Abstract:
Processes for maintaining the stability and quality of frozen desserts during storage and transportation, including an improvement. This improvement process involves introducing a gas mixture into the dispersed phase of the frozen dessert. This gas mixture may be a low molecular weight gas mixture or a high molecular weight gas mixture. The weight gas mixture would allow the cells within the frozen dessert to remain at approximately a constant volume during elevation changes, thereby reducing or eliminating shrinkage and transportation settling.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/786,626, filed Mar. 28, 2006, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND  
       [0002]    Ice cream is, essentially, a foam consisting of air bubbles dispersed in a mixture of fat, water, and ice crystals. The air fraction is typically around 50% by volume, and this is crucial for the product to have the consistency and texture desired by customers. 
         [0003]    The term “overrun”, is used to indicate how much air a particular ice cream contains. It is basically the ratio of the volume of the ice cream, less the volume of the liquid ice cream mix, divided by the volume of the liquid ice cream mix. So, if 50% of the volume of the ice cream is air, one would say that it had a 100% overrun. 
         [0004]    U.S. federal standards limit the amount of air by specifying that a liter of ice cream must weigh at least 0.54 kilograms. U.S. ice creams typically do not contain over 100% overrun. Regular, to premium ice cream, generally has 80-100% overrun, and super premium ice cream often has 20%-50% overrun. 
         [0005]    While recognizing that this large percentage of air must be incorporated into the final ice cream product, the main aim of ice cream manufacturing is to incorporate the smallest sizes and largest numbers of air bubbles, ice crystals, and fat globules into an aqueous phase. 
         [0006]    However, these colloidal components are inherently unstable, which leads to problem with maintaining the stability of ice cream structure, subsequent to manufacture. 
         [0007]    In recent times, the stability of air cells within the ice cream product during storage and transportation, has been studied extensively by researchers. Sofjan and Hartel investigated the effect of overrun on air cell stability, and demonstrated that higher overrun led to slightly more stable air cells during storage. On the other hand, Chang and Hartel, as explained in their various publications, have studied the effects of operating conditions and formulation, as well as the type, level of emulsifier, and stabilizer on the development of air cells during storage and hardening of dairy foams. 
         [0008]    Commercially, different stabilizers, such as alginates, guar, locus bean, xanthan, carrageenan, and chemically modified cellulose gums (carboxymethylcellulose, CMC) are being used in combination. It has been found that this provides a more stable emulsion and helps prevent air bubble collapse/shrinkage during storage or transportation. Emulsifiers, such as a blend of propylene glycol monostearate, sorbitan tristearate, and unsaturated monoglycerides, EDTA, proteose peptone whey fraction, a mix of mono- and diglycerides (MDG), alone, or in combination with polysorbates, as well as polyglycerols and lecithin (or egg yolk), have also been used. These tend to establish and maintain a more stable structure around the air-cell walls. The incorporation of surfactants, such as Tween 60, has been shown to be effective in stabilizing air cells in ice creams. 
         [0009]    However, despite these efforts, the problem of degradation of frozen desserts during the transportation or storage, due to pressure variations, owing to altitude changes still exists. Since trapped air bubbles (cells) form a significant portion of the total product volume, change in volume of trapped air bubbles, due to pressure variations, may lead to lids popping and leakage when shipped to high altitudes. On the other hand, product shrinkage occurs when shipped to low altitudes. 
         [0010]    While ice cream has been discussed in detail, related issues are also found with the stability of other frozen desserts. 
         [0011]    There is a need in the industry for a method to improve the stability and quality of frozen desserts. 
       SUMMARY  
       [0012]    The process in the present application is directed to a method to improve the stability and quality of frozen desserts. 
         [0013]    In one aspect, a method of improving the stability and quality of aerated frozen desserts is provided. This method uses either a low molecular weight gas mixture, or a high molecular weight gas mixture, or a combination of both. This gas mixture is introduced into the dispersed phase of the frozen dessert. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0014]    The pressure within the refrigerated transportation vehicle must be regulated with precision, as is indicated by the following examples:
       a) An common elevation change of 500 feet (e.g. from Chicago to Houston), will result in an atmospheric pressure difference of 0.25 psia (or 6.9 inches of water);   b) A modest elevation change of 1000 feet (e.g. from Birmingham to New Orleans), will result in an atmospheric pressure difference of 0.5 psia (or 13.8 inches of water);   c) An elevation change of 3000 feet (e.g. from Los Angeles to San Jose), will result in an atmospheric pressure difference of 1.5 psia (or 41.4 inches of water);       
 
         [0018]    d) A significant elevation difference of 4000 feet (e.g. from El Paso to Houston), will result in an atmospheric pressure difference of 2.0 psia (or 55.2 inches of water); and
       e) An even more significant, but entirely possible, elevation difference of 5000 feet (e.g. from Albuquerque to Phoenix), will only result in an atmospheric pressure difference of 2.5 psia (or 69.0 inches of water).       
 
         [0020]    Therefore, a pressure variation of about 2.5 psia or less, is the source of the problems with air cell growth and rupture that is leading to the shrinkage problems. It is clear that a pressure variation of 2.5 psia during shipping is far too extreme and must be reduced significantly. 
         [0021]    One embodiment of a proposed solution to this problem may be understood by way of an example. 
         [0022]    To start the analysis, assume that the gases involved obey the ideal gas law:
       PV=(mRT)/M   Where   P=pressure   V=total volume   m=mass   R=universal gas constant   T=temperature   M=molecular weight       
 
         [0031]    Therefore, if everything remains constant except for the pressure and the molecular weight, the volume would be: 
         [0000]      V=constant/(PM). 
         [0032]    Next, assume a maximum elevation change of 2000 feet occurs during transportation. Then, assume that the frozen dessert is manufactured at the point of lowest elevation, and that the point of highest elevation occurs during transportation. The frozen dessert will experience a decrease in pressure that will encourage the volume of the gases that have been whipped into the dessert to increase by almost 8%. 
         [0033]    Next, assume that air has a molecular weight of approximately 29 kg/kmol. In order for the volume within the air cells in the frozen dessert to remain constant between the base elevation and the highest elevation, a gas with a mean molecular weight of (1.08)×(29)=31.3 kg/mol, would be required. This gas may be, for example, 47% carbon dioxide and 53% neon. This gas may also be, for example, 42% nitrogen and 58% nitrous oxide. 
         [0034]    Then, assume a maximum elevation change of 3000 feet occurs during transportation. Also, assume that the frozen dessert is manufactured at the point of highest elevation, and that the point of lowest elevation occurs during transportation. The frozen dessert will experience a decrease in pressure that will encourage the volume of the gases that have been whipped into the dessert, to decrease by almost 11%. 
         [0035]    In this part of the example, in order for the volume within the air cells in the frozen dessert to remain constant between the base elevation and the highest elevation, a gas with a mean molecular weight of (0.89)×(29)=25.8 kg/mol, would be required. This gas may be, for example, 24% carbon dioxide and 76% neon. This gas may also be, for example, 30% nitrogen and 70% nitrous oxide. 
         [0036]    Such an embodiment would allow for the maintenance of the aerated cell volume within the frozen dessert during the gradual ascents and descents that would be encountered during the transportation of the frozen desserts. 
         [0037]    The low molecular weight gas mixture may be a mixture of any gases that has a mean molecular weight that is lower than that of air (i.e., 29 kg/kmol). The low molecular weight gas mixture may comprise one or more gases selected from the group consisting of air, helium, or mixtures thereof. 
         [0038]    The high molecular weight gas mixture may be a mixture of any gases that has a mean molecular weight that is higher than that of air (i.e., 29 kg/kmol). The high molecular weight gas mixture may comprise one or more gases selected from the group consisting of air, carbon dioxide, nitrous oxide, argon, krypton, xenon, neon, or mixtures thereof. 
         [0039]    The gas mixture may be a mixture of both, a low molecular weight gas mixture, and a high molecular weight gas mixture, as required by the type of frozen dessert. 
         [0040]    In one embodiment, the gas mixture may be injected into the frozen dessert, either in the premix state, or in a separate state. The premix state means that gases with different molecular weights are mixed well before injecting into the process. Separate state means that gases with different molecular weights are injected into the process separately. 
         [0041]    In one embodiment, the gas mixture is injected into the frozen dessert in a continuous motion, or in constant intervals. In one embodiment, the gas mixture is injected into the frozen dessert in batches. 
         [0042]    The gas mixture may be introduced into the frozen dessert by any means known to the skilled artisan. Examples include, but are not limited to, venturi introduction, sparging, membrane diffusion, and through ambient mixing. 
         [0043]    The flow rate of the gas depends on the load of frozen desserts, and may range from a few ml/min to several liters /min. These frozen desserts may be of any type suitable for application of this method. Examples include, but are not limited to ice cream, ice milk, sorbet, frozen yogurt, frappe, frozen treats on sticks, parfait, sherbet, and water ice. 
         [0044]    Illustrative embodiments have been described above. While the process in the present application is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings, and have been herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the process in the present application to the particular forms disclosed, but on the contrary, the process in the present application is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the process in the present application, as defined by the appended claims. 
         [0045]    It will, of course, be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer&#39;s specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but, would nevertheless, be a routine undertaking for those of ordinary skill in the art, having the benefit of this disclosure.