Nutritional Qualities and Storage Stability of Dodo Ikire Fried With Palm Oil and Pumpkin Seed Oil
Aim of the Study
This research study aim at determining the nutritional qualities and storage stability of “dodo ikire” fried with palm oil and pumpkin seed oil.
The specific objective includes the following;
- To determine the proximate composition of the dodo ikire
- To determine the microbial properties and storage stability of the dodo ikire
- To evaluate Free fatty acid, peroxide value and Thiobarbituric Acid
- And lastly, to evaluate the sensory properties of the dodo ikire.
Palm oil is now the most widely consumed vegetable oil worldwide (Mba et al., 2015). For one, its cost is low compared to other oils. The main consumers of palm oil are China, India, Indonesia and the European Union; their demand is entirely met by imports since they do not produce palm oil. Additionally, the nearly solid state of palm oil at room temperature makes it a good substitute for hydrogenated oils widely used until recently in the food industry and which contain undesirable trans-fatty acids. The ban on trans-fat in several countries including Canada and the United States, because of adverse cardiovascular effects similar to saturated fat, drives the rapid global shift in consumption from soybean oil to palm oil (Global Industry Analysts, 2015).
There is a great deal of confusion regarding the nutritional value and health effects of palm oil. The controversy and conflicting views still continue on whether or not palm oil is atherogenic. Based on current evidence, it would appear that palm oil has both favourable and unfavourable effects. The nutritional and health properties of palm oil depend not only on the amounts consumed and the other components of the diet, but also on the extent of processing and on the fractions considered. The crude (red) palm oil (RPO) is very distinct from the refined product and its high content of antioxidants including vitamin E and provitamin A may be responsible for health benefits that are no longer present in the refined oil as more than half its antioxidants have been destroyed. The health aspects of palm oil were discussed in previous chapters. It is suspected that several publications may have tended to be positively biased due to the fact that the palm oil industry has been very active at sponsoring research, as reported in two large systematic reviews and meta-analyses (Fattore et al., 2014; Sun et al., 2015). The primary focus of the present chapter is on the nutritional value of crude RPO, primarily as a source of vitamin A.
Processing and production of red palm oil
The processing of oil palm fruit into edible oils involves many different and complex steps. Besides using traditional ways of processing, there is also application of small, medium and large scall mills (Poku, 2002). The processing steps of oil palm fruit can be broken into a few steps: bunch reception, fruit sterilization, fruit digestion, pulp extraction, and oil. Bunch reception involves grading the oil palm fruit and the threshing process, removing fruit from the bunches (Obibuzor et al., 2002). After the fruits have been graded, the sterilization process will take place in the sterilizer. Sterilization is a crucial step that inactivates and destroys the enzymes to prevent free fatty acids (FFA) by using high-temperature steam. This process also softens and loosens the fruit structure for easier fruit digestion and extraction of oil. The mesocarp (flesh) and the kernel (seed) are separated in the digester. The steam-heated vessels with attached rotating shafts, and a few stirring arms that help destroy the exocarp of the fruit and reduce the oil’s viscosity.
Palm oil extraction has two common methods: the “dry” method and the “wet” method. “Dry” method uses mechanical presses such as hydraulic press and screw press to extract the oil from the digested material. The hydraulic presses are usually used in the batch system, while the screw press is used in a continuous system more often (Poku, 2002). The “wet” method, on the other hand, uses water to draw out the oil from the fruit. The hot water introduced to the fruit will break down gums and resins that cause foaming of the oil during high-temperature frying. The gums and resins will soon remove through the oil clarification process. The mesocarp fiber will retain about 5-6％ of oil after the pressing (Obibuzor et al., 2012).
Oil clarification is to separate the impurities from the oil. A mixture of oil, water and solids from the bunch fibers is transferred to the tank, and the separation of the oil is based on the density of the materials. Hot water is added to provide a barrier to the lighter oil droplets and the heavy solids. The oil droplets will stay at the top of the tank, and the solids will sink to the bottom. The crude palm oil (CPO) is decanted into a reception tank and the moisture content reduced to 0.15% to 0.25% to prevent FFA increase through the autocatalytic hydrolysis of the oil. CPO is subjected to centrifugation for purification, followed by drying step. The purified and dried oil is then transferred to the oil storage tank (Hameed et al., 2003).
Red palm oil can be obtained from the mild processing of crude palm oil while the refined, bleached, deodorized (RBD) palm oil is obtained by physical refining or chemical refining of the crude palm oil (Nagendran et al., 2000). There are two stages of processing for the refining of red palm oil from crude palm oil. The first stage involves the CPO’s pre-treatment, which uses phosphoric acid for degumming of the oil and treatment with bleaching clay. The main purpose of the pretreatment is to remove the impurities in the CPO while retaining the carotenes. The bleaching clay is removed by filtration. The next stage of the process is de-acidification and deodorization. The pre-treated oil is passed through the short-path distillation unit at about 150℃ to 170℃ under vacuum to remove the free fatty acids (FFA) without destroying the carotenes (Ooi et al., 2006).
For the RBD palm oil, physical refining involves a few degumming steps, bleaching, and deodorization. In the degumming process, the phospholipids are reduced, and gums are removed from the oil (Gupta, 2011). The next step is the bleaching process that uses bleaching clay to remove the color pigments and residual soaps from the oil (Silva et al., 2013). Physical refining is usually carried out at high temperatures and pressures in the deodorization step to remove the odor and impurities such as the FFA, volatile oxidation products and phospholipids. However, high temperatures may also destroy the carotenes and tocopherols; hence, a lower deodorization temperature is highly recommended to reduce carotenes’ losses. The oil becomes bland and light yellow (Aparicio and Harwood, 2013; Čmolík and Pokorný, 2000).
On the other hand, chemical refining is similar to physical refining but involves the alkali neutralization process. The alkaline neutralization process removes FFA and phospholipids from the crude palm oil and forms a byproduct named soap stock, a mixture of fatty acids, impurities and phospholipids (De Greyt, 2013). Besides, chemical refining is carried out at a low temperature and uses a shorter time than the physical refining process. The losses of tocotrienols and tocopherol usually higher in the physical refining process, and physically refined oil have a lower shelf life compared to chemically refined oil (Chong, 2012; Dunford, 2012).
The processing steps refining red palm oil are shorter and consume less time compared to the refining process of RBD palm oil. The mild processing steps of refining red palm oil allow it to retain most of the carotenes, tocotrienols, and the oil color. However, all the refining steps for red palm oil could not remove the volatile compounds hence red palm oil will have a slightly distinctive taste and odour. The consumers may find the taste and smell of the red palm oil unique and different from other vegetable oils (Riyadi et al., 2016). In contrast, RBD palm oil can only retain some carotenes and lost most of the tocotrienols contents during the refining, bleaching and deodorization process (Ooi et al., 2006).
MATERIALS AND METHODS
Collection of Materials
Raw palm fruits, pumpkin seed and ripe plantain were obtained from Emure-ile market in Owo, Ondo State. The other ingredients used in the production was also purchased from the main market (Oja Oba) in Owo, the product was processed in the processing laboratory of Food Science and Technology, the analysis was carried in the Chemistry Laboratory of Food Science and Technology, Rufus Giwa Polytechnic, Owo, Ondo State.
Sample Preparation (Methods)
Sample preparation of palm oil
Cleaned, fresh and ripe palm fruits (2kg) were boiled, pounded and the oil extracted by manual pressing. The oil was heated at 100 oC for 10 minutes to remove residual moisture; cooled and filtered to remove impurities. The crude palm oil was stored in an amber bottle glass container and stored at room temperature until required.
RESULTS AND DISCUSSION
Table 4.1: Proximate composition of dodo ikire fried with pumpkin seed oil and palm oil
CONCLUSION AND RECOMMENDATIONS
From the results obtained in this study, a conclusion can be drawn that pumpkin seed oil and palm oil blends can help improve the storage stability of dodo ikire due to their low moisture content, the nutritional analysis prove that dodo ikire fried with pumpkin seed oil and palm oil is good because of its promising nutritional properties. The study also revealed that Dodo Ikire offer for sale has low level of initial microbial loads, from the microbial analysis it can be observed that dodo ikire fried with 100% pumpkin seed oil has the least microbial growth, this is because of the antimicrobial properties of the seed oil. The sensory attributes of dodo ikire fried with palm oil and pumpkin seed oil generally accepted by the consumer although sample DPPA was not completely accepted like others. DCPO (dodo ikire fried with commercial palm oil) have the highest growth of organism which is due to high moisture content and perhaps from processors‟ poor handling, use of unhygienic cooking utensils and sub-standard packaging systems. In conclusion, dodo ikire fired with pumpkin seed oil is the best of all the samples because of its shelf life/storage stability and nutritional qualities.
Based on the finding above it is therefore recommended that more research should be carried out on different condition of storage and production season. I also guess as well that reduction in growth in week 4 might also be due to weather condition because the analysis was carried out around late November when there is dryness of air.
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