Food or edible material: processes – compositions – and products – Fermentation processes – Of farinaceous cereal or cereal material
Reexamination Certificate
1998-08-07
2001-02-20
Hendricks, Keith D. (Department: 1761)
Food or edible material: processes, compositions, and products
Fermentation processes
Of farinaceous cereal or cereal material
C426S027000, C426S062000, C426S549000, C435S254210, C435S255200
Reexamination Certificate
active
06190707
ABSTRACT:
The present invention relates to novel strains of cold-sensitive yeasts and methods of using these strains in bread-making.
Cold-sensitive mutants of
Saccharomyces cerevisiae
, i.e. mutants that are sensitive to low positive temperatures between 0 and 15° C., have been described abundantly in the scientific literature since long ago. There are various corresponding mutation sites, and many different phenotypes can be obtained. The mutation can affect growth in the cold, or fermentation in the cold, or both, this lack of growth and/or of fermentation can vary depending on the sugars present, it can be reversible or irreversible, i.e. it may or may not disappear when the temperature rises. The use of mutants in bread-making, for which fermentation of the sugars in the dough is limited in the cold but is restored at at least 20° C., has mainly been studied with the aim of obtaining dough for croissants or for Viennese bread and buns, or dough for pizza bases intended to be used by the housewife as a fresh product, i.e. after storage at refrigeration temperatures, in principle at +4° C., but in practice between 0 and +12° C. or more, in the distribution network, then until it is used. Preferably these refrigerated doughs for the housewife are ready to bake. In this connection we can cite the two European Patent Applications EP 487878 and EP 663441 and the International Patent Applications WO 93/01724 and WO 94/19955.
In the first two documents cited, documents EP 487878 and EP 663441, where much attention is paid to blocking the fermentation of maltose, nearly all of the measurements of CO
2
release at different temperatures as a function of time are effected on a maltose-containing synthetic medium, where maltose is the only fermentable sugar. The main application described is a pizza dough that can be stored at refrigerator temperatures, and which by reason of this storage is ready to bake by the housewife.
In International Patent Applications WO 93/01724 and WO 94/19955, several means are described for obtaining doughs intended for the housewife, and which can be stored for a long time at low temperature. The use of so-called its mutants (lts: low-temperature sensitive), which are available from university collection centres such as the Yeast Genetic Stock Center of the Donner Laboratory in the Department of Cellular and Molecular Biology of the University of California at Berkeley, is one of the options that has been investigated, the preferred solution apparently being to use strains that are unable to ferment glucose, but which can ferment either fructose or galactose, the sugar that is intended to be fermented being present in just the right amount to ensure the desired rise of the dough.
European Patent Application EP 667099 describes the production, and use in bread-making, of a cold-sensitive mutant obtained from a commercial strain of traditional baker's yeast for sugar-containing doughs, i.e. a slow strain that is not adapted to maltose. For the record, we can also cite patent application EP 556905 which is restricted to the description of various procedures that are likely in theory to enable cold-sensitive mutants to be obtained.
This copious literature has given rise to very few practical applications. Only two examples can be cited:
the marketing in Europe of a pizza dough that can be kept in cold storage for a long time and is ready to bake after this cold storage;
the rather limited marketing in Japan, at a very high price, of a yeast for sugar-containing doughs, whose fermentation activity is slowed down at low temperature.
It should be mentioned that production of pizza dough generally requires yeasts of low activity with respect to release of gas, the primary role of the yeast being the supply of aromas. It should be noted that the strain marketed in Japan is a slow-working strain that is not adapted to maltose, whereas the strains generally used throughout the world for the production of bread-making yeasts are maltose-adapted fast-working strains.
The invention relates to novel strains obtained by classical mutation techniques and which exhibit progress relative to the state of the art, fresh and dry bread-making yeasts obtained with these strains, and the application of these strains in various methods of bread-making or production of other bakery products, especially breads of the French type.
The invention also relates to novel strains obtained by directed mutagenesis, effected by molecular biology, consisting of reproducing, specifically in industrial strains of bread-making yeasts, or in the starting haploids that served for construction of the said industrial strains, the mutations, monogenic or not, giving the required phenotype in the strains selected after conventional mutation treatment, for example with chemical agents. One variant, according to the invention, of construction of strains whose fermentation is blocked at low temperature and is restored above 20° C. is the transformation of industrial strains of bread-making yeast with a gene selected because it has a direct or indirect action on the fermentation of sugars, and whose expression is temperature-dependent.
The invention relates in particular to a novel strain of bread-making yeast giving fresh or dry yeasts that can be described as fast-working yeasts at 30° C. on dough without addition of sugar, i.e. fresh yeasts giving at least 100 ml of CO
2
in the A
1
test in 2 hours at 30° C., preferably at least 110 ml of CO
2
and more preferably at least 150 ml. Moreover, these novel fresh and dry yeasts conform to the following ratio:
release
of
CO
2
in
48
hours
at
8
°
C
.
in
the
test
A
1
release
CO
2
in
2
hours
at
30
°
C
.
in
the
test
A
1
=
less than 45% and preferably less than 40% and even more preferably less than 30%. Preferably, these novel fresh and dry yeasts conform to the same percentages, if this ratio is measured with the A
5
test, and preferably with this A
5
test this ratio will be less than or equal to 20%.
The invention also relates to the use of novel strains obtained in deferred bakery methods for production of bread, especially bread of the French type or bread with low sugar content, i.e. with less than 5% of sugar.
A deferred bakery method is defined as any method where there is a period of more than 6 hours between kneading and baking, and generally more than 12 hours. In particular, the use of fresh or dry yeasts obtained with a cold-sensitive strain of baker's yeast represents an important advance in all processes of deferred bread-making such as the slow-rising or blocked-rising methods defined below; this use leads reliably to lumps of dough that remain ready to bake for a period of at least 4 hours, and preferably at least 8 hours, giving faultless baked products.
Finally the invention relates to novel bakery techniques, such as methods of production of leaven or the use of bulk doughs, based on the use of cold-sensitive baker's yeasts.
REFERENCES:
patent: 5399492 (1995-03-01), Gysler et al.
patent: 5480798 (1996-01-01), Gysler et al.
patent: 0 487 878 (1992-06-01), None
patent: 0 667 099 (1995-08-01), None
Colavizza Didier
Loiez Annie
Wadoux Isabelle
Henderson & Sturm LLP
Hendricks Keith D.
Lesaffre et Cie
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