GIFSQ Tools · Module 07 — Dairy, Milk, Cheese & Fermented Products · Tool 123 of 500
Estimate lactose in milk by difference from total solids, fat, protein and ash, and see its share of total solids.
Try sample values — fills the form with the worked example below.
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Lactose (%)
Lactose share of total solids (%)
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Total solids (%)
Equation: Lactose (%) = total solids (%) − fat (%) − protein (%) − ash (%). Lactose share of total solids (%) = lactose ÷ total solids × 100.
Method: Lactose by difference from the proximate components: total solids (ISO 6731, IDF 21), fat (ISO 1211 or ISO 9622), protein (ISO 8968-1 Kjeldahl, IDF 20-1) and ash (ISO 5545, IDF 90). Lactose itself is measured directly by ISO 22662 (HPLC) or ISO 9622 mid-infrared where available.
Assumptions: all four components are measured on the same sample; minor components other than fat, protein, ash and lactose are negligible.
Limitations: by difference, the lactose figure carries the combined error of all four measurements; it is an estimate, not a direct lactose assay.
Rounding: percentages to 2 decimal places; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Method: Lactose by difference from the proximate components: total solids (ISO 6731, IDF 21), fat (ISO 1211 or ISO 9622), protein (ISO 8968-1 Kjeldahl, IDF 20-1) and ash (ISO 5545, IDF 90). Lactose itself is measured directly by ISO 22662 (HPLC) or ISO 9622 mid-infrared where available.
Assumptions: all four components are measured on the same sample; minor components other than fat, protein, ash and lactose are negligible.
Limitations: by difference, the lactose figure carries the combined error of all four measurements; it is an estimate, not a direct lactose assay.
Rounding: percentages to 2 decimal places; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Worked example: Total solids 12.6%, fat 3.6%, protein 3.3%, ash 0.7%. Lactose = 12.6 − 3.6 − 3.3 − 0.7 = 5.00%; share of total solids = 5.00 ÷ 12.6 × 100 = 39.68%.
Enter values above to see results.
Cow milk lactose is typically 4.6–5.0%; it is the main milk sugar and the substrate for lactic fermentation. Tool 123 of 500 — GIFSQ
