IE60891B1 - Process for the flavouring of foodstuffs by treatment with yeast, and foodstuffs obtained - Google Patents

Abstract

A process for the flavouring, by yeast treatment, of foodstuffs especially based on vegetable raw materials having little or no flavour, or of compositions based on such materials, in which the said foodstuffs are treated with a yeast culture or an acellular extract of the said yeasts, these yeasts displaying a low esterase activity. It also relates to foodstuffs obtained via this process. <IMAGE>

Description

The present invention relates to a process for the flavouring of foodstuffs by treatment with yeast, f especially foodstuffs based on vegetable raw materials, as well as the application of this process to improving [ the flavour of preparations based on fruits and vegetables.

Flavouring is understood to mean the regeneration and/or enhancement of a flavour profile. This expression embraces the appearance of new flavours as well as the disappearance of certain compounds with an unpleasant smell, such as furfural. This definition applies to the whole of the text of the following description and to the claims.

The development of techniques in the agrifoodstuffs industry has resulted for many years in a very high consumption of preparations based on fruits, such as fruit juices, concentrates, compotes, etc.

These products are prepared in such a way that they can be kept for a few weeks, or even a few months, in their packaging.

To obtain a long-life product, it is necessary to subject it to a heat treatment such as sterilization or pasteurization. However, in numerous cases, this virtually obligatory step is accompanied by the loss of part of the initial flavour of the raw materials.

On the other hand, some preparations have little natural flavour and are consequently rather uninteresting for the consumer, who is actually very fond of foods having the flavour of fresh fruits.

Finally, the pasteurization of fruit purees often leads to the appearance of furfural, which has an r unpleasant flavour.

The object of the present invention is to over- * come the above-mentioned disadvantages by proposing a process for the flavouring of foodstuffs by treatment with yeast, especially foodstuffs based on vegetable materials, as well as the application of this process to improving the flavour of preparations based on fruits and vegetables.

FR-A-511967 Discloses a process using alcoholic yeasts co improve the delicacy of the flavours of some fruit and vegetables but discloses neither the specific choice of yeast nor their esterase activities.

Cellular and Molecular Biology, 26 (1980), pages 147.154 discloses che analysis of esterase activity in che baker yeast.

More particularly, the invention relates to a process for the flavouring of foodstuffs by treatment with yeast, especially foodstuffs based on vegetable raw materials which have little flavour or have been rendered flavourless, or compositions based on such materials, characterized in that the said vegetable raw materials are treated with a yeast culture or an acellular extract of the said yeasts, these yeasts having a low esterase activity.

The treatment is preferably carried out without alcoholic fermentation.

According to one characteristic of the process of the present invention, the products, especially vegetable raw materials, or the compositions are processed after heat treatment.

Vegetable raw materials are understood to mean, for example, fresh fruit purees and fruit juices, fruit concentrates, etc., and compositions are understood to mean transformed products such as syrups, drinks, etc. Finally, acellular extract refers to a yeast preparation which has been ground and from which the cell residues have been removed.

According to another characteristic of the present invention, the conversion with yeast is carried out using yeasts whose esterase activity is less than or equal to 5 jimol of p-nitrophenol/mg of cell proteins and preferably less than 2 jimol of p-nitrophenol/mg of cell proteins.

The presence of esters plays an important part in the constitution of the flavour of vegetable raw materials. Now, it has been found that the ester-forming capacity of certain species of yeasts causes the (re) generation of flavours in fruit preparations inoculated with these yeasts. The ester-forming capacity of the yeasts is associated with a low esterase ζ activity .

Although the invention is of more particular value in the treatment of products of vegetable origin, it can be used for products of different origins, such as milk products.

Within the framework of the present invention, the yeasts preferentially used are those of the genus Williopsis, Pachysolen or Candida.

The experiments which follow illustrate characteristics and advantages of the present invention and Figures la and lb illustrate the enrichment of the flavour profile of a passion fruit concentrate with a culture of a strain of Candida humicola.

EXAMPLE 1 Choosing the yeasts The strains of yeasts are selected by measuring the hydrolysis of p-nitrophenyl acetate by the yeast cells. One millilitre of reaction mixture (2 mmol/1 of p-nitrophenyl acetate in a 0.5 M phosphate buffer, pH = 6.4) is incubated for 10 min at 30°C with a quantity of cells representing 1 to 2 mg of total cell proteins (the cells originate from a standard culture in the stationary phase). The amount of p-nitrophenol produced by hydrolysis of the p-nitrophenyl acetate is determined with a spectrophotometer (Λ = 405 nm) using a range of p-nitrophenol solutions (0.01 to 0.1 ^irnol). The results „ are expressed in jimol of p-nitrophenol per mg of cell proteins. / EXAMPLE 2 Raw materials Grape, apple, peach and passion fruit concenV trates are brought to 10° Brix (a densimeter graduated in degrees Brix by weight gives, simply by reading off, the weight of pure sugar contained in 100 g of an aqueous solution at a temperature of 15°C) with water and the pH is adjusted to 3.4-3.5. The products are sterilized by filtration (0.22 nyi Millipore filter).

Strawberry, banana, pear and blackcurrant purees are prepared from 200 g of fruit ground with 50 ml of water. The preparations are then autoclaved for 20 min at 120°C.

Distillation residues of fermented pear musts are used as 1:2 dilutions with water and autoclaved for 20 min at 120°C.

EXAMPLE 3 Cultivation conditions Starting from a collection culture, a stock culture is prepared in a standard medium (3 %o yeast extract, 5 %o bactopeptone, 3 %° malt extract, 10 %° glucose) and incubated at 25°C with constant agitation (150 rpm).

The cells at the start of the stationary phase are washed with physiological salt solution and 10® cells are used to inoculate 200 ml of fruit preparation in 500 ml conical flasks provided with cotton plugs.

The cultures are agitated at 150 rpm on a gyratory agitator at 25°C. After 16 hours, the flavour conversion of the products is evaluated by sensory analysis and gas chromatography.

EXAMPLE 4 Results f Tests are performed on strains originating from public and private collections. The esterase activity of each yeast is evaluated and the flavour conversions effected are noted for each fruit preparation. The results of these tests are collated in Table I.

It is found that the yeasts whose esterase activity is less than or equal to 5 pmol of p-nitrophenol (PNP) per mg of cell proteins perform the best from the point of view of flavour. This is the case for Williopsis saturnus, Pachysolen taunophilus and Candida humicola in particular.

Table II lists other yeasts with tested esterase activities of more than 5 pmol, which do not significantly improve the flavour of the fruit preparations.

Figures la and lb illustrate the enrichment of the flavour profile of a passion fruit concentrate with a culture of a strain of Candida humicola. More precisely, Figure la represents the flavour profile of the diluted passion fruit concentrate, obtained by gas chromatography.

Figure lb represents the profile of the same diluted concentrate after treatment with a strain of Candida humicola. The reference numbers 1 to 5 correspond respectively to the appearance of the following compounds: isopentanol, isobutyric acid, furfuryl alcohol, benzyl alcohol, phenylethanol.

The flavour-improving effect is the result of reconstitution of the initial flavour lost during r sterilization by heat (fruit puree) or during production r (fruit concentrate).

An enhancement of the typical flavour of fruit is found in some preparations which have little flavour.

New fruit flavours are created which do not exist in the original product but which are capable of imparting pleasant flavours to the raw material in V question.

Finally, some compounds with an unpleasant smell, which appear during the heat treatment, disappear (for example furfural, which is reduced to the corresponding alcohol and then esterified).

TABLE I Yeast Esterase activity, peach Concentrate Puree Pear residue jimol of PNP/mg of proteins straw- berry banana black- currant grape passion fruit apple B. intermedius CBS 247 11.6 __ _ C. sorboxylosa CBS 2121 11.4 - - - - - - - - H. anomala CBS 247 10.9 - - - - - - - - Williopsis saturnus CBS 1994 2.7 RF - NF - - RF - NF W. saturnus CBS 5761 3.6 NF - NF - - RF - NF W. saturnus CBS 4610 3.2 RF - NF NF - RF - RF W. saturnus ENSIA 2.9 NF - - NF - - - - Pachysolen taunophilus CBS 4044 1.8 RF NF - RF - EF RF RF P. taunophilus CBS 4045 2.4 - NF RF EF - EF RF RF P. taunophilus A.P. James* P126-1B 1.9 EF NF EF RF NF EF EF RF Candida humicola CBS 2040 1.7 EF NF EF RF RF EF EF RF * A.P. James - National Research Council of Canada, Ottawa NF: new flavour RF: regeneration of the initial flavour EF: enhancement of the flavour -C TABLE II Yeasts Saccharomyees eerevisiae ATCC 36012 S. chevalieri ENSIA L 2010 S. bayanus CBS 429 S. diastaticus H. Tamaki ® 5305-9D Zygosaccharomyces rouxii CBS 441 Schizosaccharomyces pombe CBS 1042 Saccharomycodes ludwigii CBS 1169 Kluyveromyces lactis CBS 4372 Dekkera intermedia CBS 2796 Hansenula anomala CBS 263 H. anomala CBS 442 H. anomala CBS 1683 H. anomala. CBS 1685 H. anomala ENSIA H. anomala CRPE^-M,9 4 Brettanomyces intermedius CBS 73 B. claussenii CBS 4608 B. claussenii CBS 4461 B. lambicus CBS 5206 Candida humicola CBS 2040 C. krusei CBS 2048 C. glabrata CBS 2663 H. Tamaki Doshisha Women's College, Kyoto 602, Japan ©: Centre de Recherche Pernod-Ricard ATCC: American Type Culture Collection CBS: Centraal Bureau voor Schimmel Culture, Delft, Holland

Claims (7)

1. A process for the flavouring of foodstuffs by treatment with yeast, especially foodstuffs based on vegetable raw materials which have little flavour or have been rendered flavourless, or compositions based / on such materials, characterized in that the said products are treated with a yeast culture or an acellular extract of the said yeasts, the esterase activity of these yeasts or acellular extract being less than or equal to 5 jimol of p-nitrophenol/mg of cell proteins and preferably less than or equal to 2 jimol of p-nitrophenol/mg of cell proteins.

2. The flavouring process by treatment with yeast according to Claim 1, characterized in that, after heat treatment of the said products, especially those based on vegetable raw materials, they are subjected to the treatment with the yeast culture or acellular extract.

3. The process according to one of Claims 1 and 2, characterized in that the said yeasts are selected from the group comprising yeasts of the genera Williopsis, Pachysolen and Candida.

4. The process according to one of Claims 1 to 3, characterized in that the said yeasts are selected from the group comprising Williopsis saturnus, Pachysolen taunophilus and Candida humicola.

5. The process according to one of Claims 1 to 4, characterized in that the vegetable raw materials or the compositions are selected from the group comprising vegetable and fresh fruit juices and purees, fruit concentrates and fruit distillation residues. t il

6. A process according to Claim 1 for the flavouring of foodstuffs by treatment with yeast, substantially as hereinbefore described and exemplified.

7. Foodstuffs whenever obtained by a process claimed in a preceding claim.