What is an antioxidant?

These are chemical agents that disperse into the oil and contribute to maximum oil stability (slows the rate at which oil becomes rancid). Anti-oxidants work on the molecular structure of the oil making it more stable and delaying the rate of oxidation (oil breakdown).

What is an anti-foaming agent?

Anti-foam agents are added to oil to give it a longer shelf life by forming a surface barrier between the turbulent oil and air, reducing the rate at which oxidation takes place. Anti-foam agents also cause the bubbles, formed when moisture in food comes into contact with oil, to be reduced and to collapse more quickly reducing the surface area in contact with the air and so in turn reducing oxidation.

Neither of these substances has any effect on the sensory properties of the frying oil nor the flavour and taste of the foods fried.

How to judge a good frying oil

A good frying oil should have:

• A pale yellow to golden colour
• A clean and clear appearance
• A bland and fresh flavour to avoid flavour transference to the food
  being fried
• A clean and pleasant odour
• A smoke point in excess of 205°C
• A high flash point in excess of 315°C
• Antioxidants
• Anti-foaming agents
• Low viscosity

• Select the correct equipment - use a fryer that suits the size of the    outlet.
• Train your staff. They should understand the following:
   - Safety
   - Controls for temperature
   - Load levels for different products being fried (i.e. ratio of weight of      food to volume of oil)
   - Cleaning instructions
   - General frying practices
• Do not use copper or brass - these metals speed up oxidation and will
  severely reduce the frying life of your oil.
• Always load fryer with oil to maximum load line in your fryer.
• Top up regularly - this will maintain the frying life of the oil. Always allow
  the oil to reach the desired temperature after topping up.
• Heat the oil slowly - rapid heating causes the oil to burn around the   element causing breakdown and flavour deterioration.
• Fry at the correct temperature: Too high temperatures cause the food to
  darken too quickly before being cooked properly. Too low temperatures
  result in oil absorption, increasing oil costs, greasy food and increases
  frying time.
• Check the thermostat regularly.
• Prepare food correctly.
   - Uniform sizes to ensure even browning
   - Reduce moisture. Excess moisture shortens the frying life of oil by
     causing foaming and thus rapid breakdown. It also lowers the      temperature, rapidly causing increased oil absorption and
     hence greasy food.
   - Breaded products should have crumbs firmly pressed to the product
     to prevent crumbs falling off. Crumbs remaining in hot oil burn and
     blacken and cause strong off-flavours.
• Always use the correct food to oil ratio - 1 part food to 6 part oil. Rather
  fry smaller quantities than too large a quantity.
• Avoid mixing with other fats. With foods such as sausages, cutlets or
  hamburger patties the natural fat in these products will melt and mix
  with the frying medium. The mix of different fats plus the presence of
  other substances such as salt will cause the oil to break down. To
  avoid oil damage. These products can be coated in a batter or crumbs   as this reduces oil seepage. Rendered fat should not be added to
  fryers. This will reduce wastage and contain costs. The fat will spoil the
  quality of the high performance oils. Fat should be trimmed from meat
  before frying.
• Skim oil surface regularly. Left over particles in the fryer will brown and   smoke, hurting the eyes of the person frying, discolour fried foods and
  cause off-flavours to form.
• Drain fried food well to ensure minimum oil loss/wastage.
• Do not salt food before frying as salt accelerates breakdown.
• Once cooled keep oil covered after use to prevent unnecessary
  oxidation when not in use. Remember air, light, heat and water are an
  oil’s biggest enemies.
• Filter oil daily to extend the frying life of oil by removing microscopic   particles. This will also improve the appearance of the fried food and
  heating efficiency of the oil.
• Keep your fryer clean. A thorough cleaning should be done at least
  once a week with an alkaline/caustic cleaning agent. Rinse the
  fryer thoroughly to ensure all cleaning powders and alkalis are
  removed; if left behind, these will form soap with the frying oil and will
  give the foods an off-flavour as well as cause the oil to foam
  excessively.

Fry at the correct temperature:

Potato chips                         Blanch - 165°C
                                                       Fry - 180°C
Potato crisps                                        175°C
Potato straws                                       175°C
Vegetables                                 160 - 165°C
Onions                                                   180°C
Fritters                                                    180°C
Doughnuts                                            190°C
Fish battered & breaded                    175°C
Prawns                                                  175°C
Chicken Large                                      165°C
Small                                                      175°C
Cutlets                                                    170°C
Choux pastry                                         180°C

The perfect chip

Chips can be very low profit unless you control every step of the preparation and frying process.

Preparation of fresh potato chips

• Potatoes can be peeled either by machine or by hand; in both cases it
  is essential to train your staff not to over-peel. Careless peeling
  means a wastage of up to 15% - 2.25 kg of every 15 kg pocket.
• Chips should be cut to a uniform size either with a chip-cutting machine
  or by hand. Leave the chips to soak in water. This removes excess
  starch and sugar, both of which cause darkening of the oil, leading to a
  shorter frying life. Chip-whitener can be added to the water at this stage
  to prevent the chips from turning brown. However, chip whitener has a
  major is advantage as it produces an acid layer on the surface of the
  chips that attack the oil leading to rapid breakdown. The advantage of
  chip-whitener is that it allows for preparation of large quantities at one
  time without their turning brown, thereby achieving better utilisation of
  labour.
• Drain the chips and dry as thoroughly as possible before frying, since
  any excess water left on the chips leads to oil foaming and further   breakdown. Excessive foaming also drastically increases the risk of
  fire. Chips are now ready to be blanched.
• For convenience frozen, pre-prepared chips can be used.

There are many ways in which oil will break down when exposed to heat, water, air and light, namely:

Hydrolysis – This is the reaction of water with oil, which results in the formation of free fatty acids – FFA – and these acids accelerate breakdown of the oil and shorten the frying life.
Oxidation – The reaction of air with oil and is accelerated by heat and light. Oxidation causes oil to darken, to develop an off-flavour and odour, and to thicken and foam.
Polymerisation – This is a form of oxidation that results in an in-crease in viscosity, causing a sticky deposit on the walls of the fryer and on the heating element. When the oil has reached this stage the food will retain more oil during drainage and will become noticeably greasier. The oil will also foam excessively.
Flavour reversion – This is a chemical change, which causes the oil to degrade and develop a nutty flavour. This should not occur in oil that has been properly refined.

How do you slow down the above processes? Simply minimise the effects of heat, light, air and water wherever possible.

Several important changes occur when oil breaks down. These are follows:

Frothing – These are large bubbles of steam that cause the oil level to rise to the top of the fryer. This is caused by wet foods or foods containing a lot of moisture. Drying foods as much as possible before frying can prevent frothing.
Foaming – When the oil is almost completely broken down a fine foam appears on the surface of the oil. The bubbles are very small and remain on the surface of the oil. At this stage the oil is unsuitable for further use and can be a fire hazard (reduced flash point).
Darkening – All oil will eventually darken due to the various breakdown processes. However, dark oil is not necessarily unsuitable for use. Sugars in products such as potatoes and doughnuts will caramelise and cause the oil to darken.
Thickening – Oil tends to thicken as it breaks down. The thicker the oil the more it will be absorbed during frying and the greasier the end product.

Implications of the new legislation

Consumption of old and abused oils can cause problems such as growth retardation, tissue, liver and kidney damage and being carcinogenic. Departmental health inspectors have been appointed to monitor this section of legislation and to close any outlets contravening the Act.

How harmful is abused oil?

Edible oils and fats used for the frying of food stuffs are considered harmful or injurious to human health if they contain more than: 16% polymerised triglycerides and/or 25% polar compounds. The above compounds form when oil is repeatedly used over extended periods. This will result in poor quality fried foods and may be harmful to health.

What effect does old, abused oil have on health?

Consumption of old and abused oils can cause problems such as growth retardation, tissue, liver and kidney damage as well as being carcinogenic.

There are various tests available on the market to test the frying quality and safety of oil. Here are a few examples for your information.

Col Test

A visual test which is designed to determine significant browning of frying oil, which is an indication of the accumulation of unwanted chemical substances. This test is very accurate provided the instructions are followed closely. The Col Test consists of a mounted colour photograph showing four colour intensities of frying oil at different stages.

Standards for chips only
Colour standards specific for Crispa Gold Oil only

Do the colour test

Check oil colour daily
Take a glass container and fill it at least halfway with cooled Crispa Gold Oil. Hold container against the above colour graph and compare in bright light. If oil colour matches 1, 2 or 3, it is suitable for use. If oil colour matches 4, discard immediately

The classification is as follows:
Colour 1: The oil is good if its flavour (taste sample) is also acceptable.
Colour 2: The oil is still good if its flavour is acceptable.
Colour 3: The oil is still good if its flavour is acceptable.
Colour 4: Change of oil is recommended. The frying oil has reached the limit of acceptability by food laws, even if the flavour is acceptable.

Fritest

Frying oils rendered unfit by excessive heating turn yellow to brown when an alkaline reagent is added. The so-called alkali colour number is obtained by means of this type of test. Once the alkali colour number reaches or exceeds as specified value, the oil is considered unfit.

The classification is as follows:
Colour 1: The frying oil is perfect for as long as its taste is acceptable.
Colour 2: The oil is still fit for use.
Colour 3: A change of oil is recommended. Oil has reached the limit of its life for use with
foodstuffs, even though it may still look and taste acceptable.
Colour 4: The oil is definitely unfit for human consumption.

The Fritest is especially suitable for testing oils that are used to bake potato chips and similar foods, as well as deep-frying of only one specific type of food per fryer such as chicken or fish.

Oxifrit Test

Oils are particularly susceptible to the effect of atmospheric oxygen when heated. The so-called oxidation products, known as oxidised fatty acids (OFA) that are formed during such a chemical change are very numerous and complex.

Oxifrit is a rapid test based on the determination of oxidised fatty acids. The test solution contains indicators that change colour according to the OFA content. Fresh, unspoiled oil is blue, and oil which is no longer suitable for consumption, is olive. Between these two extremes there is a continuous spectrum of change, giving an indication of the deterioration of oil.

The results are classified as follows:
Blue colour: Fresh, unspoiled oil.
Green colour: A change of oil is recommended. The user may be committing an offence or be guilty of negligence.
Olive colour: STOP, the oil is unfit for use.

The Oxifrit Test is especially suitable for the testing of oil in which different foodstuffs have been fried, as well as where the food itself darkens the oil, such as foods containing a high sugar content (doughnuts).

Recommendation: It is possible to re-refine “old” oil so that its appearance is clear and free of odours; however, this process does not change the damage caused at molecular level, and the oil is still injurious to health, and will break down at a much faster rate than “new” oil. In South Africa, re-refining of oil does happen and this is used to dilute new oil to reduce price. To ensure that “mixed” oil is not purchased, it is recommended that well-established brands be bought from reputable suppliers.