Apple Scrap Fruit Vinegar

A thrifty raw fruit vinegar built from apple cores and peels: wild yeast on the fruit ferments the dissolved sugar to alcohol, then acetic-acid bacteria oxidize that alcohol to a bright, gently fruity vinegar. The same method works for pear, grape, or stone-fruit scraps.

Ingredients

1 Jar = a 1 L wide-mouth jar; 1 Crock = a 4 L crock. Fill the vessel about half full of scraps, then cover with sugar water, leaving headspace for the cap of foam. Sugar fuels the first (alcoholic) stage; the fruit supplies the wild yeast.

Component	1 Jar (1 L)	1 Crock (4 L)
Apple scraps (cores, peels, bruised flesh)	~250 g	~1,000 g
Non-chlorinated water	~850 mL	~3,400 mL
White or raw sugar	50 g	200 g
Raw live vinegar or mother (Stage 2 inoculum)	100 mL (10%)	400 mL (10%)

Yield

About 700-800 mL finished raw vinegar per jar, or 2.8-3.2 L per crock, after straining out the spent scraps.

Calculated Values

Sugar concentration: 50 g/L = 5% w/v → roughly 5-6% potential alcohol, which sets the acetic-acid ceiling (about 1% ABV → about 1% acetic, ~90% efficient).
Expected finished acidity: 4-5% acetic acid if the sugar is fully converted. Verify by titration — see Titratable Acidity.
Stage 1 (alcoholic, semi-aerobic): 18-24 °C, 1-3 weeks, stirred daily.
Stage 2 (acetous, aerobic): 21-27 °C / 70-80 °F, 3-6 weeks, undisturbed.
Finished pH: typically 2.8-3.4 at 4-5% acetic; taste is never the safety test, acidity is.

Readiness Window

Stage 1: 1-3 weeks at 18-24 °C — done when the bubbling slows, the smell turns winey/alcoholic, and the liquid no longer tastes sweet.
Stage 2: 3-6 weeks at 21-27 °C — done when the smell is sharply acetic and titration confirms acidity.

Done-when: titrated acidity reaches at least 4% acetic for table use (a full 5% if you intend to use it for any canning or pickling). A thin gelatinous mother on the surface is normal and desirable. Arrest / stabilize by straining and refrigerating at 2-4 °C, or pasteurize at 60-71 °C / 140-160 °F for ~10 min to lock the acidity and stop further change.

Pack scraps and sugar water

Half-fill the vessel with apple scraps. Dissolve 50 g sugar per liter in non-chlorinated water and pour over to cover the scraps, leaving 3-4 cm headspace. Weight the scraps under the liquid with a clean glass or fermentation weight so they stay submerged.

Stage 1 — alcoholic ferment (stir daily)

Cover with tight-weave cloth and a band. Hold 18-24 °C and stir once a day with a wood or plastic spoon for 1-3 weeks. Daily stirring oxygenates the yeast, releases CO₂, and keeps the floating scraps from molding. It is ready when bubbling slows and the smell is winey.

Strain and inoculate for Stage 2

Strain out the scraps (compost them) into a clean wide vessel. Stir in 10% raw live vinegar or a mother of vinegar to seed the acetic-acid bacteria. Keep the vessel wide and only two-thirds full — surface area drives the next stage.

Stage 2 — acetous ferment (do not stir)

Re-cover with cloth and hold 21-27 °C, undisturbed, for 3-6 weeks. A new mother forms on the surface; leave it intact. Oxygen is now pulled from the air through the cloth, so do not seal and do not stir.

Confirm by acid, then bottle

Titrate. When acidity reaches your target (4% table / 5% canning), strain off the mother (reserve some for the next batch) and bottle. Store cool and dark, or pasteurize first to stabilize.

Variations / mix-ins

Pear, grape, or peach scraps: swap one-for-one; sweeter fruit gives a higher potential alcohol and a stronger vinegar.
Spiced finishing vinegar: after Stage 2, steep a cinnamon stick or a few peppercorns in the strained vinegar for a week, then re-strain (do not use spiced vinegar for canning unless re-titrated).
Sweeter “drinking” vinegar: stop a touch earlier for a softer, fruitier acidity for shrubs and sodas (not for canning).

Vinegar method

Confirm the acid endpoint