibility of adjusting the protein content of consumer milk either by their concentration or by the addition of UF permeate to the
Liquid Milk Products | Liquid Milk Products: Membrane-Processed Liquid Milk
milk in order to overcome natural variations in milk composition depending on cows’ breed, their feed, the season, and their stage of lactation. Surprisingly, whilst fat standardization is commonly accepted and legally authorized for many years, the proposal to deliver consumer milk with a defined protein content has encountered incomprehensible and illogical (protein content is one of the payment criteria to milk producers!) opposition and until now, to our knowledge, no country in the world has modified its legislation to allow protein standardization of consumer milk although adjustment is allowed for milk and whey powders. Questions raised by protein standardization of consumer milk could be summarized as follows: ethical acceptance of fat standardization, one unique level (for example, 32 g l 1 or several ranging from 29 g l 1: minimum defined in EU and required from a nutritional point of view to 34 g l 1 (content found in many developed countries)), technologies to be used, and economical consequences.
Removal of Somatic Cells by MF SCs which have a size ranging from 6 to 15 mm, contain numerous thermo-resistant enzymes (protease, lipase, catalase). They are very sensitive to mechanical treatments and consequently are able to release their enzymes into the milk with a potential impact on the quality of the dairy products derived from that milk (pasteurized and UHT milks). They have been shown to protect Listeria monocytogenes during heat treatment and it has been suggested that milk leukocytes could also contain BSE prions but no demonstration of this hypothesis has been made either in milk or in colostrum. Specific removal of SC from raw whole milk by MF membranes having an average pore size ranging from 12 to 5 mm was studied by our group. Permeation fluxes between 2000 l h 1 m 2 and 1460 l h 1 m 2 were, respectively, obtained over a running time of 8 h. SC of 93–100% was retained in the MF retentate which represented 4–5% of the volume of treated milk. Permeation rates of the globular fat were, respectively, 89 and 83%. Moreover, in order to be the solution for treating milk if presence of prion is eventually demonstrated, these results open new avenues for research such as the specific effects of varied numbers of SC in normal milk (most of the published studies have been done with mastitic milk the composition of which is highly modified) on the stability of UHT milk in comparison to the residual activity of the endogenous milk plasmin or of the proteases of Pseudomonas, the potential creation of micro-heterogeneity in the microstructure of cheese, and on the other hand to be used as tracers for identifying cows or herds which produced the used milk raw material because all their genetic patrimony is contained in the SC.
309
See also: Cheese: Membrane Processing in Cheese Manufacture; Preparation of Cheese Milk; Raw Milk Cheeses. Heat Treatment of Milk: Non-Thermal Technologies: Introduction. Liquid Milk Products: Liquid Milk Products: Pasteurized Milk; Liquid Milk Products: UHT Sterilized Milks. Milk Proteins: Nutritional Quality of Milk Proteins. Nutrition and Health: Effects of Processing on Protein Quality of Milk and Milk Products. Policy Schemes and Trade in Dairy Products: Standards of Identity of Milk and Milk Products.
Further Reading AFSSA (2002) Avis relatif a` l’e´valuation de l’efficacite´ et de l’inte´reˆt nutritionnel et microbiologique d’un proce´de´ de traitement de conservation du lait de consommation utilisant la technique de microfiltration. Eino MF (1997) Lessons learned in commercialization of microfiltered milk. International Dairy Federation Bulletin 320: 32–36. Gezan-Guiziou G (2007) Filtration membranaire (osmose inverse, nanofiltration, ultrafiltration, microfiltration tangentielle): Applications en agroalimentaire. In: Ed. Techniques de l’Inge´nieur, Paris, Section Ge´nie des proce´de´s; ope´rations unitaires, ge´nie de la re´action chimique. J 2795. Goude´dranche H, Fauquant J, and Maubois J-L (2000) Fractionation of globular milk fat by membrane microfiltration. Lait 80: 93–98. Holm S, Malmberg R, and Svensson K (1984) Method and Plant for Producing Milk with a Low Bacteria Content. European Patent 0, 194, 286. Journal Officiel Union Europe´enne.(2007) Annexe XIII Commercialisation du lait destine´ a` la consommation humaine vise´e a` l’article 114. Le Squeren JC and Canteri G (1995). Proce´de´ pour e´liminer les cellules somatiques des milieux alimentaires ou biologiques et produits correspondants. Brevet FR 2, 731, 587. Lindquist A (1998) A Method for the Production of Sterile Skimmed Milk. PCT Patent WO No. 57549. Madec M-N, Mejean S, and Maubois J-L (1992) Retention of Listeria and Salmonella cells contaminating skimmilk by tangential membrane microfiltration (Bactocatch process). Lait 72: 327–332. Maubois J-L (1989) Applications of membrane techniques in the dairy industry: Proposals for a new IDF group of experts. International Dairy Federation Bulletin 244: 26–29. Maubois J-L (2002) Membrane microfiltration: A tool for a new approach in dairy technology. Australian Journal of Dairy Technology 57: 92–96. Maubois J-L and Fauquant J (2004) Re´tention des cellules somatiques du lait entier cru par microfiltration sur membrane. Rennes: Rapport ARILAIT. Maubois J-L and Schuck P (2005) Membrane technologies for the fractionation of dairy components. International Dairy Federation Bulletin 400: 2–7. Meershon M (1989) Nitrate free cheesemaking with Bactocatch. North European Food Dairy Journal 55: 108–113. Michalski M-C, Leconte N, Briard-Blon V, Fauquant J, Maubois J-L, and Goude´dranche H (2006) Microfiltration of raw whole milk to select fractions with different fat globule size distributions: Process optimisation and analysis. Journal of Dairy Science 89: 3778–3790. Mistry V and Maubois J-L (2004) Application of membrane technologies to cheese production. In: Cheese: Chemistry, Physics and Microbiology, 3rd edn.,Vol. 1, pp. 261–286. New York, USA: Elsevier. Rosenberg M (1995) Current and future applications for membrane processes in the dairy industry. Trends in Food Science and Technology 6(1): 12–19. Saboya LV and Maubois J-L (2000) Current developments of microfiltration technology in the dairy industry. Lait 80: 541–553. Trouve´ E, Maubois J-L, Piot M, et al. (1991) Re´tention de diffe´rentes espe`ces microbiennes lors de l’e´puration du lait par microfiltration en flux tangentiel. Lait 71: 1–13.
Introduction
Bacteria Removal by MF
Laboratory curiosities until the late 1960s, membrane technologies started to become an industrial reality with the pioneering work of Loeb and Sourirajan (1963) who have developed the first anisotropic membranes, made from cellulose acetate, able to deliver reasonable fluxes and permeabilities for sea water desalination by reverse osmosis. Then, remarkable progress was also accomplished in the development of more robust membranes and better designed equipment as in the applications of this ubiquitous family of technologies which include separation of molecules or particles based on size differences: reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF); separation based on ionic charge: electrodialysis (ED); and separation based on chemical potential difference (pervaporation). Among the food industries, dairying is undoubtedly that which has known the largest introduction of most of the membrane technologies, MF, UF, NF, and RO (the total installed area was in 2007 more than 500 000 m2 according to Gezan-Guiziou, 2007), except for pervaporation which has, to our knowledge, no application in milk treatment. There are numerous reasons for this success: deep knowledge of the biochemical characteristics of milk and of the co-products (mostly whey) which helped greatly the optimization of the desired differential separation; the dynamism of several research teams; the operating temperature which did not cause irreversible damage to the biological properties of milk components; the high unacceptable environmental pollution caused by the discharge of cheese whey, etc. The presence of membrane equipment in dairy plants is nowadays as common as the presence of a cream separator in many countries worldwide. Concerning drinking liquid milks, the main applications are bacteria removal by MF, which has known worldwide success and adjustment of the protein content by UF. There has also been some use of RO for the concentration of milk for the production of yogurts or powders and some recent studies have been devoted to the specific separation of somatic cells (SC), described below, and to the separation of milk fat globules according to their size which has not yet been applied industrially.
Decontamination of collected milk is generally achieved through heat treatments: thermization, pasteurization, or sterilization by autoclaving or ultra-high temperature (UHT) treatment, using various combinations of time– temperature parameters to obtain the desired bactericidal effect. While these heat treatments ensure the safety of milk and dairy products, they almost always induce irreversible modifications of milk components, alter calcium salts– protein equilibrium, and also adversely affect the organoleptic quality of fluid milk and dairy products as well as the cheesemaking ability. Moreover, the cells of dead bacteria remain in heated milk with their potentially active enzymes which, with the metabolic activity of remaining thermoduric bacteria, will cause alterations of liquid milk during storage, thus reducing commercial shelf life. Tangential membrane microfiltration offers an interesting alternative to heat treatments. Initially proposed in 1984, it has led to the technology and equipment called ‘Bactocatch’ by the Tetra Laval Company. Numerous studies, done in Sweden and in France and summarized by Saboya and Maubois (2000), have optimized the original parameters described in the patent of Holm et al. (1984). Nowadays, skim milk heated to 50 C is circulated at a velocity of 7.2 m s 1 along a ceramic membrane made of porous alumina and having an average pore size of 1.4 mm (Sterilox or equivalent) supported by a thick porous layer also of alumina. The process is carried out according to the hydraulic concept of a uniform transmembrane pressure (UTP), approximately 0.5 bar, obtained either by recirculation of the permeate or by specially designed MF membrane with a continuous variation in the porosity of its support (Membralox GP) or continuous variation of the thickness of the membrane layer (Isoflux). All the somatic cells and most of the residual fat and contaminating microorganisms present in the incoming milk are concentrated 20 times in the MF retentate. In MF industrial equipment, this retentate is then concentrated 10-fold more in a second MF apparatus, thus leading to a volume concentration factor (VCF) of 200. Fluxes obtained industrially for the microfilterated skim milk are in the order of 500 l h 1 m 2 during 10 h. For VCFs 20 and 200, the observed permeation rates are, respectively, for proteins 99.0 and 99.4% and for total solids 99.5 and 99.9%. Average observed decimal reduction (DR) of bacteria is above 3.5 for milk collected in most developed dairy countries (initial total count (TC) <200 000 cfu ml 1);
307
308 Liquid Milk Products | Liquid Milk Products: Membrane-Processed Liquid Milk
it can be higher than 6.0 in milk of poor bacteriological quality collected in some developing countries. Sporeforming bacteria, which represent the main surviving species to pasteurization, are highly retained by MF membrane (DR > 4.5) because of their large apparent cellular volume when they are in milk. Synthesis of the different studies done by Pasteur Institute and INRA have shown for Listeria monocytogenes, Brucella abortus, Salmonella typhimurium, and Mycobacterium tuberculosis respective DR of 3.4, 4.0, 3.5, and 3.7. Considering the usually described contamination of milk at farm level, such results will assure that skim milk microfiltered through 1.4 mm membranes will contain less than 1 cfu l 1 of these pathogenic bacteria which means 1.4 mm MF milk can be considered as safe as pasteurized milk. France is the only country which has officially allowed the commercialization of extended shelf life (ESL) MF raw milk. The MF raw skim milk is mixed with an amount of heated cream (95 C for 20 s) required for fat standardization; the mixture is homogenized and aseptically filled. The authorized shelf life of the packed milk, legally raw, because it has a positive phosphatase reaction, at 4–6 C is 3 weeks. The annual volume of this MF milk, to our knowledge, produced by only one dairy company under the trade mark ‘Marguerite’ (see Figure 1) reached more than 10 million liters in 2008. Other plants as in many countries in the world homogenize the mixture, before a high temperature short time (HTST) (72 C for 20 s) pasteurization step leading to a claimed shelf life of 5 weeks. The commercial success experienced by MF milk is great in many countries because of its improved flavor (no cooked taste) and because it is long storable. In some plants, MF through 1.4 mm membranes has been used as a pretreatment in the production of UHT milk in order to reduce the intensity of heat treatment (reduced to 140 C for 4 s or less instead of 150 C for 5 s)
Figure 1 Microfilterated raw milk.
with consequently less cooked taste and improved storage arising from the removal by MF of thermostable enzymes present in dead bacterial cells and in somatic cells. Use of MF membranes with a smaller pore diameter (0.8 mm instead of 1.4 mm) originally proposed by Lindquist (1998) was studied in Sweden, France (AFSSA, 2002), and Canada. At 50 C, the flux obtained was approximately 400 l h 1 m 2 and the observed DR with this MF 0.8 mm membrane was higher than 13 on Clostridium botulinum, a value which means sterility of the product. After mixing with UHT (142 C to 4 s) cream for fat standardization, followed by homogenization at 80 C, a heat treatment at 95 C for 6 s is applied with the only purpose of inactivating endogenous milk enzymes; then aseptic packaging is done at 20 C. The resulting milk called ‘Ultima’ milk by the Tetra Laval Company was recognized as commercially sterile and was allowed to be commercialized. Indeed, it is stable at 40 C for 62 days and for more than 8 months at room temperature. Its organoleptic quality was judged to be similar to that of a HTST pasteurized milk. Its lactulose content was reduced by 71% compared to commercial UHT milk. But until now, to our knowledge, the ‘Ultima’ process has not been developed commercially by the Tetra Pak Co, for unknown reasons. Nevertheless, nowadays, in some dairy plants, the 1.4 mm MF membrane is substituted by a 0.8 mm membrane for the production of ESL MF pasteurized milk in order to extend storage ability to more than 5 weeks.
Protein Standardization by UF Ultrafiltration offers the possibility of adjusting the protein content of consumer milk either by their concentration or by the addition of UF permeate to the
Liquid Milk Products | Liquid Milk Products: Membrane-Processed Liquid Milk
milk in order to overcome natural variations in milk composition depending on cows’ breed, their feed, the season, and their stage of lactation. Surprisingly, whilst fat standardization is commonly accepted and legally authorized for many years, the proposal to deliver consumer milk with a defined protein content has encountered incomprehensible and illogical (protein content is one of the payment criteria to milk producers!) opposition and until now, to our knowledge, no country in the world has modified its legislation to allow protein standardization of consumer milk although adjustment is allowed for milk and whey powders. Questions raised by protein standardization of consumer milk could be summarized as follows: ethical acceptance of fat standardization, one unique level (for example, 32 g l 1 or several ranging from 29 g l 1: minimum defined in EU and required from a nutritional point of view to 34 g l 1 (content found in many developed countries)), technologies to be used, and economical consequences.
Removal of Somatic Cells by MF SCs which have a size ranging from 6 to 15 mm, contain numerous thermo-resistant enzymes (protease, lipase, catalase). They are very sensitive to mechanical treatments and consequently are able to release their enzymes into the milk with a potential impact on the quality of the dairy products derived from that milk (pasteurized and UHT milks). They have been shown to protect Listeria monocytogenes during heat treatment and it has been suggested that milk leukocytes could also contain BSE prions but no demonstration of this hypothesis has been made either in milk or in colostrum. Specific removal of SC from raw whole milk by MF membranes having an average pore size ranging from 12 to 5 mm was studied by our group. Permeation fluxes between 2000 l h 1 m 2 and 1460 l h 1 m 2 were, respectively, obtained over a running time of 8 h. SC of 93–100% was retained in the MF retentate which represented 4–5% of the volume of treated milk. Permeation rates of the globular fat were, respectively, 89 and 83%. Moreover, in order to be the solution for treating milk if presence of prion is eventually demonstrated, these results open new avenues for research such as the specific effects of varied numbers of SC in normal milk (most of the published studies have been done with mastitic milk the composition of which is highly modified) on the stability of UHT milk in comparison to the residual activity of the endogenous milk plasmin or of the proteases of Pseudomonas, the potential creation of micro-heterogeneity in the microstructure of cheese, and on the other hand to be used as tracers for identifying cows or herds which produced the used milk raw material because all their genetic patrimony is contained in the SC.
309
See also: Cheese: Membrane Processing in Cheese Manufacture; Preparation of Cheese Milk; Raw Milk Cheeses. Heat Treatment of Milk: Non-Thermal Technologies: Introduction. Liquid Milk Products: Liquid Milk Products: Pasteurized Milk; Liquid Milk Products: UHT Sterilized Milks. Milk Proteins: Nutritional Quality of Milk Proteins. Nutrition and Health: Effects of Processing on Protein Quality of Milk and Milk Products. Policy Schemes and Trade in Dairy Products: Standards of Identity of Milk and Milk Products.
Further Reading AFSSA (2002) Avis relatif a` l’e´valuation de l’efficacite´ et de l’inte´reˆt nutritionnel et microbiologique d’un proce´de´ de traitement de conservation du lait de consommation utilisant la technique de microfiltration. Eino MF (1997) Lessons learned in commercialization of microfiltered milk. International Dairy Federation Bulletin 320: 32–36. Gezan-Guiziou G (2007) Filtration membranaire (osmose inverse, nanofiltration, ultrafiltration, microfiltration tangentielle): Applications en agroalimentaire. In: Ed. Techniques de l’Inge´nieur, Paris, Section Ge´nie des proce´de´s; ope´rations unitaires, ge´nie de la re´action chimique. J 2795. Goude´dranche H, Fauquant J, and Maubois J-L (2000) Fractionation of globular milk fat by membrane microfiltration. Lait 80: 93–98. Holm S, Malmberg R, and Svensson K (1984) Method and Plant for Producing Milk with a Low Bacteria Content. European Patent 0, 194, 286. Journal Officiel Union Europe´enne.(2007) Annexe XIII Commercialisation du lait destine´ a` la consommation humaine vise´e a` l’article 114. Le Squeren JC and Canteri G (1995). Proce´de´ pour e´liminer les cellules somatiques des milieux alimentaires ou biologiques et produits correspondants. Brevet FR 2, 731, 587. Lindquist A (1998) A Method for the Production of Sterile Skimmed Milk. PCT Patent WO No. 57549. Madec M-N, Mejean S, and Maubois J-L (1992) Retention of Listeria and Salmonella cells contaminating skimmilk by tangential membrane microfiltration (Bactocatch process). Lait 72: 327–332. Maubois J-L (1989) Applications of membrane techniques in the dairy industry: Proposals for a new IDF group of experts. International Dairy Federation Bulletin 244: 26–29. Maubois J-L (2002) Membrane microfiltration: A tool for a new approach in dairy technology. Australian Journal of Dairy Technology 57: 92–96. Maubois J-L and Fauquant J (2004) Re´tention des cellules somatiques du lait entier cru par microfiltration sur membrane. Rennes: Rapport ARILAIT. Maubois J-L and Schuck P (2005) Membrane technologies for the fractionation of dairy components. International Dairy Federation Bulletin 400: 2–7. Meershon M (1989) Nitrate free cheesemaking with Bactocatch. North European Food Dairy Journal 55: 108–113. Michalski M-C, Leconte N, Briard-Blon V, Fauquant J, Maubois J-L, and Goude´dranche H (2006) Microfiltration of raw whole milk to select fractions with different fat globule size distributions: Process optimisation and analysis. Journal of Dairy Science 89: 3778–3790. Mistry V and Maubois J-L (2004) Application of membrane technologies to cheese production. In: Cheese: Chemistry, Physics and Microbiology, 3rd edn.,Vol. 1, pp. 261–286. New York, USA: Elsevier. Rosenberg M (1995) Current and future applications for membrane processes in the dairy industry. Trends in Food Science and Technology 6(1): 12–19. Saboya LV and Maubois J-L (2000) Current developments of microfiltration technology in the dairy industry. Lait 80: 541–553. Trouve´ E, Maubois J-L, Piot M, et al. (1991) Re´tention de diffe´rentes espe`ces microbiennes lors de l’e´puration du lait par microfiltration en flux tangentiel. Lait 71: 1–13.