Introduction to GRINDSTED™ Carrageenan TM 29-2e GRINDSTED™ Carrageenan linked together and contain varying amounts of sul- Carrageenan is a high molecular weight polysaccha- phate units (fig. 2). ride derived from red seaweed (Rhodophyceae). As a Kappa carrageenan consists of: textural ingredient for food, it can be used in a wide β (1 4) D-galactose-4-sulphate and range of applications where viscosity or gelling is re- quired. α (1 3) 3,6-anhydro-D-galactose The three groups of commercial carrageenan – kappa, Some of the D-galactoses also contain a 6-sulphate iota and lambda – have different functional properties ester group while some 3,6-anhydro-D-galactoses con- and are generally obtained from seaweed harvested tain a 2-sulphate ester group. This means there are from the warm water along the coasts of the Philip- four sub-groups of kappa carrageenan. The more pines and Indonesia and cold water areas off the 6-sulphate groups present, the lower the gel strength coasts of Prince Edward Island and Nova Scotia in obtained. The 6-sulphate groups can be eliminated Canada, north France and Chile. by alkali treatment, resulting in the formation of 3,6-anhydro-D-galactose. The 2-sulphate group can- The seaweed used for Danisco Cultor’s high quality not be removed by alkali treatment. GRINDSTED™ Carrageenan is harvested in Chile, where Danisco Cultor has its own carrageenan pro- Iota carrageenan consists of: duction plant. β (1 4) D-galactose-4-sulphate and α (1 3) 3,6-anhydro-D-galactose-2-sulphate Carrageenan chemistry Like kappa carrageenan, iota carrageenan contains Carrageenan is a sulphated polysaccharide consisting 6-sulphate groups on some of the D-galactose units. of a poly-galactose chain. The galactose units are Fig. 1: Chilean seaweed used as raw material for GRINDSTED™ Carrageenan. 1 Iota carrageenan _ OSO 3 OH Iota carrageenan gels most strongly in the presence of O calcium ions, forming a very elastic and coherent gel O O which shows no signs of syneresis. An iota gel is an O O excellent water-binder in very low concentrations and OH is the only carrageenan type capable of forming freeze/ OH thaw stable gels. The frozen gel keeps its shape and is Kappa free of syneresis when thawed. Iota carrageenan is only soluble in milk and water _ OSO ° 3 OH when heated to approximately 70 C or above. O O O Lambda carrageenan O O Lambda carrageenan has limited use since it does not OH gel. It dissolves in both cold and hot water forming a _ OSO viscous solution. Iota 3 Kappa-iota hybrid carrageenan _ OSO ™ OH 3 Danisco Cultor’s GRINDSTED Carrageenan range OH consists of hybrid carrageenans produced with kappa OH O and iota carrageenan units. This provides the com- O bined advantages of both types of carrageenan, i.e. O O high gel strength and excellent water-binding with low X _ syneresis. Lambda OSO X = H (30%) 3 _ The main physical and functional properties are sum- X = OSO (70%) 3 marised below: Fig. 2: The building blocks for the three main types of carrageenan. • Ester sulphate - between 25% and 40% - highest for lambda, lowest for kappa These can also be eliminated by alkali treatment re- sulting in the 3,6-anhydro-D-galactose structure. • 3,6-anhydro-D-galactose Lambda carrageenan consists of: - between 25% and 30% when fully alkali-modi- fied β (1 4) D-galactose-2,6-disulphate and α (1 3) D-galactose-2-sulphate • Solubility in water - all carrageenan types are soluble at temperatures It is possible to form a 3,6-anhydro bond, although the above 70°C reaction is very slow. Only about 70% of the β (1 4) D-galactose units have a 2-sulphate ester group. - all salts of lambda carrageenan are soluble in water at 20°C Commercial carrageenans contain all 3 molecular con- figurations, usually with one predominant form. - kappa, iota and hybrid carrageenan are only soluble if they are in sodium form or heated above Normally, commercial carrageenans have a pH of 7- 70°C 10 which makes them very stable under normal stor- age conditions. All carrageenan types are sensitive to • Solubility in milk acid and depolymerise when exposed to acidic condi- - all carrageenan types are soluble at temperatures tions, especially when carrageenan is in solution and above 70°C at high temperature. However, once a gel is formed it - lambda, iota and hybrid carrageenan are partly is resistant to moderate acid conditions. soluble at 20°C in all salt forms and are capable of thickening milk Kappa carrageenan - kappa carrageenan is only soluble at 20°C if it is When potassium ions are added to kappa carrageenan in sodium salt form a thermo-reversible gel is formed which is very strong and brittle. When the potassium ion concentration is • High concentration of sugar or salt increased, the gel becomes more rigid and the melt- - all carrageenan types are difficult to dissolve, ing and gelling temperatures rise. The gel is subject to particularly kappa and iota significant syneresis and is not freeze/thaw stable. • Gelation in water Kappa carrageenan is only soluble in milk and water - kappa and hybrid carrageenan need potassium when heated to approximately 70°C or above. ions to form a gel 2 - iota carrageenan needs calcium ions - lambda carrageenan in all salt forms does not Seaweed Seaweed Cleaning and form a gel KCl solution washing • Type of gel - a kappa carrageenan gel is characterised as Alkali being strong, brittle and subject to syneresis. It is Processing IPA not freeze/thaw stable Water - an iota carrageenan gel is characterised as being elastic and free of syneresis. It is freeze/thaw sta- IPA Purification ble Water - a hybrid carrageenan gel is medium strong with low syneresis. It is not freeze/thaw stable Drying IPA to recovery • pH sensitivity - all carrageenan types are stable at a pH above 6 including during food processing at high tempera- tures Milling - at a pH of between 3.5 and 6, carrageenan is very stable when gelled. In solution, carrageenan may lose some of its functionality at high tempera- Blending tures, i.e. gel strength may be affected - at a pH below 3.5, carrageenan is not recom- mended for use as a gelling agent as it will be unstable and degrade, particularly at high process- Packing ing temperatures Carrageenan production GRINDSTED™ Carrageenan The production of carrageenan involves alkaline modi- fication followed by extraction and purification. During Fig. 3: Flow diagram. alkali modification, the 3,6-anhydro bridge is formed by the elimination of the 6-sulphate. Since carra- geenan is a natural product, the physical properties of Gelation in water the final product can vary according to the time of Carrageenan gels in the presence of potassium ions year and place of growth of the seaweed. For this when the carrageenan is dissolved by heating and reason, it is necessary to standardise the product by then subsequently cooled, resulting in the formation blending selected lots and adding neutral food ingre- of a three dimensional network. The carrageenan sul- dients such as sugar or salts. phate groups interact with the cations in the solution The process used by Danisco Cultor is patented and (fig. 4). One of the advantages of a carrageenan gel is involves low energy consumption compared to tradi- its thermal reversibility, i.e. it can gel and melt again tional carrageenan processes. This together with the repeatedly only losing a little gel strength at each careful selection of seaweed ensures a consistently cycle. high quality. The main steps in the production proc- Gel strength depends on the concentration of potas- ess are illustrated in fig. 3. sium and calcium ions, the most important ions for gelling. Although it is possible to make a water gel with Functional properties many cations, few can be used for food applications. As potassium concentration increases, the gel strength Carrageenan is used as a gelling and stabilising agent increases until an optimum level is reached. Beyond in puddings, flans, chocolate milk and other dairy this point, an increase in the potassium concentration products. It is also used in cooked ham and poultry, results in a decrease in gel strength due to the salting- recombined meat and poultry products to prevent out effect of the carrageenan (fig. 5). Gel strength is syneresis, reduce cooking loss and improve slicing also decreased by acid, especially when heated. The properties, texture and sensory appeal. results shown in figures 5 and 6 are based on hybrid In addition, carrageenan is used for special applica- carrageenan. Results may vary when other types of tions, such as toothpaste, photographic film, pharma- carrageenan are used. ceutical products and air freshener gels. 3 Cool Cool Heat Heat Solution Gel 1 Gel 2 Fig. 4: Proposed mechanism for gelation of a kappa carrageenan. The mechanism by which cations cause carrageenan has a greater hydrated radius due to its higher charge to gel in solution is not fully understood. It is well density. For this reason, sodium does not cause gela- known that carrageenan molecular chains form a he- tion. lix structure when cooled. The theory now is that Potassium chloride has a bitter taste which limits its potassium and calcium ions have a size and shape practical use in many food applications to concentra- which make them fit into the carrageenan helix so this tions lower than that required to obtain optimum gel structure is stabilised through the positively charged strength. In salty foods, such as meat, it is possible to ions and the negatively charged sulphate groups in use a higher potassium chloride concentration.