Figure 1:Potato Sale at an Andean Fair

Nevertheless, there exists a marked tendency to dedicate a bigger tuber volume for processing, with the aim of satisfying a mounting demand for fast food, snacks and prepared foods.

The structure of the demand in Latin America is changing, where the volume of processed products is growing. Although the available statistics don't permit clear appreciation of this fact several studies have explored the current and potential economic importance of the potato as an agroindustrial input. For example, in Colombia 12 percent of the potato production has industrial use, while between 16 and 19 percent of the potato production is dedicated to processed products for the urban market in Mexico. Table 8 outlines the potato production percentages in the United States and countries of Latin America.

The potato is still barely used as agroindustrial input in Latin America. Argentina has built a potato processing transnational plant representing an investment of 25 million dollars. Other countries, as Chile, Colombia, Ecuador and Peru will be receiving important national and foreign investments.

Table 9 shows the potato processed products consumption volumes in Peru (Metropolitan Lima).

Recently, the potato has exhibited great potential and versatility as an export item. Flakes, starch, flours and frozen potato products now join traditional fresh potato consumption and seed for import/export.

Table 10 displays the exports of processed potato products of Peru.

The main importers of frozen fried potato in the Latin America region are Mexico, Brazil, Chile, Argentina and Venezuela. Frozen fried potato comes mainly from United States and Canada.

Table 11 summarizes the imports of frozen French fries for Latin America and the Caribbean.

From season to season there are strong variations in potato prices and volumes. Processing allows the possibility to add value to fresh potato. This is particularly important in times of abundance, when the tuber price is lowest.

Processing allows part of the harvest to be retired from the market, thus introducing certain price stabilization. It also prolongs tuber shelf life (dry potato, flour), employs below standard varieties for direct consumption (bitter potatoes) and potatoes of little commercial value (very big, very small, unsightly).

The potato used for processing should have:

1. High content of dry matter;
2. Low content of reducing sugars;
3. Low glycoalkaloids content;
4. Appropriate content of phenolic compounds.

The process for dry potato is shown in Diagram 1.

Diagram 1.Technological Process for Dry Potato

The potato crop comes from the field in jute sacks or polypropylene bags. It is weighed before entering the productive process. Visual selection is carried out to eliminate the potatoes that exhibit contusions, signs of microorganism attack or any other deterioration.

Tubers are washed in a machine that generates a shower of water, with rollers fitted with nylon bristles.

A peeling machine peels the potatoes by abrasion. The peeled potatoes go into baskets and are sunk in a tub of water.

The peeled potatoes undergo a pre-cooking stage in boiling water to avoid browning and improve final yield.

Then potatoes are passed to a rectifier, to eliminate "eyes", remains of shells and damaged parts.

Potatoes are cut in strips of 1x1 cm traverse section and variable longitude, using manual or vertical disk cutters.

 Figure 2:Potato Peeled and Strips Cutting

Cut potatoes are distributed evenly on trays or meshes to facilitate drying. The load is of 8-10 kg by m2.

Drying is traditionally completed in the environment, but it is recommended to use a hot air dryer at 65 ^oC for 8-10 hours or a solar dryer for 3-6 days, up to constant weight.

Once tubers are dry and cooled to ambient temperature, dry potato is ground in a hammer mill to 1 700 RPM with a mesh of 3/4 inch diameter. Also a disk or a ball mill can be used.

A screening step separates fine dust that originated in the mill. The yield is approximately 20 percent.

Dry potato is packed in high density polyethylene bags. Its capacity varies according to the destination market and quantity (150 g, 250 g, 500 g, 10 kg, 25 kg and 50 kg). It is recommended not to store dry potato at temperature and relative humidity higher than 26.6 ^oC and 75 percent HR.

 Figure 3:Potato dehydrated by sun

The process for chuño elaboration is shown in the Diagram 2.

Diagram 2.Technological Process for Chuño

Bitter varieties are used, with a high glycoalkaloids content that cannot be consumed fresh.

The best months for Chuño elaboration are June and July, because of freezing intensity.

The potatoes are classified by size so the freezing is uniform and the final product homogeneous.

The beds dedicated to Chuño preparation is located in places with altitudes between 3 600 and 4 000 msnm, where cold is intense. They are prepared with Ichu (Stipa ichu) that extends on the floor in mesh form, to distribute the potatoes in one layer. Exposure time necessary for freezing varies from 2 to 4 nights, depending on how cold it is.

Potatoes are defrosted by sunshine in the morning. Water is thawed from cellular structure (constitution). The potatoes lose between 25 and 30 percent of their original weight.

Immediately after defrosting, potatoes are pressed by foot, to eliminate constitution water, accelerate drying and produce spallation. It should be performed quickly to avoid fermentation that oxidizes the pulp of the tuber, which partially diminishes the product quality.

After constitution water removal, the humid tubers are piled up to mature for 2 to 3 days, which creates Chuño's characteristic flavour.

The Chuño is placed on straw beds, and dries off taking advantage of solar radiation to achieve 10 percent or less final moisture content needed for good product conservation.

As Chuño dries the product is selected and shelled as other impurities like powder, straw, and others are eliminated. Chuño final yield is 26 percent. The product is packed in jute sacks for storage.

 Figure 4:Potato Khaya or Chuño

The steps to derive semi-processed potato are shown in the Diagram 3.

Diagram 3.Technological Process for Semi-Processed Potato

Raw material is weighed at time to enter to the plant.

Before washing potatoes are selected by visual inspection. Potatoes that present signs of bruising, stings, rottenness, etc. are eliminated.

Washing removes impurities stuck to the tuber with drinkable water in a rotational potato washer.

The shell is destroyed using an abrasive peeler. The peeled potatoes are deposited in a tub with water to avoid browning.

The "eyes" are extracted manually (Rectified) while the peel remains.

Cutting is carried out with an automatic or semiautomatic potato cutter.

The cut potatoes are deposited in a tub with a solution of sodium bisulfite 1.7 percent where they remain for 30 seconds. After they are drained.

Next the potatoes are weighed and packed in high density polyethylene bags of 5 kg capacity.

Since the production is carried out on request, the storage time of the final product should not be longer than 12 hours.

French fried potato process is outlined in Diagram 4.

Diagram 4.Technological Process for Fried Potato

Raw tubers are weighed at time they enter the plant.

Before washing, potatoes are selected by visual inspection. The potatoes that present signs of bruising, stings, rottenness, etc. are eliminated.

Washing purges impurities stuck to the tuber with drinking water in a rotational potato washer.

The shell is eliminated using an abrasive peeler. The peeled potatoes are deposited in a tub with water to avoid browning.

The "eyes" are extracted manually (Rectified) leaving the peel.

Cutting of peeled potatoes is accomplished with an automatic or semiautomatic potato cutter.

Cut potatoes are washed with water to remove the starch trapped in the surface. Then the water is drained.

The drained potatoes are fried in vegetable oil to approximately 350 ^oF. Duration of cooking time is a function of the quantity and fryer characteristics.

After cooking, French fries are drained of excess oil.

French fries are seasoned with 2 percent salt and packed in cellophane or polypropylene bags and laminate material. Final yield is approximately 30 percent.

The process of making potato puree is shown in Diagram 5.

Diagram 5.Technological Process for Potato Purée

Description of the Process

Raw tubers are weighed at time they enter the plant.

Initial washing can be omitted if a water peeling system is used.

Any commercial method may be applied for peeling: abrasive, vapour, chemical or direct flame peeling.

Peeled potatoes go into a rotating washing machine to remove traces of peel.

The potatoes undergo sulfation by immersion in a solution of sodium bisulfite 0.1-0.2 percent for 5 minutes.

The potatoes pass to a manual rectifier, where peel residuals, "eyes", bruising and spotted parts and other debris are removed.

The potatoes are cut in slices of roughly one half inch thickness.

Then potatoes are pre-cooked in water at 160 ^oF for 20 minutes and cooled by immersion in water to below 75 ^oF for 20 minutes.

After that tubers are further cooked with vapour at atmospheric pressure for 30-50 minutes. Potatoes should be sufficiently soft to be crushed easily.

Pressing and crushing is carried out in a device called a Ricer containing a perforated rotational cylinder upon which rotate two small rollers. The first roller squashes the cooked potato against the cylinder. The second roller forces to the mass to pass through the perforations. An interior screw discharges the product outside of the cylinder.

A simple rotational dryer is used to dry the emerging mass. The mass should contain 20-22 percent solids. It is recommended to apply a vapour pressure of 75-80 psig and a drum speed of 2.5 RPM.

The yield is approximately 22 percent.

It is packed in plastic-coated paper bags or plastic bags, which can fit inside small cardboard or corrugated cardboard boxes.

The steps to make potato starch are shown in Diagram 6.

Diagram 6. Technological Process for Potato Starch

Raw tubers are weighed when entering the plant.

The potatoes are transported in water flowing toward several washers in series equipped with a water drainage device.

The potatoes are peeled by any method: chemical, abrasive or heat.

 Figure 5:Peeled Potato Trimming

The peeled potatoes are disintegrated in a roll mill. It is required to reduce the tubers from a mean diameter of 2 to 2.5 inches until particles can pass through 100 mesh.

The product coming from the mill is sent to a deposit where it is mixed with a solution of SO₂ (1/2 pound of SO₂ by TM of actual starch).

The resulting suspension with density 1.04 is directed toward a separators group constituted by rotational sieves and screen (meshes 80 and 100). The total recovery is of 90.8 percent.

The grout of resulting starch goes by a continuous centrifugal separator where the starch free of protein goes out with a density of 1.05.

The grout coming from the centrifugal goes by a screen (mesh 120) to eliminate the fine pulp that has been able to remain. It exits with density 1.03.

The resulting grout enters to a continuous horizontal centrifuge, where its new density is 1.18.

The humid starch is subjected to the action of a vacuum continuous filter that gives a uniform product with 37 to 41 percent humidity.

The starch dries off in a drying type flash, with hot air increased to a high temperature for 3 or 4 seconds. The final humidity of the starch should be 12 to 13 percent.

The yield can vary between 10 and 20 percent.

The starch is sifted and packed in multi-sheet paper bags of 50 kg capacity.

The process of elaboration of potato alcohol is shown in the Diagram 7.

Diagram 7. Technological Process for Rectified Alcohol

Once a gross suspension of starch is obtained, this mixture should be conditioned for acid hydrolysis, with hydrochloric, or enzymatic acid, using concentrated amylases, to attain a sugary must.

Yeast is introduced into the must to begin the process of fermentation. The processes of fermentation and distillation are developed traditionally by lots. The traditional procedure is safe and simple, but takes a lot of time and propagates big quantities of water pollutants.

As an alternative a continuous process is recommended such as the Biostil, where an unique fermenter that allows feeding, vinasse retirement and yeast recycled in continuous form is coupled to an evaporation module and unfolding where goes separating the ethanol.

Diagram 8. Technological Process for Potato Paste