Food & Cooking
Jam Pectin Ratio
Sugar, pectin, and lemon juice ratios for low-sugar to traditional jam — by fruit pectin level.
Jam Pectin Ratio
Inputs
Strawberries, peaches, pears, cherries, rhubarb.
Results
Sugar
≈ 6.80 cups granulated
3.00 lb
Commercial pectin
1 box ≈ 1.75 oz powdered pectin.
1.5 boxes
Lemon juice
Bright flavor + acid pectin needs to set.
6.0 tbsp
Setpoint temperature
Or 8°F above the boiling point of water at your altitude.
220°F
How to use this
Jam sets when pectin, sugar, and acid all hit the right concentrations at the right temperature. Drop any one and you either get fruit syrup (not enough set) or a rubbery block (too much pectin / too long boiling).
Low-sugar jamsneed low- or no-sugar pectin — the standard kind relies on sugar to gel, so a 50% batch with regular pectin will not set. Pomona’s Universal pectin uses calcium to gel and works at any sugar level.
Altitude: water boils lower as you go up, so the setpoint drops too. Use 8°F above your local boiling point instead of a fixed 220°F above ~1000 ft elevation.
Formula
sugar_lb = fruit_lb × sugar_ratio
pectin_boxes = pectin_level_factor × fruit_lb ÷ 4 (high = 0.5, medium = 1.0, low = 1.5; low-sugar jams × 1.25)
lemon_tbsp ≈ 1 tbsp per lb fruit (+0.5 for low-pectin fruit, +0.5 for low-sugar ratio)
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Formula
sugar_lb = fruit_lb × sugar_ratio; pectin_boxes by pectin_level × sugar_ratio