GIFSQ Tools · Module 09 — Fruits, Vegetables, Beverages & Plant Foods · Tool 163 of 500
Penetrometer firmness for a fruit lot. Enter the readings from the lot, with the specification limits, to get the mean, range and share inside specification. Save each lot on this device.
Try sample values — fills the form with the worked example below.
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Mean firmness (N)
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Lowest (N)
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Highest (N)
Equation: Mean = sum of readings ÷ number of readings. Within specification % = readings inside [minimum, maximum] ÷ number of readings × 100. 1 kgf = 9.80665 N.
Method: Magness-Taylor penetrometer firmness, ASAE S368.4 (compression test of food materials of convex shape); readings converted to newtons (SI).
Assumptions: All readings used the same plunger and the same penetration depth; fruit were at the same temperature.
Limitations: Firmness is one maturity signal only; it varies with variety, fruit size, temperature and operator, so it cannot replace Brix, acidity and colour checks.
Rounding: Firmness to 2 decimal places; counts and percentages to 2 decimal places. Intermediate values are not rounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Method: Magness-Taylor penetrometer firmness, ASAE S368.4 (compression test of food materials of convex shape); readings converted to newtons (SI).
Assumptions: All readings used the same plunger and the same penetration depth; fruit were at the same temperature.
Limitations: Firmness is one maturity signal only; it varies with variety, fruit size, temperature and operator, so it cannot replace Brix, acidity and colour checks.
Rounding: Firmness to 2 decimal places; counts and percentages to 2 decimal places. Intermediate values are not rounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Worked example: Readings 8.5, 9.0 and 8.0 N, specification 7–10 N. Mean = 25.5 ÷ 3 = 8.50 N; lowest 8.00 N, highest 9.00 N; 100.00 % inside specification.
Saved entries
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Enter values above to see results.
Firmness falls as fruit ripens. Always use the same plunger size, the same penetration depth and the same fruit temperature when comparing lots. Tool 163 of 500 — GIFSQ
