CHẤT LƯỢNG RICE BRAN OIL.docx

8/13/2019 CHT LNG RICE BRAN OIL.docx

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LAPCrude rice bran oil contains ~96% of saponifiable fractions and ~ 4% unsaponifiable

fractions of lipids

which include phytosterols, sterol esters, triterpene alcohols, hydrocarbons, and

tocopherols

Rice bran oil contains a range of fats, with 47% of monounsaturated, 37% polyunsaturated,

and 20% saturated fatty acids

The antioxidant activity of the palm oil is due to the presence of carotenoids and Vitamin

E. Beta carotene the reason for the yellow color of the palm oil may also be an important

factor for the free radical scavenging activity gave a commentary on the antioxidant effect

of beta carotene and its role in cardio protection

In this paper, the antioxidant stability in palm oil and rice bran oil at different times ofheating is investigated using a simple marker viscosity. This parameter is measured at

different times of heating and at different temperature It is found that the antioxidant

stability in rice bran oil is greater than palm oil even under repeated thermal fluctuations.

The study of thermal degradation and antioxidant stability in the oil is carried out by heating

the oil to the frying temperature up to 250C for 0.5, 1, 1.5, 2hrs. After heating to desired

time, the viscosity of rice bran and palm oil is measured at 30C. Fig .3 shows the increase

in the viscosity of palm oil with the time of heating due to saturation of bonds in the

composition of oils. The viscosity of rice bran oil is almost constant due to antioxidant

stability in the oil. Viscosity increases with frying time due to oxidation, isomerisation and

polymerization reaction. Oxidation reaction leads to the formation of carbonyl or hydroxyl

groups bonded to carbon chain making flux among molecules that increases viscosity.

Fig.4 shows the variation of density with heating time. The density of rice bran oil is found

to be constant throughout the time of heating illustrates there is no molecular changes due

to antioxidant activity in the oil. It is observed that in palm oil there is increase in density

due to increase structural changes as there is increase in saturation composition of the oil.

Fig 5 and 6 illustrates the interaction between the ultrasonic waves and the composition of

molecules. The acoustic impedance value of palm oil increases as the reflection coefficient

increases due to increase in density and saturation in the molecules. Where as in rice bran

oil there is no disparity in the structure of the unsaturated composition present in the oil.


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Rice Bran Oil (RBO) has highest quality among other oils in terms of shelf life, fatty acid

profile, cooking quality, sensory attributes, nutritive value and oxidative stability. RBO is

an abundant source of primary antioxidants including Gamma-Oryzanol, alpha, beta,

gamma and delta tocopherol isomers, as well as the most active antioxidants, the

tocotrienols.

Due to its high flavour and oxidative stability than other oils it is used as frying oil in food

preparations.

They also mentioned that in the

processing of oilseeds for oil expression, water is sprinkled as a

pretreatment to increase the moisturecontent for better extractability. The

experiments were designed based on response surface methodology to

determine the best method to apply pressure, pressing time and moisture

content for maximum oil recovery.

The melting point of a lipid is dependent on both the degree of unsaturation and the chain length (OBrien, 2009). The melting

point increases with chain length and decreases with increased unsaturation. Among saturated acids, odd chain acids are lower

melting than adjacent even chain acids. The presence of cis-double bonds markedly lowers the melting point, the bent chains packing

less well. Trans-acids have melting points much closer to those of the corresponding saturates. Polymorphism results in two or more

solid phases with different melting points. Methyl esters are lower melting than fatty acids but follow similar trends (Scrimgeour,

2005). Vegetable oils saturated fatty acids are predominately even numbered carbon atoms ranging from 4 to 24 (OBrien, 2009).

Table 2.2. presents melting point of some fatty acid and methyl ester.

http://wideliaikaputri.lecture.ub.ac.id/2012/01/fat-and-oil/

Table 2.2. Melting Point of Some Fatty Acids and Methyl Ester

Fatty

Acid

Melting

Point (oC)

16:0 62.9 (30.7)*

17:0 61.3 (29.7)*

18:0 70.1 (37.8)*
http://wideliaikaputri.lecture.ub.ac.id/2012/01/fat-and-oil/http://wideliaikaputri.lecture.ub.ac.id/2012/01/fat-and-oil/http://wideliaikaputri.lecture.ub.ac.id/2012/01/fat-and-oil/


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18:1 9c 16.3, 13.4

18:1 9t 45

18:2 9c12c -5

18:2 9t12t 29

19:0 69.4 (38.5)*

20:0 76.1 (46.4)*

*Values for methyl esters in parenthesis

(Scrimgeour, 2005)

The fatty acids with two hydrogen atoms bonded to each carbon atom in the

chain are saturated, that is, they contain no double bonds between carbons.

Saturated fatty acids generally vary in chain length from 4 to 24 carbons

atoms. Saturated fatty acids, with some exceptions, have straight, even

numbered carbon chains. They are the least reactive and have a higher

melting point than unsaturated fatty acids of the same chain length due to

the dense packing of the unbranched chain structure into the crystal lattice.The fatty acids identified without double bonds are saturated (OBrien,

2009).

The saturated fatty acids with 2 to 6 carbon atoms are short chain fatty acid.

These short-chain fatty acids have little or no effect on cholesterol, are a

liquid at room temperature, and vaporize readily at high temperatures.

Saturated fatty acids with 8 to 12 carbon atoms are medium chain fatty

acid. Medium chain fatty acids are thought to be directed to the liver andburned as energy rather than being stored in the body as fat. They provide

8.3 calories/gram compared with 9.2 for the other fatty acids. Laboratory

animal and human research revealed that medium-chain fatty acids act

more like carbohydrates than saturates, that is, they do not raise serumcholesterol levels. Esters of medium-chain fatty acids with glycerol are


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critical ingredients in sports foods, clinical nutrition, and infant

formulations (Wainwright, 2000; Grundy and Denke, 1999; Nicolosi, 1997

in OBrien, 2009). Saturated fatty acids with 14 to 24 carbon atoms are

classified as long-chain fatty acids. The most notable long chain saturates

are those within the 14 to 18 carbon atom range (OBrien, 2009).

The fatty acids that contain double bonds between the carbon atoms are

termed unsaturated. As many as seven double bonds have been reported;

fatty acids with an excess of three double bonds are most likely of aquatic

origin. Those containing 1, 2, and 3 double bonds and 18 carbon atoms are

the most important unsaturated fatty acids of vegetable and land animal

origin. Normal double bonds in the cisform cause a bend in the carbon

chain, which restricts the freedom of the fatty acid. This bend becomesmore pronounced as the number of double bonds increase. The presence of

double bonds also makes the unsaturated fatty acids more chemically

reactive than the saturated fatty acids and this activity increases as the

number of double bonds increase. The notable reactions are oxidation,

polymerization, and hydrogenation (OBrien, 2009).

Monounsaturated fatty acids have only one double bond. This fatty acid

class is the least reactive of the unsaturated fatty acids. Of the

monounsaturated fatty acids, oleic and palmitoleic are the most widelydistributed and oleic is considered the most important. Polyunsaturated

fatty acids have two or more double bonds. Chemically reactivity increases

as the number of double bonds increase. Polyunsaturated fatty acids with

two to six double bonds are of considerable interest nutritionally. Vegetable

oils are the principal source of the two essential fatty acids: linoleic and

linolenic (OBrien, 2009).

After cleaning, the bran was sent to the cooker for stabilization.

The bran was then heated using direct and indirect steam and cooked at

a temperature of about 90 - 100o C to destroy or inactivate the

enzyme-lipase and prevent the continued production of free fatty acids.

The cooked bran was then sent to the extractor


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OILSEEOS PROCESSING TECHNOLOGY Dr. Banshi D Shukia Dr.

Prabhat K Srivastava Er. Ram K Gupta CENTRAL INSTITUTE OF

AGRICULTURAL ENGINEERING India, August 1992

The natural flavour and odour of oils are due to the presence of non-fatty matter. Their colour is due to the presence of small amounts of

fat, soluble pigments such as cartoenoids and chlorophyll or some

times due to oxidation and polymerisation products of the fatty acids.

Fat in the diet serves to increase the palatability and flavour of foods.

They provide a lubricating action and delay the onset of hunger. Theyalso improve the texture of food items.Mechanical drying of oilseeds

at 1 05110C is preferable to minimize the quantitative andqualitative losses. The dried seeds also require cleaning to remove

sand, dirt, dust, leaves sterns, weed seeds, stones, metal piecs and

other extraneous matter before storing.Flaking is essential for

preparing ollseeds for continuous solvent extriction since no other

form of oilseed will facilitate oil extraction by disruptive effect of

rolling as well as by reducing the distances so that solvent and oil

must diffuse in and out of the seed during the reduc- tion process.

Almost all the oilseeds yield oil more readily if cooked adequatedly

prior to their mechanical expression and/or solvent extraCtion. The

cooking process coagulates the proteins present in the seed causing

coalescence of oil droplets and making th3 seed permeable to the flow

of oil. The process also decreases the aflinity of oil for the solid

surfaces of seed because of which the best possible yields of oil are

obtained on expression/extraction of cooked seed. The cooking process

also helps in imparting proper plasticity to seed mass. It insolibizesthe phosphtides and related substances to reduce refining losses of oil.

The cooking process destroys the moulds and bacteria to improve the

micro-biological as well as quality of oil cake.


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Further the process destroys the heat labile antinutrictionaf factors to

improve the nutritive value of protein rich oilseed meals. Heat

supple- ments the work of water in cooking the meal and also in

coagulating the albumiroids. On one hand, it weakens the cell walls

by cooking and on the other causes volumetric expansion of the

droplets which result in the rupture of cell walls and expulsion of oil.The cooking temperatures and its duration periods for durations of

working for most oilseeds range between and 301 20 minutes

respectively. Optimum conditions for cooking of an oilseed depend on

several factors viz. initial moisture content, and bio-chemical chara-

cteristics, cooking methods, equipment used, and method of oil extrac-

tion.

Oil from oilseeds in India is mostly extracted wi'h the help of

traditional animal drawn ghanies (Koihus), power ghanies, rotary

oilmills, mechanical expellers and solvent extraction units. However,

the solvent extraction techniques are also used for recovery of oil

from soybean, rice bran and pressed oilseed cakes

Excessive use of pressures to express more oil in single or double

pressing also affects the quality of oil as well as the nutritional value

of the oilseed cake and reduces the capacity of expellers. Now a

days, the press solvent extraction technique is also being used where

oil is first expelled at low pressure from oilseeds.\

Review on Recent Trends in Rice Bran Oil Processing

Mahua GhoshJ Amer Oil Chem Soc (2007) 84:315324

DOI 10.1007/s11746-007-1047-3


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The typical composition of crude RBO is 8184% triacylglycerols (TAG),

23% diacylglycerols (DAG), 12% monoacyl-glycerols (MAG), 26%

free fatty acids (FFA), 34% wax, 0.8% glycolipids, 12% phospholipids

(PL) and 4% unsap.

Crude oil, so

obtained, contains TAG as the major component (>80%)

along with various impurities. The main object of the

refining process is, therefore, to remove the impurities such

as waxes, gums/phosphatides, FFA and coloring materials

without altering the basic TAG composition for producing

edible quality oil. Presence of impurities, besides resulting

in poor color and haziness in appearance, will also cause

catalyst poisoning and a slow rate of hydrogenation if the

oil is used for making vanaspati.RBO is difficult to process due to its

high FFA, waxes,

bran fines and pigment content.These factors lead to high

refining losses when normal refining processes are em-ployed.

Important steps involved in the processing of RBO are

(a) settling or filtration of bran fines (b) degumming, (c)

dewaxing, (d) deacidification, (e) bleaching and (f)

deodorization.


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Rice bran oil contains up to 20% of high temperature

melting saturated fatty acids, which makes it difficult to

dewax this oil at lower temperature such as 8 or 10C. The

dewaxing can be done in the oil phase as well as in the

miscella phase by winterizing without or with suitable

additives.RBO have an unusual inability to cohere and settle out of

the oil clearly and it tends to emulsify the oil under the

conditions of refining. Color compounds in vegetable oils, e.g., chlorophyll,

car-otenoids, xanthophylls and their derivatives, are removed

by adsorption on activated clay or carbon

The wax content of RBO can be somewhat variable (28%),


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CHẤT LƯỢNG RICE BRAN OIL.docx