The Effect of Homogenization Pressures on Extraction of Avocado Oil by Wet Method

Avocado tree usually planted by people of Indonesia in rural are small in scale. Mostly, in the modern and high scale industry especially company has a large avocado farm the extraction of avocado oil is extracted through vacuum drying in low temperature. However, in rural area avocado tree spread out in small number of tree, so it needs alternative method of avocado oil extraction. In this experiment, wet method of avocado extraction was applied similar to traditional extraction of coconut oil in rural area. Avocado meat was added some water and 0.05% of phosphate acid then homogenization pressure of 7 kg/cm, 71 kg/cm and 176 kg/cm, then heated at 100C until the emulsion of water-oil broken down and avocado oil, then, can be separated. Yield and characteristics of avocado oil were determined. The results showed when homogenization pressures increased from 7 kg/cm to 71 kg/cm, the yield, Iodine value and Free fatty Acid of avocado oil were also increased, however, when homogenization pressures increased from 71 kg/cm to 176 kg/cm (p>0.05) there were no significant increased of Yield, Iodine value and Free Fatty Acid of avocado oil.


INTRODUCTION
Avocado (Perseaamericana Mill.) is originally from Latin America. It is unusually high on oil, especially in its pulp. Later it was brought out of America to tropical and subtropical countries, becoming important crops in those parts of the world.
Avocado oil is obtained from its pulp (15 to 30% depending on the variety, (Hamzah, 2012). Almost all o the oil is concentrated in the pulp. There is very little oil in the seed, approximately 2% of its weight (Shahidi, 2005). Avocado oil contains oleic acid (C18:1, 69-74% of total FA-fatty acids), palmitic acid (C16:0, 9-13% of total FAs), palmitoleic acid (C16:1, 3-4% of total FAs), linoleic acid (C18:2, 10-14% of total FAs), linolenic acid (C18:3, 1-2% of total FAs), stearic acid (C18:0, 0.4-1% of total FAs), as well as desirable compounds like vitamins, phytosterols, chlorophyll and carotenes (Inturrisi, 2007;Choe and Min, 2006). Thus avocado oil is important high-oleic oil, making it as very good dietary cooking and salad oil. It is generally consumed in an unrefined state and therefore retains all of the natural unsaponifiable material, including valuable antioxidants. It is rich in chlorophyll, making it green before processing. After refining and bleaching, its color changes into emerald greenish-yellow (Swisher, 1988). Avocado oil plays positive roles in reducing risk of coronary heart disease, cataracts, diabetes, chemoprevention, prostate cancer and age-related macular disease (Ashton et al., 2006). Its use is not solely in food products, but also in cosmetics and personal care uses.
Due to its relatively high yield, avocado oil can be obtained by cold pressing the fruit pulp. Commercially, this method is the most economical way to extract the oil. But, solvent extraction is also able to get the oil out of its pulp, albeit not as good as cold pressing. The solvent has to be removed after extraction because its toxicity and odor. Another way to recover oil from the pulp is using centrifugation, but it is very expensive in small and medium scale, regarding amount of energy used to power the process (Swisher, 1988). Yet the oil is obtainable by using wet process, but researches related to this method are quite limited.
Avocado tree in Indonesia mostly spread over the land in small amount of plant. For a big scale of farm, most people like planting other than avocado. So it is hard to implement such a modern type of extractions. One of the methods of extraction is wet method which could be applied by the people that has some productive avocado tree.
The previous research showed that the yield of avocado extracted by wet method was lower than that by Soxhlet (Table 1). In the process of extraction by wet method, avocado slurry was heated at the temperature of 105°C. Relatively high temperature of 105°C was not enough to break down emulsion (Hamzah, 2012). In the avocado, there were not only water but also proteins and carbohydrates. Linkage of oil with proteins and carbohydrate made the emulsion    and the linkage slightly hard to break down during heating. By wet method and by Soxhlet of avocado extraction could get yield as following: In Table 2 there were not much differences characteristics of avocado oil between wet method extraction and the Soxhlet, except for free fatty acid. Free fatty acid of avocado extracted from wet method was higher than that from Soxhlet. The higher content of free fatty acid in avocado oil extracted from wet method probably due to hydrolysis of some fatty acid in which the process using relatively high temperature (105°C) (Hamzah, 2012).

METHODS AND MATERIALS
Wet method of extraction: Flesh part of avocado mixed with water with the proportion of 1:1 (w/w) and 0.05% of phosphate acid was added. The mixture then was homogenized by the use of blender (5000 RPM for 3 min) then homogenization pressure of 7 kg/cm 2 , 71 kg/cm 2 and 176 kg/cm 2 were applied in order in the following processed to be much easier to break down water in oil emulsion. The homogenization mixture then was heated to 105°C until oil part significantly separated. And the data obtained could be used to determine the yield of avocado oil. After the oil has been obtained, yield was determined using the following Eq. (1). The oil then was characterized for Iodine value and Free Fatty Acid:

%
(1) %Y = Yield W oil = Percentage of oil obtained from the calculation that weight of oil   (Table 3) showed that the increased of homogenization pressure from 7 kg/cm 2 to 71 kg/cm 2 , the yield also increased from 21.4 to 22.8% (p<0.05). However, there was no significant increased of yield when homogenization pressure applied from 71 kg/cm 2 to 176 kg/cm 2 (p>0.05).

Iodine value:
The data (Table 4) showed that the increased of homogenization pressure from 7 kg/cm 2 to 71 kg/cm 2 , the Iodine Value also increased from 21.4% to 22.8% (p<0.05). However, there was no significant increase of Iodine value when homogenization pressure applied from 71 kg/cm 2 to 176 kg/cm 2 (p>0.05).
The data (Table 5) showed that the increased of homogenization pressure from7 kg/cm 2 to 71 kg/cm 2 , the Free Fatty Acid also increased from 21.4% to 22.8% (p<0.05). However, there was no significant increased of Free Fatty Acid when homogenization pressure applied from 71 kg/cm 2 to 176 kg/cm 2 (p>0.05).

CONCLUSION
When homogenization pressures increased from 7 kg/cm 2 to 71 kg/cm 2 , the yield, Iodine value and Free fatty Acid of avocado oil were also increased, however, when homogenization pressures increased from 71 kg/cm 2 to 176 kg/cm 2 (p>0.05) there were no significant increased of Yield, Iodine value and Free Fatty Acid of avocado oil.