Monday 20 October 2014

How long will it last?

We are constantly bombarded with information about ‘shelf life’ and ‘sell by dates’. If we buy anything herbal it will come with a “Best before end” date which can range from three months to two years. Herbalists talk about plants which lose their efficacy quickly and those which are still being used decades later. For a newcomer to herbs it can be very confusing.

If you are reliant on other producers for all your herbal products then you are constrained by their printed labels saying how long something will last. You can make your own assessment of vibrancy by comparing what the colour, smell and taste of the product when you first purchased it compared with how it looks/smells/tastes now.  Be aware that once you expose the product to the air, it will start to denature. The more you use something, the sooner it will lose its potency.

This won’t be a problem if you’ve bought something to use regularly over a couple of weeks or months but it could be a disappointment if you open it and leave the lid off for a relatively long period of time, then seal it and go back to it a year or so later and discover it has “gone off”.

It’s helpful to look at each kind of herbal produce in turn.

Fresh Herbs
Wisdom passed down from ancient times exhorts us to pick herbs when they are dry but before the midday sun stresses the herb. If you want to experiment with timings, try picking late morning and late afternoon and see how the herb changes in those few hours. Once you have picked as much as you want, make sure your produce is not left exposed to bright sunshine or you may lose everything you have gathered. When you are picking don’t use plastic for storage of any length, cloth bags or wicker baskets are best. The plant will continue to respire even after you have cut it from its roots and the water vapour produced needs to be able to escape. Keeping it in a plastic bag overnight can mean you return to a wet, soggy mess.

You may want to use or process your fresh herb immediately or you can deliberately leave them to wilt for several days to remove excess water content before you process your harvest. Wilting time will vary depending on the amount of water present in the herb. I have seen watercress and milk thistle leaves reduce by ½ to 2/3rds of their volume in half an hour in warm weather or hot room. Most green, leafy herbs can be left to wilt for up to three days in a cool, shady, airy place.

Dried aerial parts should retain the vibrancy of colour once dried. Leaves and flowers should be removed from their stems once dry because the stem may not have dried completely but should be stored as completely as possible. Once you crush a leaf it releases its essential oil into the air and is lost, so if you crush or powder a dried herb it will not retain its potency for as long as the whole counterpart.

If you need to turn a herb into powder, do small amounts as and when needed. This is especially true of oil bearing seeds such as hemp or flax. Once ground the oil starts to turn rancid after three hours so should be consumed immediately.

If you don’t live in a climate where long periods of dry weather are possible then there will be times when you have to pick in the wet or lose your entire crop. If this happens you will have to use an external heat source to remove excess moisture. Rayburns (small agas) and hot water tanks/airing cupboards can be really useful for this but few people have access to them anymore. If you do need to dry in an oven, always dry on the lowest heat and leave the oven door open so the moisture can escape. NEVER dry in a microwave (unless you are only drying for culinary purposes and don’t care what is happening to the chemistry of the plant material) as you will end up cooking the plant, not drying it.

Seeds, roots and barks are different. You may find, if collected during autumn or winter, the increased moisture content of the seasonal air will make them prone to mould development if left in a cool place without washing and drying. Yeast spores present in the air can cause fermentation as part of the cycle of decay. This is especially true with elderberries and conkers will develop a surface mould if left untouched for a week. Smaller seeds such as fennel, dill or coriander should be picked dry and dried some more before storing but will last for several years.

Seeds, roots and barks do take more time to prepare before drying but if the preparation is done effectively so drying is complete, the finished product should last several years. The more time and effort you put in beforehand, the longer it will keep.

Dried herbs
Most dried herbs will keep their potency for twelve months and may start to lose colour and scent during their second or third year. It is colour, scent and taste which will alert you to the potency. Some herbs such as lemon balm, tarragon, dill, fennel and St John’s wort flowers are only supposed to have a shelf life of six months and people are advised to think of other ways of preserving them such as freeze drying, herbal ice cubes or frozen herbal butters.

Some herbs such as cleavers and chickweed have such high water content that they are not supposed to be effective if dried at all but herbalists in countries with very short growing seasons such as Finland have disproved this. If you are making oils or tinctures with these herbs you should use them fresh and not dried.

If you grow and dry your own delicate herbs and keep them in glass jars away from the light (I put brown paper bags around my glass jars) you will find they are active well after their supposed use by date.  I’ve seen health food shops sell straw coloured calendula petals kept in clear glass near the shop window which are obviously useless yet my homegrown petals keep their orange vibrancy for longer than twelve months, as does my St John’s wort, red clover and bergamot.

Herbs don’t realise they have a use by date. They will continue to act many years after being dried. Henriette Kress had a case where she gave five year old St John’s wort dried flowers to a client which worked perfectly well and Jim Macdonald has some fourteen year old calamas root which he chews. He said there wasn’t quite as much “zing” in the old root as a freshly dried one but the essence of the plant was still there.

If you find yourself in a situation where you need a dried herb but only have something two or three years old which has lost most of its colour and smell then double the amount you would normally infuse to provide a medicinal product.

A “normal” herbal tea brewed for ten minutes should keep in the fridge for 24 hours. This is useful if you are brewing larger amounts to use throughout the day or for eye washes, antiseptic washes etc.

A cooled decoction should keep in a fridge for up to 48 hours.

Syrups and cordials
Concentrated (i.e. reduced by evaporation to 1/8th of its original volume) medicinal syrups made with 1:2 proportion of tea: sugar should keep indefinitely if placed in sterile bottles and lids. Syrups made with 1:1 proportions of tea: sugar or honey in a sterile bottle and lid should keep for at least a year unopened and possibly two. Once opened, they should be kept in a fridge and used within six months.

Cordials made with 1:1 proportions should have the same shelf life as a syrup. Anything made with reduced sugar content will have a much shorter shelf life.

Floral waters
Floral waters are used externally and normally have 1:0.25 decoction: alcohol proportion (i.e. ¼ of the volume of decoction of alcohol is added as a preservative). I have kept these for two years successfully without opening.

Decocted bitter
If you make a bitter by decocting the plant material and preserving this with alcohol measuring ¼ of the volume of the original decoction it should last for 18 months to 2 years before it starts to grow something when stored in a cool, dark place and unopened. If the mixture becomes cloudy, discard.

Flower essence
Flower essences made by sun infusion and preserved 1:1 with brandy should keep for up to two years if unopened. Once diluted with spring or distilled water, it should be used within a week or sooner.

One of the major factors in the shelf life of your tincture is how concentrated your extracting alcohol and how often you open the bottle/jar/container. Unopened, tinctures can last for ten years or more depending on which plant you have used. Tinctures should also be stored in brown or green glass bottles and kept away from heat or light.

If you leave plant matter in the alcohol for longer than the prescribed period (most people macerate for three weeks, some for six) you tend to extract extra tannins which you may not want. Certainly when I forgot to strain a jar of vervain and skullcap for over 12 months, the tinctures were both very dark brown and exceptionally bitter which meant I'd lost the beautiful shining aquamarine of the skullcap. I used them both but in formulae rather than alone.

Some herbalists have found that leaving the fresh herb in the tincture has increased the longevity and are now doing this as their practice. This works best when the herb restricts fungal and bacterial growth as part of its repertoire.

Elixirs are made with equal proportions of brandy and honey. As such they should last at least ten years and probably longer. I do leave fresh elderberries in elixirs and haven’t had a problem with fermentation as long as they are kept cool.

Honey has been found in 2,000 year old Egyptian tombs still smelling and tasting like honey. Infused honey made from watery plant material may only last a couple of years. I recently found a year old jar of rosehip honey with the chopped hips still in it starting to grow mould on the top but once this was scraped off the rest of it was fine. Electuaries made from dried, powdered herbs should keep for as long as it takes you to eat it. I have one jar I use for demonstrations which is over six years old and still tasting the same as it did when I first made it.

If you make sun infused oils and don’t keep the plant material submerged they will grow mould and the oil will have to be discarded immediately. If you make double infused heated oils from fresh plant matter, you need to pour off the water globules before storing or the oil will go off more quickly. Unopened jars of double infused oils should last two to three years. St John’s wort oil will keep much longer if kept unopened in wide necked jars.

If you keep opening jars of oils, they will go off sooner.

The shelf life of salves can be increased by adding Vitamin e capsules or essential oils. This is personal preference. I don’ t use any preservative and my salves, unopened will last up to two years and 8-12 months once opened.

My experience with infused herbal vinegars is that, because of their acidic environment, they keep indefinitely. I have never had a herbal vinegar “go off”. Some vinegars, such as chive flower, will lose their colour after twelve months.

I don’t make glycerites so have no experience of their shelf life.