Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process... – Enzymatic production of a protein or polypeptide
Patent
1992-10-20
1995-06-27
Naff, David M.
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
Enzymatic production of a protein or polypeptide
426 49, 426 56, 426650, 426656, 426657, 435267, C12P 2100, C07G 1700, A23L 1221, A23J 100
Patent
active
054279216
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for producing yeast extracts containing a proportion of hydrolysed non-yeast protein and the product of these processes.
Yeast extract is a nutritious palatable paste prepared from brewer's or baker's yeast by autolysis. This comprises the self-digestion of the yeast cells principally through yeast proteolytic enzyme activity so that proteinaceous soluble solids can be recovered. These soluble solids are typically further concentrated to form a paste.
In order to maximise the yield of soluble solids for commercial production, yeast, such as brewer's yeast is conventionally diluted with water to a specified solids content before autolysis. Salt may also be added to the slurry to aid cell membrane rupture and exercise a degree of control over microbial flora. The yeast proteins are solubilized and hydrolysed during the autolysis process. Although the natural yeast enzymes may be sufficient to carry out the hydrolysis, the activity of the yeast proteolytic system can be augmented, if desired, by the addition of exogenous enzymes.
On completion of the autolytic process, the soluble fraction is harvested and concentrated by a series of evaporation steps to give a typical standard yeast extract. The autolytic process typically solubilises around 62% of the starting total yeast solids and yields a maximum of 80% of the yeast's original protein content.
The present invention is based on the surprising discovery that the yield of such an autolytic process can be improved and that, additionally, a range of novel flavors can be obtained by carrying out the hydrolysis on a mixture of yeast and non-yeast protein.
According to the present invention there is provided a method of making yeast extracts comprising subjecting an aqueous slurry containing a mixture of yeast protein and non-yeast protein to an at least partial enzymatic hydrolysis to form a water-soluble fraction and recovering the water-soluble fraction.
According to a preferred embodiment, the present invention comprises the steps of: a non-yeast protein source to the slurry to form a mixture: 65.degree. C. for from 6 to 20 hours;
The yeast protein is in the form of yeast cells and particularly preferred sources are brewer's yeast and baker's yeast. These may be used in any form (such as dried yeast) but a particularly preferred source is brewer's yeast in the form of a slurry obtained directly from the brewer.
Appropriate sources of non-yeast protein for use in the process of the invention may include sources of cereal proteins and sources of animal proteins. Preferred non-yeast protein sources include maize gluten, corn gluten, wheat gluten, soya bean meal, whey solids, soup stock and dried red blood. Additional protein sources such as oat bran and wheat bran may also be added. These non-yeast protein sources may be used directly in the hydrolysis mixture or may be further treated, by purification or protein extraction for example, before being used in the autolysis mixture. The non-yeast protein sources may be used individually or as mixtures of two or more such sources. Particularly preferred non-yeast protein sources for use in the present invention are soya bean meal and whey solids which have been found to impart surprisingly good flavors to the yeast extract products and also to be the most cost effective alternatives.
The process of the present invention results in a yield of soluble solids which is greater than can be accounted for by the yeast alone. This appears to be due to the ability of the natural proteolytic enzymes contained in the yeast to act on the non-yeast protein to solubilise and hydrolyse it. Not only does the use of added non-yeast protein enable the yield of normal autolysis procedures to be increased but the process may also be used to maintain production levels when other yeast sources are in short supply by using the non-yeast protein as a yeast protein extender. This is particularly useful when the source of yeast is brewer's yeast and this is in short supply.
By selecting appropriate
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Anderson Deborah A. G.
Hobson John C.
CPC International Inc.
Naff David M.
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