Open Source Apothecary At Home / The twelve-month course

Unit 8 (August): Preservation — fermentation, drying and storage

The month that turns a glut into a year's supply — and the month with the one fatal mistake.

guide

August is when the garden produces more than can be used fresh, so it is the month to learn preservation properly. It is also the month with the one mistake that kills.

Fermentation is the technique with a nutritional argument. Phytate binds iron, zinc, calcium and magnesium into insoluble complexes. Fermentation degrades phytate and measurably raises mineral absorption — the only preservation method that makes what it preserves more nutritious than it was. It also happens to be the best way to deal with a cabbage glut.

The two controls are acid and salt, and both must be right. pH below 4.6 for safety, below 4.0 for good keeping. Salt around 2.0-2.5% by total weight of vegetable plus water, using pickling or sea salt rather than iodised table salt. White film and a sour smell are normal. Fuzzy mould is not — discard the batch.

The fatal mistake is botulism, and it is anaerobic. Clostridium botulinum germinates only without oxygen, in low-acid, low-salt, moist conditions — which is exactly what brining, oil-covering, vacuum-sealing and sealed fermentation create. So:

• Never invent a canning recipe. Tested pressure-canning times for low-acid vegetables are not optional; home-canned low-acid vegetables are a documented botulism source and a water bath cannot reach the temperature required.
• Never leave fresh, wet plant material sealed under oil. Garlic in oil is the classic case.
• Never seal a ferment in a rigid closed vessel. They burst.

Drying and storage close the loop. Storage degrades: phenolic content falls in stored dried material and light accelerates it. The four enemies are light, oxygen, heat and moisture. Working lives: volatile flower and leaf 6-12 months, other leaf 12-18 months, root and bark 2-3 years, powdered herb about half.

The oxalate-versus-mineral point, both correct. For minerals, do not boil the greens and do not throw the water away. For oxalate, boil and discard the water. Different compounds, opposite advice.

What the studies found

Growing it

In season: the glut

• Elderberry — berries ripen late August into September; harvest when fully dark
• Fennel, dill — seed heads drying
• Calendula — continuing; save seed from the best plants now
• Cabbage, beans, carrots — the fermentation crops
• Mint, lemon balm — cut back hard and dry the flush

Garden work

• Let a few plants go to seed and collect it
• Cut back spent annuals; keep calendula producing by daily picking
• Start planning the autumn root harvest and the garlic planting

Preparation

Project: a lacto-ferment, a drying run, and a storage audit

Sauerkraut or a brine ferment

• Shred cabbage; 2% salt by total weight (weigh the cabbage, calculate)
• Massage until brine forms; pack into a jar, keeping it submerged
• 18-22 C, venting gas, 1-4 weeks
• pH below 4.6 for safety; strips are cheap and taste is not a safety test
• White film and sour smell: normal. Fuzzy mould: discard the batch.

Drying run for the glut

• Aromatics: shade, ambient, moving air
• Roots: 45-55 C, sliced
• Test for dryness; jar a sample and check next day

Storage audit — the habit that saves the year's work

• Amber glass, filled high, cool and dark
• Label: plant, part, date, place
• Check the oldest jars and discard what smells spent
• Powder as you need it, not a year's supply at once

Cautions and interactions

• Botulism is anaerobic — exactly what brining, oil-covering and vacuum-sealing create.
• Never invent a canning recipe. Low-acid vegetables need tested pressure-canning times.
• Never seal a ferment in a rigid closed container.
• Never salvage a batch with fuzzy mould — mycotoxins extend below the visible growth.
• Salt and sugar are part of these methods and matter on a sodium- or glucose-restricted diet.
• Under-dried material moulds. Discard it.

When this is not a self-care problem — get help

• Blurred vision, difficulty swallowing or speaking, drooping eyelids or muscle weakness after eating home-preserved food — botulism; emergency department immediately, with the container.
• A swollen or bulging can, or a spurting lid — do not taste it; discard it.
• Fever, severe abdominal pain or bloody diarrhoea after preserved food — urgent assessment.

Related

• The twelve-month course
• Preserving the harvest: which method for which crop
• Lactic fermentation: the preservation method that also raises mineral absorption
• Drying and storing so the potency survives
• Elderberry

Sources

1. Effect of different cooking methods on color, phytochemical concentration, and antioxidant capacity of raw and frozen brassica vegetables. Journal of agricultural and food chemistry 2010; doi:10.1021/jf904306r PubMed 20218674
2. Effect of domestic processing and cooking methods on phytic acid and polyphenol contents of pea cultivars (Pisum sativum). Plant foods for human nutrition (Dordrecht, Netherlands) 1994; doi:10.1007/BF01088088 PubMed 7971780
3. Fermented Plant-Based Foods and Postbiotics for Glycemic Control-Microbial Biotransformation of Phytochemicals. Molecules (Basel, Switzerland) 2026; doi:10.1016/j.fm.2013.04.007 PubMed 41599407
4. Lactic acid bacterial fermentation as a biotransformation strategy to enhance the bioavailability of phenolic antioxidants in fruits and vegetables: A comprehensive review. Food research international (Ottawa, Ont.) 2025; doi:10.1016/j.foodres.2025.116283 PubMed 40253191
5. Vegetable substrates as an alternative for the inclusion of lactic acid bacteria with probiotic potential in food matrices. Journal of food science and technology 2024; doi:10.1111/ijfs.14158 PubMed 38487286
6. Fermentation for Revalorisation of Fruit and Vegetable By-Products: A Sustainable Approach Towards Minimising Food Loss and Waste. Foods (Basel, Switzerland) 2024; doi:10.1016/j.foodchem.2024.141173 PubMed 39594095