Chips production line. How to fry pellets, preserve the taste of the product and to maintain the equipment?
What are pellet chips?
Pellet chips are a product with a harmonious combination of taste and aroma, crispy consistency, porous airy structure, made from a dry extruded semi-finished product (pellets) by quick frying in vegetable oil. Then the flavoring and aromatic additives are applied to the finished product and the product is packed in sealed polypropylene bags. To obtain high-quality chips, it is necessary to strictly comply with the requirements of their production technology and, first of all, the requirements for raw materials (additives, oil, pellets, roasting modes, packaging and storage conditions).
What are the pellets for chips, corn sticks and snacks made of?
Pellets are made using extrusion technology of gelatinization of cereals, starch, flour and potatoes, after which the product is dried to a residual moisture content of 8-11%. Gelatinized starches like flour paste and have certain properties that provide an increase in the volume of pellets during frying. Making of flour paste occurs when the moisture in the product decreases. In other words, making flour paste is the process of hydrothermal destruction of the starch, and gelatinization is the process of mechano thermal destruction, which is carried out due to the heating of the product at a given temperature and humidity. Pellets are made of potato, wheat, corn and multi-grain raw materials of various shapes — flat circle, square, corrugated rectangle, profile, pretzel, crab, oval, straw, stick, 3D pillow, etc. The pellet has a long guaranteed shelf life (1.5 years), but also can be stored for more than 10 years.
How to fry pellet snacks?
The main technological process in the production of pellet chips snacks is frying, i.e. short-term processing of pellets in oil heated to 170-200 ° C. The water contained in the pellets quickly turns into steam.
The steam escaping to the outside destroys the pellet tissue, forming a bulge and a lot of voids and increasing the volume by 2-4 times. Blistering is closely related to pellet thickness and moisture content. At the same time, a process of rapid and intensive dehydration is carried out, in which 2-3% of moisture remains in the manufactured products. The presence of voids is responsible for the crisp texture of the chips. In their absence, the pellets become tough after roasting. However, when roasting, for example, corn pellets, the firmness of the product after roasting is preserved and this is not a disadvantage of the product and is even liked by consumers.
What is the oil consumption for frying on your chip line?
During the frying process the pellets absorb oil in such an amount that its concentration in the final product can be 16 — 30% and depends on the type of pellets, therefore, fat is an essential component that determines the taste of chips. Factors contributing to good consistency and normal oil content in finished products are as follows:
- Moisture of pellets 9-11%
- Oil temperature 185-195°C
- Pellet thickness 0,8-1,5 mm
Is there a difference in the output capacity of the pellets frying line when roasting pellets of different composition?
Depending on the raw materials of the pellets and its thickness, the frying modes (temperature and time) differ significantly. The output capacity of the frying equipment is different for different types of pellets. The maximum output capacity is achieved when roasting potato pellets, the lowest output is achieved when roasting corn and multi-grain pellets. For example, it is possible to reach the output capacity of 500kg/hour for potato pellets and capacity no more than 100kg/hour for corn pellets on the same machine.
How does the oil affect product quality and how long can be used the oil?
It is important to monitor not only the amount of absorbed oil, but also its quality, which is negatively affected with the high frying temperature, as well as contact with the steam released during frying. In addition, pieces of crushed pellets can get into the oil. Charring quickly, it contaminates the oil with combustion products. The properties of the oil during frying gradually change as a result of the influence of various factors. With prolonged frying of pellets in the same oil, its color becomes dark, the taste deteriorates, becoming bitter with a flavor of drying oil. The weight, the viscosity and the content of non-oxidized substances and FFA (free fatty acids) increase, iodine number and flash point decrease. The smoke point is the feature of the resistance of the oil to heat. Changes in the properties of oils are a consequence of some complex simultaneous processes, in which the main role belongs to oxidation, then polymerization and, finally, hydrolysis. When heating oil without food, more significant changes occur in it than when frying the food. This is due to the fact that the product contains proteins and antioxidants that react with the oxidized components of the fat, preventing their further transformation. Foods rich with vitamin C and starch protect the fat in the oil from oxidation. Oxidation processes are the most important among those occurring in the oil during storage and heating them with air access. It is these processes that mainly cause the appearance of rancidity in the oil during storage and during frying, and then in the finished product.
The hydroperoxides are prone to decomposition reactions: the amount of peroxide compounds increases at the beginning, and then begins to fall as a result of destruction. Therefore, there is no correlation between the taste of the oil and its peroxide value and it is not possible to use it to assess the quality of the oil. With the decomposition of peroxide compounds, the hydroxy acids and carbonyl compounds are formed. An increase of the fat temperature, the ratio of its surface to the volume, as well as the number of double bonds, accelerates the chain oxidative reaction. The light exposure also speeds up the oxidation process. The resulting hydroperoxides are the primary molecular product of oil self-oxidation. As a result, they undergo numerous transformations, forming secondary oxidation products. With a continuous frying process, the quality of the deep-frying oil depends on the amount of oil change:
K= q / Q,
Where “К” is turnover coefficient, then TC;
“q” is the amount of oil absorbed by the finished product in one hour;
“Q “ is the amount of oil loaded into the fryer.
The higher the K value, the longer the oxidative transformations take place, it is desirable that the TC (turnover coefficient) per hour is not less than 0.1. Polymerization processes take place in oils as a result of prolonged exposure of the high temperatures. As the saturation of the oil increases, the degree of polymerization can be judged by the iodine number (it decreases). Hydrolytic processes occur as a result of the interaction of oils with moisture released in the form of vapors. At the same time free fatty acids are formed, and their value can reach 5% or more in case of an improperly organized frying process, taking into account the fact that good quality oils contain <0.08% FFA. During the normal frying process, this amount should not be higher than 0.5%. Higher values indicate deficiencies in production or poor quality of the oil used for frying. The color of the oil during frying changes to darkening as a result of increased red tones. The increase of the red pigments by 8-10 times is considered small and organoleptically not captured. An increase in their number by 100-150 times is an indicator of a significant deterioration of the quality.
When frying, a number of chemical reactions take place simultaneously with the described changes. The most important for the quality of chips / snacks should be considered the reactions of the formation of melanoidins — substances from a slightly yellow to dark brown color.
The melanoidins are formed as a result of reactions between nitrogenous substances (oftenly amino acids) and carbonyl compounds — sugars. Frying creates conditions conducive to the formation of melanoidins. At temperatures over 170 ° C, the interaction between amino acids and sugars is extremely rapid. Therefore, raw materials for the production of pellets must be selected with the least amount of sugars, especially glucose and fructose. The amino acids without sugars, like the latter without the presence of compounds with amino groups, do not produce colored products when heated.
What factors affect the quality of snacks during manufacturing and storage?
The appearance of undesirable chemical and organoleptic changes, primarily oxidation and rancidity of snacks, depends not only on the quality of the pellets and oil, but also on other reasons. The main ones are:
- the correct preparation of pellets before frying;
- the structure of the frying equipment and operation way;
- the mandatory filtration of the oil;
- the quality of packing materials;
- storage conditions for pellets, oil and fried chips / snacks.
It is necessary to monitor the moisture content of the pellets. When they are moistened above 12%, it is necessary to dry them, i.e. keep for 2-3 days in a warm room unpacked. Sometimes pellets can be dried in a stream of hot air at 110 ° C for 20 seconds. If a cold pellet is immersed in hot oil, its temperature will drop, the frying time lengthens, and the product experiences shock, which degrades the quality of the snacks. When transporting pellets over long distances, it is possible to partially crush them and form small pieces. Small pieces of pellets must be separated, because they contaminate the oil and accelerate deterioration.
Why is it better to use ovens with intermediate (indirect) oil heating and what affects the quality of the oil during frying?
The method of heating the oil and the type of heating device is an important feature of the design of the fryer with «indirect» heating. When the products of fuel combustion first heat the intermediate heat carrier, and it transfers heat through the surface of the heat exchanger to the heated oil, oil is destroyed least of all in a fryer of this design. It is possible to very accurately control the process of heating the frying oil on the surface of the heat exchanger with automation, preventing the temperature on the surface from increasing to the «critical» one. One of the most radical measures to ensure the high quality of oil in any fryer is the maximum reduction in its quantity. The turnover coefficient (TC) used for the oil renewal in the frying machine is a specification parameter of the frying equipment. This specification item contains two parameters: the amount of oil in the fryer and the amount of oil absorbed by the product. The decrease in the volume of oil in the frying oven has a limit due to the heat engineering mode of its operation. The oil should cover the pellets to be fried. In case there is a small amount of oil in the frying tank the oil temperature drops sharply after loading each new portion of raw materials, the frying process becomes longer, and the quality of products becomes worse. The daily turnover coefficient (TC) of the oil should be more than two. Also the complete elimination of steam and condensation helps to improve the quality of products, because the resulting droplets, falling back into the fryer, significantly accelerate the deterioration of the oil. The presence of 0.7% suspended condensate is sufficient to cause oil deterioration. It manifests itself in increased foaming, darkening and an increase in the content of FFA. An important measure taken to preserve the quality of the oil is to prevent its aeration. The aeration (especially simultaneously with exposure to high temperatures) promotes fat oxidation and, therefore, should be eliminated as much as possible. Aeration occurs not only in moving condition, but also when the oil is still. This phenomenon can be observed in ovens and in storage tanks, if air comes into direct contact with the surface of the oil.
During the frying of the pellets, the water vapor protects the surface of the oil from aeration in some extent. But as soon as the supply of raw materials to the frying equipment stops, atmospheric oxygen oxidizes the hot oil and accelerates its deterioration. To prevent this, the design of our fryers provides a rapid cooling of the oil and its protection by covers located directly above its surface (without an intermediate layer of air). The tanks must be completely filled with oil. Prevention of aeration contributes significantly to maintaining the high quality of the oil during frying and extending the shelf life of the finished product. Thus, for the longest possible preservation of the quality of the oil during frying, the following conditions must be observed:
- heating oil no higher than 200°C;
- the gradual refill of fresh oil to the fryer to replace the absorbed oil during frying so that the initial oil level remains constant throughout the entire operation;
- exclusion of the possibility of adding old oil that was already used for frying, as well as the ingress of condensate from the ventilation pipes of the fryer;
- rapid cooling of the oil and storing it in tanks or in a deep fryer under conditions that exclude aeration in case of interruptions in operation. Interruptions in oil heating during fryer downtime will significantly reduce oil stability.
To extend the shelf life of snacks and oil, it is necessary to remove the used oil from the fryer at the end of each day, cool and pump the oil into a separate tank without mixing with fresh oil, and clean the contact surface of the frying equipment from deposits, rinsing everything with a hot cleaning solution. Once the cleaning is complete, the cleaning solution should be completely removed by repeatedly rinsing the oil-contacting surface of the equipment with hot water from a hose. It is especially recommended to carefully control the quality of washing when using detergents containing alkali, soap, trisodium phosphate and other substances that can cause saponification of the fats.
Oil filtration is an important factor in the system of measures to ensure the long-term preservation of chips. By means of filtration, the oil is freed from charred small particles and other impurities deposited on the finished product in the form of dots, giving it a bitter taste, deteriorating color, and increasing the amount of FFA. The oil storage tanks are made of stainless steel and are not big, they are designed to consume the contents within one, at least 2-5 days. Otherwise, oil will remain in contact with air for extended periods of time as oil is added to the frypot. It is essential that piping connecting storage tanks to other equipment is always filled with oil. This will eliminate the possibility of oxidation. Oils and fats should be kept within the required temperature and not exceeded at a determined period. Light greatly accelerates the oxidative effect of air on oil.
Which oil can be used in your deep-frying ovens?
The original properties of the oils greatly influence the quality of the chips and the stability during frying. The most suitable oils and low-melting fats (melting point up to 30 ° C) with a minimum acid number (no more than 0.3 mg 0.1N. KOH) and the amount of unsaturated fatty acids. Oils containing a large percentage of unsaturated (linoleic and linolenic) acids, in particular flaxseed oil, are completely unsuitable, cause when heated, these unsaturated acids are rapidly oxidized. The best vegetable oils for the production of chips are peanut, corn, soybean and cottonseed oils or mixtures thereof. As sunflower oil is unstable during storage and heating, and also gives a large percentage of waste, it is not recommended, but in exceptional cases it can be used if it is refined and deodorized, has a low acid number and good organoleptic characteristics. Vegetable oils should be neutral in taste. Many snacks producers have recently started using palm superolein for frying. Palm olein is highly stable, has a pleasant color and is a rich source of vitamins A, D, E, K and essential fatty acids. Quality indicators of palm superolein are:
- Smoke forming temperature — 230°C
- Content of FFA — 0,08%
- Melting point — 16,7°C
- Cholesterol – 0
How are thr flavors applied to ready chips and what is the recommendation rate?
After frying and draining the oil on a mesh conveyor, the chips are directed to a coating drum for dosed application of flavoring additives. The flavor of chips is determined by the additive applied to their surface vastly. Flavoring and aromatic additives must be selected only of high quality, free-flowing and non-hygroscopic. Most oftenly, the content of additives in the product is about 4-5%. However, the rate of addition of additives depends on the preferences of the customer and the recommendations of the additive manufacturer.
What type of package is preferable for packing chips and snacks and how can they be stored for as long as possible?
It is recommended to cool the chips / snacks in natural conditions before packing. Chips/ snacks are packed in bags made of single or multi-layer films. Packaging materials must be grease-, water-, steam- and gas-tight. The most commonly used materials are single and double layer metallized polypropylene. However, the shelf life depends on the correct frying process, on the quality and properties of the packaging materials, as well as on the temperature and humidity in the room. The optimum storage temperature for pellet chips is from 0 to 10 ° C with a relative humidity no more than 75%. The organoleptic properties of oils change not only during frying, but also during storage of snacks. In case of long storage a rancid taste appears, stronger changes cause the bitterness of the product. When the temperature is increased (especially above 25 ° C), oxidation processes accelerate and cause deterioration of the oil already in the package. To extend the shelf life of your chips, we recommend:
- To use only high quality refined deodorized oils containing a small amount of EFA (linoleic and linolenic) and FFA.
- O avoid oil heating over 200°C and aeration while frying and storage.
- To clean the oil constantly and to filter the oil periodically (not less one time per day).
- To ensure a high oil changeability, turnover coefficient (TC) should be at least 2 per day.
- To cool the oil after finishing work immediately.
- To avoid overheating oil in the fryer and in the heat exchangers.
- Do not add new oil to the waste oil with a high acid number.
- To clean frying equipment after removing the oil at the end of operation, completely rinse off the used detergents with clean water.
How to control the technology of frying chips / snacks?
The control over the observance of the technological process and, first of all, frying should be especially careful, at least once an hour. It is necessary to check the oil temperature in the frypot and the frying time. Adjustments should be made to the frying mode during the shift, the best mode is set up empirically. Changes in the quality of oil during frying are monitored at least twice a shift, determining the acid number, which should not exceed 1.0 mg KOH. In order to ensure the acid number to be low, it is necessary to ensure a quick change of oil in the equipment for frying chips & snacks. The oil must be consumed for absorption into the pellets and replaced with new oil before the decomposition process begins in it, which significantly increases the acid number. The higher turnover coefficient of the oil (the TC), the less it decomposes. In order to ensure a high TC of the oil, it is recommended to operate the fryer at full load.