Field Sampling Short-day Onions for Bulb Pungency

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The marketing of onions (Allium cepa L.) based on bulb pungency as a measure of overall flavor intensity is being considered by the onion industry. Pungency is highly variable within and among fields due to genetic and environmental factors. Therefore, a study was undertaken to develop a sampling procedure to estimate onion pungency means and variances from field-grown onions with predetermined degrees of accuracy and confidence. Two shortday onion cultivars, commonly grown in the Vidalia, Ga., area, were each randomly sampled from four different fields. The sampled bulbs were analyzed for enzymatically formed pyruvic acid (EPY) and soluble solids content (SSC) to assess pungency and sugars, respectively. EPY concentration and SSC varied between the two cultivars, among the four fields within cultivars, and among the fifty samples within each field. In a combined analysis of all eight fields, at least 1.3 ten-bulb samples would be needed per acre to come within ±0.5 µmol EPY of a field's true EPY mean with 95% confidence. If the accuracy of the estimation was lowered to ±1.0 µmol EPY of a field's true mean, then at least 0.4 ten-bulb samples would be needed per acre. Because SSC was less variable than EPY, the number of ten-bulb samples needed per acre to estimate a field's true mean was lower than the number required to estimate EPY. Establishing a sampling method to estimate an onion field's EPY and SSC will provide the mechanism to standardize onion flavor in the market place and instill greater consumer confidence in purchasing onions.

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