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Studies on the Sugar Accumulation and Carbohydrate Splitting Enzyme Levels in Post Harvested and Cold Stored Potatoes

Md Rezaul Karim
Department of Applied Nutrition & Food Technology, Islamic University of Kushtia, Bangladesh

M M H Khan
Department of Biochemistry & Molecular Biology, University of Rajshahi, Rajshahi-6205, Bangladesh.

Md Salim Uddin
Department of Biochemistry & Molecular Biology, University of Rajshahi, Rajshahi-6205, Bangladesh.

N K Sana
Department of Biochemistry & Molecular Biology, University of Rajshahi, Rajshahi-6205, Bangladesh.

F Nikkon
Department of Biochemistry & Molecular Biology, University of Rajshahi, Rajshahi-6205, Bangladesh.

Md Habibur Rahman
Department of Biochemistry & Molecular Biology, University of Rajshahi, Rajshahi-6205, Bangladesh.

Abstract/ Executive Summary:

Significant differences were found in sugar content and carbohydrate splitting enzyme activities in tubers of ten indigenous potato varieties at harvesting and after keeping at cold storage. The activities of invertase, amylase, β-galactosidase and cellulase in all varieties were found to be increased by 2-12, 1.2-4, 1.9-4.5, and 1.1-3.7 folds, respectively from harvesting to cold stored potatoes. The amount of starch and sucrose were found to be decreased by 1.15-2.8 and 1.02-1.4 folds, respectively from harvesting to cold stored in all varieties. Total soluble sugar and reducing sugar contents in potatoes were increased by 1.02-1.4 and 4-11 folds, respectively from harvesting to cold stored in all varieties of potatoes. The amount of reducing sugar increased in cold stored potatoes due to the increased activities of carbohydrate splitting enzymes.

Keywords: Potatoes, Indigenous, Carbohydrate splitting enzymes, Sugars.

Location: Department of Applied Nutrition & Food Technology, Islamic University of Kushtia

Start Date:

End Date:

Program Area: Postharvest and Agro-processing

Commodity: Potato

Objectives:

This study was carried out to ascertain the relationship of sugar content and some carbohydrate splitting enzymes in ten different indigenous varieties of potato at harvesting (mature) and after keeping in cold storage at 30-35^oF for 8 weeks.

Methodology:

The varieties Ausha, Challisha, Lal pakri, Lal shil, Patnai, Shada guti, Shil bilati, Jolpai, TPS-67 and TPS-7 were collected from the plant Breeding and Biotechnology Laboratory, Department of Botany, Rajshahi University, Bangladesh.Enzyme assay: About 50 g of potato were peeled and cut into small pieces and homogenized well with cold buffer of respective pH (for amylase, invertase, cellulase: 0.1 M sodium acetate buffer, pH 6, pH 5 and pH 5.2, respectively and β-D-galactosidase: sodium citrate buffer, pH 4.1). The extracts were filtered by few layer of cheesecloth and further clarified by centrifugation at 6000 rpm for 15 minutes at 4^oC. The clear supernatant was collected and used as crude enzyme extract. Amylase, invertase and cellulase activities were assayed as described by Mahadevan and Sridhar (1982) using starch (1%), sucrose (2.5%) and carboxymethyl cellulose (0.5%) solution as substrate, respectively. One unit of amylase activity was defined as the amount required for liberating 1g of glucose from starch per minute at 37°C. One unit of invertase activity was defined as the amount required for liberating 1g of glucose and fructose from the breakdown of sucrose per minute at 37°C. Cellulase activity was measured by estimating the reducing sugar released from substrate by cellulase using dinitrosalicylic acid method (Miller 1972). One unit of cellulase activity was defined as the amount of enzyme required for liberating 1g of reducing sugar from CMC per minute at 37°C. β-galactosidase activity was assayed by the method of Lazan et al. (1993). Amount of galactose released was estimated by dinitrosalicylic acid method (Miller 1972). One unit of β-galactosidase activity was defined as the amount of enzyme that catalyzed the liberating of 1g of galactose per minute at 37°C. Estimation of starch, total soluble sugar, sucrose and reducing sugar: Total soluble sugar and starch in potato were determined colorimetrically by the anthrone method (Jayaraman 1985). Reducing sugar content was determined by dinitrosalicylic acid method (Miller 1972).

Source of Information: J. bio-sci. 16: 95-99, 2008 ISSN 1023-8654

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The amount of starch and sucrose were found to be decreased by 1.15-2.8 and 1.02-1.4 folds, respectively from harvesting to cold stored in all varieties. Total soluble sugar and reducing sugar contents in potatoes were increased by 1.02-1.4 and 4-11 folds, respectively from harvesting to cold stored in all varieties of potatoes. The amount of reducing sugar increased in cold stored potatoes due to the increased activities of carbohydrate splitting enzymes.

Knowledge Management: Journal