Acid-hydrolyzed vegetable protein
Regarding the production process a distinction can be made between acid hydrolysed vegetable protein (aHVP), enzymatically produced HVP as well as other seasonings e.g. like fermented soy sauce. Hydrolysed vegetable protein products are particularly used to round off the taste of soups, sauces, meat products, snacks and other dishes as well as for the production of ready-to-cook soups and bouillons.
Food technology has for a long time been well aware of the fact that protein hydrolysis produces a meat bouillon-like odour and taste. In 1831 Berzelius obtained products having a meat bouillon taste when hydrolysing proteins with hydrochloric acid.
Fisher concluded that it was amino acids that contributed to the specific taste. In 1954 Philipps found out that the bouillon odour could only be detected in hydrolysates manufactured from threonine-containing proteins. Glutamic acid was found to be another important substance suitable to give a particular taste to meals.
Almost all by-products rich of protein are suitable for the production of HVP, whereas today mainly protein resources of vegetable origin like maize gluten, soybean meal or wheat gluten are used.
Proteins consist of up to twenty amino acids joined together through peptide linkages. Subjected to hydrolysis the protein is broken down into its basic building blocks, amino acids. For the hydrolysis of proteins to amino acids, enzymes or acids (mainly hydrochloric acid) are used.
The manufacturing process for HVP varies depending on the desired organoleptic properties of the end product. In general common vegetable raw materials used in the production of HVP include defatted oil seeds (soy, rapeseed), and protein mainly from maize, wheat, pea and rice.
For the production of aHVP the proteins are cooked (hydrolysed) with a diluted (15 – 20%) hydrochloric acid, at a temperature between 90 °C and 120 °C for up to 8 hours. After cooling, the hydrolysate is neutralised with either sodium carbonate or sodium hydroxide to a pH of 5 to 6. The hydrolysate is filtered to remove the insoluble carbohydrate fraction (humin) and then further refined. The source of the raw material, concentration of the acid, the temperature of the reaction, the time of the reaction and other factors can all affect the organoleptic properties of the final product. Activated carbon treatment can be employed to remove both flavour and colour components, to the required specification. Following a final filtration the aHVP may, depending upon the application, be fortified with additional flavouring components. Thereafter, the product can be stored as a liquid at 30 – 40% dry matter, or alternatively it may be spray-dried or vacuum dried and further be used as a food ingredient.
For the production process of enzymatic HVP enzymes are used to break down the proteins. To break down the protein to amino-acid proteases are added to the mixture of defatted protein and water. Since no salt is formed during the production process it is common practice to add salt as an ingredient in order to meet the criteria as described in the European Code of Practice for Bouillons and Consommés. Due to the sensitivity of enzymes to a specific pH either an acid or a base is added to match the optimum pH. Depending on the activity of the enzymes it takes up to 24 hours to break down the proteins. The mixture is heated to inactivate the enzymes and then filtered to remove the insoluble humins.
Liquid aHVP typically contains 55% water, 16% salt, 25% organic substances (thereof 20% protein (amino acids) analysed as ~ 3% total nitrogen and ~ 2% amino nitrogen).
According to the European Code of Practice for Bouillons and Consommés hydrolysed protein products intended for retail sale correspond to the following characteristics:
Specific gravity at 20 °C min.: 1.22
Total nitrogen min.: 4% (on dry matter)
Amino nitrogen min.: 1,3 % (on dry matter)
Sodium chloride max.: 50% (on dry matter)
Use in convenience products
When foods are produced by canning, freezing or drying, it is almost inevitable that some flavour loss will occur. Manufacturers can use HVP to re-store these lost flavours, bring out latent taste characteristics and generally round off and improve the flavour of the food. Therefore HVP is used in a wide variety of products such as in the spice, meat, fish, fine-food, snack, flavour and soup industry.
According to European law wheat and soy are subject to allergen labelling in terms of Regulation (EU) No 1169/2011 on food information to consumers. Since wheat and soy used for the production of HVP are not exempted from allergen labelling for formal reasons, HVP produced by using those raw materials has to be labelled with a reference to wheat or soy in the list of ingredients.
Nevertheless there is strong evidence that at least aHVP is not allergenic since proteins are degraded to single amino acids which are not likely to trigger an allergic reaction. A recent study carried out in 2009/2010 by the Paul Ehrlich Institute, Germany, has shown that aHVP does not contain detectable traces of proteins or IgE-reactive peptides. This provides strong evidence that aHVP is very unlikely to trigger an allergic reaction to people which are intolerant or allergic to soy or wheat.
- Manley/Fagerson, Aspects of Aroma and Taste Characteristics of Hydrolysed Vegetable Protein, The Flavour Industry 1971, 686 f.
- Ullmanns Encyclopedia of technical Chemistry, catchword: „Würzen“, 3rd edition, Vol. 18, Munich, Berlin, Vienna 1967
- Fischer, Research about amino acids, Springer 1906
- Reineccius, Source Book of Flavours, Springer 1994, 140
- Prendergast, Protein Hydrolysate – A review, Food Trade Review 1974, 14 f.
- Code of practice for the Reduction of 3-Monochlorpropanole-1,2-Diol (3-MCPD) during the Production of acid-HVPs and products that contain acid-HVPs, CAC/RCP 64-2008; available under the following link: http://www.codexalimentarius.org/download/standards/11024/CXP_064e.pdf
- Code of practice for Bouillons and Consommés, http://www.culinaria-europe.eu/index-culinaria-europe.html/downloads
- Prendergast, Protein Hydrolysate – A review, Food Trade Review 1974, 19
- Reuter et al., Evaluation of the allergenic potential of soy and wheat based seasonings, Allergy, vol. 65, supplement 92, abstract 842.
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