BACKGROUND OF THE INVENΗON

(a) Field of the Invention

This invention relates to fluid milk in which a major amount of the lactose present therein has been hydrolyzed, to lactose-containing milk ingredients subjected to the same or similar hydrolysis process and to products derived therefrom having improved taste and suppressed sweetness. More specifically, this invention relates to fluid milk and other milk products which incorporate 2-(4-methoxyphenoxy)propanoic acid or a physiologically acceptable salt thereof in combination with potassium chloride to improve their taste and overall quality and to counteract the increased sweetness resulting from lactose hydrolysis.

(b) Information Disclosure Statement It is generally known that milk and milk products contain high percentages of lactose. For example, the lactose content of regular homogenized pasteurized milk (3.5% butter- fat) is 4.9%, of lowfat milk (2% butterfat) is 6.0%, and of fluid skim milk is 5.1%. It is well known to those familiar with the state-of- the-art, that there exists a significant population which cannot totally digest lactose. This population is generally referred to in the professional literature as lactose intolerant. The esti¬ mated number of individuals exhibiting lactose malabsorption in the USA is between 28 and 75 million. The incidence in certain population sub-groups is significantly higher than others. For example, it is estimated that lactose intolerance in American blacks may be over 60%, whereas the incidence in American whites is less than 25%.

It is generally believed that individuals suffering from lactose intolerance have lactase deficiency. Several approaches have been undertaken by the industry to alleviate this problem. Generally, these approaches may be classified into two categories:

( 1 ) Providing to the lactose intolerant individual an enzyme preparation which contains a stabilized form of lactase. This preparation is ingested within a prescribed time period from the ingestion of the lactose containing products.

(2) Hydrolyzing the lactose using lactase enzymes prior to its ingestion. For example, lactase enzymes are added to fluid milk and sufficient time is allowed to assure the hydrolysis of the lactose into glucose and galactose. Lactase is a trivial name for the β-galactosidases which catalyze the hydrolysis of lactose to its component saccharides, glucose and galactose. Sources of lactase, including commercial sources, are described in the literature. See, for example, R.R. Mahoney, Developments in Dairy Chemistry, Chapter 3, Edited by P.F. Fox, Elsevier Applied Science Publishers, 1985. Lactase enzymes used in processing dairy foods are derived from the yeasts Kluyveromyces fragilis. Kluyveromyces lactis and Candida pseudotropicalis. Lactase enzymes are available both in liquid form, e.g., as solutions in water/glycerin, or in powder form. The activity of these enzymes is based on neutral lactase units (NLU) as determined by assay and falls in the range of from approximately 1000 to 5000 NLU/gram. It requires one gallon of 1000 NLU/gram activity product to convert 1000 gallons of milk to a 70% lactose hydrolysis level in twenty-four hours at 40°F.

Conversely, it requires 1/5 of a gallon of 5000 NLU/gram activity product to accomplish 70% lactose hydrolysis in twenty-four hours at 40°F.

The literature describes several methods for hydrolyzing lactose with lactase enzyme (see R.R. Mahoney, supra'). The most widely used method today involves the addition of lactase enzymes and incubation at 40°F for the necessary time to achieve at least 70% lactose hydrolysis. The major disadvantage of this method is the cost of the enzyme. Another problem associated with this process is the inability to control closely the end point of the hydrolysis. This is because of the time required to inactivate the enzyme in a whole batch of milk in a commercial dairy. To overcome these problems a continuous process using immobilized enzymes was proposed. However, this process is not commercially feasible for the hydrolysis of milk at this time. Another method, described in U.S. Patent 5,071,763 to Somkuti and Steinberg, involves the use of a mutant strain of Streptococcus thermophilus having a defective lactose transport system which produces β - galactosidase.

Since glucose and galactose, the products of lactose hydrolysis, are sweeter than lactose, lactose-hydrolyzed milk, when tasted, is sweeter than regular milk. This detracts signif¬ icantly from its consumer acceptance.

U.S. Patent 5,045,336 issued September 3, 1991 to M.G. Lindley and E.B. Rathbone describes a method of reducing the sweetness of an ingestible product containing a sweetening sugar or sugar alcohol by incorporating therein from about

0.0001 to 0.1 % by weight of at least one of a series of certain aromatic carboxylic acids or their salts. Included among aromatic carboxylic acids specifically disclosed is (±)-2 -p- methoxyphenoxypropionic acid. Lactose-hydrolyzed milk is not among the food products disclosed.

SUMMARY OF THE INVENTION

The hydrolysis of lactose present in milk and milk products produces a product which is not as acceptable to the consumer as its non-hydrolyzed counterpart. This reduction in consumer acceptance is due in part to increased sweetness and in part due to a modification in the total flavor profile of the milk and milk products. Thus, it is evident that a need exists for more acceptable lactose-hydrolyzed milk and milk products. In our copending U.S. patent applications, Serial No.

07/842,716 and Serial No. 07/842,868, both filed February 27,

1992, there is described a lactose-hydrolyzed fluid milk whose perceived excessive sweetness, resulting from glucose and galactose produced by hydrolysis of lactose normally present in the milk, is reduced and whose overall quality is improved by incorporating therein in specified amounts either potassium chloride or 2-(4-methoxyphenoxy)propanoic acid or a salt thereof.

It has now been found that the incorporation in lactose-hydrolyzed milk of both potassium chloride and 2-(4- methoxyphenoxy)propanoic acid, each within a critical range of concentrations, suppresses excessive sweetness and improves the overall quality of the lactose-hydrolyzed milk thereby improving its consumer acceptability. Moreover, it was unexpectedly discovered that the combination of potassium chloride and 2-(4-methoxyphenoxy)propanoic acid acted synergistically to suppress the perceived excessive sweetness of lactose-hydrolyzed milk.

Thus the invention provides a lactose-hydrolyzed fluid milk comprising fluid milk, the normal lactose content of which has been reduced by at least about 70% by lactase hydrolysis, having incorporated therein from about 0.5 to about 5 ppm of 2-(4-methoxyphenoxy)propanoic acid or a

physiologically acceptable salt thereof and from about 0.01 to 0.06% by weight of potassium chloride.

The invention further provides a method of suppressing perceived excess sweetness of lactose-hydrolyzed fluid milk the normal lactose content of which has been reduced by at least about 70% by lactase hydrolysis which comprises incorporating in the milk from about 0.5 to 5 ppm of 2-(4-methoxyphenoxy)propanoic acid or a physiologically acceptable salt thereof and from about 0.01 to about 0.06% by weight of potassium chloride.

The invention also provides a process for modifying a lactose-hydrolyzed fluid milk, the normal lactose content of which has been reduced by at least about 70% by lactase hydrolysis, in order to suppress perceived excess sweetness resulting from glucose and galactose produced by the lactose hydrolysis, which comprises incorporating into the lactose- hydrolyzed fluid milk from about 0.5 to about 5 ppm of 2-(4- methoxyphenoxy)propanoic acid or a physiologically acceptable salt thereof and from about 0.01 to about 0.06% by weight of potassium chloride.

The invention also provides a dairy product derived from the lactose-hydrolyzed fluid milk described above.

DETAILED DESCRIPTION INCLUSIVE OF PREFERRED EMBODIMENTS As used herein the term "normal lactose content" refers to the amount of lactose inherently present in milk as obtained from the cow; and the term "lactose-hydrolyzed milk" refers to dairy milk the normal lactose content of which has been reduced to at least about 70% by the hydrolysis of the lactose by lactase enzyme, unless otherwise specifically indi¬ cated, and includes whole milk, lowfat milk (e.g., 1-2% butterfat content) and nonfat milk.

The compound 2-(4-methoxyphenoxy)propanoic acid (hereafter 2-MPPA) and salts thereof are known. For the purpose of this invention, the salts of 2-MPPA should be physiologically acceptable salts such as, for example, the alkali metal, alkaline earth metal or ammonium salts, particularly the sodium, potassium and calcium salts. The sodium salt of 2- MPPA is commercially available under the tradename Lactisole (Amstar Sugar Corporation).

The concentration of 2-MPPA or physiologically acceptable salt thereof to be incorporated in the lactose- hydrolyzed milk is in the range of from about 0.5 to about 5 ppm, preferably from about 0.5 to about 3 ppm, and most preferably from about 1 to about 3 ppm.

The concentration of potassium chloride to be incorporated in the lactose-hydrolyzed milk is in the range of from about 0.01 percent by weight to about 0.06 percent by weight, and preferably from about 0.02 to about 0.05 percent by weight.

The ratio by weight of 2-MPPA to potassium chloride preferably is from about 1:300 to about 1:500, and most preferably about 1 :400.

The combined amount of 2-MPPA or salt thereof and potassium chloride in the lactose-hydrolyzed milk prefer¬ ably is from about 300 ppm to about 500 ppm, and most preferably about 400 ppm.

The 2-MPPA or salt thereof and potassium chloride can be added to the milk at any stage in its processing for consumption. Thus they can be added prior to or during the incubation of the milk with lactase or subsequent thereto. In the latter case, they can be added at the dairy where the milk is processed or after purchase by the consumer. When added by the consumer, they can be in any convenient form, e.g., in liquid or tablet form. For example, there currently is commer¬ cially available to the consumer a lactase preparation in liquid

form for addition to milk which has not been subjected to lactase treatment in order to reduce its lactose content. Such preparation could additionally have incorporated therein a blend of 2-MPPA or salt thereof and potassium chloride in an amount which will provide the concentration required in the milk in accordance with the invention.

The 2-MPPA/KC1 blend, when added to the milk during processing, can be incorporated by any standard proce¬ dure. For example, it can conveniently be incorporated by sprinkling the appropriate amount into the milk and gently agitating the milk until it is dissolved.

The invention is illustrated by the following exam¬ ples without, however, being limited thereto. The 2-MPPA sodium salt used in those examples was the commercial product Lactisole.

A test was conducted to evaluate the relative sweetness and overall quality of two commercially available skim milks, one regular, i.e., not lactose-hydrolyzed, and the other lactose-hydrolyzed. The degree of lactose hydrolysis was determined using a cryoscope and confirmed by HPLC and found to be 80%. The two skim milks were evaluated using an expert panel consisting of individuals selected for their taste acuity and trained in flavor profiling techniques. In this test the expert panel consisted of seven individuals and the test was carried out two times for a total of fourteen observations.

All samples submitted to the expert panel were coded. The skim milks were evaluated for the following attributes: Sweet - on a scale of 0 (none) to 8 (very sweet) Bitter - on a scale of 0 (none) to 8 (very bitter)

Salt - on a scale of 0 (none) to 8 (very salty)

Sour - on a scale of 0 (none) to 8 (very sour)

Overall quality - on a scale of 0 (dislike extremely) to 8 (like extremely)

The results of the expert panel's evaluation, expressed as a mean of the scores, are summarized below where A represents the regular skim milk and B represents the lactose-hydrolyzed skim milk.

A t t r i b u t e A B

Sweet 1.0 3.5*

Sour 0.5 1 .0

Salty 0 0

Bitter 0 0.1

Overall quality 6.4 3.0*

^♦ Significantly different from control at the 99% confidence level

These results clearly show that the lactose- hydrolyzed skim milk (B) is sweeter and less acceptable than the regular skim milk (A).

Example 1 Lowfat milk (1% butterfat) was processed at a UHT (ultrahigh temperature) plant facility as follows:

To pasteurized lowfat milk, lactase enzyme having an activity of 955 NLU/g was added to provide a concentration of 0.02% enzyme. The lowfat milk containing the enzyme then was incubated in a refrigerator at 40°F. The temperature of the milk was measured at 42°F ± 2°F. The degree of hydrolysis was determined using a cryoscope. To 70% lactose-hydrolyzed milk so prepared, there was added 0.05% of KCl and 2 ppm of 2-MPPA sodium salt. This product was evaluated by the expert taste panel and the results are summarized below:

lactose hydrolyzed

+ 2 ppm 2-MPPA

Control (no lactose Control (lactose sodium salt and

Attribute hvd rol yi sis) hydrolvsis) 0.05% KCl

Sweet 1.5 3.0 1.4*

Sour 0.5 0 0.8

Salty 0 0 0. 1

Bitter 0 0 0.3

Dairy flavor 3.8 4.2 3.6

% lactose 67.0 72.0 hydrolysi s

Overall quality 6.2 4.0 5.6*

^■ "Significantly different from lactose-hydrolyzed control at 95% confidence level and not significantly different from lowfat control

These results show that the combination of 2-MPPA sodium salt and KCl is highly effective. Since the 2-MPPA sodium salt is highly expensive, this combination results in significant reduction in costs.

Example 2

Skim milk was hydrolyzed using lactase enzymes. To one sample of hydrolyzed milk, 0.04% of KCl was added. To another sample, a combination of 0.04% of KCl and 1 ppm of 2- MPPA sodium salt was added. The samples were UHT processed and packaged. The samples were evaluated after two months of storage at 40°F by the expert taste panel. The results are summarized below:

With 0.04% KCl Control Lactose- + 1 ppm 2-MPPA

Attribute Hydrolyzed With 0.04% KCl Sodium Salt

Sweet 3.3 1.8* 1.4*

Off-flavor 1.2 1.2 0.5**

Overall quality 3.3 4.0 5.4**

*Significantly different from lactose-hydrolyzed control at 95% confidence level

**Significantly different from lactose-hydrolyzed control and lactose hydrolyzed with 0.04% KCl at the 95% confidence level

These results demonstrate the enhanced perfor¬ mance when both 2-MPPA sodium salt and KCl are used. It is important to note that the normal shelf life of these products is about 2 months during which time there is an increase in the level of off-flavor. The above results show that the addition of KCl and 2-MPPA sodium salt reduced the off-flavor thereby increasing the life of the product.

Example 3

Nonfat milk was hydrolyzed with a lactase enzyme so that the total lactose content was reduced by 85% of the original content. To this milk 0.04% of KCl and 1 ppm of 2-

MPPA sodium salt was added. The lactose-hydrolyzed milk was spray dried to yield lactose reduced nonfat dry milk solids.

This lactose reduced product was used in recipes and in products to replace regular nonfat milk solids.

Example 4 Nonfat, lactose-hydrolyzed (82% hydrolysis) milk was used to prepare the following samples:

Control Lactose-hydrolyzed nonfat milk with no additives

0.03 KCl Lactose-hydrolyzed nonfat milk to which 0.03% of KCl was added

0.05 KCl Lactose-hydrolyzed nonfat milk to which 0.05% of KCl was added 1 ppm 2-MPPA - Lactose-hydrolyzed nonfat milk to which 1 ppm of 2-MPPA sodium salt was added

0.03 KC1/1L Lactose-hydrolyzed nonfat milk to which 0.03% of KCl and 1 ppm of 2-MPPA sodium salt was added 0.05 KC1/1L Lactose-hydrolyzed nonfat milk to which 0.05% of KCl and 1 ppm of 2-MPPA sodium salt was added.

The milk was evaluated by the expert taste panel for sweet¬ ness intensity, off-flavor and overall quality. The results are summarized below:

ATTRIBUTES

S ample Sweetness Off-Flavor Overall Ouality

Control 3.4 0 4.1 0.03 KCl 2.9 0 4.5 0.05 KCl 2.3* 0.2 4.8* 1 ppm 2-MPPA 3.2 0 4.2 0.03 KC1/1L 1.7* * 0 5.4* * 0.05 KC1/1L 1 .9** 0 5.5 * *

^♦ Significantly different from Control

^♦♦ Significantly different from Control and from 0.03 and 0.05 KCl samples

These results demonstrate the unexpected synergistic effects of the incorporation of a combination of KCl and 2-MPPA sodium salt.