GB2111816A - Starch-based snack products - Google Patents

Abstract

Starch-based snack products are prepared from a starch-based mixture having a moisture content between 26 and 40%. The mixture is extruded through a die to form a product having a thickness of between 0.35 and 2.0 millimetres at a pre-die temperature within the range 40 to 75 DEG C and at a pre-die pressure within the range 50 kg/cm<2> to 140 kg/cm<2>. The starch in the extrudate is partially gelatinised by steaming for from 4 seconds to 25 minutes at between 85 and 140 DEG C. Following steam treatment the product may be air dried and/or stabilised before it is expanded eg by frying. The starch based mixture can contain potato granules, farina, pregelatinised starch & salt. <IMAGE>

Description

SPECIFICATION A method of producing snack products This invention relates to the production of snack products utilising reversibly modified extrusion equipment normally applied in the manufacture of pasta shapes. Desirable dough rheology and sophisticated shape formation is executed in such equipment and this is followed by a steaming process in which the specific objective is to physically modify the dough to give the required final product characteristics.

Prior art It is known from the prior art that equipment for extruding pasta can be used to form snack half products and snack products. In our prior proposal (GB Patent Specification No 2063643) we disclose a method of producing a rapidly rehydratable pasta which includes preparing a mixture of semolina and/or wheat flour and water, having a moisture content between 28 and 40%, extruding the mixture through a die to form a product having a thickness between 0.3 and 0.7 millimetres, and subjecting the product to super-heated steam at a temperature between 106"C and 140"C fo r from 9 to 14 minutes to reduce the moisture content sufficient to give a shelf stable product.

It has also been suggested to make a careful selection of raw materials having desirable characteristics with the specific object of avoiding the gelatinisation of native starch during extrusion, since this is seen as having detrimental effects with regard to process stability and the effect on product quality. Although this method is seen as an advantage it does nevertheless require highly specific and sophisticated raw materials.

Statement ofinvention According to the present invention there is provided a method of producing starch-based snack products for subsequent expansion prior to consumption, which includes preparing a starch-based mixture having a moisture content between 26 and 40%, extruding the mixture through a die to form a product having a thickness of between 0.35 and 2.0 millimetres at a pre-die temperature within the range 40 to 75"C and at a pre-die pressure within the range 50 kg/cm2 to 140 kg/cm2 at which conditions gelatinisation is inhibited; and partially gelatinising the starch by the use of a steam process for from 4 seconds to 25 minutes at a temperature of 85 and 140"C.

General description It is recognised in the manufacture of snack products utilising extrusion equipment that it is usual for some gelatinised starch to be present in the final product. Frequently, the gelatinised starch is added as a raw material, but proposals have been made for the use of high temperature extrusion for snacks, this equipment being specifically designed to cause gelatinisation in the extruder. A conventional pasta extruder is unable to operate under these conditions particularly when a high degree of shape definition and sophistication is a prime requisite in the product.

The present invention, however, uses reversibly modified pasta extrusion plant in order to blend the wet and dry raw materials and to yield carefully defined shapes. These pellets are then subjected to steam within a chamber for a specific time and at a specific temperature in order to achieve the required degree of gelatinisation. Different textures and eating qualities are achieved through the selection of raw materials; the degree of subsequent processing; and the processing conditions within the steam chamber. This particular technology was developed to meet the need in the snack market for products with more continuous crunch and cleaner eating characteristics. It is a surprising feature of the process that very short steaming times cause dramatic improvements in these textural properties. It is hypothesised that this observed change is a result of the non-homogenous distribution in the pellet of gelatinised and ungelatinised starch; this could cause variations in the distribution of water and ionic salts, leading to a change in the expansion characteristics.

The present invention can be applied using saturated steam, steam/air mixtures and super-heated steam (i.e. steam elevated to a temperature in excess of 100"C at atmospheric pressure).

It will be clearly apparent, therefore, that the full flexibility of the pasta extrusion equipment can be used to give carefully defined shapes since extremes of extrusion conditions are not necessary.

Factors which effect this invention may be itemised as follows:- 1. Conventional pasta extrusion equipment, reversibly modified.

2. A wide range of raw materials may be selected, including those manufactured from tubers, roots, pulses, cereals, native starch and pregelatinised/modified starches. The use of ionic salts in such products is well recognised.

3. The versatility-of a pasta extruder can be fully utilised.

4. Mix moisture content is 26 to 40%. The preferred range is 28 to 36%.

5. Extrusion pressures 50 to 140 kg/cm2; pre-die temperatures 40 to 75 C.

6. Dies of aperture size 0.35 to 2 mm.

7. Generally a pre-drying/cooling stage.

8. Steaming process; preferred temperature range85 Cto 110 C; overall range 85"C to 140"C.

9. Steaming residence time 4 sec. to 25 minutes.

10. Moisture of pellet ex-steamer 8 to 40% moisture.

11. Optional further reduction of moisture to give a final moisture of 6 to 20%. Products with higher moisture content may be produced, but these tend to exhibit characteristics which are less desirable when expanded.

12. Such pellets may be fried or otherwise processed immediately or subsequent to a stabilisation period to give the expanded final product.

Drawings Figure 1 of the accompanying drawings is a flow diagram showing typical routes for carrying out the method of the present invention, the numbers referring to the examples herein; Figure 2 is a graph produced when testing a product made by a conventional method; and Figure 3 is a graph produced when testing a product made according to exampie 6 herein.

Examples 1. Potato granules 35.0% Native potato starch (farina) 55.0% Pregelatinised starch 6.5% Salt 3.5% A mix moisture of 33%; extruded through a shell die with aperture size 0.5 mm and processing conditions of 95 kg/cm2 pre-die pressure and a pre-die temperature of 55"C. Steamer process conditions 107"C for 10 mins.

Moisture content of pellet ex-steamer 17%.

This product was fried immediately at 200"C for 12 seconds and yielded a desirable light but crunchy textured product, with clean eating characteristics.

2. As in 1 above, but further dried down to 10% moisture on discharge from steamer. The product was fried at 200"C for 7 seconds and yielded a more expanded, lighter textured, crunchy and lower bulk density product.

In both cases excellent shape identity of the product was retained.

3. Potato granules 25.0% Farina 65.0% Pregelatinised starch 6.5% Salt 3.5% The processing conditions were as in 2 above and the texture of the product was somewhat lighter and the product less substantial with a more porous structure. Shape identity was still good.

4. Formulations as in 2 above but utilising a grille die with aperture size 1.3 mm. Steamer conditions 112"C for 12 mins. Pellet moisture ex-steamer 15%. The pellet was then dried down in conventional pasta equipment at controlled temperature and humidity yielding a shelf stable pellet at 9.5% moisture. The product was fried at 200"C for 10 seconds and yielded a well expanded crisp crunchy product which was more substantial that those given in the Example above.

5. Potato granules 27.0% Farina 60.0% Pregelatinised starch 10.0% Salt 3.0% The product was extruded at a mix moisture of 37% through a Hoop die having an aperture size of 0.85 mm.

The pellet was extruded under conditions of 77 kg/cm2 pressure and a pre-die temperature of 54"C. The product was passed through a conventional pasta pre-drier at 30'C for 3 mins. The pellet was steamed under super-heated conditions at 11 50C for 20 mins. The product from the steamer had a moisture content of 10% and was in a shelf stable form. On frying at 200"C for 6 seconds a firm, well expanded product was achieved.

6. Potato granules 25.0% Farina 65.0% Pregelatinised starch 7.0% Salt 3.0% A mix moisture of 33%; extruded as a grille die with aperture size 1.3 mm and processing conditions of 90 kg/cm2 pre-die pressure and a pre-die temperature of 56"C. The product ex-extruder was cooled to 1 8"C using a shaker pre-drier to give a moisture content of 32%. The product was steamed (93"C for 4 seconds) increasing the moisture content to about 35%. This was progressively reduced to 33%, 29% and 12% by three drying stages. On frying this yielded a product substantially similar to that in Example 4.

7. As in Example 6, but with a residence time in the steamer of 6 minutes. On frying this yielded a product substantially similar to that in Example 4.

8. Crushed flake yellow maize 30.0% Farina 30.0% Potato granules 30.0% Pregelatinised starch 7.0% Salt 3.0% The product was extruded at a mix moisture of 35% through a large shell die having aperture size of 0.9 mm.

The pellet was extruded under conditions of 100 kg/cm2 pressure and a pre-die temperature of 57"C. The subsequent process conditions were as in Example 2 above and the product on frying at 200"C for 12 seconds yielded a crisp and crunchy product with clean eating characteristics.

9. Ground rice flour 30.0% Farina 30.0% Potato granules 30.0% Pregelatinised starch 7.0% Salt 3.0% The product was extruded at a mix moisture of 35% through a large shell die having an aperture size of 0.9 mm. The pellet was extruded under conditions of 90 kg/cm2 pressure and a pre-die temperature of 53"C. The subsequent process conditions were as in Example 2 above and the product on frying at 200"C for 10 seconds yielded a light but crisp and crunchy product.

All the above examples give products with clean eating characteristics, i.e. it does not adhere to the teeth or palate. These can be demonstrated by comparing the sounds made and the forces required when an instrument is used to simulate the molar bite. The acoustic prints and force curves shown were produced using an Instron 1122 and compare the product manufactured according to Example 6 (Figure 3) with a product that is identical except that the 4 second steaming stage is omitted (Figure 2). They show that the new product is distinctly different, requiring less force to bite through it, and having a much more even fracture pattern; both these factors are relevant to the perceived difference in texture.

In all the above examples, the percentages are by weight. It should be noted that the products of the above processes may be expanded in hot oil or by the use of microwaves, a fluidised salt bed, hot air, micronisation and the like.

Claims (8)

1. A method of producing starch-based snack products for subsequent expansion prior to consumption, which includes preparing a starch-based mixture having a moisture content between 26 and 40%, extruding the mixture through a die to form a product having a thickness of between 0.35 and 2.0 millimetres at a pre-die temperature within the range 40 to 75"C and at a pre-die pressure within the range 50 kg/cm2 to 140 kg/cm2 at which conditions gelatinisation is inhibited; and partially gelatinising the starch by the use of a steam process for from 4 seconds to 25 minutes at a temperature of between 85"C and 140"C.

2. A method of producing starch-based snack products as claimed in Claim 1, in which the mix moisture content is between 28 and 36%.

3. A method of producing starch-based snack products as claimed in either Claim 1 or Claim 2, in which steaming is carried out for from 4 seconds to 12 minutes at a temperature of between 93 and 112 C.

4. A method of producing starch-based snack products as claimed in any one of the preceding claims, in which the moisture content after steaming is 8 to 40%.

5. A method of producing starch-based snack products as claimed in any one of the preceding claims, in which, subsequent to steaming, a drying process is carried out.

6. A method of producing starch-based snack products as claimed in any one of the preceding claims, in which the mixture contains potato granules, farina, pregelatinised starch and salt.

7. A method of producing a snack product for consumption, which includes preparing a half product in accordance with any one of the preceding claims and expanding the half product in hot oil or by any other conventional expansion technique.

8. A method of producing starch-based snack products substantially as herein described with reference to any one of the Examples herein.