WO2006009428A1

WO2006009428A1 - Use of yeast cell walls for improving the crispness of fried potato products

Info

Publication number: WO2006009428A1
Application number: PCT/NL2005/000498
Authority: WO
Inventors: Stefan Hendrikus Schaafsma; Peter Philip Lankhorst; Peter BUSINK
Original assignee: Dsm Ip Assets B.V.
Priority date: 2004-07-16
Filing date: 2005-07-11
Publication date: 2006-01-26
Also published as: EP1786276A1

Abstract

The present invention relates to the use of yeast cell walls for improving the crispness of fried potato products such as French fries or potato chips. In order to increase crispness, the potato product is coated with yeast cell walls. This may be done in any manner known in the art, e.g. by spraying, dipping or any other means suitable for depositing a thin layer of coating solution onto the potato product. The results show that the crispness and texture of the crust was improved when fries were coated with yeast cell walls, in particular when a coating solution in the range of 2,5 - 10% Celltex (R) was used. Moreover, the taste of coated fries was less floury than the control group without the coating.

Description

USE OF YEAST CELL WALLS FOR IMPROVING THE CRISPNESS OF FRIED POTATO PRODUCTS

The present invention relates to a process for improving the crispness of fried potato products such as French fries or potato chips.

Previous attempts have been made to improve textural quality of finished French fried potatoes. One solution is the selection of particular raw potatoes with high specific gravity. While successful, this approach is quite expensive since it increases raw material and processing costs substantially and limits the effective processing season.

A second well-known method is to coat the potato pieces before initial frying. It has been proposed to coat potato pieces with a gelatinized starch solution of either a modified or unmodified starch. This practice has never proven too effective, however, and the finished product lacks uniformity. In addition, this method introduces additional cumbersome process steps since gelatinized starch solutions are difficult to handle. Other methods for preparing and applying coatings to the outer surfaces of frozen potato products are also well known in the art. Murray et al. in U.S. Pat. No. 3,597,227 disclose a process in which raw potato strips are coated in a hot aqueous solution of modified gelatinized amylose derived from corn or potato starch. The process is said to produce a finished product that has superior strength and rigidity.

Van Patten et al., U.S. Pat. No. 3,751,268 disclose the coating of blanched potato pieces with an ungelatinized unmodified high amylose starch having an amylose content of at least 50 percent. The coated potato strips are deep fat fried during which the starch in the coating is gelatinized. Lenchin et al., WO 85/01188 disclose batters comprising the flour of high amylose corn hybrids for producing microwaveable pre-fried foodstuffs. The use of flours of high amylose corn hybrids is said to provide pre-fried foodstuffs with improved crispness after microwave cooking which otherwise tends to make such products soggy. Sloan et al., U.S. Pat. Nos. 5,059,435 and 5,141 ,759 disclose a process for preparing frozen coated potatoes wherein raw potatoes are washed, cut, blanched and partially dehydrated. The cut potatoes are then coated with an aqueous starch slurry comprising 15 to 35% by weight modified ungelatinized potato starch, 2 to 10% by weight modified ungelatinized corn starch, 2 to 10% by weight rice flour and other optional ingredients. The coated potato strips are par fried in oil and then frozen. The frozen strips are prepared for consumption by either finish frying in hot oil, or heating in an oven. The starch coating is said to enhance the holding quality of the ready to consume product and to improve the acceptability of the finished product.by increasing the crispness of the outer surface, and helping to maintain the tenderness of the interior of the cut potato. In particular, the potato starch and cornstarch are said to contribute crispness to the coating, and because they are not gelatinized prior to the par frying step they decrease clumping of the strips during processing.

Also of interest are the disclosures of Calder et al., U.S. Pat. No. 5,302,410 and Brusacker et al., U.S. Pat. No. 5,393,552, which relate to the use of hydrolyzed starch products such as dextrins and maltodextrins as components of aqueous enrobing slurries. Specifically, the patents disclose contacting blanched potato strips with an aqueous solution which contains from 3% to 12% by weight of a hydrolyzed starch product characterized by a DE (Dextrose Equivalent) less than 20 such as a DE of less than 12 and preferably from about 2 to 10.

Despite the exhaustive quantity of research devoted to improving coatings for potato products, there remains a desire in the art to develop coating formulations that are inexpensive, readily applied and provide improved organoleptic qualities to the finished product, such as French fries.

It has now surprisingly been found that potato products have a higher crispness after finish frying when they are coated with yeast cell walls. Accordingly, the present invention relates to the use of yeast cell walls for improving the crispness of fried potato products such as French fries or potato chips. In brief: the potato product is coated with yeast cell walls in any manner known in the art, e.g. by spraying, dipping or any other means suitable for depositing a thin layer of coating solution onto the potato product. The results show that the crispness and texture of the crust was improved when fries were coated with yeast cell walls, in particular when a coating solution in the range of 2,5 - 10% Celltex ^(R) was used. Moreover, the taste of coated fries was less floury than the control group without the coating.

Yeast cell walls are herein defined as a fraction from whole yeast cells that predominantly contains the solid layer surrounding the yeast cell. Yeast cell walls are typically obtained from comminuted yeast. Yeast cell walls are commercially available, mostly in a dried form, and may then also be referred to as dried cell walls of yeast or bakers yeast glycan.

Yeast cell walls may typically be composed of long chain carbohydrates, typically not less than 85% on a dry solid basis. The carbohydrate may be composed of glycan and mannan units in an approximately 2:1 ratio.

Methods for obtaining yeast cell walls are well known in the art. The preparation of yeast cell walls has for instance been described by Kollar et al. in J. Biol. Chem. 272; 17762-17775 and in J. Biol. Chem. 270; 1170-1178. The procedure for obtaining yeast cell walls may optionally include a washing and pasteurization step. Yeast cell walls may also be obtained by still further modifications of the above procedures, i.e. the procedures may be modified to impart specific properties to the yeast cell walls. For instance, Japanese laid-open patent application No. 2000-44878 describes yeast cell wall fractions consisting of cell residue obtained by removing the internal soluble cell components after enzyme treatment of the yeast.

Kasai et al (Int. J. Pharm. 204; 2000, 53-59) describe a process using an acid treatment after enzyme digestion of the cell content.

EP 1375616 describes that acid-treated yeast cell wall fractions may be prepared in the form of yeast cell residue by treating the yeast with an enzyme to remove the soluble internal cell components, and treating the resulting yeast cell wall fractions with an acidic aqueous solution to then further remove the solubilized components. More specifically, the yeast cell wall fractions are treated with 0.01 to 2 N, and preferably 0.1 to 0.5 N, acid such as hydrochloric acid, sulfuric acid, or nitric acid, the resulting suspension may then be centrifuged or the like to separate the supernatant and yeast cell residue, and the yeast cell residue can be harvested to prepare the yeast cell walls. The material is also preferably heated to around 80 ⁰C during the acid treatment. The resulting yeast cell walls consist of a film that is relatively durable in physical and chemical terms, consisting of glucan, mannan, and chitin layers.

The term yeast cell walls is intended to cover the resulting insoluble components of all the above mentioned procedures including their modifications.

Yeast cell walls may also commercially be obtained from DSM Food Specialties, Delft, The Netherlands. They are traded under the name Celltex ® powder. Celltex ® powder is the cell wall fraction which is isolated from inactive specially - A -

selected primary grown yeast (Saccharomyces cerevisiae). Celltex ® is spray-dried on a MSD drier. Yeast cells can also dried by drum drying , flaking, spray granulation, flash dryers and other drying methods known to the person skilled in the art.

Yeast cell walls may be prepared in all of the above-describe ways from all kinds of yeasts. Any yeast taxonomically belonging to yeasts may be used as the starting material for preparing yeast cell walls. Examples include brewer's yeast, wine yeast, baker's yeast and torula yeast. More specific examples include Saccharomyces cerevisiae, Saccharomyces rouxii, Saccharomyces carlsbergensis, Candida utilis, Candida tropicalis, Candida lipolytica, and Candida flaveri. Such yeasts can be used alone or in combination. The use of live yeast is preferred, although yeasts in configurations other than live yeast such as dried yeast can also be used, and can, for example, be treated in the same manner as live yeast by being suspended in water or the like. The size or configuration of the yeast that is used is not particularly limited, although the configuration is preferably as close as possible to spherical, and the size preferably ranges from between 1 and 20 micrometer.

DETAILED DESRIPTION OF THE INVENTION

The invention relates to the use of yeast cell walls for improving the crispness of fried potato products. A potato product may comprise or consist of processed potatoes, such as mashed or sliced potatoes. Examples of potato products are French fries, potato chips, potato crisps, potato nuggets, potato balls, potato crochets, mashed potato products, potato shells, French fries of mashed and or compressed potatoes. Preferably the potato product is a French fry. In order to increase crispness, the potato product is coated with yeast cell walls. This may be done in any manner known in the art, e.g. by spraying, dipping or any other means suitable for depositing a thin layer of a coating onto the potato product.

For ease of handling it is preferred to apply the coating to the potato product in the form of a solution comprising yeast cell walls. For that purpose the yeast cell walls may be suspended in water or any other suitable liquid. Such liquid may also comprise additives to increase the viscosity of the solution in order to increase adhesion to the potato product. In addition the solution may also comprise additives such as pectin that decrease the absorption of fat by the potato product, thereby decreasing the fat content of the finish fried product. The viscosity of the coating solution may be increased by a number of additives known in the art, such as starch, modified starches, agar-agar, carageen, pectin, amidated pectine, Locust bean gum, Guar gum, Tragacanth, cellulose, tara gum, gellan gum, konjac gum, or modified cellulose. In the below examples Xanthan was used for this purpose.

The potato product may be blanched before coating. In particular when the potato product is French fries, this proved to be particularly advantageous for both texture and taste of the finished product.

The coated potato product may then be processed further in order to obtain the end product. This processing may be done in one or more steps. In case of French fries and similar products it is particularly advantageous to include a par frying step before final heating of the product. The invention therefore also relates to par fried potato products coated with yeast cell walls.

The term par frying in this respect encompasses a frying process wherein the product is cooked to a level where it is not yet considered suitable for consumption.

The term finish frying is used herein to describe a process wherein the product is fried until a stage where it is usually considered suitable for consumption

Finish frying of the product may occur by heating in an oven or microwave, however, oil frying resulted in particularly crispy products, in particular with French fries. The invention therefore also relates to finish fried potato products coated with yeast cell walls.

The par fried product may be stored for some time before final heating or finish frying. It may then be advantageous to cool the par fried product in order to prevent a loss of quality. When the par fried product is to be stored for a longer period of time, it may be advantageous to freeze it. The invention therefore also relates to frozen par fried potato products coated with yeast cell walls.

The potato product may be coated with yeast cell walls at any time during its processing. It is however advantageous to coat the potato product before the first frying step, in that way the adhesion of the coating to the potato product is optimal. Moreover, a good crispness of the end product is obtained in that way.

Decolorized yeast cell walls may be obtained by washing yeast cell walls, such as Celltex &, with an alkaline solution with a pH of preferably higher than 8, such as between 9 and 10. WO2004018650 also provides guidance on how to obtain decolorized yeast cell walls. Such decolorized cell walls are useful for some applications where the normal brown color of the coating is undesired. Such decolorized cell walls are also said to be odorless, thereby providing an extra advantage in those cases where the normal flavor of yeast cell walls is not desired.

The crispness of other fried products then the ones exemplified herein may also be improved using a method according to the invention. Examples of such other products are meat products coated with a layer of starch from corn or potato. When yeast cell walls are added to the traditional coatings of such products, the crispness of the finish fried product may be remarkably improved.

EXAMPLES

Example 1 : Preparation of fries

Potatoes were peeled with a knife peeler and cut into strips (10x10mm). Suitable fries were selected (about 500 g) and blanched in two steps: 2 min at 80⁰C and 20 min at 65⁰C. The blanched fries were dipped for 50 seconds in a 0.5% solution of SAPP (sodium acid pyrophosphate) at 70°C and dried to 85% of the original weight (70°C). The dried fries were dipped in 1 L coating solution (20 seconds dip, 30 seconds drain) and par fried in oil for 1 min at 180⁰C. The par fried fries were cooled for 20 min at 3°C, frozen for 20 at -30° and stored at -20°C until finish frying. Frozen fries (-20⁰C) were fried in oil for 3 min at 180⁰C.

Example 2: Coatings

The coating solutions were prepared by adding water to a commercial Celltex ® suspension (obtained from DSM Food Specialties Delft, The Netherlands) and stirring for ca. 15 minutes with a stirring device (Janke & Kunkel, IKA Labortechnik, Germany).

In the first series, a Celltex ® concentration range (0-12,5%) was tested. Also, the % uptake of Celltex ® relative to the strips (w/w) after battering was determined. In addition, the amount of Celltex ® relative to the surface of the strips was determined. Table 1

The results depicted in table 1 show that the crispness and texture of the crust was improved when the fries were coated with yeast cell walls, in particular when a coating solution in the range of 2,5 - 10% Celltex ^(R) was used. Moreover, the taste of coated fries was better, i.e. less floury then the control group without the coating. The amount of Celltex, related to surface of the strips determines the quality of the French fries. Quality is also determined by the coating thickness and uniformity of the coating. When small strips are cut more Celltex will be needed as the specific surface of the strip increases. For large cut strips less Celltex is needed. The amount of Celltex is related to the specific surface of the fries and can be recalculated by a person skilled in the art.

Example 3: Sensorial analysis

Directly before and after finish frying, a small expert panel of at least two persons evaluated the product sensorially. Before finish frying, the fries were evaluated visually (spots and discoloration). Besides spots and discoloration, also texture, crispness and taste were determined after finish frying.

Example 4: Increased viscosity coatings

The experiment of example 2 was repeated. In addition, however, the viscosity of the Celltex ^(R) preparation was increased. It was found that a higher viscosity increases the adhesion of the coating solution (batter) to the French fries. The viscosity was determined by running 105 ml of coating solution through a postumus-like funnel (diameter of the hole was 4 mm) and determining the time with a stopwatch. The viscosity of the coating solution may be increased by a number of additives known in the art, such as starch, modified starches, agar-agar, carageen, pectin, amidated pectine, Locust bean gum, Guar gum, Tragacanth, cellulose, tara gum, gellan gum, konjac gum, or modified cellulose. In this case Xanthan was used in a concentration of 0,21%, resulting in a viscosity of 19 seconds. The skilled person will be aware of the fact that a wide range of concentrations may be applied ranging for instance between 0,11 and 0,42% Xanthan, other concentrations may be appropriate as well, depending on the desired result. A skilled person will know how to determine (e.g. in an empirical way) the optimal viscosity of the coating solution. Table 2 shows that the texture of the crust as well as the crispness of the fries is improved when the viscosity of the batter is increased.

Table 2

Claims

1. Use of yeast cell walls for improving the crispness of fried potato products

2. Use according to claim 1 wherein the potato product is selected from the group consisting of French fries, potato chips, potato crisps, potato nuggets, potato balls, potato crochets, mashed potato products, potato shells, French fries of mashed and or compressed potatoes.

3. Use according to claims 1 or 2 wherein the potato product is coated before frying

4. Use according to claims 1 to 3 wherein decolorized yeast cell walls are used

5. Use according to claims 1 to 4 wherein a coating solution of 2.5 - 10%, preferably 2.5 -7.5% of yeast cell walls is used.

6. Process according to claim 5 wherein Xanthan is added to the coating solution, preferably in a concentration of 2.5%

7. Par fried or finish fried potato products coated with yeast cell walls in an amount between about 5 to about 27 gram of yeast cell walls per square meter of surface area of potato product.

8. Potato products according to claim 7 wherein the potato product is selected from the group consisting of French fries, potato chips, potato crisps, potato nuggets, potato balls, potato crochets, mashed potato products, potato shells,

French fries of mashed and or compressed potatoes.

9. Potato products according to claims 7 or 8 wherein the potato product is coated before frying

10. Potato products according to claims 7 to 9 coated with decolorized yeast cell walls.

11. Potato products according to claims 7 to 10 in a frozen form.