COMPARATIVE ANALYSIS AND SENSORY EVALUATION OF GROUNDNUT OIL AND OLIVE OIL ON THE QUALITY OF FRIED RICE

ABSTRACT
This research work examined the comparative analysis and sensory evaluation of comparing of olive oil and groundnut oil with the quality of fried rice. The objective of this research work is to examine if the fried rice prepared with olive oil is better in flavour, taste, colour/appearance and texture compared to fried rice prepared with groundnut oil. Materials for the production were procured from Auchi market and the production was carried out in the hospitality department kitchen, Federal Polytechnic Auchi. A set of panelist were invited within the polytechnic to taste the food and give their comment. Data obtained were computed and analysis. The result shows that fried rice cook with olive oil is more acceptable in terms of texture, colour, flavor, taste. Hotel operators/catering establishment should use more of olive oil for cooking so as to improve the quality of the food.

BACKGROUND OF STUDY
Rice is a food crop of world-wide importance and forms the foundation of the diet of over 3 billion people, constituting over half of the world’s population R. P. Cantral and T. G. Reeves, (2002). It is widely cultivated throughout the world and has become the second most important cereal in the world after wheat in terms of cultivation, due to a recent decline in maize production M. Frei and K. Becker, (2003). It is utilized mostly at the household level, where it is consumed as boiled or fried with stew as in Nigeria. Different cultures have different preferences regarding the taste, texture, colour and stickiness of the rice varieties that they consume. For example, dry flaky rice is eaten in South Asia and the Middle East; moist sticky rice in Japan, Taiwan Province of China, the Republic of Korea, Egypt and northern China; and red rice in parts of southern India. Many countries have signature rice recipes, such as sushi, fried rice, curry, paella, risotto, pancit, and beans with rice. There are also many sweets and candies made from rice.

The agronomic classification of rice into glutinous and non-glutinous or translucent rice includes qualitative characteristic of the endosperm. The glutinous rice type is by far the most important; accounting for about 90-100 % of the total in different countries. The non-glutinous type is not sticky when cooked while the glutinous types have a soft endosperm that is composed of dextrin instead of starch. When cooked, they become sticky but are more preferred by some people due to softness after cooking. Fat content is higher in non-glutinous rice than glutinous rice and the protein content is lower in the glutinous than in the non-glutinous rice type. Varieties of rice are classified according to cooking properties on the basis of gelatinization temperature C. K. Shin, (2007).

Pomeranz reported that rice composition differs according to the variety and processing method used. Among the many forms which rice is processed, parboiling of rice is widely used which is the hydrothermal treatment of raw rice prior to milling. The quality of milled parboiled rice is being assessed based on physical parameters like degree of milling, percentage head rice, broken grain, chalkiness, red streak grain, grain size, colour, and shape at 1000g weight. Except for Burkina Faso and Niger, rice is a staple crop throughout West Africa, especially in Cote d’lvoire, the Gambia, Guinea, Guinea Bissau, Liberia, Senegal and Sierra Leone. The River Niger drainage system is a major rice-growing environment in the region. Nigeria has a leading role in rice production in West Africa, ranking highest as both the producer and consumer of rice in the sub-region with production figures slightly above 50% C. K. Shin, (2007).

The economic value of rice depends on its cooking and processing quality, which can be measured in terms of water uptake ratio, grain elongation during cooking, solids in cooking water and cooking time. Rice varieties with amylose content of more than 25% absorb more water and have a fluffy texture after cooking M. Frei and K. Becker, 2003. Within an individual rice particle, various processes occur during cooking. The heating, water uptake and swelling of the rice particle all involve diffusive processes. When water is present at sufficiently high temperatures, the starch undergoes a gelatinization reaction. Many rice studies have concentrated on the soaking of rice grains at fixed temperatures or the parboiling process. For temperatures below 50℃, the grains absorb a limited amount of water up to approximately 30% moisture content (wet basis). The resulting grains are not cooked because the starch has not undergone gelatinisation. From common experience with small samples, it is known that soaking rice grains in water at 25℃ for about one hour is required before cooking at temperatures above 70℃ for 20 minutes or more. As water is taken up by a rice particle, the starch granules undergo a gelatinization reaction, the term generally used to describe the swelling and hydration of the granular starch.

Linear elongation of rice on cooking is one of the major characteristics of good rice. Some varieties expand more in size than others upon cooking. Length-wise expansion without increase in girth is considered a highly desirable trait of high quality rice. Soaked milled rice of high gelatinization temperature elongates less during cooking than low and intermediate gelatinizing rice. Thus, Gelatinization tem- perature correlates positively with grain elongation C. K. Shin, (2007).

Thus far, most of the published research on cooking and eating qualities in rice have focused on physico-chemical properties i.e. amylose content (AC), Gel consistency (GC) and gelatinization temperature (GT) which are directly related to rice cooking quality. Apparently, the amylose content reported for rice samples ranges from 24.6 – 28.8% and the level vary within each location.Amylose consists of linearly linked glucose molecules and is relatively resistant to digestion, hence the term “resistant starch”. This means that rice varieties with a greater proportion of starch in the form of amylose tend to have a lower glycemic index. Amylose content of milled rice has been found to correlate positively with hardness values of cooked rice and negatively with stickiness values M. Frei and K. Becker, 2003. Cooking quality of rice mainly depends on amylose content and gelatinization temperature. Amylose contents determine the texture of cooked rice. Rice varieties with amylose content of more than 25% absorb more water and have a fluffy texture after cooking.

Rice starch is usually digested quite rapidly, compared to other starchy foods such as noodles, sweet potato or cassava. This leads to a prompt and pronounced increase of the blood glucose level (= high glycemic index) after the ingestion of rice, similar to that of white bread or pure glucose R. P. Cantral and T. G. Reeves, (2002). Rapid starch digestion is regarded as unfavorable, because fast digestion can cause a sensation of hunger only shortly after the ingestion of rice, and the energy released is quickly used. Farmers cultivating rice landraces in the Philippines reported a relatively long feeling of satiation after the ingestion of certain varieties.
Consumers’ choice of rice varieties are largely based on grain and cooking qualities. More so, the high rate of influx of hybrid varieties and other new rice varieties to local farmers who then abandon their hitherto cherished indigenous varieties without critical comparison is unacceptable. Rice quality differs according to the variety and processing method used M. Frei and K. Becker, 2003. The differences in quality which are mainly attributed to differences in colloidal structure and the extent of swelling of any variety of rice on cooking have always been used as index of its quality.

OLIVE OIL TASTE/ COLOUR
Olive oil tastes best when it is fresh. Think of olive oil on a freshness continuum that goes from just-made, harvest-fresh at one end, to completely rancid at the other. How long it takes an olive oil to go from one end of this freshness continuum to the other depends on many factors: storage temperature, exposure to air and light, and the amount of natural antioxidants in the olive oil in the first place. All olive oils, even the finest ones, will get rancid eventually.
There are certain light-tasting, light-coloured oils containing minute proportions, if at all, of virgin oils. Olive oils have 125 calories per tablespoon – exactly like all olive oils, and all fats. Grading of olive oil is done, to a less significant degree, based on colour. Most olive-based oils have colours ranging from pale yellows to deep cloudy greens. The latter colour may indicate that the oil is from green, barely ripe olives – but not always. It is possible that an excess of olive leaves slipped into the crusher, sometimes inadvertently sometimes not, resulting in pale oils acquiring a deeper aura (which can give it a better price). The authentic green colour should indicate a wholesome, intensely fruity taste and freshness.
Yellow oils indicate that the olives were black and ripe when they were picked late in the season, yielding a sweeter, rounder oil. However, a lighter colour may also signify oxidation arising from exposure to sunlight. If that happens, the delicate aromas and vitamin E content in such oils generally have suffered, and the oil may taste rancid.