FERMENTED MILK PRODUCT PRODUCTION PROCESS

Abstract: The present invention is directed to a fermented milk production process in self-rehydrating container comprising a carbohydrate, a fermented milk product forming starter culture, milk powder and eventually other edible solutes, and to a self-rehydrating container adapted thereto. The container contains a semi-permeable membrane which allows the preparation of substantially sterile water solutions using osmotically driven filtration.

Description: Fermented Milk Product Production Process. Field of invention. The invention relates to a self-rehydrating container adapted for the production of fermented milk products, to a process for the production of fermented milk product using a self- rehydratmg container, to a container adapted thereto and to the fermented milk product produced as such Background of the invention. The use of yoghurts or fermented milk products in general as part of the human diet is perceived extremely beneficial for many reasons including major bacterial contamination in the upper intestine are prevented by beneficial organisms colonisation, problems with lactose intolerance are reduced, due to lactose conversion, antibiotics are produced locallv by lactobacillus type bacteria, certain minerals are potentially more available within the foodstuff for digestion, fermented milk products have a better stability than equivalent milk products However, to prepare yoghurts or fermented milk products in general on the field is often difficult m many locations around the world This is mostly due to contamination (poor hygiene and sanitation) , and a lack of necessary heat stable organisms Moreover, it is essential that the fermented milk product forming organisms can grow in the correct environment A secondary benefit of fermented milk product forming organisms is their probiotic property This is where growth of potentially pathogenic organisms present in the food product is suppressed or severely lowered by the presence of large numbers of beneficial organisms due to their rapid growth, which is known as a colonisation effect It has been explained that it is the low pH resulting from lactic acid production which prevents growth of harmful bacteria The classic fermented milk product production process is known to the man skilled m the art As much as the starter culture needs to be free of contaminating micro-organisms, it is indicated that the vessels wherein the fermented milk product is produced are as clean and disinfected as possible Notwithstanding the fermented milk product producing bacteria have a colonising effect, other pathogenic micro-organisms might equally develop This is certainly so when the temperature at which the fermented milk product is prepared is lower than 40- 45°C Aims of the invention. Taken into account the beneficial effects of a fermented milk product and the need to provide convenient and non-infected fermented milk product preparation vessels, especially in countries where pure water is not easily available and when the need for healthy food is very important, the present invention aims at providing a fermented milk product which allows yoghurt to be prepared on the field, even in a heavily biologically contaminated environment It is another aim of the invention to exploit the colonising property of the beneficial fermented milk product cultures when the shelf life of rehydrated food products, potentially contaminated, need to be increased. Description of the invention. According to the invention, a fermented milk product (such as yoghurt or buttermilk) is produced within a self-rehydratmg container comprising, as at least a portion of its walls, a semi-permeable membrane. In a preferred embodiment, the self-rehvdratmg container has two compartments as disclosed in our copending British patent application No 9705455 5 In this comparted container, a compartment has water- and optionally oxygen-tight walls and contains a material to be rehydrated Another compartment which is osmoticallv active has at least a portion of its walls which is semi-permeable allowing obtention of sterile water through the process of osmoticallv driven filtration as described in EP 360,612 or in USP 4,920. 105, and contains osmoticallv active solutes These compartments are separated bv a non-permanent seal The container which is thus used in the fermented milk product production process of the present invention contains fermented milk product forming organisms and milk powder in admixture with a carbohydrate such as e g sugar which can function as the osmoticallv active solute In the variant using the comparted container, the fermented milk product forming organisms and the milk powder are retained in the watertight compartment and the osmoticallv active solute m the osmoticallv active compartment A 'fermented milk product according to the present invention may contain at least one of the following organisms Lactococc s lactic (different sub-species), Streptococcus salwarus, Streptococcus cremorts, Streptococcus lactis. Streptococcus diacetilactis or Streptococcus thermophilus (different sub-species), Lactobacillus bulgancus (different sub-species) , Leuconostoc cremons or Leuconostoc lactis. but other fermented milk product forming organisms are known from those skilled in the art These organisms can be tailored to provide products of different consistency, I e liquid fermented milk product, thick fermented milk product, yoghurt, kefir, buttermilk, cheese-like products, etc Organism grades have been identified that have excellent shelf stability if kept dry and free from oxygen The comparted container allows to fulfill this requirement as the watertight compartment mav be further provided with excellent oxygen barrier and can be gas flushed to remove oxygen before closing This container can further be contained itself within a hermetically sealed pack The self-rehvdratmg container is an indicated fermented milk product production vessel because the present applicant has found that using these organisms in conjunction with carbohydrate and dried skimmed milk, conversion of lactose into lactic acid and water is possible withm the container As a consequence, a reduction m pH is achieved along with a significant growth of said organisms. A combination of these effects helps suppress potential growth of pathogenic organisms within the pack and generates fermented milk products, substantially free from microbiological contaminants. The carbohydrate which is needed for osmotically driven filtration to occur is favorably any carbohydrate which can sustain the yoghurt producing organisms in converting lactose into lactic acid and favour their growth. Preferably, the carbohydrate is lactose, sucrose, dextrose, and the like; most preferably one uses lactose. Either solid or liquid fermented milk products which are perceived to have extreme consumption benefits can be produced within the self-rehydratmg container using known cultures. The milk powder contained in the container can be any dried milk type. Best results are obtained though with skimmed milk powder. A milk powder useful for specific applications such as High Energy Therapeutic Milk may equally be used The fermented milk product preparation process according to the invention comprises immersing a self-rehydratmg container m water and leaving the container immersed until the filtered water has reached a sufficient level. The osmotically active carbohvdrate, the starter culture and the milk powder are contained altogether m the container Once the container is immersed in water, rehydration of the different solutes starts and the starter cultures is activated. Using fermented milk product organisms in conjunction with a carbohydrate and dried milk powder results m a pH reduction and a significant growth of said organisms. The combination of these effects helps therefore to suppress potential growth of contaminating organisms withm the bag and generates a fermented milk product In a variant, the fermented milk product production process according to the present invention comprises immersing a comparted self-rehydrating container in water, wherein the watertight compartment contains the starter culture and the milk powder, while the osmotically active compartment contains an osmotically active carbohvdrate, leaving the container immersed until the filtered water has reached a sufficient level, breaking a non- permanent seal separating the two compartments, leaving the waterproof compartment to be filled with the sterile water of the other compartment, allowing the starter culture and the milk powder to dissolve, keeping the container at a temperature above 25°C, preferably between 30°C and 45°C depending on the thermal resistance of the fermented milk product forming organism and allowing for the fermented milk product to be formed When the starter culture is sufficiently resistant to be kept without particular measures to improve its shelf- stability and/or when the starter culture has a sufficiently high colonising potential (thus preventing the growth of contaminating micro-organisms), the single- compartment container is particularly suitable On the other hand, when it is necessary to keep the starter culture dry and free from oxygen to have an acceptable shelf life or when the colonising potential of the culture is not high enough, it is preferable to use the comparted container. Normally, 6 to 7 hours are needed for a mixture of milk and starter culture to change into a fermented milk product. It is thus necessary to foresee a starter culture which can overgrow the contaminating micro-organisms potentially present m the other solutes during rehydration time, the milk powder /water /starter culture mixture is not at its full growing capacity. A preferred "single compartment" self-rehydratmg container comprises a composite semi- permeable membrane comprising a support layer with a relatively high molecular weight cut- off selected from the group consisting of cellulose, regenerated cellulose (CELLOPHANE® or cuprophane), benzoylated cellulose and collagen, and a thin layer with low molecular weight cut-off as disclosed m our copending British patent application No. 9705454.8. Preferably the thin layer consists of an hydrophihc polyurethane such as those which are conventionally used for covering textile with a protective coating which is waterproof but water vapour permeable Lowering the molecular weight cut-off of the overall membrane structure allows for more solute compounds to be maintained withm the milk solutions of the present invention, thus resulting m a more nutπtious yoghurt especially when High Energy Therapeutic Milk is used for example. It is well withm the possibilities of the man in the art to develop more sophisticated fermented milk products by using for example additional beneficial micro-organisms (such as bifidus), additional solute powders (like fruit juice powder, thickeners, etc.) colouring agents, etc. Again the colonising effect (pH and growth rate) of the fermented milk product organisms will prevent the contaminating organisms possibly present in such solutes to develop Preferably, fermented milk product organisms with pH lowering properties ensuring a pH decrease to pH 4 - 4 5 within 6 hours of rehvdration are used The examples which follow illustrate the invention without anv intention to limit its scope in any way Yoghurt has been embodied as fermented milk product, but other kinds of fermented milk products are well withm the scope of invention Examples. Example 1 A container is prepared with a composite membrane consisting of a support membrane of regenerated cellulose film with a molecular weight cut-off of 1800 and of a thin hydrophihc polyurethane layer applied by direct gravure coating at 10 g/m2 (wet weight) The hydrophihc polyurethane is prepared as follows A solution of 133.02 g of polyethyleneglycol (PEG 600 (HOECHST)) having a molecular weight of about 600 and 79 00 g of 1 , l '-methylenebιs(4-ιsocyanatocyclohexane) in 342.00 g of toluene is introduced into a 2 -liter four necked round bottomed flask equipped with a mechanical stirrer, a thermometer, an air condenser, a nitrogen inlet and a dropping funnel The mixture is heated at 90°C whύe stirring and 25 mg of dibutyltmlaurate (DABCO T12 (AIR PRODUCTS)) as catalyst, is introduced. The reaction mixture is maintained at 90°C for 6 hours and then cooled. A solution of 13.68 g of isophorone diamme in 350.00 g of isopropyl alcohol is introduced in a second 2-liter four necked round bottomed flask equipped with a mechanical stirrer, a thermometer, an air condenser, a nitrogen inlet and a dropping funnel. The content of the first flask is cooled at room temperature and it is then added slowly to the mixture alcohol/ amme (second flask). Chain extention is complete after about 3 hours. 44 2 g of fumed silica (TS 100 DEGUSA) and 50 g of toluene are added to the mixture. Example 2 Self-rehydrating containers containing Infant Formula Milk (IFM) 30 7 g or Therapeutic milk (TM) 36 5 g and different yoghurt forming organisms are placed in water When the internal volume has reached 200 ml, 7 5 hours for Infant Formula Milk and 8 5 hours for Therapeutic milk, the bags are gently removed from water The bags are then stored at different temperatures, in the fridge (at about + 4"C), at ambient temperature (at 25°C, with a relative humidity of 75%), in tropical oven (at 38°C, with a relative humidity of 90%C) Hourly (over 24 hours) a bag is open and the pH of its content is measured The TABLE I shows the measured values of the pH The Blank samples do not contain any yoghurt forming organisms, the strain 1 samples contain 6 mg of RA024 (from TEXEL) as yoghurt forming organisms, the strain 2 samples contain 6 mg of MY087 (from TEXEL) as yoghurt forming organisms, the strain 3 samples contain a mixture of 3 mg of RA024 (from TEXEL) and of 3 mg MY087 (from TEXEL) as yoghurt forming organisms, the strain 4 samples contain 6 mg of MAO 16 (from TEXEL) as voghurt forming organisms, TABLE I pH . change over 24 hours Milk Condition Sample 0 1 2 3 4 5 6 7 IFM Fridge Blank 6.68 6.68 6.73 6.85 6.55 6.67 6.89 Strain 1 6.68 6.67 6.69 6.74 6.44 6.53 6.77 Strain 2 6.50 6.50 6.57 6.65 6.43 6.54 6.69 Strain 3 6.50 6.49 6.54 6.46 6.32 6.64 6.80 Strain 4 6.46 6.44 6.40 6.34 6.26 6.24 6.14 6.03 Ambient Blank 6.65 6.64 6.62 6.44 6.40 6.47 6.54 Strain 1 6.64 6.60 6.57 6.40 6.27 6.09 5.95 Strain 2 6.65 6.64 6.68 6.40 6.60 6.62 6.72 Strain 3 6.63 6.60 6.60 6.35 6.22 6.16 6.10 Strain 4 6.50 6.39 6.19 6.01 5.73 5.38 5. 12 4.76 Tropical Blank 6.47 6.44 6.49 6.49 6.46 6.43 6.30 Strain 1 6.37 6.05 6.63 4.71 4.26 4.26 4.20 Strain 2 6.44 6.39 6.35 6.21 5.36 4.78 4.40 Strain 3 6.42 6.23 5.93 5.53 4.50 4.36 4.30 Strain 4 6.55 6. 15 5.64 5. 16 4.77 4.41 4.30 4.23 TM Fridge Blank 6.53 6.49 6.55 6.66 6.39 6.54 6.73 Strain 1 6.68 6.47 6.53 6.61 6.33 6.42 6.58 Strain 2 6.50 6.50 6.57 6.65 6.43 6.54 6.69 Strain 3 6.50 6.49 6.54 6.46 6.57 6.64 6.80 Strain 4 6.51 6.54 6.51 6.44 6.44 6.47 6.51 6.55 Ambient Blank 6.48 6.46 6.51 6.53 6.56 6.64 6.75 Strain 1 6.47 6.45 6.46 6.30 6.25 6.21 6. 17 Strain 2 6.45 6.46 6.51 6.35 6.30 6.43 6.53 Strain 3 6.47 6.44 6.46 6.20 6. 18 6. 13 5.98 Strain 4 6.44 6.40 6.36 6.30 6.25 6.21 6. 17 5.91 Tropical Blank 6.26 6.21 6.24 6. 15 6. 10 5.90 5.40 Strain 1 6.19 6.04 5.84 5.08 4.85 4.64 4.52 Strain 2 6.26 6.19 6. 14 5.55 4.89 4.63 4.43 Strain 3 6.23 6. 11 5.96 5.49 4.88 4.64 4.48 Strain 4 6.47 6.22 6. 18 6.09 5.97 5.84 5.68 5.27 TABLE I (contmuation - 1) Milk condition sample 8 9 10 1 1 12 13 14 15 IFM Fridge Blank 6.89 Strain 1 6.75 Strain 2 6.89 Strain 3 6.66 Strain 4 5.78 5.80 5.72 5.40 5.49 5.38 5.27 5.13 Ambient Blank 6.59 6.59 6.58 6.58 Strain 1 5.63 5.30 4.94 4.61 Strain 2 6.76 6.63 6.50 6.33 Strain 3 5.86 5.55 5.24 4.93 Strain 4 4.47 4.30 4.32 4.24 4.24 4.22 4.21 4. 18 Tropical Blank 5.83 5.32 4.81 4.30 Strain 1 4. 15 4. 12 4 08 4.03 Strain 2 4.25 4.18 4.1 1 3.99 Strain 3 4.22 4. 17 4. 12 4.06 Strain 4 4. 10 4.08 4.07 4.04 4.04 4.05 4.02 4.02 TM Fπdge Blank 6.99 Strain 1 6.75 Strain 2 6.99 Strain 3 6.66 Strain 4 6.46 6.70 6.62 6.55 6.54 6.57 6.6; 6.42 Ambient Blank 6.76 6.70 6.63 6.56 Strain 1 5.98 5.68 5.36 5.07 Strain 2 6.56 6.43 6.30 6. 18 Strain 3 5.66 5.30 4 94 4.57 Strain 4 5.81 5.66 5.48 5.24 5.05 4 89 4 77 4.66 Tropical Blank 4.88 4.65 4.42 4 19 Strain 1 4.42 4.34 4.26 4. 17 Strain 2 4.28 4.20 4 12 4 02 Strain 3 4.35 4.27 4. 19 4. 1 1 Strain 4 5.08 4.86 4.73 4.60 4.51 4.49 4.46 4.43 TABLE I (continuation - 2) Milk condition sample 16 17 18 19 20 23 24 Fridge Blank 6.72 Strain 1 5.19 Strain 2 6.82 Strain 3 6.15 Strain 4 5.02 4.94 4.81 4.73 4.69 Ambient Blank 4.35 Strain 1 4.24 Strain 2 4.24 Strain 3 4.23 Strain 4 4.19 4. 19 4.21 4.21 4. 19 Tropical Blank 3.80 Strain 1 3.79 Strain 2 3.64 Strain 3 3.64 Strain 4 4.02 3.98 3.99 4.00 3.99 Fridge Blank 6.62 Strain 1 5.95 Strain 2 6.63 Strain 3 6.24 Strain 4 6.40 6.50 6.55 6.45 Ambient Blank 4.17 Strain 1 4.24 Strain 2 4.33 Strain 3 4. 13 Strain 4 4.60 4.62 4.58 4. 19 Tropical Blank 3.82 Strain 1 4.07 Strain 2 3.68 Strain 3 3.78 Strain 4 4.38 4.38 4.36 4.21 From TABLE I, it appears that both infant formula and therapeutic milks show a similar trend under cool conditions that is there is no drop m pH for any sample. Further a general trend is observed in infant formula milk and therapeutic milk in that only the samples containing RA024 show any pH drop at ambient temperature. That drop is initially noted after 8 hours storage and drops to a pH 4.5 in both cases after 1 1 hours. At tropical conditions: Infant formula: The pH shows an initial drop after 3 hours in all samples except the blank. After 5 hours both samples containing RA024 have reached a pH of 4. After 7 hours the sample containing MY087 only has reached a pH of 4. After 11 hours the blank itself has drop to a pH of 4.5. Therapeutic milk: All samples containing probiotic show a drop in pH after 2 hours. All samples appear to act similarly. A after 5 hours reaching a pH of 4.5, except the blank which reaches a pH of 4.5 after 11 hours. In this TABLE, tropical conditions would appears to be the optimum conditions to induce pH reduction i.e. culture growth, producing yoghurt. The best culture is probably either the MAO 16 or the RA024. Both induce a quick drop m pH in both tested milks.

Claims: CLAIMS 1. Self-rehydratmg container comprising a semi-permeable membrane which allows the preparation of substantially sterile water solutions using osmotically driven filtration, containing a carbohydrate, a fermented milk product forming starter culture, milk powder and eventually other edible solutes. 2. Self-rehydratmg container according to claim 1 , characterized m that the carbohydrate is selected from the group consistmg of lactose, sucrose and dextrose and preferably is lactose. 3 Self-rehydratmg container according to claim 1 or 2, characterized in that the container is divided into two compartments separated by a non permanent seal, a watertight compartment containing a fermented milk product forming starter culture, milk powder and eventually other edible materials, and a second osmotically active compartment containing a carbohydrate and eventually other osmotically active solutes. 4 Self-rehydratmg container according to claim 3 characterized m that the watertight compartment is also substantially oxygen-tight. 5 Yoghurt production process characterized in that it comprises the steps of a) immersing m water a self rehydratmg container comprising a semi-permeable membrane and containing a carbohydrate, a yoghurt forming starter culture, milk powder and eventually other solutes; b) leaving the container immersed until the filtered water has reached a sufficient level; and c) optionally, keeping the bag at a temperature above 25°C for a sufficient further period of time allowing the fermented milk product to be formed. Yoghurt production process using a self-rehydratmg container according to anv one of claims 3 or 4 comprising a) immersing the container in water, b) leaving the container immersed until the filtered water has reached a sufficient level, c) breaking the non-permanent seal separating the two compartment, d) allowing the watertight compartment to be filled with the sterile water of the other compartment, e) allowing the starter culture and milk powder to dissolve, f) keeping the bag at a temperature above 25°C and allowing for the fermented milk product to be formed. Fermented milk product obtained using a process according to any one of claims 5 or 6

Inventors: MARSHALL COLIN, SEALBY LESLEY, TAYLOR LEWIS, MARSHALL, COLIN, SEALBY, LESLEY, TAYLOR, LEWIS
Applicants: MARSHALL COLIN, SEALBY LESLEY, TAYLOR LEWIS, UCB SA, MARSHALL, COLIN, SEALBY, LESLEY, TAYLOR, LEWIS, UCB, S.A.
Application year: 1998
Main classification: A23C9
IPC codes: A01J11, A23C9