( 27 ) Food Preservation Science VOL. 23 NO. 4 1997 (Research Date 207

Utilization, Storage and Evaluation of Oil from Scrapings

DIZON,E. I*., MENDOZA,M. G.* and IINO H.**

* Institute of Food Science and Technology, University ofthe Los Banos, College, 4031, Philippines;

** Showa Women's University, Taishido 1-7, Setagaya-ku, Tokyo 154, Japan.

Crude oil from nata de coco scrapings was extracted using the modified Cruz-Bernardo process and oil refining was done by alkaline method. Chemical properties of the refined oil revealed that the differences in the sources of coconut, extraction method and refinement process do not affect the properties of oil as evidenced by the values obtained which fall within the acceptable established constants for from fresh . Storage stability studies of the extracted crude oil at ambient room temperature for six-and-a-half months showed that oil stored in colored containers and treated with .035% a-tocopherol was significantly less prone to hydrolytic rancidity as compared with the untreated samples. However, crude oil from nata de coco cream has significantly higher free fatty acid values when compared with oil samples from fresh coconuts. Utilization of refined oil from nata de coco cream for deep-frying of plain prawn crackers showed in no significant difference the over-all quality of the samples deep-fried in two commercial brands of coconut oil.

Nata de coco, a sticky of gelatinous substance, of coconut and nata de coco was one of the main is formed by a bacterium called Acetobacter aceti products of this effort. subsp. xylinum. The bacterium acts on the medium Nata de coco has gained in popularity in both consisting of , glacial acetic acid, domestic and international markets, specifically in water and sugar to form a smooth, transparent or Japan, with its peak observed in 1993 to 1994. The opaque film that floats on the surface of the demand for nata de coco in foreign markets substrate. The medium contains the nutrients increased tremendously when it was repored that which stimulates the growth of the nata organism. nata is preventive for colon cancer due to its high However, these nutrients are not transmitted to amount of fiber content. Figure-conscious people the nata formed. Thus nata de coco may be used nata de coco as part of their diet too because considered as a food without nutritive value. It is of its low calorie content . mainly composed of water and polysaccharides The nata de coco industry became so popular in (fiber) . the Philippines, that the large volume of waste The technology of nata making originated in products from its production became a problem. Pagsanjan, Laguna in the Philippines, a century When nata de coco is harvested, a slimy substance back. However, the main substrate was the juice which adheres to the underside of the film in extracted from peelings. In 1954, the contact with the medium is scraped off. It was Philippine Coconut Authority spread the wonders found out that these nata de coco scrapings 208 Food Preservation Science VOL. 23 NO. 4 1997 (28) consists mainly of oil by CABRERA,F. 1995 2).Thus, nata de coco scrapings considering the relatively in mass production of nata de coco, a large high production of nata de coco and the increasing volume of oil can be extracted from these waste demand for coconut oil as well. products. Instead of dumping these wastes in the Coconut oil, like any other oil, is composed of soil or directly in to bodies of water, there by carboxylic esters from a single alcohol, glycerol, causing increased acidity of the system and HOCH2CHOHCH2OH. These carboxylic esters are pollution in the environment, the oil may be known as glycerides. Coconut oil is mainly a extracted for utilization in products where oil is a triglyceride, or more appropriately called main ingredient. triacylglycerol and consists of three fatty acids Tapping the oil from the waste products of nata bound to one glycerol. de coco production will be beneficial as an Hydrolysis of 100g commercial coconut oil will additional source of income for the nata growers produce 96.7g fatty acids and 13.9 glycerol. This and to manufacturers of coco-based products. fatty acid mixture is made up of nine different Thus, the aims of this study were (a) to extract fatty acids (Table1) . and evaluate the chemical properties of crude and Because of the high degree of saturation and refined oil from residual nata de coco crem, (b) fatty acid compositions of coconut oil, it is used to compare the storage stability of oil from nata de extensively both in the food and non - food coco cream to that of oil from fresh coconut and industries. Similarly, basic oleochemicals are selected commercial brands of coconut oil, and produced from coconut oil, namely, glycerol, fatty (c) to evaluate the efficacy of refined oil from nata acids, fatty acid methyl esters, fatty alcohols and de coco cream for cooking purposes. fatty amines (PCARRD, 1993) .13) Several studies have been conducted regarding Table 2 shows that the physical and chemical nate de coco production howerer, there were no properties of crude oil from fresh coconut and nata published articles available concerning coconut oil de coco cream have no marked difference. The from nata de coco. It is sential to study the saponification and iodine values of recovered oil possibility of extracting utilizable coconut oil from from nata de coco cream were reported 2 )

Table 1. Fatty acid composition of crude coconut oil13) (29) 〔Research Date〕 Evaluation of Coconut Oil from Nata De Coco Scrapings 209

Table 2. Physical and chemical properties of coconut oil from fresh coconut and nata de coco cream.2)7)

pre,-treated scrapings were placed in clean, dry plastic containers, covered with aluminum foil and frozen at ordinary freezer temperature for 48 hours. The frozen scrapings were thawed and centrifuged at 45,000 rpm for 10-15 minutes. The liquid portion was discarded and the emulsion that remained in the centrifuged tube was transferred to a pan, heated and the oil that separates from the emulsion was filtered and weighed. The percent oil recovery was calculated as follows Amount of oil recovered/ %Oil recovery= •~ 100 Figure 1. Nata de coco scrapings Amount of scrapings

Preparation of Crude Oil from Matured, Fresh

(CABRERA,1995) to fall within the range of values Coconuts set for coconut oil from fresh coconut. This Matured, fresh coconuts were cracked open and indicated that the oil recovered from nata de coco the meat was machine-grated. The coconut milk cream has undergone no substantial changes even was extracted by pressing the grated coconut after the nata organism has acted on the coco - manually, and filtered through a cheesecloth. The based substrate. coconut milk was placed on a pan and heated to

MATERIALS AND METHODS boiling with constant stirring. When all the water had evaporated, the oil that oozed out was filtered.

Preparation of Crude Oil from Residual Nata De The extracted oil was weighed and the percent

Coco Cream recovery was calculated. The process flow

Nata de coco scrapings (Figure 1) were obtained diagram for the extraction of crude oil from from various nata de coco growers around Los matured coconuts is given in Figure 3.

Banos, Laguna, Philippines. The film adhering to Stability Studies of Oil from Nata de Coco Cream the underside portion of nata in contact with the A. Effect of antioxidant addition and packaging substrate was scraped after harvest. The scrapings material The total oil recovered from nata de coco were blended to a creamy state and neutralized cream was divided into two portions: one portion with 5N sodium hydroxide to until pH7. 0. was treated with ƒ¿-tocopherol (as antioxidant) at

The oil was extracted from the neutralized a concentration of 0.035% by weight, while the scrapings using the modified Cruz - Bernardo other portion served as control. Each portion was process ( Figure 2 ) , a process suggested by further divided into two : one was stored in a clear

CABRERA(1995) 2) to be the more efficient method container while the other in a container fully of extracting oil from nata de coco scrapings. The wrapped with a carbon paper to protect the 210 Food Preservation Science VOL. 23 NO. 4 1997 (30)

samples from exposure to light. The containers (ANOVA) and Duncan's New Multiple Range were filled with oil up to the brim, covered with Test (DNMRT) to find out if significant rubber stopper and sealed with paraffin wax. differences exsisted among samples.

Then, all tubes were stored at 28-30•Ž for six-and Refinement of Oil from Nata de Coco Cream -a-half months . The crude oil from nata de coco cream was

Crude oil extracted from fresh, matured coconuts refined for further utilization. Oil refining was also served as control. done using the method developed by LOZADA,

B. Use of Accelerated Test The stability of SUMALDE and KOONTZ (1993) 6) and the flow crude oil from nata de coco cream was studied diagram of the process is presented in Figure 4. using a simple accelerated (Schaal) test. The method is known to result in a bland and

About 100 ml of oil from nata de coco crem was odorless edible cooking oil.

One kilogram of crude oil was placed in a placed in a clean, dry bottle, covered with

aluminum foil, and stored in a well-aerated drying stainless steel container. This was neutralized

oven at a temperature of 60•Ž. The increase in free slowly for 20 minutes using 2% sodium hydroxide

fatty acids and peroxide values were monitored solution. The oil-water mixture was heated with

every 48 hours until rancidity developed. constant agitation up to 60-65•Ž. The mixture was

Chemical Analysis of Oil After Storage allowed to stand overnight to give time for the

Chemical analysis of the treated and untreated oil soapstock formed to settle.

samples were determined after strage for six-and After settling, the water was drained from the -a-half months at 28-30•Ž . Analyses were done on mixture and 0.5 kg water was added to the

free fatty acids and peroxide values following the neutralized oil for washing. Slow agitation was

method of MADAMBA (1987)7). Data obtained was performed for 20 minutes. With constant stirring,

analyzed using the Analysis of Variance the mixture was heated up to 80 t . The water

Figure 2. Process flow diagram for the extraction of crude oil from nata de coco scrapings (modified Cruz-Bernardo process) (31) •k Research Date•l Evaluation of Coconut Oil from Nata De Coco Scrapings 211

Figure 3. Process flow diagram for the extracion of crude oil from matured coconuts

portion was drained-off after settling was done for the oil. 4 hours. Washing was performed twice but an Utilization of Refined Oil overnight settling period was given for the second The refined oil was utilized for frying plain prawn washing. crackers. The over - all quality of the prawn The washed oil was dried to remove the last crackers cooked by deep-frying using the refined traces of water. This was done by heating the oil oil from nata de coco cream was compared with up to 140•Ž . The oil was cooled and packed in a the samples fried using two commercial brands of clean, dry bottles. The process flow diagram for coconut oil (Minola and Baguio oil) . refinement of crude oil from nate de coco cream is Sensory Evaluation presented in Figure 5. Sensory evaluation of the crude and refined oil The saponification number and iodine number of from nata de coco cream was done. The oils were the refined oil were analyzed to determine if the evaluated in terms of color, odor and general refining process altered the chemical properties of acceptability. The sensory attributes of the crude 212 Food Preservation Science VOL. 23 NO. 4 1997 (32)

Figure 4. Process flow diagram of coconut processing for cooking oil (LOZADA,et al, 1993) and refined oils were compared with two RESULTS AND DISCUSSION commercial brands of coconut oil, Minola and Baguio oil. A sample of the sensory evaluation Recovered Oil from Nata De Coco Cream sheet on quality scoring used is given in Appendix The nata de coco scrapings may be described as A. The data were analyzed using ANOVA and an off-white, slimy film with a strong acid odor. DNMRT to find out if significant difference exists The acid odor is brought about by the acetic acid, among oil samples. which is one of the key ingredients in nata de coco Likewise, the prawn crackers fried using the production. The initial pH of the homogenized different oil samples were subjected to sensory scrapings was obtained and on the average, the evaluation by 25-member panel of judges using the values fall within the range of 2.7-3.6. difference from the control test. A sample of the Homogenization process resulted to a creamy sensory evaluation sheet used is shown in white emulsion (Figure 6) due to the mixing of the Appendix B. cream and water during blending. Addition of sodium hydroxide solution was done to neutralize the remaining acetic acid and the free fatty acids that was formed by the action of microorganisms. There was an observable partial (33) •k Research Date•l Evaluation of Coconut Oil from Nata De Coco Scrapings 213

Figure 5. process flow diagram for refinement of crude oil from nata de coco cream separation of non-oil components from the emulsion large ice crystals. Upon thawing, the contents of during the neutralization process. the cells leak out. The oil globules which can be Extaction of oil from the nata acrapings was done found in the cells are surrounded with a membrane following the modified Cruz - Bernardo process made up of phospholipid cephalin as emulsifier, which is composed of four major steps-freezing salt, and unknown protein stabilizers (NUEVO,et thawing, centrifugation and rendering. This al., 1977)12).During freezing there is unfolding of process was reported by CABRERA2) to be more the proteins in the membrane (cold denaturation) . efficient in recovering oil from residual nata de When the frozed pre-treated scrapings are coco cream than the other methods that she used. thawed, the oil from the globules will leak out. During freezing, a liquid to solid transformation After centrifugation of the thawed scrapings, the called crystallization occurred. Here, the water lower layer formed is mainly water while the upper molecules of a food system aggregate in a layer is the cream, where the oil is concentrated. crystalline arrangement on nucleants. Using the The intensity of centrifugation should not caused conventionl freezer temperatures, the rate of any partial extraction of oil from the cream nucleation or ice crystal formation is very slow, because the oil will go with the aqueous layer producing large ice crystals. Conventional freezing during draining off. tend to disrupt the structure and destroy the The cream recovered (Figure 7) was placed on a turgidity of the cells because of the formation of pan and heated (rendering) . Rendering is a 214 Food Preservation Science VOL. 23 NO. 4 1997 (34)

Figure 6. Homogenized nata de coco scrapings. Figure 7. Extracted cream from nata de coco scrapings

Table 3. Yield(%) of crude oil from nate de coco scrapings.

Figure 8. By - product (coagulated protein) of oil extraction (rendering)-"" Figure 9. Crude oil from nata de coco cream process by which fat is removed from the tissue by heat through denaturation of the proteins (Meyer, The amount of cream recovered from nata 1960)11). Heat allows the oil to separate from the acrapings ranged from 10.53% to 28.43% with a globules and coalesce. Table 3 presents the mean value of 18.39%•}5.614. The remarkable percentage yield of crude oil from nata de coco deviation may be explained by the differences in acrapings based on five different trials/batches. the amount of water that goes into the scrapings. (35) •k Research Date•l Evaluation of Coconut Oil from Nata DeCoco Scrapings 215

During the removal of the film, water from nata de that the second extraction yields only half the coco is exuded when force is applied to it. The amount of the first batch. Some of the factors that amount of water that goes with the scrapings contribute to this significant difference in oil yield depends on the force applied. Higher amount of may be attributed to the following: maturity of water in the scrapings would result to a lower coconuts, amount of force applied during milk percentage recovery. extraction and efficiency of the rendering process . The average amount of crude oil that was recovered was 5.34% and 30.45%, based on the Table 4. Yield (%) of crude oil from fresh, weight of the scrapings and cream, respectively. matured coconuts The percentage recovery of oil is obviously affected by the maturity of coconuts used and the extraction process. Higher amounts of oil can be obtained in the scrapings which used older coconuts during nata de coco production. Moveover the extraction process (centrifugation and rendering) also affects the efficiency of oil Refinement of Crude Oil from Nata de Coco recovery. Longer period of centrifugation at 45,000 Cream rpm results in partial extraction of oil which is The task of oil and fat technology does not end lost when the aqueous layer is discarded. In the after extraction of the oil from the materials. A same way, rendering or heating the cream to refining process is often done for oils which are extract the oil also affects the amount of oil intended for cooking. Coconut oil has several recovered. Efficient rendering process means not impurities and undesirable constituents like fat- only breaking the protectiv membrane of the oil insoluble particles, materials held in colloidal globules but also that the oil has separated fully suspension and fat - soluble substances. These from the denatured protein, "latik" (Figure 8) . substances should be removed to make the oil The rendering process should be done in such a suitable for edible purposes. way that the maximum oil can be extracted The first treatment done to crude oil is settling. without affecting the color of the oil. It was Settling is allowing fat - insoluble impurities to observed in this study that longer rendering time separate from the oil. These impurities include resulted in a dark - colored oil. The crude oil fragments of cell tissues, traces of moisture and extracted from nata de coco cream is shown in coagulated proteins. The presence of these figure 9. insoluble substances hastens deterioration and tend Percentage oil recovery should be based on the to increase the losses in subsequent refining amount of cream recovered after centrifugation. process (ANDERSEN,1962) . Here, the cream is not greatly affected by the Observations done during oil extraction showed amount of water since it is separated after that the color of the extracted oil was influenced centrifugation. The percent yield of crude oil based by the time and temperature of rendering. A on the scrapings however, is not a reliable bassis darker color of oil was obtained when the because the values of oil recovered will have a coagulated protein (latik) is dark brown in color great deviation depending on the amount of water due to prolonged heating. incorporated in the mixture. Clarified oils contain other impurities that were Recovered Crude Oil from Fresh, Matured not removed during settling. The fat - soluble Coconuts substance should be removed and may be done by Table 4 shows the percent yield of crude oil from addition of alkali solution. This is termed as coconuts based on two extractions. It can be seen refining. This process has the combined effects of 216 Food Preservation Science VOL. 23 NO. 4 1997 (36)

use of equipment minimized oil losses during purifying, neutralizing and decolorizing. When soap particles are formed during the neutralization draining. Chemical Characteristics of Refined Oil from process, the temperature should be high enough to permit the soap to separate and settle Nata De Coco Cream immediately. Slow agitation was done to facilitate The chemical properties of fats or oils are neutralization and prevent formation of emulsion. important for identification, evaluation of purity

As cited by ANDERSEN (1962)1), Feuge and co- and the degree of deterioration in oil. Table 6 workers (1956) the high rate of shear between the presents the chemical characteristics of crude and oil and alkali reduces the color of the oil. refined oil from residual nata de coco cream.

The third step in refining process is alternate Figure 12 shows the oil from nata de coco settling and washing. After settling, three distinct creambefore and after refining. layers (Figure 10) were formed. The bottom layer Table 6. Comparison of the chemical properties of is composed of the aqueous portion, the middle crude and refined oil feom residual nata de coco layer is the soapstock and the upper layer is the cream. refined oil. The soapstock appeared as white thick emulsion (Figure 11) . During washing, the soap particles and other water-soluble substances are removed from the oil. The oil and water mixture was heated to 80•Ž to facilitate washing. The mixture is when left undisturbed to allow separation of water and oil. The saponification number, also known as

The last step of the refinement process of Koettstorfer number, is defined as the milligrams coconut oil is drying. This was done by heating the of potassium hydroxide required to saponify 1

oil up to 140•Ž or until no bubbling sounds can be gram of fat. It is used as an index of the mean heard. Refined oil should not contain any traces of molecular weight of the glycerides in the oil or fat.

water to prevent hydrolytic rancidity to occur. The saponification number of coconut oil is

The refine oil obtained from nata de coco cream relatively high ( Table 2 ) and this may be

was observed to be clear and odorless. explained by its fatty acid compositions. As shown in Table 1, coconut oil is made up of 62.2% short - and medium - chain fatty acids Table 5. Percent recovery of refined oil from crude oil . The caproic, of nata de coco. caprylic, capric and lauric acids contribute to the high saponification value of coconut oil. Results obtained in this study revealed that the saponification number of refined oil from nata de coco cream was 255.11. This confirmed the report of CABRERA (1995)2) that oil from this substance The mean valuse for percent recovery of refined falls within the acceptable established values set oil from nata de coco cream were 48.37% based on for coconut oil (246-260) . This also supports the the recovered crude oil ( Table 5) . This shows idea that if the glyceride of the oil is composed of remarkable small percentage recovery compared short - chained fatty acids, there are more to the results obtained from fresh coconuts glyceride molecules per gram oil than the long- processed by LAZADA and co -workers (1993) 6), chained fatty acids. which is 95%. This big deviation may be due to the Another chemical property of oil that was special equipment they used whereas this study analyzed was the iodine number. This is the adopted the design for home-based activity. The number of grams of iodine absorbed by 100 grams (37) 〔Research Date〕 Evaluation of Coconut Oil from Nata De Coco Scrapings 217

of oil. The amount of iodine added, iodine number, is a measure of the amount of unsaturation. The iodline number of coconut oil from fresh coconut (8-10) is low since only 8.2% of its fatty acids are unsaturated. Results show that the refined oil from nata de coco cream (Table 6) has an iodine number of 9.47 which is within the acceptable values mentioned above. Based on these findings for saponification and iodine numbers, it can be deduced that the refinement process does not affect the chemical properties of coconut oil. Stability Studies of Oil from Nata De Coco Cream A. Effect of antioxidant addition and packaging Figure 10. Separation of oil (top), soapstock material on the storage stability of crude oil from (middle ) and aqueous ( bottom ) nata de coco cream Stability studies of fats substances during alkaline refining of oil and oils focus on rancidity. Rancidity results in the from nata de coco cream development of undesirable odors and flavors in fats and oils. To prevent or delay rancidity, manipulation of packaging materials, storage conditions and the addition of antioxidants have been found to be effective. Determination of the free fatty acid number and peroxide value of oil give an indication of the degree of rancidity of the oil. The free fatty acid number measures the degree of hydrolytic rancidity. This is a measure of the amount of fatty acids which have been freed by hydrolysis from their glyceride combination through the action of water and lipases (TRIEBOLDand AURAND,1963)14). Peroxide value on the other hand, measures the Figure 11. By-product of oil refining: extent of oxidative rancidity in fats and oils. soapstock Oxidative rancidity develops when atmospheric oxygen attacks the unsaturated bonds present in fats and oils resulting to the formation of primary, secondary and tertiary oxidation products. During storage, there are times when peroxide decomposition is greater than its formation, resulting in decrease peroxide value (MADAMBA,et al., 1991)8). Table 7 shows that the free fatty acid number of crude oil from nata de coco cream and fresh coconuts treated with a -tocopherol is lower than the untreated samples. Also, oil samples stored in colored bottles have lower free fatty acid numbers Figure 12. Coconut oil from nata de coco cream, after (A) and before (B) refining 218 Food Preservation Science VOL. 23 NO. 4 1997 (38)

Table 7. Effect of cr-tocopherol addition and packagingmaterial on the degree of rancidity of oil extracted from nata de coco cream and fresh coconut

than the oils stored in cleared bottles. No peroxide oil is lower when stored in clear containers value was detected. Among the treatments, crude compared to colored bottles at ambient oil treated with a - tocopherol and stored in temperature. The effect of antioxidant addition colored bottles had the lowest free fatty acid cannot be clearly seen since peroxide values were number. This indicates the sample with the slowest not detected in any of the all samples. rate of hydrolytic rancidity. In general, it was observed that the free fatty If the free fatty acid number is calculated as % acid value of the crude oil samples from nata de lauric acid (2 FFA) , treatments I , II and IV are coco cream were higher than those of fresh already considered rancid after 6.5 months of coconuts. The exposure of the coconut milk to high storage since their free fatty acid numbers exceeds amounts of water and microorganisms during the the maximum allowable limit of 1.5 %. All oil formation of film of nata de coco may have samples from fresh coconuts however, are still contributed to the high rate of hydrolytic rancidity regarded as not rancid as evidenced by its low FFA of the crude oil from nata de coco cream. values. Harvesting of nata de coco takes place after 8-10 Statistical analysis of, the values of FFA days, thus there is enough time for hydrolysis of numbers of oil samples from nata de coco cream fats by water and microbial lipases. During showed that these treatments are not significantly pretreatment of scrapings, complete neutralization different from each other. However the samples of of free fatty acids using an alkali solution is not oil from fresh coconut did show a significunt an assurance because the oil molecules are still difference. enclosed in protein membranes. Neutralization Results obtained proved that light is a catalyst only assures that the residual glacial acetic acid is for rancidity development. The stability of coconut neutralized. The free fatty acids are retained in (39) 〔Research Date〕 Evaluation of Coconut Oil from Nata De Coco Scrapings 219

the extracted crude oil. On the contrary, oil from having an initial tocopherol (natural antioxidant) fresh coconuts are not exposed to high amounts of content of 712.06 micrograms/ g oil was decreased water and other environmental factors because to only 38 micrograms/ g oil when subjected to a the rendvering process is done immediately after refining process. They further concluded that extraction of the coconut milk from the meat. refining with subsequent washing and drying During the six - and - a - half months storage, causes a loss in tocopherol amounting to 64.8% of oxidative rancidity was very slow as shown by the the original amount. Furthermore, a study done by results of peroxide value analysis which was GORDONand RAHMAN (1991) 3) on the effect of below detectable levels in all oil samples. This can processing on the composition and oxidative be explained by the low amount of unsaturated stability of coconut oil showed that the Rancimat fatty acids in coconut milk. induction period of crude oil is 36.9 hours but after B. Stability of Crude and Refined Oil from Nata the alkali refining process, it was reduced to 5.8 De Coco Cream Using the Accelerated Test hours. The Metrohm Rancimat method is a process Table 8 shows the peroxide values of oil samples: for the determination of oxidative rancidity done crude and refined oil from nata de coco cream , by placing the oil samples in a special Rancimat crude oil from fresh coconut and commercial tubes and subjecting it to a temperature of 120t . coconut oil (Baguio brand) after storage at 60t Table 8 also shows that the commercially for 567 hours. There was a remarkable difference available coconut oil ( Baguio brand) has lower in the peroxide values among the oil samples. At peroxide values compared to refined oil from nata 0 time,the peroxide value of crude oil from nata de de coco cream despite the fact that it also coco cream was undefectable while the refined oil underwent the process of alkali refining, washing, was already 2.45 meq O2/kg oil. Crude oil from bleaching, deodorizing and filtering. This is fresh coconut had the smallest value of 0.0593 meq because the commercial coconut oil normally had 02/kg oil. Data obtained for the peroxide values antioxidant like BHA or BHT added to suppress during storage at various time intervals revealed oxidative rancidity, thus lengthening the keeping that refined oil from nata de coco cream has the qual; ity of the oil. highest mean value among the oil samples. These The free fatty acids present in the oil also results implied that refinement process causes the influence tocopherol stability. According to oil to be more prone to oxidative rancidity. This YOSHIDAand co-workers (1992)15),the shorter the observation supports the claimed of MANALACand chainlength, the lower the degree of unsaturation HARDER-SOLIVEN(1967)9) that crude coconut oil and the higher the levels of free fatty acids, the Table 8. Peroxide values (meq O2/kg oil) of coconut oils subjected to accelerated test 220 Food Preservation Science VOL. 23 NO. 4 1997 ( 40 ) greater is the loss of antioxidant activity of for sensory evaluation are shown in Figure 13. tocopherol in vegetable oils. This applies also for The refining process did not alter the odor of the coconut oil. oil from nata de coco cream. Statistical analysis Sensory Evaluation shows that no significant difference in odor was Table 9 shows the sensory attributes, namely, observed between the crude and refined oil from color, odor, and general acceptability, of four oil nata de coco cream which were both described as samples. The color of refined and crude oil from slightly nutty and buttery. When compared with nata de coco cream was significantly different two commercial brands of coconut oil, refined oil wherein refined oil was judged to be colorless was found to be significantly different from Minola while crude oil was light yellow. However, no oil but not from Baguio oil. Minola oil was significant difference was noted in the color of described as bland while refined oil from nata de commercial oil and crude oil from nata de coco coco cream was slightly nutty and buttery. cream. Oil samples presented to the panel of judges Based on the results of sensory evaluation, the

Figure 13. Oil samples used in sensory evaluation: A-refined oil from nata de coco cream, B-Minola cooking oil, C-Baguio cooking oil, D-Crude oil from nata de coco cream

Table 9 . Mean sensory scores of the reference oils (Minola and Baguio ) , crude and refined oil from nata de coco cream using a 7-point hedonic scale. (41) 〔Research Date〕 Evaluation of Coconut Oil from Nata De Coco Scrapings 221 refining process did not alter the general in colored containers compared to samples stored acceptability of oil from nata de coco cream. The in clear containers without addition of antioxidant. refined oil is comparable to two commercial Significant differences though were found brands of coconut oil. between the two crude oil samples. In general, Efficacy of Refined Oil from Nata de Coco Cream crude oil from nata de coco cream has a faster rate for Deep-frying of hydrolytic rancidity than oil extracted from Using the Difference from the Control Test fresh coconut. The crude oils were found to be (Appendix A and B), the refined oil from nata de more resistant to oxidative rancidity as supported coco cream was used for deep-frying plain prawn by the non-detection of the peroxide values. crackers and compared to the two commercial An accelerated test was done by storing the brands of coconut oil ( Minola and Baguio ). crude and refined oil from nata de coco cream, Statistical analysis shows that there is no crude oil from fresh coconuts and Baguio cooking significant difference found in the over-all quality oil at 60 t for 576 hours. The accelerated test of prawn crackers deep-fried in three oil samples. which determines the period/time that the oil will This result indicates that refined oil from nata de reach a peroxide value of 20 meq O 2 / kg oil coco cream may be used as substitute for (critical level of oxidative rancidity) was not commercial brands of coconut oil. reached throughout the whole period of storage. The refined oil from nata de coco cream which was SUMMARY AND CONCLUSION accelerated for 288 hours had the highest peroxide Crude oil from nata de coco cream was value of 8.35 meq 02/kg oil, still way below the extracted using the modified Cruz - Bernardo critical level for oxidative rancidity. process. The oil was refined using an alkali Regarding the possibility of using the refined oil method. The resulting refined oil was judged to be for cooking purposes, sensory evaluation showed colorless, clear with a slightly nutty and buttery that no significant differences was found among odor. Statistical analysis showed that the color of the plain prawn crackers deep-fried in refined oil the oil after refining is significantly lighter in from nata de coco cream and two commercially color than its original material. On the other hand, available coconut oils. the odor and general acceptability of crude oil In general, results of this study indicated the from nata de coco cream is comparable to the following: refined oil sample and Baguio oil (a commercial I. Crude coconut oil, whether from nata de coco coconut oil) . cream or from fresh coconuts, has a longer shelf- Analysis revealed that the chemical properties life than the refined oil from nata de coco cream. or refined oil were not significantly altered since 2. Hydrolytic rancidity of coconut oil is more prone the values obtained for iodine and saponification to occur than oxidative rancidity because the numbers fall within the established constants for majority of the triglycerides are short-chained and coconut oil from fresh coconuts. This shows that saturated. the differences in source, extraction method and 3. Utilization of coconut oil from nata de coco refinement process did not affect the chemical scrapings is possible for cooking purposes. properties of the oil. 4. Destruction of the environment can be lessened Studies on the effect of cr-tocopherol addition if nata de coco scrapings, which have a strong and packaging material on crude oil from nata de acidic nature, are used as an alternative source of coco cream and fresh coconuts stored at ambient coconut oil. room temperature for six - and - a - half months RECOMMENDATION revealed a slower rate of hydrolytic rancidity for oil samples treated with a-tocopherol and stored This particular study proved that the coconut oil 222 Food Preservation Science VOL. 23 NO. 4 1997 (42)

extracted from nata de coco scrapings can be delaying hydrolytic rancidity because this is the utilized for food. Future investigations on the most prominent type of rancidity in coconut oil. method of extraction of oil from nata de coco By-products of extraction and refinement may scrapings should focus on an industrial level. be utilized. The coagulated protein (latik) from Results also show that the efficiency of refining fresh coconuts is used in the Philippines as a process of crude oil from nata de coco cream was for traditional , however further low. Studies should be done to determine the studies should be done to determine the chemical optimum conditions to obtain a higher recovery composition of latik from nata de coco cream to and prolonged the shelf-life for the refined oil. understand its possible use. The soapstock which The degree of rancidity of the refined oil was is a by-product of alkali refining can be made into found to be higher than its crude form. Ways soap. should be found to prevent fast deterioration of the Further studies on the utilization of refined oil refined oil. Efforts should be concentrated on from nata de coco scrapings as an ingredient in

APPENDIX A SENSORY EVALUATION ON QUALITY SCORING (43) 〔Research Date〕 Evaluation of Coconut Oil from Nata De Coco Scrapings 223 various types of food products may also be College of Arts and Sciences, U. P. Los Banos, explored. College,Laguna (1987) REFERENCES 8) MADAMBA, L. SP., FLAVIER, M. E., VASQUEZ, M. 1) ANDERSEN, A. J. C.: Refining of fats and oils for T. L. and QUIMADO, R. O.: Storage study on Pili

edible purposes. second edition Pergamon Press, (Canarium ovatum) nut and pulp oil. The Philippine Oxford (1962) Agriculturist. 74 (2) : 253 •` 260 (1991) 2) CABRERA, S. F. : Extraction and evaluation of oil 9) MANALAC, G. C. and HARDER - SOLIVEN , A.: from residual nata de coco cream. Undergraduate Keeping qualities of edible coconut oil: Correlation thesis. IFST-UP Los Banos, College, Laguna (1995) of organoleptic assessment with accelerated tests. 3) CORDON, M. H. and RAHMAN. I. A.: Effect of Phil. Jour. of Sci. 98 (2) , 133 •` 138 (1969) processing on the composition and oxidative 10) MABESA, L.B.: Sensory evaluation of foods : stability of coconut oil Journal of American Oil Principles and Methods. CA Publication, UPLB, Chemists Society, USA. 325-327 (1991) College, Laguna (1986) 4) IUPAC: Standard methods for the analysis of oils, 11) MEYER, L. H.: Food Chemistry. Reinhold fats and derivatives. Sixth ed. Pergamon Press, Publishing Corporation.N. Y. (1960) Oxford (1979) 12) NUEVO, C. R., SANTOS, M. P., GONZALES, A. L. 5) LAWSON, H. W.: Standards for fats and oils. AVI and BIROSEL, D. M.: Rendered quality water-white Publishing Inc. New York (1985) coconut oil. Journal of American Oil Chemists Society, 6) LOZADA, E. P., SUMALDA,Z. M. and KOONTZ, A. USA. 54 (8) , 325 •` 327 (1977) T.: Integrated coconut processing: Los Banos fresh 13) PCARRD: The Philippine Recommendations for -dry method . Philippine Agricultural Mechanization Coconut. PRARRD, Los Banos, Laguna (1993) Bull, UP Los Banos, Philippines. 1 (3) , 11 - 16 (1993) 14) TRIEBOLD, H. and AURAND, L.: Food composition 7) MADAMBA, L. SP.: Laboratory Instruction and analysis. D. Van Nostrand Co., Inc. New Jersey Manual for Technical Analysis: Foods and Feeds. (1963)

APPENDIX B DIFFERENCE FROM THE CONTROL 224 Food Preservation Science VOL. 23 NO. 4 1997 (44)

15) YOSHIDA, H., TATSUMI, M. and KAJIMOTO, G.: American Oil Chemists Society,USA. 68 (2) : 119-125 Inflence of fatty acids on tocopherol stability in (1992) vegetable oils during microwave heating. Journal of

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