Introduction Paper No.: 07 Paper Title: TECHNOLOGY OF MILK AND MILK PRODUCTS Module 11: TECHNOLOGY OF ANHYDROUS MILK FAT Anhydrous milk fat (AMF) is a milk fat-based dairy product in its purest form. In terms of a packaged good, AMF is an efficient and economical means of transporting and storing butterfat. AMF possesses a light yellow colour and has a clean bland taste, free from sour, bitter, rancid, oxidized or other objectionable flavours. Intense heat treatment is not used in the manufacturing process. Consequently, AMF lacks heated butter flavours. ANHYDROUS MILK FAT OR BUTTEROIL As per Food Safety and Standards Authority of India (FSSAI 2011), Milk fat/butter oil (BO) and Anhydrous Milk fat (AMF)/Anhydrous Butter oil means the fatty products derived exclusively from milk and/ or products obtained from milk by means of process which results in almost total removal of water and milk solids not fat. It shall have a pleasant taste free from off odour and rancidity. It shall be free from vegetable oil/ fat, animal body fat, mineral oil, added flavour and any other substance foreign to milk. The permitted antioxidants include ethyl, propyl, octyl, dodecyl gallates, singly or in combination @ max. 0.01%; butylated hydroxy anisole/ascorbyl palmitate/tertiary butyl hydro quinone @ max. 0.02%. Other specifications for Anhydrous milk fat and Butter oil laid down by FSSAI are collated in Table 1. Table 1. FSSAI requirement for Anhydrous milk fat and Butter oil Parameters Milk fat/butter Oil Anhydrous Milk Fat/Anhydrous Butter Oil Moisture %, Max. 0.40 0.10 Milk fat %, Min. 99.60 99.80 Butyrorefractometer reading at 40 o C 40-44 40-44 Reichert Meissl value, Min. 24 24 Free Fatty Acids, % as oleic acid, Max. 0.40 0.30 Peroxide value (meq. of O 2 /kg 0.60 0.30
fat), Max. Baudouin test Negative Negative For sake of comparison, the standards laid down for AMF at Berkshire, South East England is depicted in Table 2. The highest grade AMF is suitable for the production of recombined milk. Table 2. Berkshire standards for AMF I. Physical Colour Flavour and aroma Body and texture II. Chemical Moisture Max. 0.15% Milk fat Min. 99.8% Peroxide value Max. 0.3 m.eq. Free fatty acids, % oleic acid Max. 0.3% III. Microbiological SPC Max. 10,000/g Coliform Max. 10/g Yeast and Mold Max. 10/g Fat aspect relevant to frying Smoke point Flash point Fire/Ignition point Uniform light golden Bland, uncultured, unsalted, free from foreign or rancid flavors. Product should be solid at 70 F or less, should be completely melted at 105 F. It should possess a smooth and waxy texture. 380 o F 550 o F 800 o F Shelf life of AMF as per Berkshire standards Item Days storage Shipping temperature 432# Steel Drum 45º F All other Containers 180** 45º F # Shelf life of one year at 45 F; 6 months if > 45 F ** Shelf life of 30 days at ambient temperature. AMF should be stored at 40 F, if not used in 30 days. Technological means AMF can be prepared either from cream or even from white butter. The technological principles underlying both these processes are discussed herein.
I. Manufacture of AMF from cream Sweet cream of about 40% fat is heated to 55-60 C in a plate heat exchanger (PHE). This temperature ensures that the cream to be concentrated remains liquid in the separator bowl. The cream is concentrated to 75-78% fat in the cream concentrator and conveyed to the buffer tank of the homogenizer. The phase inversion process takes place under high pressure. At this stage, the cream should have a fat content of 65-70% for optimum phase inversion in the homogenizer. The emulsion and serum phase (heavy phase) is separated from the oil (light phase) in the downstream oil concentrator. The oil with a concentration of ~ 99.5% is heated in the PHE to 90-95 C. Oil washing or free fatty avoids (FFA) reduction can be achieved by integrating an oil polishing separator. The remaining moisture is evaporated in the vacuum evaporator, and the AMF leaving the vacuum evaporator has fat content exceeding 99.8%. The heavy phase discharging from the oil concentrator is recycled back into the buffer tank of the cream concentrator; it is then separated again and concentrated. The heavy phase (i.e. referred to as buttermilk) from the cream concentrator is skimmed in the skimming separator. The cream recovered from the skimming separator is also recycled back into the process. II. Manufacture of AMF from white butter The butter will usually kept under cold storage at -18 to -20 C in 20 or 25 kg blocks, before further processed into butter oil. Frequently, the butter coming from cold storage is intermediately stored in order to raise the temperature by ambient air to >32 F (>0 C). The butter is then melted in a steam-heated system. GEA Westfalia Separator has developed the a butter melting system which eliminates costly conditioning and the disadvantages of steamheated melting system.. When sweet cream butter with a ph of ~ 6.5 is to be processed and no chemical agents (e.g., citric acid) are allowed for denaturing the proteins, the emulsion layer has to be taken into account. Centrifugation and destruction of this emulsion layer is carried out by specially designed separators and phase inversion. For processing sweet cream butter, it is necessary to use a separator which allows concentration to 99.5% fat. The emulsion has to be discharged with the serum phase. When sour cream butter with a ph of 4.5-4.6 and with increased protein content is to be processed, a decanter can be used. Separate concentration of the solids is possible. A separator (polishing separator) has to be installed downstream of the decanter to increase the fat concentration to 99.5%. A polishing separator is necessary for butter processing and for FFA reduction. The butter blocks are taken from cold storage (-20 C), and are melted in the melting system. The product temperature in the buffer tank is between 45 and 65 C. The temperature of the product is raised to 70-75 C in a PHE. Phase inversion by means of a homogenizer is required to minimize the emulsion phase. The oil concentrator, a separator with disc type bowl, achieves separation of 99.0-99.5% fat. The heavy phase, a mixture of buttermilk and residual emulsion particles, is fed
to a skimming separator. The oil phase (light phase) is heated to about 90 C and then separated again in another separator. Before the oil is fed to the polishing separator, wash water is added to improve the quality of the oil. In the downstream vacuum evaporator, the residual moisture content is adjusted to < 0.1%. Manufacturing process of Anhydrous Milk Fat I. Direct Process (from cream) Milk Pasteurization Separation Skim milk Cream (~35% fat) Pasteurization (75 o C/15 sec) Cool to 55-58 o C Clarifixator Skim milk Oil (80-85% fat) Balance tank Fat concentrator Serum
Oil (96-98% fat) Preheat to 90-91 o C in PHE Vacuum concentrator (29 inches of mercury) AMF (< 0.1% moisture) Cool to 21 o C Nitrogen sparging (100-140 Kpa pressure) II. Indirect Process (from butter) Package in large (200 kg) metal drums White Butter Melting in steam-heated melting kettle or revolving plate-type melters Molten butter Pass through stainless steel mesh filter Holding vats (55-60 o C) Sharples centrifuge Serum Oil (90-92% fat)
Pass through battery of Sharples Vapour-type Super Centrifuges/ Oil Clarifiers Serum Oil (96-98% fat) Vacuum concentration (< 0.1% moisture) Cooling and Packaging of AMF Comparison of AMF with Ghee Though compositionally, AMF is quite close to that of ghee. However, there are few glaring differences and hence their application in dairy/food industry is varied. The comparison of the compositional characteristics of AMF with Ghee is shown in Table 3. Table 3. Comparison of composition of AMF/BO and Ghee Product Fat% Moisture% FFA% Fat-free dry mass,% Peroxide value per kg of fat AMF 99.8 0.10 0.30 0.20 0.20 Butter oil 99.6 0.30 0.5-0.7 0.40 0.80 Ghee 99.5 0.50 3.00 - - FFA Free fatty acids Difference between AMF, BO and Dry butterfat According to the US standards, three types of fat include anhydrous milk fat, butter oil and dry butter fat. The specifications for the same is depicted below. Anhydrous Milk Fat Butter Oil Dry butterfat Milk fat, Min. 99.8% Milk fat, Min. 99.8% Milk fat, Min. 99.3% Moisture, Max. 0.1% Moisture, Max. 0.1% Moisture, Max. 0.5% Should be made from fresh cream or white butter Made from cream or white butter of varying age Made from cream or butter or any age
Alkali is not permitted to neutralize the free fatty acids Peroxide value max. 0.2 m.eq. of O 2 /kg fat Taste - Pure and mild at 20-25 o C Alkali is permitted to neutralize the free fatty acids Peroxide value max. 0.3 m.eq. of O 2 /kg fat Taste - No pronounced impure or any other imperfect taste or aroma Alkali is permitted to neutralize the free fatty acids Peroxide value max. 0.8 m.eq. of O 2 /kg fat Taste - No pronounced impure or any other imperfect taste or aroma Common aspects in AMF and BO Free fatty acids Max. 0.30 Copper Iron Coliform Max. 0.05 ppm Max. 0.2 ppm Absent in 1 g In case of AMF no additives are permitted i.e. for neutralization of FFAs. Packaging and storage of AMF AMF is commonly stored in 200 kg drums and may be stored at ambient temperatures. Typically packed in containers in which air is replaced with nitrogen or carbon dioxide to prevent oxidation. In some cases AMF may be stored at a temperature of 4.4 o C to promote extended shelf life. Utility of AMF Milk fat has many functional properties which makes AMF a most valuable food ingredient. These functional properties include: Air incorporation antistaling (through moisture dispersion and retention) creaming flavor and flavour carrier gloss layering shortening
AMF is a convenient dairy ingredient to use in liquid form mainly because it is easy to mix with, and meter into, food recipes and formulas. Since water and solids-not-fat have been extracted, AMF does not burn at high temperatures. In the dairy products industry, it is used for recombination into liquid milk and other milk products, especially since it is bland in taste. Lecithin dispersed in AMF is used to produce instant milk powder. In baking, AMF can be sprayed on cracker surfaces to enhance gloss and appearance. AMF is also used in the chocolate manufacturing industry. AMF is used as an industrial or food service ingredient; it s an exceptional medium for frying because the lower moisture levels reduce spattering. It s also a delicious base for sauces such as Hollandaise and Béarnaise. The advantages of using AMF are: No spattering or burn-on during sautéing Increased puff for pastries and pie shells Aroma and flavour enhancement in bakery items Control of fat bloom in chocolate candy Ease of melting, pumping and mixing with other food ingredients Butter oil is also available in a lipolyzed form, modified enzymatically by lipases to produce a concentrated source of creamy and buttery flavours for use in bakery, low-fat and low-calorie caramel food products. Powders of spray-dried butter oil encapsulated in sugar or flour are used as food ingredients in bakery, confectionery and ice cream manufacture.