IL29783A - A method of producing expanded formed foodstuff - Google Patents

Description

A METHOD OF PRODUCIHG EXPANDED FORMED FOODSTUFF Improved process for producing expanded formed foodstuff from potatoes which permits control of reducing sugar content in the potato flour and use of more grades of • potatoes and shows reduced potato losses and water disposal problems.

In U.S.Patent No. 2,863,770, there is described a method of making a crispy fried expanded foodstuff comprising extruding a preswelled potato flour containing between 30 and 0 water into strands, drying the strands to a moisture content of between 6 to 10 , cutting the strands into piecelets andfrying the piecelets in hot fat. The frying expands the piecelets about five times their original volume to produce a crispy expanded fried foodstuff used as a snack food. Other patents relating to this process are 3,076,711 and 3,131,063.

The potato flour previously used to produce the expanded crispy foodstuff required the use of potatoes having a low reducing sugar content and as high a solids content as possible, which potatoes are not always readily available and usually sell at a premium price. The potato flour was prepared by washing and peeling the potatoes, adding a bleaching agent, cutting the peeled potatoes into small pieces, such as 1/4 x 1/8 x 2 inches, blanching the potato pieces to inactivate enzymes and to gelatinize the potato starch, drying the potato pieces with warm air until the moisture content was below about 10 , grinding the dried pieces to 100 - 40 mesh, 70% - 50 mesh and 50% - 70 mesh,mixing the resulting powder with salt and sufficient water to obtain a moisture content between 30 and 40%, preferably about 33%, and extruding the preswelled flour to form the desired strands.

One of the disadvantages of this process was the high loss of solids content in the preparation of the potato flour and the necessity to use potatoes having a reducing sugar content of between 1-2% which were also in demand for making potato chips and therefore of higher price. In said prior process about 15% by weight of the solids content was lost in the washing and peeling step and another 15% by weight of the solids content was lost during the cutting and washing of the potatoes. Even the sharpest knife destroys a considerable portion of the potato cells, and cell juice and solids content was washed away by rinsing the cut pieces.

The blanching of the cut potatoes performs a dual function; namely, inactivation of enzymes to prevent undesired chemical reactions and gelatinization of the potato starch.

The better the gelatinization, the higher is the water binding ability of the flour. The blanching purposes were best achieved by using as small potato pieces as possible; high ' blanching temperatures and long blanching times but solids content losses in the processed potatoes was increased by degradation, by overcooking and by leaching out. Therefore, the blanching process has %o balance the two factors and, in practice, the water blanching is effected at about 99°C for 7 to 9 minutes but solids content loss here is still about 5 % by weight.

Care also had to be taken in the air drying step since the water binding properties of the potato flour decrease if the drying temperature is too high and/or if the drying time is prolonged. Preferably, the drying is effected at about 70°C for approximately four hours to obtain a final moisture content of about 3%.

The two most critical properties of the potato flour for a satisfactory expanded foodstuff are the water binding property and the reducing sugar content of the flour. Too low water binding property gives an insufficient expansion during frying and a cookie-like bite to the expanded foodstuff and too high a water binding property makes the dried piece-lets and the expanded fried product too hygroscopio and the expanded food product is expanded too much and is too brittle. If the reducing sugar content of the potato flour is too high the expanded formed foodstuff has a brown color and a bitter taste while a reducing sugar content which is too low gives a pale-colored expanded foodstuff. The reducing sugar content is preferably between 1 to 2 by weight of the potato flour and this has previously required the use of special grades of potatoes.

It is an object of this invention to provide an improved process for the production of an expanded foodstuff with low solids content loss and reduced waste waters.

It is another object of the invention to provide a novel process for the preparation of potato flour in which the reducing sugar content and the water binding property can be simply and uniformly controlled.

It is a further ohject of the invention to provide a process for the preparation of a crispy, expanded foodstuff from a wider variety of raw potatoes.

These and other objects and advantages of the invention will become obvious from the following detailed description.

The improved process of the invention for producing an improved crispy expanded fried foodstuff comprises grinding raw potatoes in the presence of a bleaching agent to form a liquid slurry of ground potatoes, adding from 0 to 70 parts by weight of a starch to 100 parts by weight of the slurry to form a liquid mass having a solids content of 18 to 50%, drying the liquid mass on a dryer to obtain a powder having a moisture content of less than 10 , grinding the powder to obtain a flour and adjusting the reducing sugar content of the flour to about 1 to 2% by weight, mixing said flour with water and salt to produce an extrudable mass having a moisture content of 28 to 35 , extruding said mass under pressure to form coherent bands, cutting the bands into piecelets, drying the piecelets to a moisture content between 6 and 10 and frying the dried piecelets in hot fat to produce a crispy expanded foodstuff. The resulting potato flour of the first step can also be used in the similar process of U.S. patent No. 2,863,770 to make the expanded, crispy fried foodstuff.

By adding raw starch to the potato slurry it is no longer necessary to use potatoes having a reducing sugar content between 1 and 2 %. Potatoes having a higher reducing sugar content may be used, and the final reducing sugar content adjusted to within the 1 to 2% range by the amount of raw starch added or potatoes of a lower reducing sugar content may be used and the reducing sugar content adjusted by the addition of a reducing sugar or of a potato product having a sufficiently high reducing sugar content to bring the reducing sugar in the final product to within 1 to 2%. If the intermediate product, or "half material" hereafter referred to is not shipped to warm areas, and is fried shortly after production, the reducing sugar content of the intermediate product can be up to 2,5% on the dry matter content. This material when fried will produce a golden brown colored expanded crispy food product. However, if the intermediate product is to be stored in a warm climate, the reducing sugar content should be below 1%.

The process of the present invention has many advantages over the prior artjprocess. While the prior art blanching of the diced potatoes in a water blancher has the favorable effect of lowering the reducing sugar content, the blanching has the undesirable effect of washing away a considerable proportion of the soluble cell material which decreases the yield of potato flour, adversely affects the taste of the fried product and causes waste water disposal problems. Blanching of large slabs of potatoes which would reduce losses could not be done since the outer layers overcook and become sticky while the inner layers are insufficiently gelatinized. The slicing of the potatoes also causes losses of cell juice and starch during cutting and washing (about 20% of soluble cell content) and increases the waste water disposal problems.

The process of the invention has the advantage over the prior art process, in that the substantial losses which occur in the cutting and washing and blanching of the prior art processes do not occur, since the slurry of potatoes is dried completely on a drum dryer so that there is no loss of starch or cell juice and gelatinization of the potatoes is instantly effected. Moreover, the drying time in the drum dryer is so short that there is not time for oxidative deterioration. The drum dryer effects blanching and drying in one operation and there is no waste water disposal problem since there is no washing or blanching water required. In addition, the potato pulp coming from the drum dryer is thin and soft so that the potato starch may be much more easily ground .

Since in the present process there is no loss of soluble cell contents, the content of the solubles, when no starch is added, is about twice as high in the dried product of the present process as was present in the prior art process. Also, the reducing sugar content of the dried potato produced by the present process remains the same as it was in the raw potatoes, as long as no starch is added to the slurry, whereas in the prior art process the reducing augar content was appreciably decreased. Depending upon the reducing sugar content of the original potatoes, the reducing sugar content may have to be adjusted to the desired sugar content by the ad- dition of raw starch to the potato slurry. Although potato starch is preferred since it adds to the potato taste of the final product, other starches, such as cornstarch, tapioca, and the like, may be used. Since the raw starch is not enclosed in cell walls, it will add greatly to the swelling power of the potato powder after the drum treatment, provided there is sufficient water for gelatinization. The potato powder obtained from the drum dryer has a swelling power much greater than that of the prior art process because all the starch is fully gelatinized and is practically free from enclosing cell walls.

This swelling power of the potato powder is usually too high for use in producing the expanded fried pro¬ duct, since the expanded product would be too brittle and breakage would occur and the expanded product would also ab¬ sorb moisture too readily. To overcome this, low grade potato powder may be mixed with the ground product from the drum dryer to adjust the reducing sugar content and the swelling power to the desired level. This gives the process the advan¬ tage of being able to always obtain a uniform potato powder regardless of the reducing sugar content and size of the raw potatoes and makes it possible to use as starting material a wide variety of potatoes not previously available for use in these processes.

- - These potatoes used in the prior art process had to have a certain maximum amount of reducing sugar content and had to be large and of equal size to avoid losses in peeling; The large size potatoes with a low reducing sugar content are the same type of potatoes used by potato chippers and, therefore, potatoes which were not always readily available except at premium prices. The present process has the advantage that any type of potato can be used and, therefore, there is always a ready supply at the prevailing market price.

In a modification of the process of the invention, it is not always necessary to peel the potatoes,provided that the peels are not tco thick, since a certain amount of peel fragments can be tolerated. Also, the peel adds more fiber and improves the potato taste of the expanded food product. The more raw starch that is added to the potato slurry, the more peels can be permitted.

The low grade potato flour used to adjust the swelling power during frying and to a lesser degree also the reducing sugar content is well known. Examples of suitable low grade potato flour are instant potato products, potato flakes and potato flour which are off grade and do not come up to the standards required for making an expanded potato product. Instant potato products and potato flakes of good quality al- ways have a low modified rehydration factor, since starch not enclosed in the cell walls makes the product sticky. These products can be used as an admixture in our process, even if the amount of free starch is too high to make them acceptable as an instant potato product. Also, dried potatoes which have been stored for a long time and which have a relatively high degree of retrograded starch may be ground and added to the potato flour from the drum dryer.

In summary, the present process has the advantages that there is almost a complete freedom of choice in the selection of the raw potatoes used to produce the product ,·that the approximately 35$ loss of potato dry matter in the prior art process is diminished to 15% or less, since the cutting, washing and blanching steps are omitted and a uniform product can be always obtained. Moreover, the waste water problem is practically eliminated. The amount of energy required for the grinding and drum drying is substantially lower than the energy requirements of the prior art process.

I have found that the swelling power of the half material in the hot oil can be accurately measured beforehand by measuring the rehydration factor of the ground potato powder. The measurement of the rehydration factor of dried starch materials, i.e. their ability to readsorb water is described in "Food Dehydration", Wallace Van Arsdel and Michael Copley, the Avi Publishing Co., Inc., 1963, p.81 to 82. The rehydration factor, as there described, is for dried vegetables, meat and potatoes in the form of pieces.

For a ground potato, rice, tapioca and corn flour, a modification of this method, developed by the inventor must be used, The method used in the present invention gives a somewhat modified rehydration factor. The method of measurement is as follows: From the dried potato or other powder to be investigated, a portion is sieved and the portion which passes through a sieve 70 mesh and is retained on a sieve 100 mesh is used. 2 Grams of this sieved powder are put into a cali-brated measuring cylinder with an inner diameter of 1 inch. 40 ml of tap water of room temperature (20-25°C) are added, and the mass is stirred with a glass rod, care being taken that no lumps remain. The cylinder is now left quiet for two hours and the swollen potato meniscus is^read. This reading, divided by two, is the modified rehydration factor (mrf) .

In the following examples, there are described •several preferred embodiments to illustrate the invention.

However, it should be understood that the invention is not intended to be limited to the specific embodiments.

Example 1.

Field crop potatoes of the Bintje variety containing 22% solids oontent and 5.4% reducing sugar based on the solids content were washed and lye peeled. The peeled potatoes were then ground in a hammer mill to obtain a thin slurry of finely divided potatoes and sufficient sodium bisulfite was added thereto to obtain an S02 content of 250 ppm. 300 kilos of the said slurry were admixed with 200 kilos of raw potato starch to obtain a mass containing about 50% solids content and which was still transportable by a pump. The said mass was passed once through a scraped surface heat exchanger such as a double drum dryer in which the drums were heated with steam under a pressure of 100 lbs. per square inch, whereby 100% gelatinization of the starch and drying of the mass to a moisture content of 8% was effected and the dried mass was then ground to a size whereby 100% was -40 mesh, at least 70% was -50 mesh, and at least 50% was -70 mesh. The powdered flour had a reducing sugar content of 1.3% and a modified rehydration factor of 18.

The said potato flour was admixed with 120 kilos of mashed potato flakes having a reducing sugar content of 1.9 by weight and a modified rehydration factor of 4 to obtain a final mixture having a reducing sugar content of 1.5% and a modified rehydration factor of 14, 100 kilos of the said mixture was then made into a dough by the addition of 5 kilos of salt and 35 kilos of water. The dough was extruded under pressure into coherent bands and the bands were cut into piecelets of about .30 mm and dried to a moisture content of 8%. This intermediate product or "half material" may be fried immediately or shipped to a frying point and then fried into the final crispy expanded food product. When the piecelets are fried for about 15 seconds in fat at 180°C, a crispy expan ded food product having a straw yellow color and a weight-to-volume ratio of 0.18 and an agreeable taste and bite is produced.

Example 2.

A mixture of low grade potatoes, (culls), of several varieties having a solids content of 23 and a reducing sugar content of 5.0% based on the solids content were lightly lye peeled and then ground in a hammer mill to obtain a low viscosity, thin slurry of potato, and sufficient sodium bisulfite was added to obtain an SQ^ content of 200 ppm. 300 kilos of the low viscosity slurry were admixed with 100 kilos of raw potato starch to obtain a pumpable mass with a solids content slightly below 40%. The resulting slurry was passed through a drum drier having one big drum and 3 smaller application drums heated with steam under pressure of 100 lbs/sq. in. to obtain a fully gelatinized potato flour having a moisture content of S%. After grinding as in Example 1, the potato flour had a reducing sugar content of 2.1% and a modified rehydration factor of 18.

The resulting potato flour was admixed with 40 kilos of the potato flakes used in Example 1 to obtain a potato flour having a reducing sugar content of 2.0% and a modified rehydration factor of 15. As in Example 1, the flour was used to produce a crispy expanded food product having a golden brown color and a distinct potato taste, good bite and a weight to volume ratio of 0.17.

The potato flour removed from the drum driers according to Examples 1 and 2 is fully blanched, and may be used for other purposes than for making a crispy expanded fried food product as described in these examples.

In place of raw potatio starch used in the above examples other starches, such as cornstarch, tapioca, and the like may be used.

Various modifications of the process of the invention may be made without departing from the spirit or scope thereof, and it is to be understood that the invention is to be limited only as defined in the appended claims.

What we claim is :

Claims (8)

1. A process for producing an improved crispy expanded fried foodstuff which comprises grinding raw potatoes in the presence of a bleaching agent to form a liquid slurry of ground potatoes, adding from 0 to 70 parts by weight of a starch to 100 parts by weight of the slurry to form a liquid mass having a solids content of 18 to 50$, drying the liquid mass on a dryer to obtain a powder having a moisture content of less than 10%, grinding the powder to obtain a flour and adjusting the reducing sugar content of the flour to about 1 to 2% by weight, mixing said flour with water and salt to produce an extrudable mass having a moisture content of 28 to 35%, extruding said mass under pressure to form coherent bands, cutting the bands into piecelets, drying the piecelets to a moisture content between 6 and 10% and frying the dried piecelets in hot fat to produce a crispy expanded foodstuff.

2. The process of claim ljwherein 35 to 55 parts by weight of the starch are added to 100 parts by weight of the liquid slurry.

3. The process of claim 1, wherein the bleaching agent is sodium bisulfite.

4. The process of claim 1, wherein the expanding power of the flour is adjusted by addition of an instant potato product- thereto.

5. The process of claim 1, wherein the bleaching agent is added during or after grinding of raw potato.

6. The process of claim 1, wherein the liquid mass is dried on a drum dryer or on a scraped heat exchanger surface.

7. The process of claim 1, wherein the potatoes are peeled before grinding.

8. The process of claim 1, wherein 25 to 70 parts by weight of the starch is added to 100 parts by weight of the slurry, to form a liquid mass having a solids content of 35 to 50 . For the Applicants DR,