Chapter 4 Results and Discussion
CHAPTER 4
RESULTS AND DISCUSSION
In this chapter the results obtained from the experiments described in chapter 3 are discussed in detail, to highlight the remarkable observations and to offer possible interpretation for those observations.
The results are given in five sections. The first section describes the comparison of oil extractions from various types of rice bran. Second section deals with the mass transfer coefficient of rice bran oil extraction. The cross flow extraction of different bran types are explained in the third section and in the fourth section the oil extracted from raw and parboiled bran are compared. Finally the suitability of rice bran oil extracted from different varieties of bran available in Sri Lanka as a raw material for food items, pharmaceuticals and bio-fuel production is discussed.
4.1 COMPARISON OF OIL EXTRACTIONS FROM VARIOUS TYPES OF RICE BRAN
4.1.1 Yield of different varieties of bran
Different varieties of bran were experimented for extracting oil using the soxhlet apparatus with 8 mm diameter and 5mm height pellets and the results are shown in table 4.1 in Annex II. The IPA extractable oil percentage is shown in Figure 4.1 and different varieties showed different extractable oil contents with highest percentage of oil in Red Samba LD356.
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20 18 16 14 12 10 8
Yield(%) 6 4 2 0 LD356 BG450 BG360 BW364 BG352 AT307
Bran Type
Figure 4.1: Extractable oil percentages of rice bran varieties available in Sri Lanka
The yields are different in different varieties of bran. Due to the difference in degree of polishing and seeding times, the yields may differ. Different types were milled and polished in batch wise and since, polishing is partly done by humans; the degree of polishing can be different from one type to another (Taira, 1989).
There is no clear distinction between the bran layer and endosperm. The harder the rice is polished, the more bran is generated. Some of the endosperm is going into the bran and so the properties unique to rice bran are diluted as the rice is polished harder. This will lead to differences in yield.
Variation of oil percentage also depends on properties of different varieties such as oil content and porosity of the bran particle. Moreover, the difference in yield is due to the genetic variations of paddy (Fernando, et al., 2003).
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4.1.2 Properties of oil from different varieties of bran
4.1.2.1 Free Fatty Acid (FFA) content of oil
Oil extracted in section 4.1.1 was tested for the FFA content by the ASTM D1639 method and the results obtained are given in table 4.2 in Annex II. FFA content against the different varieties of bran is plotted in figure 4.2.
2.50
2.00
1.50
1.00 FFA (%) FFA
0.50
0.00 LD356 BG450 BG360 BW364 BG352 AT307
Bran Type
Figure 4.2: FFA content of oil obtained from different varieties of rice bran
The amount of free fatty acids depends on the nature of oil, method of extraction, storage conditions, humidity, temperature and lipase activity in rice bran. In this scenario, all the parameters except for the lipase activity in rice bran are the same for all these varieties. Type BW364 shows a significantly higher value of free fatty acids and this might be due to high initial free fatty acids as a result of lipase activity.
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LD356, BG450 and BG352 show low and somewhat equal values, whereas BG360 and AT307 show average values.
The acid value which is a measure of the free fatty acid content of oil, is an index of the measurement of freshness of oil. Humidity and high temperature result in an increase of the acid value due to hydrolysis of glycerides into free fatty acids. Higher values indicate undesirable changes as it not only results in greater refining losses but also increases susceptibility of oils to rancidity. It is thus very important in economics of oil refining. The oils intended for dietary purposes should not contain higher amounts of free fatty acids. The presence of free fatty acids in oils & fats is not desirable because they impart a sharp and unpleasant flavor to edible fats & oils.
4.1.2.2 Saponification value (SAP value)
By following the ASTM D1962 method, the saponification values (SAP value) for the above extracted oil samples were found and the table 4.3 in Annex II shows the SAP values. The graph related to this table is shown in figure 4.3.
300
250
200
150
100
50
0
Saponification Value oil) (mg KOH/g Value Saponification LD356 BG450 BG360 BW364 BG352 AT307
Bran Type
Figure 4.3: SAP value of oil obtained from different varieties of rice bran
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Saponification value is a measure of the molecular weight of the fatty acids present in oil. Shorter the average chain length (C4-C12) the higher is the saponification number (Tamzid, et al., 2007). The oil with low molecular weight fatty acids has a higher saponification value (Adepoju, et al., 2013). LD356 and BW364 have the highest and relatively equal saponification values, whereas BG360 has the lowest value.
4.1.2.3 Unsaponifiable Matter
The Unsaponifiable matter content was found using ASTM D1965 method and the values obtained for the oil extracted for the above mentioned rice varieties are given in table 4.4 in Annex II and the relevant graph is given figure 4.4.
4.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50 Unsaponifiable MatterUnsaponifiable (%) 0.00 LD356 BG450 BG360 BW364 BG352 AT307
Bran Type
Figure 4.4: Unsaponifiable matter content of oil obtained from different varieties of rice bran
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Unsaponifiable matters are bioactive components with nutraceutical value, mainly composed of sterols, triterpene alcohols and less polar components such as squalene or tocotrienols. Recently, rice bran oil has gained attention because of its unique health claims attributed by its high level of unsaponifiable matter.
Currently, efforts are being made to develop RBO with retained non-saponifiable components, while minimizing levels of problematic free fatty acids. There are several mechanisms by which unsaponifiables improve serum bio-chemical profile such as by interrupting the absorption of intestinal cholesterol rather increasing the excretion of fat and neutral sterols and increased fecal steroid excretion through interference with cholesterol absorption (Ginsberg, et al., 1998).
4.1.2.4 Iodine Value
Oil extracted from different varieties of rice bran was tested for the Iodine value by the SLS313 Part II and the results obtained are given in table 4.5 in Annex II. Iodine value against the different varieties of rice bran is plotted in figure 4.5.
43.40
43.20
43.00
42.80
42.60 Iodine Value Iodine 42.40
42.20 LD356 BG450 BG360 BW364 BG352 AT307
Bran Type
Figure 4.5: Iodine value of oil obtained from different varieties of rice bran
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The iodine value is a measure of the degree of unsaturation of fatty acids and expressed in terms of the number of grams of iodine absorbed by 100g of oil. It also indicates the stability of oil towards oxidation. It is observed, higher the iodine value, greater the degree of unsaturation. Considerably high and low iodine values are seen in AT307 and BW364 respectively as 43.29 and 42.63.
4.1.2.5 Specific Gravity
AOCS Official Method To 1a-64 was used to measure the specific gravity of the oil obtained from different varieties of rice bran and the results are shown in table 4.6 in Annex II. The graphical representation of the results is displayed in figure 4.6.
0.950
0.945
0.940
0.935
0.930
0.925
0.920 Specific Gravity Specific 0.915
0.910
0.905 LD356 BG450 BG360 BW364 BG352 AT307
Bran Type
Figure 4.6: Specific Gravity of oil obtained from different varieties of rice bran
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The presence of the number of double bonds and increase in chain length of the fatty acids tend to increase the specific gravity. It is evident from the results that the specific gravity of rice bran oil samples ranged from 0.919 to 0.944. For oils, the value of specific gravity is always <1 and normally ranges from 0.850 to 0.950.
4.1.2.6 Color of oil
The oil obtained from different varieties of rice bran demonstrated different colors. Following are the colors of the oils and figure 4.7 is an image of the oil samples showing the colors.
LD356 – Dark greenish, closer to black BG450 – In the middle of light and dark green, closer to dark green BG360 - In the middle of light and dark green, closer to light green BW364 – In the middle of light and dark brown, closer to dark brown BG352 – Light brownish AT307 – In the middle of light and dark brown, closer to light brown.
AT307 BG450 BG352 LD356 BW364
Figure 4.7: Colors of oil obtained from different varieties of rice bran
Color is mainly influenced by quality of bran, processing methods, storage conditions and method of extraction.
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4.1.3 Reason for variation in properties of oil from different bran varieties
The quality and the composition of each paddy variety are determined by a number of genetic and physiological characteristics. The genetic factors that can influence quality include genetic make-up, seed size and bulk density (International Rice Research Institute, 2009). The physical or environmental characteristics comprise of injury during planting and establishment, growing conditions during seed development, nutrition of the mother plant, physical damage during production or storage by machine or pest, moisture and temperature during storage and age or maturity of seed. Furthermore, specific traits such as the length and width, shape, size, color, aroma and the crop characteristics such as, plant height, time to maturity, plant color and plant growth habit distinguish one variety from another.
Three samples of oil were extracted from one variety of bran and the results obtained for the three samples were different to one another. The reason for this is the human error in extracting oil such as variation in compactness of pellets, handling the stabilization process, etc. and differences in seed quality. The seed quality depends upon the physical conditions that the mother plant is exposed during its growth stages, as well as harvesting, processing, storage and planting. Temperature, nutrients and other environmental factors also affect seed development and influence seed quality. In order to obtain high quality seeds good production practices are essential (Seed Management, 2003). These practices include, proper maintenance of genetic purity, good growing conditions, proper timing and methods of harvesting, appropriate processing during threshing, appropriate seed storage and seed distribution systems.
BG is a variety from Batalegoda and out of for the varieties chosen for the research, BG450 is the oldest and has the highest maturity period. Most recent release is BW364 and it is from Bombuwela. LD356, which is from Labugama is formed from BW451 and BW351 varieties and it is recommended for Kalutara and Galle districts. Lowest maturity period is of AT307 and it is from Ambalantota. The variety by
62 maturation duration, year released, pedigree, recommended area, maturity duration, highest yield recorded and attributes for each type is given in Annex II-table 4.7.
4.1.4 Fatty Acid Composition of Rice Bran Oil
Test results of the Gas Chromatography (GC) showing the fatty acid composition of types LD356 and AT307 are given below in table 4.1 and 4.2 respectively. The method used was ISO 5509:1978 with flame-ionization detector (FID).
The results record sheets and the gas chromatograms are given in Annex II-table 4.8 and 4.9 and figure 4.1 and 4.2 respectively.
Table 4.1: Fatty acid composition of bran type LD356
Fatty Acid Content (g/100g) Capric acid 0.02 Lauric acid 0.07 Myristic acid 0.36 Palmitic acid 21.02 Palmitoleic acid 0.38 Stearic acid 1.98 Oleic acid 39.47 Linoleic acid 34.31 Linolenic acid 1.38 Eicosanoic acid 0.75 Behenic acid 0.26
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Table 4.2: Fatty acid composition of bran type AT307
Fatty Acid Content (g/100g) Lauric acid 0.1 Myristic acid 0.5 Palmitic acid 22.6 Stearic acid 1.6 Oleic acid 40.2 Linoleic acid 31.2 Linolenic acid 1.0 Eicosanoic acid 0.7 Eicosenoic acid 0.4 Behenic acid 0.3 Lignoceric acid 1.4
In LD356, Capric acid and Palmitoleic acid were found in addition to the acids in AT307. Eicosenoic acid and Lignoceric acid were found in AT307, additionally to the acids in LD356. Oleic, Linoleic and Palmitic acids are the acids of highest content in both types. The lowest amounts are of Lauric and Capric acids.
The high content of monounsaturated fatty acids (MUFAs) especially oleic acid (18:1) is associated with a low incidence of coronary heart disease (CHD) because it decreases total cholesterol (10%) and low-density lipoprotein cholesterol (Dennys, et al., 2006). Unsaturated (especiallypolyunsaturated) fatty acids are also more prone to oxidation. In contrast, dietary intake of certain unsaturated fatty acids, in particular conjugated linoleic and fat-soluble antioxidants (e.g., α-tocopherol) has been linked to potential health benefits (Gillian, et al., 2008).
It is widely known that the physical and chemical properties of oils are a strong function of the fatty acid composition. By changing the natural, physical and
64 chemical characteristics of oil, it offers greater functionality for a large number of product formulations (Abdulkarim, et al., 2010). Physical-chemical properties of triglyceride and its applications depend upon fatty acid constituents in molecule. However, the differences are due primarily to chain length degree and position of unsaturation. The short chain fatty acids are of lower melting point and are more soluble in water. Whereas, the longer chain fatty acids have higher melting points (Chayanoot, et al., 2005).
The fatty acid composition is different from one type of bran to the other due to the genetic variations of the types.
4.2 MASS TRANSFER COEFFICIENT OF RICE BRAN OIL
The percentage of oil extracted using IPA from types BG352 and AT307 with 8 mm diameter and 5 mm height pellets at different times with 10 minute intervals are presented in Annex II table 4.10 and 4.11 respectively. These data are graphically shown in figure 4.8 and 4.9 as percentage of Oil Extracted vs. time.
14.00 y = -0.000307x2 + 0.088x + 6.198 12.00
10.00
8.00
6.00
4.00 % of Oil %of Oil Extracted 2.00
0.00 10 20 30 40 50 60 70 80 90 100 110 120
Time (min)
Figure 4.8: Extractable oil percentages of type BG352 at different times
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12.00 y = -0.0377x2 + 0.8812x + 6.1982 11.00
10.00
9.00
8.00 % of Oil Extracted%of Oil
7.00
6.00 10 20 30 40 50 60 70 80 90 100 110 120 Time (min)
Figure 4.9: Extractable oil percentages of type AT307 at different times
Rate of change of oil weight per minute in types BG352 and AT307 is indicated in figure 4.10 and 4.11 respectively and the relevant data are given in Annex II table 4.12 & 4.13.
0.14
0.12
0.10
0.08
0.06 (dw/dt) (g/min) (dw/dt) 0.04
0.02 Rate of change of oil wt. per min of oil min wt.Rateof change per 0.00 10 20 30 40 50 60 70 80 90 100 110 120
Time (min) Figure 4.10: Rate of rice bran oil extraction of type BG352
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0.16 0.14 0.12 0.10 0.08
(g/min) 0.06 0.04 0.02 0.00
Rate of change of oil wt. per min min (dw/dt) Rateof change of oil per wt. 10 20 30 40 50 60 70 80 90 100 110 120 Time (min)
Figure 4.11: Rate of rice bran oil extraction of type AT307
4.2.1 Calculation of Mass Transfer Coefficient
Using the below equation derived in Chapter 2, section 2.3.3, mass transfer coefficient can be calculated. c K A ln s L t cs c V
When the solution is saturated: cs 0.008g/ml (Treybal, 1980)
For Type BG352;
The graph of ln(Cs/(Cs-C)) vs.time was plotted by, Substituting the above value at every 10 minutes (Figure 4.12).
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4.00
3.50
3.00 y = 0.0338x
2.50 C)) - 2.00
1.50 ln(Cs/(Cs 1.00
0.50
0.00 0 10 20 30 40 50 60 70 80 90 100 110
Time (min) Figure 4.12: ln Cs/ (Cs-C) vs time for determination of mass transfer coefficient for rice bran oil extraction for type BG352
The mass transfer coefficient KL , for rice bran oil in IPA can be determined from the gradient (KL A/V) of the graph. -1 Hence, 0.0338 min = KL A/V
(0.0338/60 s -1 ) V KL = A
V=300 cm3
A= no.of pellets (2rl 2r 2 )
Where; r- Radius of the cylindrical pellet = 4mm= 0.4cm l- Length of the pellet = 5mm= 0.5cm
Total mass of pellets (m) = 20.89g
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Density of Rice Bran ( ) = 0.438g/cm 3
m 20.89g Total volume of pellets (v ) = = = 47.69 cm 3 p 0.438g / cm3
v No. of pellets = p r 2l
v 2v A = p (2rl 2r 2 ) p (l r) r 2l rl
Substituting the above values;
247.69cm3 A= (0.5 0.4)cm 429.22cm2 0.4cm 0.5cm
Substituting A & V;
(0.0338/60) 300 6 1 KL = 100 3.93710 ms 429.22
Therefore, Mass transfer coefficient for type BG352 is 3.937106 ms1 .
Similarly, for type AT307; taking the same CS value as above and plotting the graph of ln(Cs/(Cs-C)) vs.time, figure 4.13 was obtained as below.
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3.5
3 y = 0.0298x
2.5
2 C) - 1.5
ln Cs/(Cs ln 1
0.5
0 0 10 20 30 40 50 60 70 80 90 100 110 Time (min)
Figure 4.13: ln Cs/ (Cs-C) vs. time for determination of mass transfer coefficient for rice bran oil extraction for type AT307
The mass transfer coefficient KL, for rice bran oil in IPA can be determined from the gradient (KL A/V) of the graph.
-1 Hence, 0.0298 min = KL A/V
(0.0298/60 s -1 ) V KL = A
V=300 cm3
A= no.of pellets (rl 2r 2 )
Where; r- Radius of the cylindrical pellet = 4mm = 0.4cm
70 l- Length of the pellet = 5mm = 0.5cm
Total mass of pellets (m) = 20.07g
Density of Rice Bran ( ) = 0.438g/cm 3
m 20.07g Total volume of pellets (v ) = = = 45.82 cm 3 p 0.438g / cm3
v No. of pellets = p r 2l
v 2v A= p (2rl 2r 2 ) p (l r) r 2l rl
Substituting the above values;
245.82cm3 A= (0.5 0.4)cm 412.40cm2 0.4cm 0.5cm
Substituting A & V;
(0.0298/60) 300 6 1 KL = 100 3.61310 ms 412.40
Therefore, Mass transfer coefficient for type AT307 is 3.613106 ms1 .
4.2.2 Formation of a common equation
K A ( L )t c c (1 e V ) s
Data required to find the concentration (c) at time t are, K L ,cs , A and V. Therefore,
c =f (K L , cs , A, V, t)
v 2v A= p (2rl 2r 2 ) p (l r) r 2l rl
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m When calculating the value of A; v ( ), r and l should be known. Therefore the p initial variables to be known are the total mass of pellets (m), the radius (r) and the length (l) of a pellet.
Therefore, if the volume of IPA(V), total mass of pellets (m), the radius (r) and the length (l) of a pellet and the plot of concentration (c) vs. time is given ( cs can be found), the concentration at time t can be found for the types BG352 and AT307, by taking the above calculated K L values.
4.2.3 Effect of extraction time and Reason for various MTC for different types
In figures 4.8 and 4.9 it can be clearly seen that the percentage of oil extracted increases with time and saturation has reached after about 115 min in BG352 and 110 min in AT307. The saturation concentration is important in determination of diffusivity of solvent through bran. The rate of extraction as a function of time can be obtained from the gradient of figure 4.8 and 4.9 for types BG352 and AT307 respectively and are shown in figure 4.10 and 4.11. The rate of extraction decreases with time and this is because, as time increases the concentration of oil in the pellet and hence the driving force the mass transfer decreases. Therefore, the bulk of the oil extracted rapidly and after a certain period of time the rate becomes very low. Further, extraction may not be practically economical at these low rates of extraction. The parabolic equations obtained for different types of bran differ because; the amount of oil in each type is different from one another. Further,the particle size, stiffness may differ due to the milling process and sieving process differences. Therefore, the diffusion of the solute does not take place in the same way in all types and the Mass Transfer Co-efficient differs from one another and the time taken for saturation differs from one another.
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4.3 RICE BRAN OIL EXTRACTION USING CROSS FLOW EXTRACTION METHOD
Percentage of oil extracted using IPA for bran types BG352 and LD356 are given in table 4.14 and 4.15 respectively in Annex II and the relevant graphs are figure 4.14 and figure 4.15. As explained by figure 3.2, this experiment contains three extracts and three raffinates for each type.
9.00 8.00 7.00 6.00 5.00 4.00
%of Oil %of ExtractedOil 3.00 2.00 1.00 0.00 1 2 3 Stage No. Figure 4.14: Percentage of oil extracted by LD356 in different stages
9.00 8.00 7.00 6.00 5.00 4.00
%of Oil Extracted Oil %of 3.00 2.00 1.00 0.00 1 2 3 Stage No. Figure 4.15: Percentage of oil extracted by AT307 in different stages
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4.3.1 Calculation for cross flow extraction
Assumption: There is no preferential adsorption. Hence, the composition of the solution in the raffinate is as the same as the composition of the extract.
Calculation of the amount of solution retained in the raffinate: Note: This test was carried out for a random sample and it was assumed that the percentage of solution retain in the raffinate is the same for every bran type.
Weight of the empty thimble = 3.47g Weight of bran =156.37g Initial weight of the thimble + bran=3.47+156.37g=159.84g
Initial volume of the solvent-IPA (Vs ) = 500ml
3 Density of IPA (s ) 0.786 g/cm
3 3 Weight of IPA (ms ) s Vs = 0.786 g/cm 500cm 393g Weight of the oil in the extract = 26.83g Assume; total weight of the oil extracted (g) = y Weight of the solution formed = wt. of solvent+ wt. of oil extracted = 393+y g
After the extraction; Final weight of the thimble + Raffinate or used-up bran (inert + solution) = 135.09g
Weight of Raffinate or used-up bran (inert + solution) = 135.09-3.47g=131.62g
Since, the oil in the bran is extracted, the final weight of bran = (156.37-y) g
Weight of the solution retained in the raffinate = 131.62-(156.37-y)g = (y-24.75) g
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Weight of solutioninthe raffinate % of solution retained in the raffinate = total weight of the solution
Assume; % of solution retained in the raffinate = x% y 24.75 x %= eqn.1 y 393
Since it is assumed that there is no preferential absorption; Composition of the solution in the extract = Composition of the solution in the raffinate i.e; Extract solvent: Extract solute = Raffinate solvent: Raffinate solute
Taking solute in to consideration;
y y 26.83 y 393 x( y 393)
y 26.83 x eqn.2 y
After solving equation 1 and 2; y =26.973g x =0.53%
Calculation of the composition of Feed, Extract and Raffinate:
For LD356; For step1 in the cross flow extraction,
If the oil(solute) retained in the raffinate from the solution is z, Amount of oil (solute) in the extract = 6.245g Total solution weight = solute weight+ solvent weight = (6.245+z) + 393g =399.245+z g
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Amount of solution in the extract = (399.245+z) x 99.47% Amount of solution in the raffinate = (399.245+z) x 0.53%
Considering the solute in the extract and the raffiante; Extract, 6.245 Solute as a proportion of the solution in the extract = (399.245 z)99.47% Raffiante, z Solute as a proportion of the solution in the raffinate = (399.245 z) 0.53%
Since, there is no preferential absorption; Composition of solution in the extract = Composition of solution in the raffinate
Therefore,
Solute as a proportion of the solution in the extract = Solute as a proportion of the solution in the raffinate
6.245 z = (399.245 z)99.47% (399.245 z) 0.53%
6.245 0.53 z = 0.0333g 99.47
Composition of feed;
Total weight of the pellets = 74.33g
From yield calculations in Chapter 4, it is been found that the yield of LD356 is 18.64%. Hence,
Amount of oil in the pellets (bran) =74.33 x 18.64% =13.86g
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weight of bran without oil 60.47 Inert = = 81.36% total weight of bran 74.33
weight of oil in bran 13.86 Solute = 18.64% total weight of bran 74.33
Solvent = 0%
Composition of Raffinate;
Wt. of solute = total amount of oil in bran - wt.of oil in extract + wt. of oil retained with the solution = 13.86-6.245+0.0333 = 7.64g
Wt. of solvent = total amount of the solution retained- amount of oil retained with the solution = ((399.245+0.0333) x (0.53/100))-0.0333 = 2.08g
wt. of bran without oil 60.47 Inert = 86.15% Wt. of bran + solute + solvent 60.47 7.64 2.08
wt. of solute 7.64 Solute = 10.89% Wt. of bran + solute + solvent 60.47 7.64 2.08
wt. of solvent 2.08 Solvent= 2.97% Wt. of bran + solute + solvent 60.47 7.64 2.08
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Composition of Extract; Inert = 0%
Wt. of oil in the extract 6.245 Solute = 1.57% Wt. of solution in the extract (399.245+ 0.0333)99.47/100
Solvent= Wt. of solution in the extract - Wt. of oil in the extract ((399.245+ 0.0333) 99.47/100)- 6.245 Wt. of solution in the extract ((399.245+ 0.0333) 99.47/100) 98.43%
Similarly, composition of the next 2 stages for the cross flow extraction of LD356 was calculated.
Composition of each stream in terms of inert, solute and solvent is tabulated as below.
Table 4.3: Composition of cross flow extraction streams of LD356
Inert (D) % Solute (A) % Solvent (S) %
F 81.36 18.64 0.00
R1 86.15 10.89 2.97
R2 91.04 5.81 3.15
R3 94.39 2.34 3.27
E1 0.00 1.57 98.43
E2 0.00 0.95 99.05
E3 0.00 0.59 99.41
S1 0.00 0.00 100.00
S2 0.00 0.00 100.00
S3 0.00 0.00 100.00
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Likewise, for type AT307 the composition of each stream was calculated and shown in the below table.
Table 4.4: Composition of cross flow extraction streams of AT307
Inert (D) % Solute (A) % Solvent (S) %
F 83.95 16.05 0.00
R1 87.70 8.45 3.85
R2 90.33 5.70 3.77
R3 92.81 3.12 4.07
E1 0.00 1.14 98.86
E2 0.00 0.40 99.60
E3 0.00 0.36 99.64
S1 0.00 0.00 100.00
S2 0.00 0.00 100.00
S3 0.00 0.00 100.00
Triangular diagrams for type LD356 and AT307 in three stage cross flow extraction are given in figure 4.16 and 4.17 respectively. Since, the solvent percentage is zero in the feed; the feed points are marked in the solute axis. Raffinate phase contains a higher percentage of inert and a very low percentage of the solvent. The solute content in the raffinate reduces from the first to the third stage.
Since fresh solvent is being used for all three stages, solvent is 100% for all the steps and this point is marked in the solvent axis. Extract phase contains a high solvent content with the extracted solute. In this phase, from stage one to three, the solute percentage reduces with a slight variation in the solvent percentage. Tie lines are drawn by connecting the corresponding raffinate and extract points.
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20 F 18
16
14
12
10 tie 1
Solute(%) 8 tie 2 R1 tie 3 6
4 R2 2 E1 E2 E3 0 S 0 R3 20 40 60 80 100 120 Solvent (%) Figure 4.16: Triangular diagram for type LD356 in three stage cross flow extraction
18
16 F
14 Feed 12 Solvent
10 Extract Raffinate 8 R1 tie 1 Solute (%) Solute 6 tie 2 R2 4 tie 3
2 R3 E1 E2 0 E3 0 20 40 60 80 S 100 120 Solvent (%)
Figure 4.17: Triangular diagram for type AT307 in three stage cross flow extraction
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From the composition of cross flow extraction streams, the material flow diagram for types LD356 and AT307 are being drawn in figure 4.18 and 4.19 respectively.
D % A % S % D % A % S % D % A % S % 0 0 100 0 0 100 0 0 100
Fresh Fresh Fresh Solvent(S) Solvent(S) Solvent(S)
D % 86.15 D % 91.04 D % 94.39 A % 10.89 A % 5.81 A % 2.34 S % 2.97 S % 3.15 S % 3.27
R R R 3 Feed (F) Stage 1 1 Stage 2 2 Stage 3
D % A % S % 83.95 16.05 0 E E 1 2 E3
D % A % S % D % A % S % D % A % S % 0 1.57 98.43 0 0.95 99.05 0 0.59 99.41
Figure 4.18: Material Flow sheet for type LD356 in cross flow extraction
Fresh Solvent (S)
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D % A % S % D % A % S % D % A % S % 0 0 100 0 0 100 0 0 100
Fresh Fresh Fresh
Solvent(S) Solvent(S) Solvent(S)
D % 87.7 D % 90.33 D % 92.81 A % 8.45 A % 5.7 A % 3.12 S % 3.85 S % 3.77 S % 4.07
R R R Feed (F) Stage 1 1 Stage 2 Stage 3 3 2 D % A % S % 81.36 18.64 0 E E E 1 2 3
D % A % S % D % A % S % D % A % S % 0 1.14 98.86 0 0.4 99.6 0 0.36 99.64
Figure 4.19: Material Flow sheet for type AT307 in cross flow extraction
If the raffinate could be re-extracted with fresh solvent using the cross flow extraction method, a higher yield can be obtained. This is an extension of the single step extraction because more single step units are combined. The raffinate of each step is contacted in the following step with the pure solvent. The extracts are withdrawn from each step and given to the solvent regeneration. Use of fresh solvent 3 times was not a waste, due to the regeneration of the solvent (IPA).
The percentage of oil extracted is reduced from stage 1 to 3, because the amount of oil left in the raffinate is reduced from stage to stage. Since, the raffinate becomes the feed to the consequent step; the amount of oil that is left to be extracted is lesser.
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The extracted percentages are different in LD356 and AT307 due to the difference in the oil content. As explained before, genetic and environmental variables such as, temperature, soil, climate conditions, etc. would have caused the difference in the oil content.
Bertucco & Vetter, et al. (2001) has stated that the advantages of the cross flow extraction method in terms of supercritical fluid extraction are that the parameters such as pressure, temperature and solvent to feed ratio can be varied in each extraction step. A very accurate fractionation of the different compounds included in the feed can be achieved and highly soluble substances are extracted in the first step at low fluid density. Further, it has been stated that the flow rate of the supercritical fluid at each extraction step can be adjusted by the use of this method. Cross flow extraction method is not installed yet in the industrial scale for supercritical fluids due to the high investment costs for high pressure vessels, high pressure pump, etc.
Cross flow extraction is ideal when there is only one component to be extracted, but for multi-component system extractions, countercurrent extraction can be used. Countercurrent extraction allows both high recovery and the achievement of high product purity when properly designed.
4.4 COMPARISON OF RAW AND PARBOILED BRAN
Percentage of oil extracted using IPA from type BG450 in both raw and parboiled form are given in table 4.16 and 4.17 respectively in Annex II. These results are graphically shown in figure 4.20.
Figure 4.21 shows the comparison of FFA percentage of oil extracted from raw and parboiled bran and the relevant data are given in table 4.18 & 4.19 respectively in Annex II.
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18
16
14
12 Parboiled bran Raw bran 10 Poly.Trend (Parboiled-Parboiled bran) 8 Trend-Raw Yield (%) Yield 6
4
2
0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 Time (days)
Figure 4.20: Percentage of oil extracted by BG450 raw & parboiled bran at different times
10.00 9.00
8.00 7.00 6.00
5.00 Parboiled
FFA % FFA 4.00 Raw 3.00 TrendLog. (Parboiled-Parboiled ) 2.00 TrendLog. (Raw)-Raw 1.00
0.00 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 Time (days)
Figure 4.21: FFA content of oil extracted by BG450 raw & parboiled bran at different times
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4.4.1 Variation of oil extracted in raw and parboiled bran
The parboiled rice bran has comparatively higher levels of protein, fat, fiber and ash contents. In the parboiled bran, since the paddy was steamed at the beginning the lipase enzyme activity is reduced. Lipases catalyze the hydrolysis of glycerides into free fatty acids and glycerol and cause the reduction of oil yield during refining. Further, parboiling increases the oil content in bran due to less endosperm contamination, better extractability of oil by solvents and outward movement of oil from aleurone and germ cells to the bran layer (Bhattacharya, 1985; Keerthi & Swarnasiri, 1985; Amarasinghe & Gangodavilage, 2004). Therefore, the yield or the percentage of oil extracted in parboiled bran is higher than the raw bran. However, it has the disadvantage of darkening the oil due to the influence of heat on the color precursors.
According to figure 4.20, it is apparent that the parboiling has a definite effect on the yield of rice bran as the trend line for parboiled bran is at a higher level than for the raw bran.
4.4.2 FFA differences in the oil obtained from Raw and parboiled bran
Rice bran contains lipases, primarily responsible for the hydrolysis of triglycerides into glycerol and free fatty acids; further oxidized by peroxidases, provoking bran’s rancidity. Rancidity is the chemical decomposition of fats, oils and other lipids and this result in undesirable odors and flavors. This is the principal cause of deterioration occurring rapidly during the first few days or weeks after milling.
As shown in figure 4.21, the amount of FFA is lesser in the oil obtained from parboiled bran when compared to the oil from raw bran. This may be due to the destruction of enzyme during parboiling treatment of rice. The FFA amount of oil from parboiled paddy is less compared to that of oil from steam stabilized bran. Parboiled rice bran gives greater stabilization to the bran.
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Free fatty acids concentration in rice bran is dependent on the changes in temperature and moisture content experienced by the bran during storage (Fernando and Hewavitharana, 1993). The nutritional quality and palatability of rice bran deteriorate rapidly as the oil undergoes hydrolytic and oxidative rancidity. Vacuum and polybag packed parboiled rice bran is said to have a significant effect on rancidity level (Priyankara, et al., 2009).
In addition to higher yields and lower FFA contents, parboiling could help in lesser breakage of kernels. If performed properly, parboiling, a three-step hydrothermal treatment consisting of soaking, heating and drying of paddy could substantially reduce the level of broken kernels (Gunathilake, 2012).
4.5 SUITABILITY OF RBO EXTRACTED FROM VARIETIES OF BRAN IN SRI LANKA AS A RAW MATERIAL
In this research, bran from 6 types of paddy, namely LD356, BG450, BG360, BW364, BG352 and AT307 were used. The percentages of oil extracted and the properties such as free fatty acid content, saponification value, Iodine value, unsaponifiable matter content and specific gravity was different from one type to another.
Rice bran oil has many uses and bio-fuel, pharmaceutical, food, cosmetics, spa and personal care products are the most common uses.
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Table 4.5: Applications of rice bran oil and vital properties (Gupta, et al., 2007; Mohanty, 2013; Sharma & Rukmini, 1986; Feuge & Reddi, 1949; Huang, et al., 2009; Ammar, et al., 2012)
Application FFA% Sap. Iodine Unsap. Specific Preferred Value Value Matter Gravity Special Features Bio-fuel Lower No Low No High Low the significant significant viscosity better effect effect and high volatility Pharmaceutical High No No High No High Oleic
significant significant significant and Low effect effect effect Linolenic Food Low as No Low High High High Oleic possible significant and Low effect Linolenic Cosmetics, Spa Low Low High Depends on High and Personal the Oryzanol, care products requirement tocols & ferulic acid
4.5.1 Suitability for bio-fuel production
Yield and quality of biodiesel is dependent on feedstock quality specially structure of oil, moisture and free fatty acid (FFA) content. Crude rice bran oil (CRBO) with high free fatty acid content is not suitable for edible purposes unless it is refined. If FFA concentration of the feedstock is higher, the alkali catalyst should not be used in the transesterification reaction due to the soap formation. According to the results obtained for the FFA content, the most suited order for biodiesel production is type BG450, LD356, BG352, BG360, AT307 and BW364 when the reaction takes place in the presence of an alkali catalyst.
Moreover, the fatty acid chain composition of the triglyceride in the feedstock, such as its length or degree of unsaturation, has important effects on the characteristics of biodiesel. Esters with polyunsaturated fatty acid chains are less stable than saturated
87 fatty acid chains as a result of relatively fast oxidation during storage. The higher the iodine value, the more unsaturation is present in the oil and according to the results the iodine value from lowest to highest is BW364, LD356, BG360, BG352, BG450 and AT307. Biodiesel made from feedstock containing higher concentrations of high melting point saturated long fatty acid chains tends to have relatively poor cold flow properties. Furthermore, impurities present in the feedstock also affect the quality of the biodiesel. The conversion levels into esters using refined oils can be higher than using crude vegetable oils under the same condition. Biodiesel productivities of oils rich in linoleic acid (18:2) are slightly higher than those of oils rich in oleic acid (18:1). Both types, LD356 and AT307 have produced oils rich in Oleic acid and hence the biodiesel productivity of these two types would not be significantly different. Based on the above discussion LD356 is the ideal bran type for biodiesel production when the FFA and iodine value is taken into consideration.
Biodiesel production is a very modern and technological area for researchers due to the relevance that it is winning every day because of the increase in the petroleum price and the environmental advantages. Currently, biodiesel is mainly prepared from conventionally grown edible oils such as rapeseed, soybean, sunflower and palm thus leading to alleviate food versus fuel issue. About 7% of global vegetable oil supplies have been used for biodiesel production in 2007 (Balat, 2011). The use of non-edible plant oils when compared with edible oils is very significant in developing countries because of the tremendous demand for edible oils as food, and they are far too expensive to be used as fuel at present. Even though, rice bran oil has a promising potential to be used for biodiesel production, the production of biodiesel from different non-edible oilseed crops and waste cooking oil have been investigated. The challenge is that the physical and chemical properties of biodiesel produced from any feedstock must comply with the limits of ASTM and DIN EN specifications for biodiesel fuels.
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4.5.2 Suitability for Pharmaceutical production
Tocols and gamma-oryzanol are the unsaponifiable constituents of rice bran oil and higher the unsaponifiable matter content is better it is for pharmaceutical use. In the paddy varieties used in this research, BW364 has the highest potential for pharmaceutical purposes and BG360, LD356, BG352, BG450, AT307 has the next highest unsaponifiable matter content in the descending order.
4.5.3 Suitability for food items
The Oleic and Linolenic contents can be obtained from table 4.1 and 4.2 for oil from bran types LD356 and AT307. In both of these types the oleic content is the highest and LD356 has a higher value than AT307. Linolenic acid is relatively lower in both types, with LD356 having the lowest value. When comparing the suitability of LD356 and AT307 for food applications, LD356 seem to be the best option.
In the unsaponifiable portion of rice bran oil, tocotrienols and gamma oryzanol are the two groups of antioxidant compounds. It has been found that bran collected from shorter milling times resulted in higher levels of tocopherols and tocotrienols than for longer milling times (Schramml, et al., 2007). Higher the unsaponifiable matter content and lower the FFA, better it is for food applications. By comparing the unsaponifiable matter and FFA content of the oil obtained from the 6 types of bran, LD356, BG360 and BG352 is the order of suitability in descending form. AT307 has a very low level of unsaponifiable matter and FFA. Even though the unsaponifiable matter content is the highest in BW364 it has the highest amount of FFA as well. BG450 has the lowest amount of FFA but, the amount of unsaponifiable matter is at a lower level.
Winterized rice bran oil is extremely light, versatile and delicious and it is suitable for making salad dressing.
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In the study of Kaur, et al. (2012), rice bran oil has been found to have a higher content of essential fatty acid linoleic acid as compared to that of bakery shortening (5.14%). From the two types of oil from bran types LD356 and AT307 tested for the fatty acid content has given the linoleic acid content as 34.31% and 31.2% and both these values are way above the bakery shortening value.
Comparison tables of smoke point and balance of fats and the natural antioxidants in some commonly used oils such as olive, palm, soya bean, sunflower and canola are given in Annex II-table 4.20 and 4.21.
Rice bran oil wax is solvent extracted to produce pure wax which is further refined and bleached to procure hard wax of food. It is white to yellowish in color and can be made available in flakes form as well. Its major consumption is in food industries as constituents of chocolate enrobers, vegetable coating and wax emulsion for fruit preservation.
4.5.4 Suitability for cosmetics, spa products and personal care products
Rice bran oil is an ingredient for personal products such as shampoo and hair conditioner as Ferulic acid and its esters stimulate hair growth and for soap. A certain amount of alkali (lye) is required to change the rice bran oil them into soap, or saponify them. This amount is denoted from the saponification value and low saponification value is preferred. The order of suitability for saponification is type BG360, AT307, BG450, BG352, LD356 and BW364. The iodine value is a measure of unsaturated level of a fat. This value allows us to predict the tendency of soap to become rancid: soap with a high iodine value will go off sooner than soap with a lower value. Therefore, the suitability order in terms of iodine value is BW364, LD356, BG360, BG352, BG450 and AT307. High ratios of linolenic acid should be avoided because it is the quickest to deteriorate and from the fatty acid composition obtained for LD356 and AT307, AT307 has the lowest linolenic content with 1%. Hardness is calculated by considering mainly lauric, myristic, palmitic and stearic acids. Thus, fats containing these acids result in harder soaps. The quantity of
90 bubbles the soap produces is mainly due to lauric, myristic, linoleic and ricinoleic acids. Lather persistence is mainly calculated on the basis of palmitic and stearic acids. These acids prolong the duration of the lather and give the soap a creamy consistency. The ability of soap to clean is also proportional to the amount of lauric, myristic and ricinoleic acids. A soap that cleans too much is harsh for the skin. Conditioning is the ability of the soap or conditioner to smooth and nourish the skin or hair. It is provided principally by linoleic, oleic, ricinoleic and linolenic acids. By comparing the two results of the GC for the two bran types; stearic, linoleic and linolenic are higher in LD356 whereas, lauric, myristic, palmitic and oleic are higher in AT307.
It can be suggested that the rice bran wax is a suitable substitute for carnauba wax and it can be used as coating agent, as a base in cosmetic preparation (Maru, et al., 2012). Rice bran wax can be used for cosmetic products like moisturizing lotions, lipsticks, creams, etc.
Rice derived ingredients generally are considered to be non-allergenic. Use of rice bran oil grows as a specialty ingredient in the cosmetic and personal care market. The demand is for natural, value-added healthy ingredients.
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