WO2008043752A2

WO2008043752A2 - Method for peeling potatoes

Info

Publication number: WO2008043752A2
Application number: PCT/EP2007/060700
Authority: WO
Inventors: Lisbeth Kalum; Hanne Vang Hendriksen
Original assignee: Novozymes A/S
Priority date: 2006-10-12
Filing date: 2007-10-09
Publication date: 2008-04-17
Also published as: WO2008043752A3

Abstract

The present invention relates to a method for peeling potatoes using a pectin degrading enzyme.

Description

METHOD FOR PEELING POTATOES

TECHNICAL FIELD

The present invention relates to a method for peeling potatoes using at least one pectin degrading enzyme.

BACKGROUND OF THE INVENTION

Industrial peeling of potatoes is usually performed by mechanical methods or by steam treatment. Since these are rather harsh treatments a considerable amount of potato material adheres to the skin and is lost by removal with the skin. When steam peeling is used peeling losses is typically in the range 25-40%. Treating intact potatoes with pectin degrading enzymes has not been effective in removing or loosening potato skin (Suutarinen et al., J. Sci. Agric. 83 (2003) 1556-1564). There is a desire for methods to facilitate skin removal from potatoes with reduced loss of potato material.

SUMMARY OF THE INVENTION

The present inventors have found that perforating the skin of potatoes and treating the potatoes with pectin degrading enzymes results in loosening of the skin and a reduced peeling loss during subsequent peeling of the potatoes. Consequently, the present invention relates to a method for peeling potatoes, comprising: a) perforating the skin of potatoes to be peeled; b) treating said potatoes with an aqueous solution of at least one pectin degrading enzyme; and c) removing the skin from said potatoes; wherein step a) is performed before or simultaneously with step b), and step b) is performed before or simultaneously with step c).

DETAILED DISCLOSURE OF THE INVENTION

Pectin degrading enzyme

Pectins are naturally occurring heteropolysaccharides composed primarily of a backbone of (1 ,4)-linked alpha-D-galacturonic acid units interrupted by (1 ,2)-linked alpha-L-rhamnose residues. The carboxyl groups of the galacturonic acid units are partly esterified by methanol. The degree of methyl-esterification of potato pectin is usually around 60%. Side chains of neutral sugars are bound to the backbone, especially at the rhamnose rich regions. Side chains are predominantly made up of galactan, arabinan and arabinogalactans, mainly attached to the C-4 position of rhamnose residues, although attachment to C-2 and C-3 positions of galacturonic acid units may also occur. Side chains may also include other sugars, such as D-glucose, D-xylose, D-mannose, L-fucose and glucuronic acid.

A pectin degrading enzyme according to the invention may be any enzyme capable of degrading pectin. Enzymes capable of degrading pectin include enzymes that are capable of hydrolysing bonds between galacturonic acid residues, such as e.g. polygalacturonase (EC 3.2.1.15), pectin lyase (EC 4.2.2.10), and pectate lyase (EC 4.2.2.2); enzymes capable of deesterification of galacturonic acid units, such as e.g. pectinesterase (EC 3.1.1.11 ) and acetylesterase (EC 3.1.1.16). Other pectin degrading enzymes include e.g. rhamnogalacturonan hydrolase (categorised in group EC 3.2.1 ), rhamnogalacturonan lyase (categorised in group EC 4.2.2), rhamnogalacturonan acetylesterase (categorised in group EC 3.1.1 ), endo-xylogalacturonan hydrolase (categorised in group EC 3.2.1 ), endo-alpha- arabinanase (EC 3.2.1.99), endo-beta-galactanase (EC 3.2.1.89), alpha-arabinofuranosidase (EC 3.2.1.55), and galactosidase (EC 3.2.1.23). In the method of the invention at least one pectin degrading enzyme is used, such as e.g one pectin degrading enzyme, or two or more pectin degrading enzymes. In the method of the invention at least one pectin degrading enzyme may be used in combination with other enzymes, e.g. cellulase (EC 3.2.1.4). EC (Enzyme Commission) numbers refer to the enzyme categorisation of the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (IUBMB).

The source of enzyme is not critical for use in the methods of the present invention. Accordingly, a pectin degrading enzyme may be obtained from any source such as a plant, microorganism, or animal. A pectin degrading enzyme is preferably obtained from a microbial source, such as a bacterium or a fungus, e.g., a filamentous fungus or yeast and may be obtained by techniques conventionally used in the art.

In the process of the invention a pectin degrading enzyme may be purified. The term "purified" as used herein covers enzyme protein free from components from the organism from which it is derived. The term "purified" also covers enzyme protein free from components from the native organism from which it is obtained, this is also termed "essentially pure" enzyme and may be particularly relevant for enzymes which are naturally occurring and which have not been modified genetically, such as by deletion, substitution or insertion of one or more amino acid residues.

Accordingly, a pectin degrading enzyme may be purified, viz. only minor amounts of other proteins being present. The expression "other proteins" relate in particular to other enzymes. The term "purified" as used herein also refers to removal of other components, particularly other proteins and most particularly other enzymes present in the cell of origin of the pectin degrading enzyme. A pectin degrading enzyme may be "substantially pure", i.e. substantially free from other components from the organism in which it is produced, e.g., a host organism for recombinantly produced enzyme. Preferably, the enzyme is at least 75% (w/w) pure, more preferably at least 80%, 85%, 90% or even at least 95% pure. In a still more preferred embodiment a pectin degrading enzyme is an at least 98% pure enzyme protein preparation.

In one embodiment of the invention potatoes are immersed in an aqueous solution of at least one purified pectin degrading enzyme.

The aqueous solution of at least one pectin degrading enzyme according to the invention may comprise additional components, e.g. salts, bases, and/or acids, e.g. to ensure proper conditions for enzyme activity, such as pH and ionic strength. pH of the solution may e.g. be between pH 3 and 9, such as between pH 4 and 8, or between pH 5 and 7.

Potato

A potato according to the present invention is a tuber of the potato plant (Solanum tuberosum) and may be of any variety. Potato varieties include, but are not limited to, Agata, Agria, Alex, Amadeus, Arno, Artana, Asparges, Asva, Atlantic, Balanse, Berber, Bintje, Burren, CaIIa, Carrera, Centennial Russet, DaIi, Danva, Desiree, Ditta, Exempla, Exquisa, Fakse, Filea, Folva, Fontane, Godiva, Green Mountain, Hamlet, Hanna, Hansa, HeIa, Imperia, Inova, Irish Cobbler "BC", Jaerla , Jutlandia, Kardal, Kardent, Karida, Karnico, Kennebec, Kenva, Keswick "NB 1", King Edward, Kuras, Lady Rosetta, Laura, Liva, Marabel, Marion, Mercury, Milva Revelino, Minea, Nicola, Norchip, Norgold Russet "BC", Norland, Octavia, Oleva, Panda, Posmo, Primula, Producent, Raja, Raja Bonanza, Red Pontiac, Red Warba, Revelino, Russet Burbank , Sava, Sebago, Secura, Senator, Seresta, Shepody, Sibu, Sieglinde, Sirtema, Stefano, Superior, Sydens Dronning, Symfonia, Tertus, Timate, Tivoli, Torva, Ukama, Victoria, Vivaldi, and White Rose.

Perforating the skin of potatoes

In the method of the invention the skin of potatoes is perforated to facilitate the access of the aqueous solution of pectin degrading enzyme to the underside of the skin. Perforation may be achieved by any suitable method known in the art e.g. with needles, by scoring, cutting, or otherwise penetrating the skin without excessive damage to the potato. Treatment with pectin degrading enzyme

In the method according to the invention potatoes are treated with an aqueous solution of at least one pectin degrading enzyme. The treatment may be carried out by any method suitable to bring the potatoes into contact with the enzyme solution, e.g. by immersing the potatoes in the enzyme solution, by spraying the enzyme solution onto the potatoes, or by sprinkling the potatoes with the enzyme solution. The treatment with enzyme solution may be carried out simultaneously with the perforation of the skin of the potatoes, e.g. by perforating the potatoes when they are immersed in enzyme solution, and the potatoes may be left in contact with the enzyme solution after perforation for sufficient time to achieve the desired effect. The treatment with enzyme solution may also be conducted after the skin has been perforated. The treatment may be conducted at any temperature whereat the enzyme is active, e.g. usually in the range from 5 to 70⁰C, such as from 10 to 60⁰C, from 10 to 50°C, or from 20⁰C to 50°C.

The effect of the enzyme treatment is to loosen the skin to facilitate removal of the skin by gentle mechanical treatment. The mechanical treatment needed to peel potatoes in the method of the invention is gentler than during conventional peeling of potatoes since the skin has been loosened by the perforation and enzymatic treatment and consequently the loss of potato material with the skin, peeling loss, may be reduced.

Removal of skin

According to the method of the invention the skin of potatoes is removed. The skin may be removed by any suitable method known in the art, e.g. by mechanically rubbing potatoes with any suitable device, e.g. brushes, and/or by steam treatment.

Heat treatment

The potatoes may be heat treated before treatment with the at least one pectin degrading enzyme, e.g. before, during or after the skin is being perforated, to facilitate the loosening of the skin and/or to improve the oxidative and microbiological stability of the potatoes during and/or after the enzymatic treatment. Heating may be carried out by any suitable method, e.g. by treatment of potatoes with steam, by immersing the potatoes in hot water, by sprinkling or spraying potatoes with hot water, or by treatment of the potatoes with hot air. If hot water is used it may e.g. have a temperature of between 60 and 100⁰C, such as between 80 and 100°C, or between 85 and 95°C. Example 1

12 groups of potatoes each containing 4 large potatoes of Bintje variety (approx. 800-1000 g) were weighed and in 6 groups the skin was perforated by puncturing/piercing using a needle bench. Each group of potatoes were placed in a beaker in approx 1 L 0.05M citrate- phosphate buffer pH 6.0 (potatoes are completely covered with buffer solution) with or without enzyme (Pectinex Ultra SP-L, a pectin degrading enzyme complex, Novozymes A/S, Bagsvaerd, Denmark) as detailed in Table 1. The potatoes were incubated for 20 hours at 40⁰C. After incubation the water was drained and the potatoes were peeled by gentle rubbing. The peeled potatoes were weighed. The amount of peel removed was evaluated visually and peeling loss was calculated as (g fresh weight - g peeled weight)/(g fresh weight)^*100. The results are given in Table 1.

Table 1

Example 2

Treatment of potatoes was conducted as in example 1 except that all potatoes were perforated and different incubation times and enzyme concentrations were used as detailed in Table 2. Results are shown in Table 2.

Table 2

Claims

1. A method for peeling potatoes, comprising: a) perforating the skin of potatoes to be peeled; b) treating said potatoes with an aqueous solution of at least one pectin degrading enzyme; and c) removing the skin from said potatoes; wherein step a) is performed before or simultaneously with step b), and step b) is performed before or simultaneously with step c).

2. The method of claim 1 wherein the at least one pectin degrading enzyme is a polygalacturonase.

3. The method of any of the preceding claims wherein potatoes are treated with at least one purified pectin degrading enzyme in step b).

4. The method of any of the preceding claims wherein said potatoes are heat treated before, during or after step a).

5. The method of any of the preceding claims wherein said potatoes are heat treated before, during or after step b).

6. The method of any of claims 4 or 5 wherein said heat treatment is performed by treating said potatoes with steam.

7. The method of any of the preceding claims wherein said potatoes are immersed in an aqueous solution of at least one pectin degrading enzyme in step b).