Science notes
Science notes Brewing ginger beer
Stephen Rowcliffe
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Brewing ginger beer Stephen Rowcliffe Having finished a module on respiration with time to spare before half term, I decided I would like to try brewing a batch of ginger beer for a party with my grade 12 (17–18 year-olds) IB HL biology class. The idea was to link fermentation (anaerobic respiration), elements of aseptic technique and biotechnology with a bit of old-fashioned fun and a party. Aside from the curricular relevance of the activity, it also links biology to potential future careers in brewing and helps connect biology with ‘real life’ situations, boosting the perceived authenticity of the subject. The opportunity to discuss the societal implications of binge drinking in youth culture also presents itself. Biology teachers could consider this as the basis for a potential internal assessment activity at ages 16–18. I could find no practical worksheet on brewing in the biology department archives, nor any member of staff who had ever tried it. In fact, many teachers expressed doubts as to the wisdom of the idea. I
trawled the Internet and found many ginger beer recipes but nothing pertaining to a school-based brewing activity. I thus resolved to write my own worksheet and risk assessment based on what I could find. The NZASE (New Zealand Association for Science Education) has a useful guide to fermenting and distilling in schools (see Websites), which informed much of what is written below. Important considerations/risks I wanted my students to produce something they could safely consume within a week, but was very concerned about the possible implications. The following all need to be considered: l If necessary, parental consent should be sought
before the beverage is consumed. Seek advice from an experienced senior colleague if in doubt.
School Science Review, June 2008, 89(329)
Science notes l Cultural issues must be carefully considered;
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Muslim students must not participate in the consumption of ginger beer as it contains alcohol, albeit at low levels (see Websites). Food allergies or sensitivities must be taken into consideration. (To find out more about yeast allergy and alcohol intolerance see Websites.) Due to the high sugar content, diabetic students should be warned of potential hyperglycaemia if they are planning to drink the ginger beer. Only food-grade glass, plastic or metal containers and utensils that are exclusively for brewing use must be employed – science department beakers or stirrers must not be used for obvious reasons. All equipment must be sterilised before use. I used ‘Feeding Bottle Steriliser Tablets’ for the purpose, but boiling is another option. Only commercially available yeasts should be used. You can find brewer’s yeast at the chemist, but baker’s yeast also works (not recommended in terms of taste by connoisseurs of fine beers, but I doubt this is a major consideration). A food technology room would be the best venue although an ordinary classroom would suffice. All work surfaces must be cleaned and sterilised before the experiment begins. You must be aware that ginger beer will contain ethyl alcohol. However, the concentration will not be high if the method I describe is followed carefully. When Dr Fankhauser of Clermont College measured the alcoholic content of his root beer (see Websites) it was found to be no higher than 0.5% after four days of fermentation. This is not sufficient to cause any degree of intoxication if a small volume is consumed. A standard drink of ethanol is 10 g, and a student would have to drink three litres of ginger beer at 0.5% ABV to ingest this dose – and would still be safe to drive (if not intoxicated by the sugar itself). Details of the symptoms of alcohol intoxication can be found on the eMedicineHealth website. The NZASE state that tasting is permitted but shall be limited to a minimum volume. This gives a fair degree of scope for interpretation. I suggest that teachers have the good sense to determine what a sensible ‘minimum’ volume might be. Once the experiment is over, the ginger beer should be disposed of safely or passed directly into the hands of the parents if it is to be taken home.
Ginger beer and the law Fentiman’s produces an award-winning ginger beer that is botanically brewed. This ginger beer may be purchased by persons of any age from the supermarket as it has an alcohol content of less than 0.5% ABV. This means it is classed as a ‘soft drink’ under UK law (see IAS website). Hence, if your ginger beer is below 0.5%, you can supply it legally to those under the age of 18 without fear of prosecution. To check the alcohol content of your ginger beer, use a hydrometer (available from some chemists, wine shops and brewing outlets). Notes for teachers Ensure the students understand why they must wash their hands with antiseptic soap before the experiment. They must not use thermometers, glassware, etc., which have been used in other experiments. If you cannot find fresh ginger or lemons, substitute a teaspoon of powdered ginger and a tablespoon of concentrated bottled lemon juice. Watch carefully for students who want to elevate the alcohol concentration of the ginger beer by adding excessive quantities of sugar, and be careful not to let the fermentation continue for longer than a few days. The students must bring, wash and sterilise strong plastic pop bottles – mineral water bottles must not be used as the plastic is too thin and there is a danger of explosion. If in doubt – try it out. I ran the experiment myself first, using smaller quantities to ensure I knew the procedure well before the students had a go. My students were thrilled to have the opportunity to carry out this investigation and, with a little care and effort it is possible to do so safely. Websites Alcohol intolerance: http://www.foodreactions.org/ intolerance/alcohol/index.html Fankhauser’s root beer: http://biology.clc.uc.edu/fankhauser/ Cheese/ROOTBEER_Jn0.htm Institute of Alcohol Studies factsheet on Alcohol and the law (UK): http://www.ias.org.uk/resources/factsheets/law.pdf Muslim students and alcohol: http://www.islamonline.net/ English/News/2004-08/03/article04.shtml NZASE (New Zealand Association for Science Education) guide to fermenting and distilling in schools: www.nzase. org.nz/safety/Fermenting.pdf Symptoms of alcohol intoxication: http://www. emedicinehealth.com/alcohol_intoxication/article_em.htm Yeast allergy: http://www.allergy-details.com/yeast
Stephen Rowcliffe teaches biology at the United World College of South East Asia, Singapore. Email:
[email protected]
School Science Review, June 2008, 89(329)
Science notes
Brewing Ginger Beer Apparatus 400 g caster sugar
20 g yeast
4 litres (4 dm ) water
1 sterilising tablet
1 lemon
Utensils – knife, peeler, grater, stirrer, chopping board
3
35 g root ginger 20 g baking soda
1 five litre (5 dm3) bucket
Method 1
Wash your hands thoroughly with antiseptic soap and hot water.
2
Wash and sterilise all equipment using the chemical tablets provided.
3
Peel and grate the ginger, and then put the grated ginger into the bucket.
4 Finely peel or grate the lemon, keeping the dark yellow rind aside. Squeeze the juice into the bucket, using a sieve to prevent pips entering the pre-beer. 5
Place the lemon rind and baking soda into the bucket.
6 Pour 1 dm3 (litre) of freshly boiled water into the bucket, add the sugar and stir well until all the sugar crystals have dissolved. 7 Top the bucket up with 3 dm3 of cold water and check the temperature is not above 30 °C. Hotter water will kill the yeast and hence you will not produce any beer. 8
Remove a cup of the pre-ginger beer and mix with the yeast powder until the lumps are gone.
9
Stir the yeast solution into the liquid.
10 Cover the bucket with a clean cloth (make sure the cloth doesn’t dip into the beer) and tie with string. This is to stop things falling into the ginger beer and to let the carbon dioxide escape. 11
Leave at room temperature for 24 hours.
Stage 2 – the next day 12 Being careful not to disturb the sediment of yeast at the bottom of the bucket, siphon the ginger beer (with a freshly sterilised rubber hose) into strong polycarbonate bottles. Leave a gap of 1/8 of the bottle to allow room for the carbon dioxide that will be produced. 13
Add half a teaspoon of sugar per dm3 of ginger beer and screw on the cap tightly.
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Store the bottles in a cool dark place for two days.
15 Refrigerate for several hours to deactivate the yeast. If it is to be tasted, decant carefully into a glass. Yeast sediment will be present at the bottom of the bottle and has an unpleasant taste. Warning! this beverage will be alcoholic. you may taste only a bare minimum of the ginger beer and with caution.
School Science Review, June 2008, 89(329)
