SOP: Determination of Weight-to-Length Ratio of French Beans

GIFSQ — Global Institute for Food Safety & Quality

Principle

In French (green) beans, the factors contributing to sensory tenderness, appearance and flavour change together as the bean matures; in the Burpee stringless variety, the weight-to-length (W/L) ratio has been found, on the basis of ten physico-chemical characteristics studied during growth, to be closely correlated with the sensory characteristics. A single objective test with a good simple correlation to the sensory quality factors therefore correlates highly with the others as well.

Apparatus required

• Balance, for weighing the beans
• Ruler or measuring scale, for measuring bean length

Procedure

Weigh the beans and record the total weight in grams

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Measure the length of the beans and record the total length in centimetres

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Calculate the weight-to-length ratio in g/cm

Calculation

W/L ratio = (weight of beans, g) / (length of beans, cm)

Where,

• Very tender: W/L ratio up to 0.4 g/cm
• Tender: W/L ratio from 0.41 to 0.5 g/cm (the optimal mature stage)
• Mature: W/L ratio from 0.51 to 0.6 g/cm
• Over-mature: above 0.6 g/cm

Precautions

• Use beans of one variety and uniform growing conditions for comparable results.

References

Ranganna, S., Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd edition.