Food or edible material: processes – compositions – and products – Products per se – or processes of preparing or treating... – Protein – amino acid – or yeast containing
Reexamination Certificate
1999-07-16
2001-11-06
Weier, Anthony J. (Department: 1761)
Food or edible material: processes, compositions, and products
Products per se, or processes of preparing or treating...
Protein, amino acid, or yeast containing
C426S657000, C426S583000, C530S386000, C530S366000
Reexamination Certificate
active
06312755
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method for retaining the nutritive properties of whey. Specifically, this invention relates to the treatment of whey to enrich the &agr;-lactalbumin fraction.
BACKGROUND OF THE INVENTION
Whey is the liquid component of milk. During the process of making milk into cheese, whey protein is separated from the curds. Whey is a dilute liquid containing lactose, proteins, salts, and residual fat.
Until recently, a major portion of commercially produced whey was discarded, causing major environmental pollution problems. With the advent of stricter environmental controls and regulations, whey proteins have been reexamined for their utility in the pharmaceutical, dietetic and food industries. Whey proteins have become more heavily incorporated into ice cream, bread, canned soup, infant formulas, and various other food products. Whey is also used as a livestock feed.
Whey proteins possess interesting nutritional, functional, physiological, and pharmaceutical properties. The proteins in whey are divided into two principal groups: 1) the globulin protein fraction containing mainly &bgr;-lactoglobulin (&bgr;-lg) and immunoglobulins (Ig); and 2) the albumin fraction including &agr;-lactalbumin (&agr;-La) and serum albumin. &agr;-La typically constitutes about 40% by weight of the total proteins in human milk, while cow's milk contains only about 4-5% &agr;-La by weight of the total proteins.
Whey proteins have been used in infant formula and as a protein source in nutritional mixtures for humans and animals. Since &bgr;-lg is not a protein found in human breast-milk, it acts as an allergen to infants. It is therefore desirable for whey proteins in breast-milk substitutes to have either a low concentration of &bgr;-lg to reduce the concentration of allergen or a relatively high concentration of &agr;-La to make it more similar to human milk.
Recent methods of preparing &agr;-La enriched fractions from milk or whey have included ultrafiltration, heat precipitation, and ion exchange methods. Ultrafiltration methods use membranes which will allow only molecules up to a given size to pass through into the permeate. U.S. Pat. No. 5,008,376 to Bottomley describes a &agr;-La separation technique using ultrafiltration. Heat precipitation methods involve the application of heat to the whey at a given pH range for a time period sufficient to promote the flocculation of &agr;-La. Such heat precipitation methods are described in U.S. Pat. No. 5,4 55,331 to Pearce. Ion exchange methods involve contacting the whey with an anion or cation exchanger so as to selectively retain a protein fraction. Such a process is described in U.S. Pat. No. 5,077,067 to Thibault.
The present inventor has now determined that adjusting the pH of the whey to a more acidic level during processing, causes a change in protein conformation and improved retention of the &agr;-La during later processing. This change in conformation and improved retention provides a high concentration of &agr;-La in the protein fraction without the need for heat processing or other expensive separation processes.
Accordingly, it is a primary objective of the present invention to provide a method and means of processing whey to obtain a protein fraction having a high concentration of &agr;-lactalbumin.
It is a further objective of the present invention to provide a method and means of processing whey to obtain a protein fraction having a low concentration of &bgr;-lactoglobulin.
It is yet a further objective of the present invention to provide a method and means of processing whey which does not necessitate the application of high temperatures.
It is still a further objective of the present invention to provide a method and means of processing whey to achieve a high concentration of &agr;-La in the protein fraction which is convenient and economical to use.
The method and means of accomplishing each of the above objectives as well as others will become apparent from the detailed description of the invention which follows hereafter.
SUMMARY OF THE INVENTION
The invention describes a method of processing whey to obtain a filtrate or precipitate having a high concentration of &agr;-lactalbumin. The method involves the addition of an acid during the processing method to lower the pH of the whey to less than 4.0, with a preferred pH range being from about 3.3-3.8. The pH adjustment results in an enriched &agr;-lactalbumin fraction after further processing. This pH adjustment process may be accommodated to membrane filtration and precipitation methods.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention relates to a method and means for processing whey to obtain a protein fraction having an increased concentration of &agr;-lactalbumin (&agr;-La). The invention consists of the addition of an acid during the whey processing steps to obtain a pH of 4.0 or less. &agr;-La contains 1 mol of bound calcium per mol of protein. Hiraoka et al. (1980), &agr;-lactalbumin: A calcium metalloprotein. Biochem. Biophys. Res. Comm. 95:1098-1104. This atom of calcium stabilizes the tertiary structure of the protein. It has been found that the binding of calcium to the &agr;-La molecule is pH dependent, especially below pH 5. Eraumaud et al. (1995): Thermal Isoelectric Precipitation of &agr;-Lactalbumin from a Whey Protein Concentrate: Influence of Protein-Calcium Complexation. Biotech. and Bioengin. 47:121-130. At pH 1.7, &agr;-La does not bind calcium any longer. Id.
The present inventor has now unexpectedly discovered that when the pH of the &agr;-La molecule is lowered below 4.0, the molecule changes, and behaves as a much larger protein. This phenomenon in turn allows for recovery of an enriched &agr;-La fraction during membrane filtration. This pH lowering also causes the &agr;-La molecule to release calcium. Once this calcium is removed, the &agr;-La can be effectively precipitated to form a &agr;-La concentrate.
As used herein, the term “whey protein product” refers to cheese or acid casein whey, or to a whey protein concentrate obtained from the whey. The whey protein concentrate may also be a whey protein powder. If a whey protein powder is used as starting product, the powder must be brought into solution prior to Applicant's pH lowering step described below.
Applicant's process involves the treatment of whey protein concentrate to further concentrate the &agr;-La proteins using either a precipitation or membrane filtration process. The whey protein concentrate starting product may be prepared in any conventional way. For example, the whey protein concentrate may be obtained from skimmed and/or clarified whey. The whey may be concentrated and/or desalted by common means, e.g. by ultrafiltration and/or diafiltration.
Whey is typically obtained during the cheese making or casein process as a result of whey separation and clarification from casein. The whey produced from cheese-making is generally referred to as “sweet whey” while whey from cottage cheese sources and acid casein is referred to as “acid whey”. The whey source is preferably bovine, however the milk source may be from any mammal, including goats, sheep, buffalo, water buffalo, yak, rabbit, human, llama, and mouse.
The whey is preferably pasteurized, although it does not have to be pasteurized to be processed in accordance with this invention. Such pasteurization conditions are well known by persons skilled in the art.
In the filtration process, the whey is first concentrated through ultrafiltration using a 100-100K molecular weight cut-off membrane (MWCO). The portion which passes through the membrane is known as the ultrafiltrate or permeate, while the larger molecules that are retained are known as the retentate. The permeate is processed in accordance with this invention, while the retentate may be dried as whey protein concentrate (WPC). Ultrafiltration of the whey may be performed using any of the ultrafilter housings and membranes known in the art, including hollow fiber or spiral membranes. While temperature is not
AMPC
Weier Anthony J.
Zarley McKee Thomte Voorhees & Sease
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