Masters Theses

Date of Award

5-1996

Degree Type

Thesis

Degree Name

Master of Science

Major

Food Science and Technology

Major Professor

Sharon L. Melton

Committee Members

Carl E. Sams, John R. Mount

Abstract

The accuracy (percentage recovery) and precision (coefficient of variation or CV) of extraction and an anion-exchange HPLC method using amperometric detection for measurement of free sugars in spinach were determined. Five samples of fresh spinach leaves were extracted and analyzed by the HPLC method for glucose, fructose and sucrose. Different amounts (0.093 to 0.453% of spinach, wet basis or WB) of each of the latter sugars were added to each of five spinach samples and these spiked samples were analyzed in a similar manner as the unspiked samples. The average percentage recoveries of glucose, fructose and sucrose were respectively, 106.6, 101.5 and 106.0. CV's of percentage recoveries for the five spiked samples were 7.8% for glucose, 6.8% for fructose and 2.8% for sucrose.

The reported levels of total sugars in market fresh spinach in Europe range from 0.1 to 1.5% (WB) but have not been determined in the U.S.A. The recognition threshold for sweetness of sugars is approximately in the middle of the reported concentration range of sugars in spinach; thus the higher concentration ranges of sugars probably add a desirable sweetness to the fresh spinach. If levels of the sugars in fresh spinach in the U.S.A. were known, then a basis for assessment of sweetness to the flavor of such spinach could be made. Therefore, market fresh spinach samples in Knoxville, TN, were collected from four markets weekly for an eight week period in the spring of 1995. This spinach, which is shipped in primarily from California, should be fairly representative of that consumed by Southeastern U.S. customers during that time of the year. Sugar (glucose, fructose and sucrose) levels, moisture content, and chlorophyll a and b levels were also measured. On a dry basis (DB) , the fresh spinach contained 0.09 - 0.40% glucose, 0.02 - 0.20% fructose, 0.13 - 0.37% sucrose, 0.53 - 0. 78% chlorophyll a and 0.18 - 0.25% chlorophyll b the fresh spinach also contained from 90.0 - 91. 7% moisture. Spinach from one market had (p<0.05) higher levels of sucrose but lower moisture and chlorophyll contents than spinach from the other three markets. All spinach samples were dark green in color with crisp texture and were acceptable as fresh samples.

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