Effects of lipid oxidation on french fries in re-used cooking oil

Effects of lipid oxidation on french fries in re-used cooking oil

Chapter one: INTRODUCTION

Background information

Cooking oil is a plant-animal or synthetic fat used for frying baking and other types of cooking. It is also used in food preparation and flavouring not involving heat such as salad dressing and bread dips.it is commonly known as edible fats the word oil comes from Latin word oleum typically,oil is liquid at room temperature,,there is a wide variety of cooking oils from plants sources such as olive palm oil,soya barn oil, corn oil, sunflower oil,peanut oil, and sunflower oil as well as animal based oils such as Butter and lard . Fats and oils are also called triglycerides obtained from animal sources, which are generally solid while those from plant sources are usually liquid. Pure oils are colourless, odorless and tasteless but due to some foreign substances that are liquid soluble causes changes in oilcomposition(Melendez et Al 2001). Oils that are highly saturated includes, coconut oil, palm and palm kernel oil, saturated fats should be replaced with poly saturated fats and monosaturated fats, soya beans, sunflower, are good sources of poly saturated fats while peanut oil, cashew nuts and nut based oils may present a hazard to person with nut allergy(kamisa et al2012)

Lipid oxidation is the oxidative degradation of lipids.its the process in which free radical s steals electrons from the lipids in cell membrane resulting in cell damage, itmostly affects polyunsaturated fatty acids because they contain multiple double bond in between (

Re using cooking oil is one of the most common practice due to raise in cost of living mainly in preparation of fried foods, frying improve quality and sensory properties of food by forming compound’s that impact aroma, attractive colour crust and texture which is highly appealing to consumers ( Choe and min 2015)

Frying using the same oil for two or more times causes raeaction such as oxidation of lipids which generates hydroperoxidase that are rensponsible for given side affects such as health effects ie hypertension and cancer, reusing cooking oil on french fries or any other foods affects the colour of fried food, the oil also turn darker in colour an indicator that oxidation of lipids took place due to development of pigments( non volatile decomposition of products) during thermal decomposition of fatty acids which diffuses into oil during frying and oxidation(Nayat et Al 2016)

There are three types of oxidation that takes place when re used cooking oil are used this includes, thermal oxidation, autooxidation and photosynthensized oxidation, deep frying also causes mass transfer which cause dissipation of oil, protein, cabohydrates, vitamins and moistures from fried foods(Krokids et Al 2006) affecting food chemical properties.different brands of cooking oil have different extent of lipid oxidation hence best brand of cooking oil should be used during frying that has little or no effect of lipid oxidation

Objectives

General objectives

To recommend the most suitable brand of oil that can be re used without possing health hazards to consumers.

Specific objectives

To determine effects of re used cooking oil on saponification value and acceptability of french fries to consumers.

To determine effects of re used cooking oil on peroxide value and acceptability of french fries to consumer.

To determine effects of re used cooking oil on iodine value and acceptability of french to consumer.

Research hypothesis

No significant(p=0.05) difference in saponificaion value and acceptability of french fries.

No significant (p=0.05) difference in saponificaion value and acceptability of french fries

No significant ((p=0.005) difference in iodine value and acceptability of french fries.

Problem statement

Cooking oil with it’s diverse applications and major consumer preference is mostly reused by consumers who lack the knowledge on effects of reusing cooking oil on french fries , this repeated heating of cooking oil may cause thermal oxidation which produces free radicals that might be source of diseases such as hypertension and cancer.re using cooking oil on french fries also changes the appearance of french fries on colour hence lowering it’s acceptability in the market and different cooking oils have different rates of oxidation, some have low oxidation rates while some have a higher oxidation rate

Justification

When Cooking oil is heated lipid oxidation occurs different cooking oils have different rates of lipid odlxidation. Reusing cooking oil may lead to health hazards such as cancer and hypertension. Our research aiming at identifying and recommending oil that can be reused with low rates of lipid oxidation cooking oil that can withstand prolonged heat avoiding or reducing thermal oxidation.

Chapter two litrature review

Due to raising standards of living residents in Kenya tharakanithi county re use cooking oil durig prouction of fried food and this is a common practice in hotels and local food vendors that deal with fried foods without knowing the effects that are associated with continues using of cooking oil cause lipid oxidation, cooking oil is a plant , animal or snythetic fat used in frying baking and other type of cookingCooking oil consists of edible vegetable oils derived from olives, peanuts, and safflowers, to name just a few of the many plants that are used. Liquid at room temperature, cooking oils are sometimes added during the preparation of processed foods. They are also used to fry foods and to make salad dressing.

People in many regions began to process vegetable oils thousands of years ago, utilizing whatever food stuffs they had on hand to obtain oils for a variety of cooking purposes. Early peoples learned to use the sun, a fire, or an oven to heat oily plant products until the plants exuded oil that could then be collected. The Chinese and Japanese produced soy oil as early as 2000 b.c., while southern Europeans had begun to produce olive oil by 3000 b.c. In Mexico and North America, peanuts and sunflower seeds were roasted and beaten into a paste before being boiled in water; the oil that rose to the surface was then skimmed off. Africans also grated and beat palm kernels and coconut meat and then boiled the resulting pulp, skimming the hot oil off the water. Some oils have become available only recently, as extraction technology has improved. Corn oil first became available in the 1960s. Cotton oil, watermelon seed oil, grapeseed oil, and others are now being considered as ways to make use of seeds that were, until recently, considered waste.(Bhattachary et Al 1996)

The first efforts to increase output were undertaken independently in China, Egypt, Greece, and Rome, among other places. Using a spherical or conical stone mortar and pestle, vertical or horizontal millstones, or simply their feet, people began to crush vegetable matter to increase its available surface area. The ground material would subsequently be placed in sieves such as shallow, flat wicker baskets that were stacked, sometimes as many as 50 high. The matter was then pressed using lever or wedge presses. The Greeks and Romans improved this process by introducing edge runners to grind and a winch or screw to operate a lever press. Their method was used throughout the Middle Ages. the value of saponification is used to determine the amount of fatty acids into soaps with the help of aquoes alkali such as NaoH.soaps are fatty acid of salts that consists of long carboxylic acid carbon chains, saponificaion value shows how much pottasium hydroxide in milligrams required for agram of fat to be saponified, therefore,one can easily get to know about the gram of saponifie fats present in the food sample.Iodine value can be used to measure the degree of unsaturation of oils and fats. The results are normally expressed as the number of grams of iodine absorbed by 100 g of oil or fat, considering the conditions of the test. This parameter is extremely important in the palm oil industry, where it is used to follow the fractionation process. The protocol for iodine value determination usually comprises a titration procedure, such as the Wijs method.In this procedure, iodine chloride is used for double-bond saturation analysis, and the content of consumed iodine is measured by titration with 0.1 mol L

− 1

sodium thiosulfate solution.lipids and triacylglycerol naturally occur in oils and fats.Their chemical composition contains saturated and unsaturated fatty acids and glycerides. Edible oils are vital constituents of our daily diet, which provide energy, essential fattyacids and serve as a carrier of fat soluble vitamins. Corn oil which is obtained from seeds of Zea mays is an important component usually used as food and also as a vehicle in certainpharmaceutical formulations such as in suspensions and emulsions. (Alvarez and Rodrı´guez, 2000) Mustard oil from Brassica nigra has 30 per cent protein, calcium, phytins, phenolics and natural anti-oxidants. Mustard oil contains a high amount of mono-unsaturated fatty acids and a good ratio of polyunsaturated fatty acids, which is good for the heart.Mustard oil contains the least amount of saturated fatty acids,making it safe for heart patients.Different physical and chemical parameters of edible oil were used to monitor the compositional quality of oils (Ceriani et al., 2008; Mousavi et al., 2012). These physicochemical parameters include iodine value (IV), saponification value (SV), viscosity, density and peroxide value (PV). Edible oils are one of the main constituents of the diet used for cooking purposes. Several researchers studied the impact of temperature on the stability, viscosity, peroxide value, and iodinevalue to assess the quality and functionality of the oil (Farhoosh et al., 2008; Li et al., 2010; Jinfeng et al., 2011). Deep frying is one of the most common methods used for the preparation of food. Repeated frying causes several oxidative and thermal reactions which results in change in the physicochemical, nutritional and sensory properties of the oil (Che Man and Jasvir, 2000). During frying, due to hydrolysis, oxidation and polymerization processes the composition of oil changes which in turn changes the flavor and stability of its compounds (Gloria and Aguilera, 1998). During deep frying different reactions depend on some factors such as replenishment of fresh oil, frying condition, original quality of frying oil and decrease in their oxidative stability (Choe and Min, 2007). Atmospheric oxygen reacts instantly with lipid and other organic compounds of the oil to cause structural degradation in the oil which leads to loss of quality of food and is harmful to human health (Bhattacharya et al., 2008). Therefore, it is essential to monitor the quality of oil to avoid the use of abused oil due to the health consequences of consuming foods fried in degraded oil, to maintain the quality of fried foods and to minimize the production costs associated with early disposal of the frying medium (Vijayan et al., 1996). Different analytical methodologies used for quantitative evaluation of heated oils are Gas Chromatography (GC), High Performance Liquid Chromatography (HPLC), Ultra Visible Spectrometry (UV) and Fourier Transform Infrared (FT-IR) Spectroscopic techniques. There are several advantages of the FT-IR technique over the other conventional physical and chemical methods due to its ease of sample handling, quickness and low requirement of sufficient quantity of hazardous solvents, improvement in the signal to noise ratio, reduction in the scan time, and requirement ofhigh energy throughout, in this technique all wavelengths are recorded simultaneously (Che Man et al., 2010). The aim of the present study is the quantitative analysis of the properties of Mustard and Corn oils and the effect of temperature on the properties of oils after heating and frying with carbohydrate using potato pieces and also the use of same oil for frying three times to check the changes in oil quality. Changes in the physicochemical properties of oils are also analyzed by FT-IR analysis to evaluate the degree of oxidation after heating and frying.

ADVANTAGES AND DISADVANTAGES OF USING COOKING OIL

.5 Common Types of Cooking Oil and the Advantages and Disadvantages of Each

1. Olive Oil

This is one of the most popular types of cooking oils with various uses aside from kitchen use. It is considered as a superfood associated with a healthy heart but is not ideal for all situations.

Advantages

High content of mono-unsaturated fats that help lower heart disease risks.

The extra virgin olive oil is abundant in essential fatty acids and antioxidants which helps in fighting free radicals, weight management, and inflammation.

Lowers blood pressure and reduces breast cancer risks.

Disadvantages

Expensive.

Contains high amounts of saturated fat that is considered as bad fat.

Not suitable for frying due to its low smoke point. Heating the oil beyond its smoke point modifies the oil and is harmful to the health.

Can cause dermatitis, weight gain, and respiratory complications to those who are allergic to it.

2. Canola Oil

Advantages and Disadvantages of Using Cooking Oil

Canola oils are extracted from rapeseeds and used in most kitchens for frying in medium heat.

Advantages

An inexpensive source of healthy cooking oil.

High content levels of mono-unsaturated fats.

Low content of saturated fat.

Contains Omega-3 fatty acids good for the heart.

Subtle taste that won’t affect the flavor of the dish.

Disadvantages

Easily spoils.

Can emit toxins when subjected to high temperature.

Contains high levels of Omega-6 fatty acids that are associated with inflammation – the primary cause of chronic diseases.

3. Vegetable Oil

Vegetable oils are usually made from the combination of various oils such as corn, palm, soybean, and sunflower.

Advantages

Inexpensive and longer shelf life.

Contains high levels of good fatty acids.

Disadvantages

Heavily processed from ingredients extracted from genetically modified organisms (GMO).

Some are partially hydrogenated which can destroy the good fatty acids in the oil. Trans fatty acids can be formed which increases the risk of weight gain and heart diseases.

4. Coconut Oil

Coconut oils are full of flavor and are regarded as healthy by most. But it has stimulated controversies because of its high content of saturated fat.

Advantages

High levels of antioxidants.

High smoke point.

Some studies show that coconut oil can improve the brain health of elderly people susceptible to Alzheimer’s disease.

Disadvantages

The natural flavor of coconut oils might overpower the desired flavor of specific dishes.

5. Corn Oil

Corn oils have a golden yellow color extracted from maize kernels. It is suitable for baking and frying but must be only cooked under medium temperatures.

Advantages

Less smoke is produced.

Does not discolor easily.

Low saturated fat content.

High omega-3 content.

Disadvantages

Easily becomes rancid.

General Advantages and Disadvantages of Cooking Oil

Now, let us discuss some of the general advantages and disadvantages of cooking oil including the ones related to the environment.

Advantages

Used oil can be recycled. Recycling used cooking oils does not only benefit you but also the environment.

They can be used as renewable energy in the form of biodiesel which is environmentally friendly. Used cooking oil can be used to power machines in engines and vehicles designed to run on diesel. Because it is clean, it can help in minimizing pollution. Thus, reducing the number of greenhouse gasses in the atmosphere.

Recycling used cooking oil owers cleanup costs. When establishments recycle used oil instead of draining them down to the sink, cleanup costs are lowered tremendously. As solidified chunks of cooking oils can clog the sewage system causing the drainage pipes to fail. When this happens, the establishments will incur greater costs.

Disadvantages

As mentioned earlier, draining used cooking oil down your sinks can clog your sewage pipes.

The majority of establishments and households discard used cooking oils through their kitchen drains. Their reason for doing this method is because it is the most secure way of disposing of used cooking oils.

As it is similar to wastewater which is disposed of the same way.

But they lack the knowledge that cooking oil and water have differing properties.

Used cooking oil will solidify into chunks under low temperatures. This will end up clogging drain pipes and sewage systems.

Your drain will stop working properly and the sewage pipes on your streets will start spurting smelly contents containing disease-causing organisms.

Furthermore, clogged pipes can cause backflow of water which can flood your basement and other areas. Although this can be prevented if a backflow prevention valve, commonly check valves, is pre-installed in local drainage systems. But not all check valves can handle harsh environments.

CHAPTER THREE

Methodology

The project will be carried out in Chuka University tharakaka nithi county Kenya ,different brands of cooking oil that is, Top fry,golden fry, elianto, because they are the most consumed brands in kenya Will be purcahsed for nearby supermarket ,the Irish potato(solanun tuberosum)will be purchased from the municipality market in Chuka town

Processing of Irish potatoes

potatoes will be sliced washed , air dried for 1h hour and 500g of sliced rish potato will be weighed then fried for 15 minutes approximately in 2 litre of each of the above

mentioned cooking oils which will be heated separately to 180degrees

After frying compeletly ,the remainig cooking oil will be left to cool and reused the next day .The cooking oil will be sampled and analysed before reusing the next day.

Flow diagram

Peeling

Washing

Drying( for 4 hours)

Frying (for 180 degrees)

Data collection

Data annalysis

Annalysis

PEROXIDE VALUE

The peroxide value gives the concentration of peroxides in mmol/kg oil. The peroxides present are determined by titration against thiosulphate in the presence of potassium iodide and Starch as the indicator ((Mohdaly et al.)).

One gram of oil will be weighed into a boiling tube and one gram of potassium iodide added and 20 ml of solvent mixture (acetic acid and chloroform). Then Boil the liquid for 30 seconds, transfer the contents quickly to a conical flask containing 20 ml of 5% potassium iodide solution. Wash the tube twice with 25 ml water, collect into a conical flask and titrate against N/500 sodium thiosulphate solution until yellow color almost disappears. Then add 0.5 ml starch and shake vigorously until blue color disappears. Set a blank.

Where;

S= ml of sodium thiosulphate (test blank)

N= normality of sodium thiosulphate

SAPONIFICATION VALUE

It is number of milligrams of potassium hydroxide required to saponify one gram of fat under specified conditions. It measures the average molecular weight of all fatty acids present.

About 2 grams (w) of oil will be weighed accurately into a conical flask. Dissolve the oil in 25 ml of 0.5 N alcoholic potassium hydroxide solution. Reflux the reaction mixture using a water condenser on a water bath for half an hour. The resultant solution cooled and titrated against 0.5 N HCL solution adding 1ml phenolphthalein, the number of ml of acid required will be noted. An identical blank experiment will be performed. The number of ml of hydrochloric acid required will be noted.

IODINE VALUE

Is the measure of the degree of unsaturation of oils using Wijs Method .The higher the level of unsaturation the greater the rancidity of oils, Using iodine solution, potassium iodide, methyl chloride an sodium thiosuiphate .

10 ml of fat sample will be dissolved in chloroform and labeled test. Add 20 ml of iodine monochloride reagent and mix the contents in the flask thoroughly. Incubate the flask for half an hour in dark. Set up a blank in another iodination flask by adding 10 ml of chloroform to the flask. Add 20 ml of iodine monochloride reagent and mix the contents thoroughly and incubate in the dark for 30 minutes. Take the test from the incubation and add 10 ml of potassium iodide solution. Titrate the test against standardized sodium thiosulphate solution until pale straw color is observed. Add 1 ml starch indicator into the contents in the flask. A purple color should be observed. Continue the titration until the color in the flask turns colorless. Repeat the procedure for the flask labeled blank.

Where;

N= normality of Na2S2O3 (0.1)

Sensory evaluation

Samples of french fries will be taken and sensory evaluation will be conducted by a pernel of thirty using hedonic scale of one to five..

Budget

Items

Quantity

Prices

Irish potato

I backet

700

Top fry

2litre

400

Golden fry

2litres

400

Elianto

2litre

600

Starch

500g

450

Pottasium hydroxide

500g

850

Potassium iodide

100g

2500

Hydrochloric acid sln

I litre

500

Iodine

I litre

600

Sodium thiosulfate

500g

310

Total cost

7,310

Budget.