A Quick Botany Lesson
Strawberries are unique in many ways. Their seeds are inside tiny dry fruits known as achenes, stuck on the outside. These are shed when the fruit rots away, which it does rather quickly, which optimises the high vitamin C content while they are still edible. The juicy bit is the swollen tip (or receptacle) of the flower stalk, normally much smaller, as in the raspberry. Hence strawberries are not berries at all because the seeds are in the wrong place. True berries (eg gooseberries) have all their seeds on the inside and depend on ingestion by animals for their dispersal (1).
Nutritional Profile
- Glucose, fructose and sucrose are the main sugars found in strawberries, with the disaccharide or "double sugar" sucrose forming 20% of the total - hence the sweetness of the ripe fruit (2).
- Pectin content is relatively low, which explains why strawberry jam is difficult to set.
- A 100g portion of the fresh fruit contains approx. 27kcals, which is modest compared to an apple (47kcals) or a banana (95kcals).
- A high water content of 89% makes them a good choice for a weight reducing diet. However, the addition of 100g of double cream tips the scales a little further...adding an extra 500kcals!
- Strawberries contain 77mg/100g of vitamin C, exceeded only by blackcurrants and guava at 200 and 230mg/100g respectively (3)
- Folic acid, potassium and calcium are present in generous amounts.
A Little History
Strawberries are so named because of the tendency of the runners to "stray" from the parent plant. Modern cultivated plants are natural hybrids of two American species, Fragaria virginiara and Fragaria chiloesis and are listed under the specific name of Fragaria x ananassa. The generic name refers their fragrance - difficult to ignore at the height of summer. The wild strawberry, Fragaria vesca is smaller and has a low yield, but has a delicious flavour and fetches a good price when sold. As a wild plant, it is globally ubiquitous in temperate climes, and was cultivated to some extent in Europe in the 14th century, but it took the introduction of the American species, initially F. virginiara to enhance both the yield and size of the fruit, so the essential "Englishness" of the strawberry tea is questionable...
The pioneering work of the French botanist Antoine Nicholas Duchesne in 1766 played a major part in successfully establishing robust cultivars for marketing, followed by the plant breeding techniques of Thomas Andrew Knight (UK) during the 19th century. The market gardener Michael Keens (UK) produced the successful "Keens Seedling" in 1821 and this is the stock from which all modern varieties are obtained (4).
The demand for strawberries in all seasons has resulted in some very tired and tasteless specimens reaching our supermarket shelves. We can do better than that this summer - savour the moment and buy locally while you can. You can always import the Jersey double cream!
References
- Fritsch F. & Salisbury E. (1967) Plant Form and Function. Bell London.
- Garrow J.S. James W.P. T. Ralph A. (2000) Human Nutrition and Dietetics. Churchill Livingstone.
- Food Standards Agency (2002) The Composition of Foods. Royal Society of Chemistry.
- Davidson A. (2002) The Penguin Companion to Food. Penguin Books.
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