Developing and designing french fry lines for more than 45 years
Classic French Fries
The processing of French Fries has been optimized over several years by companies like Rosenqvists Food Technologies. The market for frozen French Fries is global and represents interesting growth opportunities for producers all around the world.
Classic French Fries is a typical cut potato product with several different variations of it. Thickness and shape may differ, you may even want a specific length or pattern in the cut, or perhaps cover it with coating.
Every single strip of French Fries should ultimately get the same frying treatment regardless of where its location is in the fryer. A single-layer product flow in the 1st stage fryer and a higher product bed in the 2nd stage fryer of 80-100 mm. In both fryers it is crucial to have a laminar oil flow throughout the width of the fryer ensuring smooth equal transport and processing of each French Fry. The laminar oil flow is of extra importance in the 1st stage for keeping the individual strips separated and to control oil velocity ensuring that the coating is set onto the product and not washed away.
Rosenqvists Food Technologies has extensive knowledge of the potato as raw material and how to design an effective process. We combine the latest technologies using computer simulation programs and build efficient and reliable process equipment.
We take full responsibility for design, manufacture and installation. We will commission the line and make sure that your staff get professional training in process control and maintenance.
The processing steps
As potatoes are received to the plant, they are sorted and pre-graded to correspond with the type of French Fry or other product to be produced. Potatoes then enter the line and pass through the Cyclone destoner and pre-washing units before conveyed to the peeler.
Cyclone Destoner with Prewasher
Steam peeling and inspection
In the Steam peeler, steam is injected during a short period, which makes the skin loosen from the potato flesh. Steam peeling is gentle and efficiently resulting in low peeling losses. The potatoes are directly conveyed to De-skinner, which removes the peel waste. This waste is pumped away. The potatoes are then washed clean prior to being inspected at the Roller Trimming Table and transported to the cutting process.
The cutting is performed by either a hydro-cutting or mechanical cutting system. The Hydro Cutting system uses water that is pumped together with the potatoes, through an exchangeable cutting block. In a Mechanical Cutter the potatoes can be cut into straight or crinkle cut, dices or other types. In the next step, the cut product passes a Sliver Remover, where small triangular shaped pieces are removed. A vibratory Nubbin Remover will sort out all short strips over exchangeable screens.
The potato strips pass through a blanching system, consisting of two Screw blanchers. Blanching is used to gelatinize starch, inactivate enzymes for colour and leak out sugar. The first blancher is designed for short time and high temperature and the second one for low temperature and long time. After blanching, the strips go through a SAPP-dipping unit before being pre-dried.
During the drying process, the moisture content is reduced and will prepare the strips for the frying process so that the final texture and colour can be achieved. In the Belt Dryer, air with low temperature and high humidity will ensure even drying result of each strip. The Belt Dryer uses the counter–air–flow principle where the air flow covers the full width of the belts. Drying is used to maintain uniform colour, stabilize product quality, avoid weak and soggy products to get final crispy fries. Before entering the fryer, the dried strips are slowly conveyed on the Equilibration Belt to get an even and uniform moisture content.
Multi Zone Frying
The Multi-Zone Frying System consists of; frying pan, drum oil filter, oil circulation pump and tube heat exchanger. The Frying pan with controlled oil flows together through multiple oil in- and outlets will give you the best tools to achieve the desired texture and colour. The frying belt lays directly on the pan bottom and with the belt return on the outside, it results in a very low total oil volume in the complete system. The drum oil filter continuously filters every drop of oil every 30 -45 seconds. The oil pump transfers the oil to the tube heat exchanger, where the vegetable oil is heated indirectly by steam or thermo oil. After frying the product will pass a de-fatting step, which can be a special designed de-oiling vibratory conveyor or an oil miser. For coated fries and other potato products, a batter applicator, settling belt and 1st stage-frying step is added before the normal frying system.
Read more about Rosenqvists coated French Fry system here!