How to Make Flaked Mashed Potatoes? A Detailed Guide to the Production Method

1. Production process

Potatoes → washing → peeling → slicing → precooking → cooling → steaming → grinding → drying → crushing → packaging → finished product.

2. Key production points

(1) Raw material selection: Remove sprouted and greened potatoes as well as rotten and diseased tubers. If there is sprouting or greening, the sprouted or greened parts must be cut off, or the entire potato must be discarded before use, to ensure that the solanine glycoside content of the potato product does not exceed 0.02%; otherwise it will endanger personal safety.

(2) Washing: Pour the potatoes into a water tank and stir to wash away sand and surface dirt. In a continuous-flow operation, the raw materials are generally first poured into the feed inlet, and rotten potatoes, stones, sand grains, etc. are picked out on the conveyor belt; after cleaning, they are sent through a flume or elevator bucket into a washing machine for cleaning. Washing is usually carried out by scrubbing in a drum-type washing machine, which allows continuous operation.

(3) Peeling: Peeling methods include manual peeling, mechanical peeling, steam peeling and chemical peeling. Manual peeling generally uses a stainless steel knife and is very inefficient. Mechanical peeling uses a rotating drum or roller coated with emery and having a rough surface, relying on friction to scrub off the skin; the commonly used equipment is a peeler, which can be used for batch or continuous production. Lye peeling involves placing the potatoes in a strong alkali solution of a certain concentration and temperature for a certain time to soften and loosen the skin and eyes of the potatoes, then spraying them with high-pressure cold water to cool and peel them. The suitable alkali mass fraction for lye peeling is 15%-30%, and the temperature is above 70°C. Steam peeling involves treating the potatoes briefly in steam so that blisters form on the outer skin, then rinsing off the skin with running water. Steam peeling acts evenly on the entire potato surface and can remove about 5mm of the skin layer.

The ideal method is to alternate steam peeling and lye peeling. This is because the longer the interval between potato harvest and processing, the more difficult peeling becomes and the greater the loss. Early in the processing season, steam peeling or low-temperature lye peeling causes less loss. Later in the processing season, when peeling becomes more difficult, in addition to lye treatment, a brief high-pressure steam treatment followed by rapid pressure release and finally cold water rinsing to remove the skin will make peeling more effective.

(4) Slicing: Potatoes are generally cut into slices 1.5mm thick so that they can be heat-treated more evenly during precooking and cooling.

(5) Precooking: Precooking can not only destroy the enzymes in potatoes and prevent browning of the tubers, but also produce non-sticky mashed potatoes. Potato slices are generally heated in water at 71°C-74°C for 20min. After precooking, the starch must be thoroughly gelatinized. In this way, during cooling the starch will retrograde and reduce the stickiness of the potato slices after rehydration.

(6) Cooling: Wash the cooked potatoes with cold water to remove free starch, avoiding gumming or scorching during dehydration and reducing the viscosity of the resulting mashed potatoes to a suitable level.

(7) Steaming: Steam the precooked and cooled potato slices at atmospheric pressure for 30min so that they are fully cooked.

(8) Grinding: After steaming, the potatoes are ground immediately so that they can be quickly mixed with additives and cell rupture can be avoided. The machinery used is generally a screw-type grinder or a disc grinder with round holes.

(9) Adding additives: Before drying, food additives are injected into the mashed potatoes to improve their texture and extend their shelf life. There are generally two types of additives. One is a dilute solution of sodium bisulfite, which can serve as a source of sulfur dioxide to prevent non-enzymatic browning of potatoes; the amount of sulfur dioxide usually used is 0.2%-0.4%. The other is spraying glyceride onto the dried potato slices; generally, before addition, the potatoes are cooled to (65±5)°C and kept at this temperature. In addition, adding antioxidants can extend the storage life of mashed potatoes. Adding butylated hydroxyanisole and 2,6-di-tert-butyl-p-cresol to the mashed potatoes at 0.50% before drying can extend the shelf life by 6 months. During drying, steam distillation of the antioxidants will occur, so about 75% of the antioxidants will be lost. In addition, adding sodium acid pyrophosphate can react with iron and inhibit the discoloration caused by recooking; the amount added is 0.1% of the potato mass.

If fortified potato flakes are being made, each serving of potato flakes (85g) may be supplemented with 75mg of vitamin C, 3mg of vitamin B2, 20mg of niacin, and 1200IU of vitamin A.

(10) Drying: The mashed potatoes can be dried in a single-drum dryer or in a single-drum dryer equipped with 4-6 drums; after drying, dried potato flakes of maximum density can be obtained, with a moisture content below 8%.

(11) Crushing: The dried potato flakes can be crushed into flake form with a hammer mill; it is a product with suitable texture and bulk density.

Production shows that most potato flake processing plants use potatoes with a dry matter content of 20% as raw material, and 1t of finished product requires 6.6t-7.0t of raw potatoes. For the most suitable potatoes for processing, peeling loss is about 7%, slicing loss about 1.5%, precooking loss about 3%, cooling loss about 1.5%, steaming loss about 1%, and loss from the drum during drying is about 3%-5%.

3. Quality control

(1) Product structure: Many factors affect the structure of mashed potatoes, such as the extent of cell rupture, the amount of gelled starch, the absorption effect of cytoplasm, etc. These factors must be effectively controlled during production to ensure a good product structure.

(2) Product color: Adding acid phosphate can control the gray color produced by cooking, so controlling the color change of potato slices during cooking is no longer a problem.

(3) Bacterial content: Escherichia coli no more than 10 per g, no Staphylococcus aureus, mold count no more than 10 per g.

(4) Moisture content: The moisture of the dried product is required to be below 8%, generally 5%-6%.

(5) Reducing sugar and total sugar content: On a dry weight basis, reducing sugar should be limited to within 2%, and total sugar limited to within 3%.