Histochemical and Organolyptic Analysis of Major Aroma Compound (2-acetyl-1-pyrroline) in Kalanamak Rice Landraces and Some Basmati Rice Varieties

Anita Kumari*, Anil Kumar and Anil Kumar Gaur

Molecular Biology and Genetic Engineering, Collage of Basic Sciences and Humanities, G.B. Pant University of Agriculture and Technology, Pantnagar, India Collage of Basic Sciences and Humanities, G.B. Pant University of Agriculture and Technology, Pantnagar (Uttrakhand), India, Tel: 8449327911; Email: anitaani91@gmail.com .Abstract rice quality.

Introduction

Rice (Oryza sativa L.) is the staple food for more than two billion people in Asia. The cultivation of high-quality rice has significantly increased in recent years, and consequently, the aromatic rice cultivars grown in Asian countries are attracting attention [1]. Small variations in sensory properties can change the perception of the consumers, whether highly desired by or unacceptable to consumers [2]. Consequently, aroma and flavor have been rated as the major criteria for preference among consumers [3]. To increase the production of aromatic rice and satisfy the diversification of the demand from current rice consumers worldwide, it is necessary to develop the suitable breeding methods of aromatic rice.

Materials and Methods

The evaluation of rice aroma is not easy, and classical smelling or chewing methods are not supposed to be totally reliable because of their subjective nature [4]. For the sensory evaluation, seeds of all the genotypes of Kalanamak, Type-3 and Pusa basmati-1 and non-scented Pantdhan-18 were collected from Norman E. Boralog Crop Research Centre of GBPUA & T, Pantnagar (U.K.), India. All the genotypes of Kalanamak, Pantdhan-18, Type-3 and Pusa Basmati-1 were manually dehusked. For the test using seeds, 10 seeds of each genotype were taken in Stoppard test tubes. About 10ml 1.7% KOH solution was added to each Stoppard test tube and left at room temperature for 30 min. After 30 minutes, each Stoppard test tube was opened and the degree of aroma was evaluated by sniffing and was scored on the 1-4 scale with 1, 2, 3 and 4 corresponding to the absence of aroma, slight aroma, moderate aroma and strong aroma. The score for each sample was recorded by a panel of 5 experts according. All measurements were recorded in triplicates and these were expressed as mean ± SE. For histochemical studies, Seeds of all the varieties were soaked overnight to soften the seed-coat and were manually dehusked and hand-cut transverse sections were obtained using a razor blade. Theses thin sections were transferred through 60% alcohol grade. Afterward, Sections were transferred to 2, 4-dinitrophenyl hydrazine reagent in a beaker and incubated in hot air oven at 60°C for 30 min. Later sections were mounted by Canada balsam and observed under bright field microscope [5].

Results and Discussion

The presence or absence of aroma in the rice seeds was assessed for 70 Kalanamak rice accessions, Type-3, Pusa Basmati-1 and PantDhan-18 from Uttrakhand region. Table 1 lists the aroma responses of the rice cultivars. The result showed that most of the Kalanamak Genotypes were found give moderate to the slight aroma. Out of 70 Genotypes, 4 genotypes had the strong aroma, 38 genotypes had the slight aroma and 26 genotypes had the moderate aroma.

Table 1: Organolyptic analysis of Kalanamak rice accessions, Type-3, Pusa Basmati-1 and PantDhan-18. From the earlier studies, it was concluded the 2-AP was present in the aleurone layer than the endosperm [6, 7]. Histochemical studies revealed that aromatic compound i.e. 2-acetyl-1-pyrroline was present in the aleurone layer. 2, 4- dinitrophenyl hydrazine reacts with methyl ketones to give an orange-red color.

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Organoleptic test with consumer preferences of different rice accessions provides information for improvement of valuable grain quality traits. So it is important to identify the aromatic substances determining the aroma in rice. In addition, further studies should be carried out to confirm the precursors and pathways of 2-AP formation in aromatic rice cultivars to elucidate the nature and expression of the aroma trait in rice.

Acknowledgements

We are thankful to the Department of Biotechnology, Government of India, for funding this work under the Program Mode Support in Agricultural Biotechnology Initiative.