Nuts

Nut Frying

WHAT NUTS ARE FRIED?

Nuts are traditionally produced by roasting. This means dry roasting in an oven or oil roasting in a fryer of some sort. At one time almost all nuts were oil roasted, but fears that oil roasting increased calories in the product resulted in some processors abandoning their oil roasters. This does create confusion in that the same term is used for two different process applications. The type of nuts which are fried includes both tree nuts and ground nuts; standard peanuts, walnuts, cashews, almonds, brazil nuts, hazelnut macadamia nuts, sunflower kernels, and pistachios. In addition, many of these products are further glazed, coated or treated prior to frying.

Nut Frying

Nut Frying-b

FILTRATION / TREATMENT

One of the biggest challenges with this application is food allergens. All tree nuts and ground nuts (peanuts) are deemed to be food allergens. A nut roaster typically fry’s numerous products in many different types of oils per customer requirements. Their processes and sanitation
programs must, therefore, be designed to reduce the potential for cross-contact. They have to change out the fryer oil between products, store the segregated oil and completely clean the fryer. Storing dirty oil further reduces the oil quality unless the processor develops and
implements programs to maintain oil quality, which may include but need not be limited to properly cooling the oil after use and sparging with nitrogen to protect the oil from oxidation.

Filtration components must also be cleaned between products and consumable filters replaced. One final point, however; there is a great need to do more research in the area of frying oils, frying and allergen transfer. There is simply not enough information available to properlyevaluate this situation.

Peanuts, especially, have a very fine dust that is washed off in the fryer and causes a mud in the bottom of the fryer. This is a very hard particulate to remove and will not be removed by a screen type filter, typically the first stage filter on a fryer. It needs a paper or bag type filter, but will blind the surface very quickly. A belt paper filter or papers in a Star type filter with frames works well. This means when utilizing active treatment systems in nut frying, a good particulate pre-filtration system is a necessity prior to fine filtration and treatment. We would expect such a pre-filter to be in the 30 to 50um range.

nut-frying-continuous-paper_and-pre-filter

Filtration / Treatment

One of the biggest challenges with this application is food allergens. All tree nuts and ground nuts (peanuts) are deemed to be food allergens. A nut roaster typically fry’s numerous products in many different types of oils per customer requirements. Their processes and sanitation
programs must, therefore, be designed to reduce the potential for cross-contact. They have to change out the fryer oil between products, store the segregated oil and completely clean the fryer. Storing dirty oil further reduces the oil quality unless the processor develops and
implements programs to maintain oil quality, which may include but need not be limited to properly cooling the oil after use and sparging with nitrogen to protect the oil from oxidation.

Filtration components must also be cleaned between products and consumable filters replaced. One final point, however; there is a great need to do more research in the area of frying oils,

Nut Type %Oil
Peanuts 49 - 54
Almonds 48 - 54
Walnuts 60
Cashews 43 - 47
Nut Type %Oil
Hazelnuts 60- 64
Pistachio Nuts 48 - 60
Macadamia 67 - 71
Pecans 65 - 69

Oil Pickup

Another challenge with nut frying is that peanuts and tree nuts contain large amounts of oil. The table below derived from the “Natural Food Guide for Nuts” summarizes oil levels in different nuts.

Oil pick up when oil roasting nuts is very low, typically in the 2 - 4% range. As may be seen from the table, nuts are very high in natural oil content. During oil roasting (frying), there is an exchange of oil between the nuts being roasted and the frying oil. It is for this reason, that many nut roasters use oils derived from the products they are roasting, i.e., almonds are fried in almond oil. However, there are many other oils used. It depends upon the processors and the demands of the market.

Debris

As described above the debris is a very fine dust which causes a mud to form on the bottom of the fryer or the surface of a fine filter. Some people have actually described the product that forms on filters during peanut roasting as peanut butter. There is larger debris, typically broken nut particulate, that will come out on a screen, but this is not as problematic as the fines.

Fryer

Nut roasters use many different fryers from small batch fryers to larger continuous fryers. The type of heating can be both external or direct fired. There is no standard in this industry. Frying temperature is low at approximately 300oF (150oC). The larger continuous fryers may also have a drag bar system to remove debris. The direct fired fryers will need to be dug out regularly to remove the mud build-up.

Examples of fryer size and capacity;

400 gallons (1500 litres) producing 4000lbs (1820kg) of product per hour, running 16 hours per day.

100 gallons (378 litres) producing 1800lbs (820kg) of product per hour, running 16 hours per day.

120 gallons (454litres) producing 2000lbs (910kg) of product per hour, running 16 hours per day.

Potential Benefits:

  • Extended oil life due to removal of fines. Important as oil maybe stored between product runs to avoid cross contamination. Typically, peanuts have their own oil, which is removed and stored when other nuts are fried. This is required to ensure segregation due to different nut allergens.
  • Maintain a cleaner oil, fryer and heat exchanger with reduced polymer build-up. This reduces maintenance (labour saving) and makes for more efficient heat transfer to the oil.
  • Potential for energy saving (not proven).