NO170192B - PROCEDURE FOR INHIBITING CRYSTAL GROWTH IN FROZEN FOOD PRODUCTS - Google Patents

Description

The present invention relates to a method for inhibiting the growth of ice crystals in frozen food products. A partially delignified plant fiber, a hemicellulose B or mixtures thereof, is specifically added to foods before freezing to inhibit the growth of ice crystals in the food after it has been frozen.

Frozen food technology, and especially the fast freezing technology, has recently been very appropriate. The frozen food industry, on the other hand, has been plagued with a phenomenon caused by the growth of ice crystals present in frozen foods into large clumps, resulting in frozen food products having a granular or grainy consistency. The growth of the ice crystals draws water out of the food and can destroy the consistency and mouthfeel of the food. Overwhelming growth of ice crystals is a particular problem in foods where there is a sensitive relationship between water and the other ingredients in the food, such as ice cream, ice cream and other frozen products. Overwhelming growth of ice crystals occurs over a period of time, and is accelerated when frozen food products are subjected to freeze/thaw cycles. In the case of ice cream, the leakage of water out of the crucible and into large crystals mainly destroys the ice cream and results in a grainy, cardboard-like consistency. Ice crystal growth is not limited to the outer surface of the frozen food, but occurs throughout the frozen food.

The present invention provides a method for improving the stability of frozen foods by inhibiting ice crystal growth by reducing the excess size of the ice crystals and reducing the growth rate of the ice crystals.

The present invention therefore relates to a method for inhibiting ice crystal growth in frozen food products, e.g. ice cream, ice milk, dessert ice slices, fruit popsicles or juice popsicles, characterized in that 0.01-5, preferably 0.05-2 weight-$6, of a partially delignified plant fiber, hemicellulose B or mixtures thereof are added to the frozen food product.

Of particular interest in carrying out the present invention is that frozen products, such as ice cream, are stabilized by adding to the frozen product an ice crystal growth-inhibiting amount of one or more ice crystal growth inhibitors. The frozen products are suitable for long-term storage and can be subjected to freeze/thaw cycles with less chance of spoilage caused by ice crystal growth. Hemicellulose B is preferably used as an ice crystal growth inhibitor and especially hemicellulose B extracted from PDPF.

As used herein, "partially delignified plant fibers" and "PDPF" refer to any plant fibers that have been partially delignified. Generally, from about 30 to about 70, and preferably about 40 to 60 percent, of the lignin should be removed from the plant fiber substrate.

The term "hemicellulose B" refers herein to the hemicellulose fraction which is precipitated by ethanol from an acidified hemicellulose mixture isolated from the plant material by extraction with alkaline solutions.

The term "inhibiting ice crystal growth" refers herein to a method in which the ice crystals that have formed in the frozen foods are prevented from growing into large crystals. This term does not refer to a method of preventing the formation of ice crystals, but rather only refers to a method of inhibiting the average size of the ice crystals and their growth rate.

In carrying out the present invention, a frozen food product is composed by incorporating a partially delignified plant fiber (PDPF), a hemicellulose B or mixtures thereof, i.e., ice crystal growth inhibitors into the frozen food. The ice crystal growth inhibitor is added to the food product during manufacture to form a food product suitable for freezing. The mixing can be achieved by well-known standard mixing techniques, such as physical mixing, or by standard dry or wet mixing techniques. The crystal growth inhibitors are advantageously added to the aqueous phase or component of the food product. The order of the mixture and the addition of the ingredients is not critical when carrying out the present invention.

Partially lignified plant fibers (PDPF) can include any plant fiber in which 30 to 70, and preferably 40 to 60 percent, of the lignin has been extracted or removed. The partially delignified plant fibers are preferably conversion products of lignocellulosic substrates that have been treated with alkaline peroxide. Treatment of non-woody lignocellulosic compounds with alkaline peroxide is described in the following US patents or patent applications: US Patent 4,649,113, US Application 06/809,803 filed 12.16.85 and US Application 06/912,296, filed 9.29.86. In addition, all of the specifications of the previously referenced patents are available from the National Technical Information Service, 5285 Port Royal RD., Springfield, VA 22161.

Hemicellulose B can be obtained from any lignocellulosic plant according to known extraction methods, such as, for example, the extraction method described in Methods in Carbohydrate Chemistry, vol. 5; General Polysaccharides, 1965, Academic Press, pp. 144-145. On the other hand, it is preferred to extract hemicellulose B from lignocellulosic plants according to the methods previously described.

PDPF and hemicellulose B are provided from any lignocellulosic substrate, but preferably from non-woody lignocellulosic substrates. Suitable substrates include corn bran, corn silage, corncobs, wheat bran, pressed sugarcane, alfalfa hay, barley bran, barley hulls, oat bran, oat hulls, rice bran, sugar beet pulp, citrus pulp, citrus hulls, peanut hulls, banana peels, abelmusk silage, soybeans and esparto grass. Preferred substrates include wheat bran, corn bran, corn meal, barley bran, rice bran and wheat bran.

Existing ice crystal growth inhibitors are added to the frozen food products in amounts effective in inhibiting ice crystal growth in the frozen food product.

Present ice crystal growth inhibitors are added to any frozen food product containing water, and especially to those frozen food products subjected to freeze/thaw cycles. Typical frozen food products include ice cream, frozen products, dessert slices, fruit slices, puddings and juice slices. When these food products have been prepared with the present ice crystal growth inhibitors, they are less susceptible to spoilage caused by strong ice crystal growth.

Ice crystal growth can be inhibited in any frozen system including "regular" foods and dietetic "foods" containing strong sweeteners and/or low fat. Powerful sweeteners that can be mixed into frozen food products include aspartame, salts and complexes of aspartame, aminoacyl sugars, saccharin, sucralose, al itam, acesulfame K, thaumatin, stevioside and others. Foods with a low fat content include food products containing fat substitutes, such as sucrose polyester.

When PDPF is used as an ice crystal growth inhibitor, PDPF is preferably wet ground in a ball mill just before the fiber break-up time. Ground PDPF is then mixed into the frozen food product during the product compounding process. The ground PDPF ice crystal growth inhibitor is preferably passed through a 0.149 mm sieve; i.e. particle size less than 0.149 mm.

In a preferred embodiment of the present invention, hemicellulose B is used as an ice crystal growth inhibitor in a frozen food product. Any hemicellulose B can be used. It is preferred to use hemicellulose B extracted from PDPF as described herein, and in particular wheat bran PDPF. Hemicellulose B is preferably used in amounts of between 0.05 and 1.0 total weight # of the food product, and even more preferred is 0.25 total weight # of the food product.

The following examples illustrate the implementation of the present invention.

EXAMPLE 1

Hemicellulose B as an ice cream growth inhibitor

Hemicellulose B was extracted from partially delignified wheat bran (obtained from treatment of wheat bran according to the methods described in US 4,649,113) in a 16 hour aqueous extraction procedure at room temperature using NaOH and a pH of 13.0. The reaction mixture was continuously stirred, and after the 16-hour extraction, the supernatant was adjusted to pH 5 with acetic acid. Hemicellulose A precipitated out of the supernatant and was removed by filtration. Ethanol was added to the supernatant in an amount that provides a 70 wt% ethanol concentration, which results in the precipitation of hemicellulose B. About 11 percent by weight of partially delignified wheat bran was extracted as hemicellulose B. The hemicellulose B provided is added to the aqueous phase of the frozen food products during food preparation to inhibit ice crystal growth.

EXAMPLE 2

PDPF as an ice cream growth inhibitor

PDPF obtained from wheat bran is ground to pass through a 0.149 mm sieve. This PDPF material is added to the frozen food products to inhibit ice crystal growth. The resulting frozen food product is stable under freezing conditions. In addition, this frozen food product is stable when subjected to freeze/thaw cycles.

EXAMPLE 3

Frozen food product mixes

Below is a list of frozen food product mixtures containing an ice crystal growth inhibitor according to the present invention. They are prepared using standard food preparation techniques.

I. Ice cream

II. Pudding III. Frozen goods IV. Sugar-free, frozen dessert

<*> Mixture of mono- and diglycerides, guar gum, carboxymethyl cellulose (CMC), Carrageenan.

V. Sugar-free water ice

WE. Chocolate! milk slice without added sugar VII. Fruit slice without added sugar VIII. Fruit ice cream without added sugar IX. Fruit ice cream and ice cream without added sugar

In similar methods, PDPF and hemicellulose B, provided from the various sources described herein, are effective ice crystal growth inhibitors in frozen food products. The resulting frozen food products are more freeze-stable than frozen foods that do not contain the present ice crystal growth inhibitors.

EXAMPLE 4

Hemicellulose B as an ice crystal inhibitor

1 a product of the sorbet type

The following formulation was prepared using hemicellulose B obtained from wheat bran by the method described in the previous examples:

The resulting frozen dessert was creamy, resulting in a soft mouthfeel due to minimal ice crystal growth. A control was also prepared, which did not contain hemicellulose B. The control was ice-like with a rough feeling in the mouth.

Claims (1)

Method for inhibiting ice crystal growth in frozen food products, e.g. ice cream, ice milk, dessert ice slices, fruit popsicles or juice popsicles, characterized in that 0.01-5, preferably 0.05-2 weight-£, of a partially delignified plant fiber, hemicellulose B or mixtures thereof are added to the frozen food product.