TNO’s Professor Marc van der Maarel looks at how enzyme use in the food industry has expanded from highly specific sectors to address a wide variety of today’s food production needs
Enzymes are proteins produced by living organisms to accelerate chemical reactions and thereby make life possible. Humans have learned to exploit enzymes in producing food products from raw materials in the production of beer, cheese and wine - yet most people remain unaware of their presence. Traditionally, production of these products was seen as an art. Today, however, various enzymes are used across artisinal and industrial food production. The traditional craft has evolved into a high technology business, where a thorough understanding of enzymes has become key to the success of their application.
Various benefits can be derived from using enzymes. Due to the fact that they result in specific reactions, little to no waste products are produced. Additionally, enzymes are an eco-friendly, cost effective processing aid that has high consumer acceptance.
The common way enzymes are used in food production is through addition to a particular process stream and subsequent inactivation by heating. Price in such bulk applications needs to be as low as possible - Euro 5-15 per kilo of enzyme - to make the process economically feasible. The worldwide market for enzymes is in the order of Euro 1.5M, with detergents (37%), textiles (12%), starch hydrolysis (11%), baking (8%) and feed (6%) being the main application areas.
The European Commission’s definition of a food enzyme is “a product obtained by extraction from plants or animals or by a fermentation process using micro-organisms and which is added to food to perform a technological function in the manufacture, processing, preparation, treatment, packaging, transport or storage of foods, including enzymes used as processing aids”. A processing aid is an example of an enzyme that will be present in a finished food in the form of a residue without having an effect. An example of this is the use of anti-staling enzymes in bread, which are inactivated during the baking process but are not removed from the end product.
For the sake of simplicity, food enzymes are divided into three major categories, on the basis of the type of substrate they act on: carbohydrases, hydrolysing carbohydrates producing simple sugars such as glucose, maltose; lipases, acting on fats and oils; and proteases/peptidases releasing flavour components.
Carbohydrases
The largest group of hydrolases used in food production is the carbohydrases, i.e. enzymes hydrolyzing the O-glycosidic bonds between two sugar residues. Commonly used carbohydrases are amylases, cellulases, pectinases and xylanases. Pectinases are a group of enzymes acting on different parts of the very complex pectin molecule. Pectin is present in the cell wall of plants, fruits and vegetables, and pectinases are mainly used in the production of fruit juices to control viscosity, increase pressing efficiency or clarify juices. Pectinases are also used in wine production.
Amylases hydrolyse starch into smaller maltooligodextrins. They are used in combination with other starch-hydrolyzing enzymes such as glucoamylase and pullulanase in the bulk production of maltose and glucose syrups used as sweeteners. Other application areas of amylases are the production of bread, noodles, pasta, and beer brewing.
A relatively new market for a specific type of amylases is the use as anti-staling agents in bread making. The Danish enzyme company Novozymes was the first to introduce an anti-staling amylase under the brand name Novamyl. This amylase originates from the bacterium Bacillus stearothermophilus and acts on starch by releasing maltose units. Last year, the Danish company Danisco launched a maltotetraose-releasing amylase under the brand name Grindamyl as an anti-staling agent. Besides amylases, xylanses are also used in bread making. These enzymes hydrolyse xylan, a carbohydrate that can cause unwanted viscosity effects.
Another example of a recent novel application of an enzyme acting on O-glycosidic linkages present in starch is the use of the enzyme amylomaltase from the thermophilic bacterium Thermus thermophilus. Amylomaltases or 4-alpha-glucanotransferases are closely related to amylase enzymes, but instead of hydrolysing the starch substrate they add parts of the amylose onto the amylopectin molecule. This results in a thermoreversible gelling agent with properties similar to gelatin. The Dutch potato starch company Avebe, TNO and DSM have developed this innovative food ingredient with the trade name Etenia. An additional property of Etenia is that it is also an excellent fat replacer.
Proteases
Proteases are a group of enzymes that hydrolyse the peptide bond in proteins and peptides. The most well known protease is rennet, a collection of acid proteases extracted from animal tissues. Rennet clots milk by removing a highly charged peptide fragment from one of the casein parts of milk. This causes the destabilization of casein micelles that then aggregate to form the milk clot, that is acidified by lactic acid bacteria ultimately forming cheese. Denmark’s Christian Hansen A/S produced the first standardized rennet preparation in 1874 from ruminant stomach, and this was probably the first commercial enzyme preparation to be produced. Today, fungal proteases used to coagulate milk are available, for example the aspartic proteinase from the Rhizomucor miehei.
Proteases are also used to modify protein structure, thereby improving solubility, emulsification, gelling and even foaming properties. They also improve the nutritional properties of food proteins from vegetables or by-products, such as left over meat from slaughterhouses. Some examples are serine protease from Bacillus licheniformis (Novozymes’ Alcalase), metalloprotease from Bacillus amyloliquefaciens (Novozymes’ Neutrase), and aspartic protease (Novozymes’ Hannilase). Proteases also play an important role in the formation of the typical soy sauce flavors.
A growing market for proteases is their use in reducing the risk of allergenicity to human breast milk substitutes. Certain amino acid sequences present in milk proteins can give rise to the production of antibodies and thus cause (severe) allergenic reactions. Using specific proteases that recognize and hydrolyse these sequences, such as trypsin, chymotrypsin or papain, reduces the allergenic reaction considerably. Another application of proteases is the cross-linking of proteins or peptides by the enzyme transglutaminase (e.g. Ajinomoto’s Activa TG). The enzyme catalyzes the formation of a covalent bond between a peptide bond glutamine and an amino group of lysine. This gives a gelling network that effects the rheological properties of a protein. Examples of the use of transglutaminase are in upgrading low quality fish by gluing small pieces of fish, such as salmon, together or to bind small pieces of meat into a whole meat serving, an application developed by TNO.
A new outlet for milk protein hydrolysates was developed by the Dutch company DSM. The key in this application was to use a specific protease from the fungus Aspergillis niger to hydrolyse in a stretch of amino acids immediately after a proline, an amino acid prone to cause bitter taste. It turned out that the resulting peptide mixture, named PeptoPro, helps athletes to recover faster from their exercise by acting on their insulin levels, and thus the storage of glycogen, while also having a positive influence on muscle protein synthesis.
Lipases
Lipases catalyze the hydrolysis of ester bonds in lipids. Their main function is to degrade triglycerides into fatty acids and glycerol. Traditionally, lipases are derived from the gullet of goats and lambs, from pig pancreas and from calf abomasum. To increase consumer acceptance, especially with vegetarians and certain religious groups, bacterial lipase preparations have been developed. Examples include DSM’s Piccantase and Novozymes’ Lipopan and Lipozyme. The major application areas of lipases are dough preparation, the production of pasta and noodles, bread making, cheese production (ripening, flavour production), and milk fat modification.
Other food enzymes
Although not a typical protease or peptidase, the use of the enzyme asparaginase in the reduction of acrylamide is worth mentioning. Acrylamide, a carcinogen, is formed during the heating of carbohydrate rich products such as French fries, bread, cake, or potato chips as a result of the reaction of the amino acid asparagine with free glucose or other reducing sugars. By adding the enzyme asparaginase, the levels of asparagine are reduced to such an extent that virtually no acrylamide is formed. Examples of asparaginase enzymes introduced recently are Preventase from DSM, and Acrylaway from Novozymes.
Besides carbohydrases, proteases/peptidases and lipases, several other types of enzymes are used in food production. Lysozyme from hen egg white, an enzyme that hydrolyzes bacterial cell walls, is used in controlling microbial spoilage in, for example. cheese; glucose isomerase, converting glucose into fructose, is used to produce high fructose corn syrups (beverage sweetener); catalase, converting hydrogen peroxide into water and oxygen, is used in combination with glucose oxidase to remove oxygen.
The use of enzymes in food production has evolved into a multi-million-dollar, high-tech business. New technological and scientific developments and ever more information from genome sequencing efforts will, without doubt, boost the development of new enzymes and their use in food production. |
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