WHAT are Tortilla Chips?
Tortilla chips are produced with corn. Different corns can be used, yellow, white, whole wheat, flour etc. The corn is cooked and then steeped in water and lime. The lime is required to breakdown the hulls. After steeping the product, now called Nixtamal, is drained and washed to remove the residue lime. The Nixtamal is now ground producing a Masa (dried ground corn flour). The degree of grinding determines the grade of Masa. A course Masa is used for Tortilla chips (fried) where a finer grade maybe used for soft tortillas. After grinding the Masa is rolled into a sheet form and the tortillas shapes cut out, triangles discs, rectangles. The thickness of the sheet determines the weight of the final chip. The chips then go through a tiered oven at 500 to 554 oF (260 to 290 degC) for 35 to 50 seconds which reduces the moisture content ready for frying. The chips are then cooled prior to frying.
In commercial production of Tortilla chips, the chips are typically fried at temperatures of between 338 – 374oF (170 – 190 degC) for 50 to 80 seconds. But for yellow corn tortillas this could be as low as 320 oF (160 degC) and for a blend of white and yellow corn tortillas be as high as 410 oF (210 degC) for 60 to 90 seconds. The fried chip contains approximately 22 to 24% oil by weight.
The frying process tends to be continuous and best to have an indirect heated fryer giving better efficiency, but at a high capital cost. until they meet the desired quality parameters, which includes oil pickup. Kettle-style chips
Directly after frying the chips are seasoned and cooled in a rotary drum. There are a number of seasoning options, the basic option being just salted. On cooling the oil forms a seasoning coat on the chip.
The chips are then cooled to ambient and packaged in appropriate sealed bags.
FILTRATION / TREATMENT
Due to the nature of the preparation of the Masa (corn being soaked in lime), there tend to be a high content of metal ions in the chips that will wash out into the frying oil and act as catalysts leading to an accelerated oil degradation. The SuperSorb filter media, making up the filter modules, has been developed specifically for the adsorption of metal ions, Ca, Na, K etc.
Oil pick up will be 22 to 24% (possibly up to 28%), so for a continuous fryer operating at 1000kg/hr, that’s approximately 220kg/hr oil turnover, in a 1500 to 2000litre fryer that’s 6 to 9 hours’ oil turnover, quite a quick turnover.
End point will typically be 0.6 to 0.8% FFA.
The debris from this product is a hard granular solid, which is relatively easy to remove. There will be a need for a pre-filter to remove the bulk of this and if no pre-filter is in place then a twin bag filter arrangement with metal baskets should be ideal. Micron rating of baskets between 50 and 100um.
A better option would be a continuous rotary screen filter at 50 to 100um..
Normally continuous fryer type, external heat exchanger, temperature around 350 to 360oF (170 to 190oC).
May have a drag bar system or similar prefilter/crumb catcher system.