Enzymes: the hidden extras in almost everything we eat
This is extended version of an article which was published in The Food Magazine issue 79
29th November 2007
Introduction
Enzyme production
Enzymes and the law
GM enzymes
Bread
Cheese production
Bone cleaning and meat extracts
Fruit and vegetable juices
Ready peeled fruit
Fake meat
Modified starch
Changing corn to sugar
Inverted sugar syrup
Enzymes are used in almost all aspects of modern food production. They modify the raw ingredients of the food we eat and the food itself. However, enzymes go unmentioned in ingredients lists and food manufacturers remain curiously shy about their use. Ian Tokelove reports.
As you read this, enzymes will be at work within your body. They act as catalysts, controlling chemical reactions involved in digestion, respiration and metabolism. Our own bodies produce many different types of enzyme, as do all living things, right down to the humblest mould and the smallest bacteria.
Enzymes are able to break down, or modify, chemical compounds such as starches and proteins. This ability has been utilised by humans for thousands of years. For example, using naturally enzyme-rich plant or animal matter, our ancestors produced cheese, bread and alcohol.
Perhaps the best known use of an enzyme in food production is rennet, traditionally derived from the stomach linings of young calves. Rennet contains enzymes that coagulate milk causing it to separate into solids (curds) and liquid (whey). The curds are then used for cheese production.
Enzyme production
Enzymes have traditionally been sourced from the tissues of plants and animals, where they occur naturally. However, microorganisms such as mould and fungi can also be used to produce vast quantities of enzymes. Some of these microorganisms produce the enzymes naturally, but many more have been genetically modified so that they produce ‘copies’ of animal or plant enzymes.
Microbial production has many advantages over plant and animal sources. The raw products required – the microorganisms and the substrate on which they feed – can be supplied wherever they are required. This frees companies from having to rely on a regular supply of enzyme-rich, plant or animal based materials, which may be expensive to collect and transport, and which will also need processing and purifying before use.
Enzymes and the law
Enzymes are not listed as food ingredients because they are regarded as ‘processing aids’, which do not have to be mentioned on food labels. A processing aid is a substance added during food processing for technical reasons, but which has no function (e.g. flavour, colour, preservation) in the final food product.
Most enzymes are also inactivated (broken down) during processing and are no longer technically active in the final product, although a residue will often remain.
However, enzymes have hugely important functional roles during food processing. They are used specifically to affect flavour, texture, aroma, colour, and many other food qualities – often dramatically.
Despite their widespread use in the UK, there is little specific legislation regarding the use of enzymes. Throughout the EU they are regulated as processing aids, covered by laws which vary from country to country. In the UK there is no list of ‘permitted’ enzymes, although enzymes must be considered safe under General European Commission (EC) Food Law.
It is worth noting that there is neither safety evaluation nor authorisation of food enzymes at European level, except for those that are considered as food additives (of which there are just two enzymes, E1103 and E1105).
In July 2006, an EC proposal on the regulation of food enzymes pointed out that rapid advances in production technology has resulted in, “more complex and sophisticated,” enzymes which could cause, “potential hazards arising from their chemical nature and source such as allergenicity, activity-related toxicity, residual microbiological activity, and chemical toxicity.”
The EC proposal, which has yet to be formally approved, would seek to create a harmonised list of food enzymes, following safety evaluation by the European Food Safety Authority (EFSA). The proposal says that, “all food enzymes and their use in food will be evaluated for safety, technological need, benefit to the consumer and (to ensure) that the consumer is not being misled by their use.”
As with food additives, terms such as these can be subject to very loose interpretation by both the food industry and its regulators. Even after approval, we won’t see enzymes appearing on food labels, as they will still be regarded as ‘processing aids’.
Assuming the proposal is accepted, companies will be allowed a period of two years to submit data for evaluation, so we are unlikely to see any progress until after 2010.
GM enzymes
The majority of enzymes appear to be produced using genetically modified microorganisms, but with no public access to the food industry’s secret files, it is impossible to know which enzymes are used where.
Perhaps surprisingly, we can be sure that almost all vegetarian cheese has been produced using enzymes from GM microorganisms. The GM process is approved by the Vegetarian Society, who regard it, in this instance, as a preferable alternative to the wholesale slaughter of calves.
The only way to avoid GM produced enzymes is to purchase organic food, as organic standards completely forbid all use of GM ingredients or derivatives.
Bread
Whether you prefer a slice of white, a french baguette or a seed-encrusted granary loaf, almost all the commercially manufactured bread in the UK is made with enzymes.
Enzymes allow manufacturers to significantly pump up loaf volume, adjust texture, produce a better crust colour and prolong shelf life. They make the dough easier to put through machines, increase dough stability and control ‘crumb structure’ – which in a sliced white loaf might be silky and uniform, but in a baguette may be chewy and variable, with large holes. Enzymes can even give bread a whiter appearance.
What most of us would recognise as a modern loaf would be impossible to produce without enzymes. But what does all this mean for the consumer? Andrew Whitley, an artisanal baker and writer, warns that some enzymes are potential allergens, notably the very widely used alpha-amylase (used in baking to break starches down into sugars, for yeast to feed on).
Bakery workers can become sensitised to enzymes from bread improvers, and industry experts warn that liquid or granular preparations of enzymes are safer than powdered forms, because of the allergenic potential of enzyme dust. This should not be a problem to the end consumer if enzymes are destroyed during processing, but Whitley has quoted research from the University of Bochum, in Germany, which shows that up to 20% of the allergenicity of alpha-amylase can survive in the crusts of bread.
Whitley has also revealed that an enzyme called transglutaminase, which may be used to make dough stretchier in croissants and some breads, may render part of the wheat protein toxic to people with a severe gluten intolerance. Such unintended and unanticipated effects suggest that the safety testing of some enzymes may not be up to scratch, and raises the possibility of other, as yet unnoticed, side affects. However, unless enzymes are fully labelled on ingredients lists, it will be virtually impossible to correlate possible side effects in the general population with enzyme use.
Cheese production
Enzymes are essential to cheese production. They act by coagulating milk, allowing the ‘solid’ curds to be separated from the ‘watery’ whey. The curds are then pressed and matured to produce cheese.
Traditionally the enzymes would have come from the stomach linings of young calves, where they are naturally produced to enable the calf to digest its mother’s milk. Commercially produced preparations of standardised, enzyme-rich matter for cheese production were first made in Denmark in 1874.
Today, over half of the enzymes used in UK cheese production are microbial in origin. The enzymes are produced from genetically modified (GM) yeast and moulds which contain copies of the calf gene for the production of chymosin, the main enzyme involved in milk clotting.
Bone cleaning and meat extracts
Modern food production can be extremely efficient. When it comes to meat production, nothing is left to waste. Cattle and pig bones are turned into gelatine, a standard ingredient in jellies, chewy sweets and many desserts. Before the bones can be processed they must be cleaned, and to do this enzymes can be used.
The bones are first crushed and mixed with hot water. Enzyme preparations with names such as NeutraseTM, AlcalaseTM, EsperaseTM or FlavourzymeTM are then added singly or in combination and the ‘bone soup’ is stirred so that the enzymes can get to work. The enzymes break down the meat protein which is still sticking to the bones, and this dissolves into the water around it.
The cleaned bones are used for gelatine production and the protein solution is extracted for use as a flavour enhancer in processed meat products, soups, sauces and snack foods. This ‘hydrolysed protein’ should be listed in the ingredients list, although you will not be able to tell how it was produced. Similar protein extraction processes can be used for plant based protein – for example, the production of soya milk from soya beans.
Fruit and vegetable juices
If you thought that your fruit juice had been ‘freshly squeezed’ and that was all, you may need to think again. Enzymes have been routinely used in fruit juice production since the 1950s. One of the very first commercial enzymatic products was Pectinol K, launched in 1938 and used in the production of clear apple juice.
Juice manufacturers want to extract as much juice as they can from fruit or vegetables, and enzymes can help them to break the fruit structure down, releasing more juice. UK fruit juice regulations allow three types of enzymes to be used: pectolytic enzymes, proteolytic enzymes and amylolytic enzymes.
Enzymes have several other functions in fruit juice production. They can be used to clarify and prevent clouding in juices, and modern ultrafiltration processing (the use of very fine filters to remove solid matter) is highly reliant on enzymes, which are used to completely break down pectin and starch solids, and to remove blockages that form on the costly filtration membranes.
Juices are heat treated before being sold, and this inactivates the enzymes, although their remnants invariably make it into the final product.
Ready peeled fruit
An orange comes with its own perfect packaging, but that has not stopped food companies from selling us pre-peeled oranges and other such fruit, plastic wrapped for our ‘convenience’ or mixed into ‘ready to eat’ fruit cocktails. Removing the skin of such fruit by hand is time consuming, messy and can damage the fruit, but enzymes can provide a high-tech, quick-fix and cheap answer to the problem.
The peel is scored and the fruit is then immersed in a solution of the enzyme pectinase. This is followed by an ‘infusion’ stage where the solution is forced deep into the fruit using low or high pressure processes. After one to two hours the enzyme will have got to work on the fruit and the skin can be easily peeled off, and the segments easily separated without damage.
Fake meat
Some meat just isn’t meat anymore. If you choose to buy your meat in processed form, sliced and shaped and ‘ready to eat’ it is worth a close look at the ingredients label.
Alongside added water you may find other, unexpected, meat ingredients, such as chicken in your ham. Other proteins may also be added, such as soy, casein and gluten. Food manufacturers use a small arsenal of food additives to bind all these ingredients together, but new enzymatic technology may also be giving them a helping hand.
For instance, an enzyme called transglutaminase (produced by microorganisms) can be used to ‘cross-link’ these proteins, sticking them together. The food industry refers to this as a ‘food adhesive’.
An alternative (and yuckier) enzymatic method has also been described in which plasma is taken from cow blood. The plasma is ‘activated’ by an enzyme which encourages the plasma to clot, just as our blood coagulates and clots over a wound. As the plasma clots, cross-linkages are formed between the different proteins, binding them together. Tasty!
Modified starch
Modified starch is a curious ingredient which turns up in a huge variety of processed foods. It is typically used as a bulking or thickening agent, padding out products that would otherwise be too thin or watery. From a nutritional point of view it provides the same amount of calories as sugar, but that’s about it – all the other good stuff has been removed.
To produce modified starch, the food industry typically takes highly processed maize flour and breaks it down in huge vats using either enzymes (which can be genetically modified) or acids.
Changing corn to sugar
Maize and other starches can be broken down by enzymes or acids in order to produce a wide range of sugars, many of which are commonly added to the foods and drinks we buy each day. Glucose, maltose, dextrose and fructose can all be produced using enzymes (unlike sucrose, which is a natural sugar extracted from sugar cane or beet). In the US corn-derived sugars have outsold natural sugars since 1985.
Such sugars are no better or worse for us than normal sucrose, but there is an argument that the easy availability of such cheap calories in our food and drink encourages obesity.
Enzymes are also used in the production of high fructose corn syrup (HFCS) – a sweetening agent widely used in the US and less so in the UK. In January of this year Cadbury Schweppes was forced to stop calling 7 Up "All Natural" in the US after the Center for Science in the Public Interest (CSPI) threatened to file a lawsuit against them.
CSPI successfully argued that HFCS is not “natural” because of the high level of processing and the use of at least one genetically modifed enzyme required to produce it. HFCS is a ‘novel’ man-made ingredient which does not occur in the natural world.
Inverted sugar syrup
Widely used in baked goods, inverted sugar syrup can be produced by treating a sucrose-based syrup with an enzyme called invertase. If the enzyme isn’t used, a suitable acid will do the job. Invert sugar can be used to make a product that stays moist longer than if sucrose was used and is less prone to crystallization.
Useful resources
Making the slice right: A new, Real Bread Campaign is being started by Andrew Whitley of Bread Matters and Sustain: The alliance for better food and farming. The campaign aims to increase the enjoyment, production and consumption of bread made with natural ingredients, appropriate fermentation and no adulterants (such as industrially produced enzymes) so that good bread may play a larger part in the physical, mental and social wellbeing of the nation. See http://www.realbreadcampaign.org/
The publication Enzymes in Food Technology, Whitehurst & Law, ISBN 0 8493 97820 was of use in researching this article.