The present invention relates generally to the provision of a whipped milk product which is commonly known as a milk shake. More particularly, the present invention relates to a whipped product which can be ~rozen and subsequently thawed to provide a product having the characteristics of a milk shake.
Milk shakes are a well known product which are made in the home or sold by the food-serving industry, which includes restaurants, ice cream parlors and fast-serve operations. The milk shake is usually made by combining milk with ice cream and a flavoring material to provide a mix and thereafter whipping the mix to provide a milk shake having some overrun.
In the food-serving industry it is relatively time con-suming to prepare individual milk shakes. Moreover, milk shakes must often be prepared in advance in anticipation of peak husiness during certain hours of operation. It is often difficult to anticipate the correct number of milk: shakes which should be prepared and wastage is incurred. In the home, preparation of milk shakes requires the setting up of equipment, scooping of ice cream, and availability of liquid milk.
It has been recognized that it would be desirable to provide milk shakes in a frozen condition which could be thawed to provide a product like that which is made by the conventional method. However, conv~ntionally prepared milk shakes made by mix-ing together ice cream and milk are not suitable for freezing and subsequent thawing. Conventionally prepared milk shakes, when frozen and subsequently thawed, lose their overrun and break down into stratified layers of flavoring and milk. Various attempts have been made to provide a milk shake suitable for freezing but they have not resulted in products which are sufficiently like the conventionally prepared milk shakes upon thawing to be competitive or satisfactory to consumers.
Accordingly, the principal object of the present invention is to provide a milk shake which is suitable for whipping and freezing. It is another object of the present invention to pro-vide a frozen milk shake which upon thawing is sufficiently like conventionally prepar~d milk shakes to be satisfactory to con-sumers. It is a further object of the present invention to provide a method for making a milk shake which is suitable for freezing and upon subsequent thawing provides a milk shake sub-stantially similar to conventional milk shakes.
Generally, in accordance with the present invention, a milk shake is provided from edible protein, fat, disaccharide sugar, monosaccharide sugar, stabilizer, emulsifier and a poly-hydric freezing point depressant. The milk shake contains suit-able flavoring materials to provide a desired flavor. Prefer-ably, the milk shake of the invention comprises dairy ingredients selected from whole milk, skim milk, casein, sweetened con-densed whole milk, condensed skim milk, skim milk powder, whole milk powder and cream in such proportions as required to pro-vide fat and protein in the ranges indicated below. The disaccha-ride sugar and monosaccharide sugar are present in the mix at a particular ratio and at levels within the ranges indicated below. The polyhydric freezing point depressant is provided at a level sufficient to establish an initial freezing point of less than -4C and preferably within the range of from about -~C to about -17C.
The components of the milk shake of the invention are present at levels sufficient to provide a milk shake having the ingredients indicated below in Table I within the indicated range:
Ingredient Weight Percent Protein 2.4-3.4 Fat Disaccharide Sugar 4.0-6.0 ~onosaccharide Sugar 5.0-9.0 Water 66 - 74 It is a further requirement for the milk shake of the invention that the ratio of monosaccharide sugar to disaccharide sugar in the mix be within the range of 1.2:1 to 1.6:1. When dairy ingredients provide protein and fat, they also provide the disaccharide sugar, lactose. In general, from about 3 to about 4 percent lactose is provided by the dairy ingredients. If further disaccharide sugar is required, it is prefexred to use sucrose to provide the balance of disaccharide sugar. A pre-ferred monosaccharide sugar is dextrose.
The preferred fat source in the milk shake of the in-vention is whole milk or cream. ~Iowever~ other fats derived from vegetable and animal sources which are incorporated in ~illed milks and whipped toppings can be used. In particular, partially hardened vegetable oils which have physical properties substan-tially similar to those of milk fat can be used.
The preferred protein source in the milk shake or the invention is whole milk, skim milk and modified whey products.
However, imitation milk, containing a vegetable protein, can be used.
The polyhydric fxeezing point depressant is used in the milk shake of the invention to provide the milk shake with an initial freezing point of -4C or less. During dynamic cooling of the milk shake, latent heat is removed from water in the mix and ice crystals are formed. A new freezing point is established for the remaining solution since it has become more concentrated in respect to the soluble constituents. The transfer of sensi-ble heat from the unfrozen solution lowers the temperature to a new freezing point and more water is converted into ice.
Thus, the freezing point of the liquid portion of the milk shake is continually changing as water is ~rozen during the freezing proce~s. It is an important feature of the present invention that the milk shake have an initial freezing point of -4~ or less. Such initial freezing point is substantially lower than heretofore known mixes used to prepare frozen whipped desserts, such as ice cream. As explained more fully hereinafter, the temperature of the milk shake is reduced by dynamic cooling to a temperature within the range of -7C to -14C. This temperature range is below the temperature nor-mally associated with dynamic cooling of ice cream mixes and other frozen comestible mixes. The use of the polyhydric freez-ing point depressant in the milk shake of the present invention permits use of such lower temperatures and provides a semi-frozen mix with desired level of overrun upon exit from a heat exchanger used for dynamic cooling. Upon subsequent further 2n cooling of the semi-frozen mix a desirable crystal size, tex-ture and mouth feel are imparted to the milk shake.
Suitable polyhydric freezing point depressants are glycerin and propylene glycol. A parti¢ularly preferred polyhydric freezing point depressant for reasons of flavor is glycerin. As indicated, the polyhydric freezing point depressant is used at a level sufficient to provide a milk shake having an initial freezing point of -4C or less, pre-ferably within the range of -4C and -17C. In general, the freezing point depressant is used in the milk shake mix at a level of from about 6 to about 9 percent by weight of the mix to provide the desired initial freezing point.
The use of a polyhydric freezing point depressant in accordance with the invention in combination with the use of lower dynamic cooling temperatures greatly enhances the sta-bility of the milk shake of the invention. Stability is an expression of the ability of a fat-water emulsion, such as the milk shake of the invention, to resist the de-emulsifying effect of whipping and freezing. Stability depends not only on a balance of ingredients, but on their state of dispersion and interaction.
Due to the high level of moisture and low level of fat in a milk shake, the foamed milk shake is inherentl~ unstable.
In accordance with the present invention, it has been found that the interaction of the polyhydric freezing point depressant with selected stabilizers and emulsifiers provides the milk shake of the invention with sufficient stability to withstand the whipping-freezing-thawing cycle and provide a milk shake with the desirable foam, texture and body characteristics associated with conventional milk shakes. Stability is dependent on emul-sion (water-fat) stability, colloid (protein-gum stabilizer) and the interaction between the emulsion and the colloid.
The milk shake mix is homogenized so as to reduce - the fat to a fine degree of subdivision and a high degree of dispersion. This results in providing a greatly e~panded fat surface. The globules in the homogenized milk shake are surrounded by an interfacial layer of protein which is com-ple~ed with the stabilizing agents used in the invention.
It should be understood that the milk shake of the present in~ention is a very high moisture, low fat product compared to frozen dessert products which have been heretofore known. While not wishing to be bound by any theory, it is ~elieved that the stability of the mil~ sha~e is xelated both to the presence of the polyhydric freezing point depressant, the stabilizer and the emulsifier, and to the particular method for manufacture of the frozen milk shake, wherein lower than usual dynamic cooling temperatures are used.
The stabilizing agents useful in the present invention are any of the gums normally associated with the manufacture of ice cream. Such gums include carboxymethylcellulose (CMC) in the sodium salt form, carrageenan, sodium alginate, propylene glycol alginates, locust bean gum and guar gum. It is preferred to use a mixture of gums. It has been found that the use of a particular mixture of gums is greatly preferred to provide the highest level of stability. In this ~onnection, it is preferred to use a mixture of sodium alginate, carboxymethylcellulose in the sodium salt form and carrageenan. Preferably, the mixture of gums contains sodium alginate a~ a level of 50 to 80 weight percent, sodium carboxymethylcellulose at a level of 10 to 30 weight percent and carrageenan at a level of 10 to 30 weight percent. The stabilizing agents are used in the milk shake at a level of from about 0.05 to about 0.10 weight percent, pre-ferably from about 0.06 to about 0.08 weight percent.
The emulsifier can be any monoester normally used as an emulsifier in the preparation of frozen desserts. Particularly useful are the monoester emulsifiers identified as propylene glycol monostearate and glyceryl monosteara~e. It should be understood that the reference to propylene glycol monostearate and glyceryl monostearate is to the highly distilled commercial products which contain at least about 90 percent of the mono-ester. Also useful as an emulsifier in the present invention are mixtures of propylene glycol monostearate and glyceryl monostearate stabilized in the alpha crystalline form in accordance with the teachings of United States Patent No.
3,453,116 to Freund and United States Patent No. 3,673,106 to Jonas et al~
A particularly preferred emulsifier for use in the milk shakes of the invention is propylene glycol monostearate.
It has been found that for chocolate flavored milk shakes, pro-pylene glycol monostearate enhances the ability of the milk shake to prevent syneresis upon thawing and to prevent separ-ation of chocolate color during the thawing cycle. Moreover, it has been determined that propylene glycol monostearate provides an emulsion which is more compatible with the colloid system (protein-gum stabilizers) of the invention. This en-hanced compatibility results in ice retention, slower melting and more even melting.
In the method of manufacture of the ~rozen milk shake, whole milk, imitation milk or filled milk~ is added to a jacketed kettle equipped with agitating means. Any remaining portion of dry sugar which is to be used is added to the kettle~ The remaining non-~olatile fluid ingredients, in-cluding the polyhydric freezing point depressant, are added to the kettle and the mix is pasteurized under suitable time temperature conditions. A suitable condition for pasteurization is to heat the mix to 160F for 30 minutes. After pasteurization, the mix is maintained at a temperature of from about 60C to about 82C until the mix is homogenized.
It is sometimes preferred to hydrate the emulsifier prior to adding the emulsifier to the remaining ingredients.
In this connection, the emulsifier is heated to a temperature sufficient to melt the emulsifier and hot water is thereafter added to the emulsifier in a jacketed mixing kettle. The à~
hydrated emulsifier is then fed to the main mixing kettle by means of a metering pump. Salt and a vitamin-mineral premix, if used~ are then added to the mix in the kettle.
The remaining dry ingredients including, the stabilizing agent and a portion of any dry sugar used, are mixed with non-volatile dry, powderedt flavoring materials and are combined with the mix in the main kettle.
While the mix is maintained at an elevated temperature of from about 60C-82C the mix is pumped in a closed loop to thoroughly disperse all of the ingredients in the mix. There-after the mix is homogenized single stage at a pressure of from about 500 to about 2,000 psig.
The mix is then preferably pre-cooled to a temperature in the range of about ~C-16C prior to whipping and cooling the mix. The pre-cooling is desirable to lessen the cooling load on the heat exchanger used for dynamic cooling. Just prior to introducing the pre-cooled mix to the heat exchanger, any volatile flavoring materials to be used are added.
The mix is then dynamically cooled in the heat exchanger to a temperature of less than -7~ while a gas is injected into the mix at a level sufficient to generate from about 50 to about 100 percent overrun. Any suitable heat exchanger can be used.
The heat exchanger- is preferably a scraped wall heat exchanger provided with an inlet whereby an inert gas can be injected into the mix as it is being cooled. A conventional ice cream freezer is suitable for dynamic cooling of the mix. In this connection, it is not usual to lower the temperature of ice cream mixes and other related frozen dessert products to a temper-ature less than about -5~C by use of an ice cream freezer.
In the method of the present invention, it is desirable that less than about 80 percent of the water present in the milk shake mix be frozen during passage of the milk shake mix through the freezer. Preferably, from about 55 percent to about 80 percent of the water is frozen during passage of the milk shake mix through the freeæer.
It is known that fast freezing of ice cream mixes under dynamic conditions induce the formation of small ice crystals , which is a prerequisite for a smooth texture ice cream. However, it is not the intention of the fast cooling step under dynamic conditions of the present invention to provide small ice crystals.
In fact, it is preferred that a relatively small portion of the water of the milk shake mi~ be frozen during the cooling step in the ice cream freezer. The melt down characteristics of the ice cream and the melt down characteristics of the milk shake of the present invention are totally different. Furthermore, sub-sequent freezing of the milk shake of the present invention after the intial dynamic cooling step results in a product which upon subsequent thawing has the desired characteristi~s of a conventional milk shake. There is no similarity between thawed ice cream and conventional milk shake. It is believed that the ice crystal structure of the ice cream and the frozen milk shake of the present invention are entirely different.
The use of the polyhydric freezing point depressant in the milk shake mix of the present invention permits the use of low dynamic cooling temperatures without attaining a significant freezing of the water present in the milk shake mix during the dynamic cooling step.
The following Examples illustrate various features of the present invention but are intended to in no way limit the scope of the invention which is defined in the appended claims~
A chocolate milk shake mix having the following ingre-dients at the indicated levels was prepared:
INGREDIENT WEIGHT PERCENT
Homogenized Whole Milk 72.6 Sweetened Condensed Whole Milk (Butter fat 8.5~, Non-Fat Milk Solids 20g6, Water 29.5% !
Sucrose 42%) 2.6 Cream (about 38% butterfat) 3.0 Glycerin 7.6 Dextrose 7.1 Emulsifier (Hydrated) 3.9 Water 3.5 PGMS .14 Glycerol Monostearate .18 Sodium Stearoyl-
2-lactylate .08 Stabilizers .07 Sodium alginate .o5OO
Cocoa 2.4 Vitamin-Mineral Mix .23 Malt Powder .20 Salt .16 Artificial Flavors .11 Water .10 The homogenized whole milk at a temperature of 1.7C is added to a jacketed kettle equipped with scraper blades. The milk is heated to a temperature of (46-49C) with agitation and two thirds of the dextrose is added. The cocoa is slowly added and is dispersed over a 15 minute hold period. The L~
sweetened condensed whole milk is added slowly with agita-tion and the temperature of the mixture in the kettle is allowed to rise to 54-57C. The glycerin is then added fol-lowed by addition of the cream.
In a separate jacketed, scraper equipped ke-ttle, the emulsifiers ar~ hydrated. The propylene glycol monostearate (PGMS), glycerol monostearate (GMS) and sodium stereroyl-2-lactylate are blended. The blend is slowly added to hot water (49C) in the kettle with agitation. The mixture is heated to 77C and held for 15 minutes with agitation. The emulsifier mixture is then slowly cooled with agitation to a temperature of 15-21C. After cooling, the hydrated emulsifier may be held for daily use.
An amount of the hydrated emulsifier sufficient to provide the indicated level of emulsifier is added to the batch in the kettle with agitation.
In a separate blender, one sixth of the dextrose, sodium alginate, carboxymethyl c~llulose, carrageenan and malt powder are blended. This dry blend is added to the heated (54C) batch from the kettle by means of a powder funnel system with recirculation and agitation. Recirculation is continued until the dry ingredients are completely dispersed. Thereafter, the salt is added and the temperature of the batch in the kettle is raised to (71C) with agitation. The batch is held in the kettle at 71C for 30 minutes to pasteurize the batch.
Five minutes after pasteurization is completed, vitamin-mineral mixture is added to the batch. The vitamin-mineral mixture is combined with one sixth of the dextrose which serves as a carrier and insures good dispersion~
After pasteurization, the batch is homogenized at 1,000-1,500 psig, single stage, at a minimum temperature of 150F to provide a milk shake mix. The homogenized milk shake mix is cooled to a temperature of 10-16C. A liquid mixture of the artificial flavors and water is prepared. Just prior to dynamic cooling of the milk shake mix, the liquid mixture of artificial flavors is added to the milk shake mix.
The milk shake mix is introduced into a conventional ice cream freezer at a temperature of 10C. During passage of the milk shake mix through the freezer, the temperature of the mix is reduced to -10C and air is injected into the milk shake mix at a level sufficient to provide 75 percent overrun. At the time of exiting from the dynamic cooling step about 40-60 percent of the water present in the milk shake mix is frozen.
260 ml samples of the milk shake mix is stored in a freezer at a temperature of -29C for a period of ~-2 days. At this temperature 100 percent of the water in the milk shake is fro~en.
Samples of the milk shake are removed from the freezer and stored for 30 days at -12.aoC after which they are equili-brated at 21C for 24 hours to determine phase separation (stability). Containers of the samples were opened and the ex-tent of syneresis and color separation are measured. The syneresis as determined by the extent of an aqueous layer which formed is 113 ml (43.5 percent). The samples also demonstrated a high degree of color separation. The percentage of unmelted iceas afunction of thaw-time was zero at 2 hours.
A chocolate milk shake mix was prepared in accordance with the formulation and method of Example I with the exception that PGMS was used as the sole emulsifier. The PGMS was added directly to the batch in the kettle prior to pasteurization heat treatment of the batch.
260 ml samples of the milk shake are removed from a freezer (-29C) and stored for 30 days at (-12C), after which they are equilibrated at (21C) for 24 hours to deter~ne phase separation. The syneresis as determined by the extent of free water is 99 ml (38 percent~. These samples indicated absolutely no degree of color change. The percentage of unmelted ice as a function of thaw-time was zero at 3.5 hours.