Pectin is a very common hydrocolloid in most kitchens. There is a variety of different types of pectin that react differently to changes in ingredients used. The two most common types of pectin that I have come across are; high methoxyl, and low methoxyl. Both types of pectin are extracted from natural means. Most commonly they are obtained from the skins and pomace of citrus and apples. The two types of pectin mentioned above (high and low methoxyl) differ in the degree of esterification. Esterification meaning in this case a chemical reaction between alcohol and acid reactants. Basically the higher the DM (degree of methylation) the faster the set will be in the pectin. (taking into consideration other ingredients used). High methoxyl pectins are characterized by their; thermoirreversability and ability to gel in high sugar, low pH (acidic) solutions. Low methoxyl pectins are characterized by their; thermoreversability, and ability to gel in the presence of calcium. Whether you are using low or high methoxyl pectins in your formula you must take into consideration a few variables; the ammount of sugar you are using, pH level, calcium level, ammount of solids, and the reactivity of the pectin. By knowing how each ingredient will react to the ammount of pectin used you can begin to formulate recipes to achieve your desired texture and consistency. This will take trial and error...fortunately you can always learn from your mistakes.
Gelatin may be the most common of the hydrocolloids. It is a protein derived from the collagen and connective tissue of animals. Gelatin can usually be found in 2 different forms; powdered or leaf. Gels made using gelatin are characterized by there transparent appearance and are also thermoreversible. Gelatin forms a soft elastic gel that gives a melt in your mouth feeling. When using gelatin as your main gelling agent you have to take into consideration the bloom strength of the gelatin (the gelling strength). Most leaf gelatins are classified by their bloom strength and given names; Bronze, Silver, Gold, and Platinum. Bronze being the weakest and Platinum being the strongest. Gelatin is a very useful hydrocolloid because it can be used synergistically with other gelling agents to give a variety of different textures and properties. To use gelatin you must first hydrate or bloom your gelatin in cold water. I usually throw in a couple ice cubes as well. After a few minutes the gelatin leaf will become elastic and soft. To add your gelatin to your mix you must heat a small portion of the mix and dissolve your bloomed gelatin leaf in the heated mixture. You can then add your heated gelatin mix to your original mix and leave to set. Gelatin is a very versatile hydrocolloid with many uses in the kitchen. It is one of my favorite gelling agents because of its ease of use, the soft elastic texture it gives to your product, and the fact it can be used in conjunction with other gelling agents to form a variety of different textures.
Gellan Gum is a man made polysacharide made by fermentation. There is a variety of different variations of this gelling agent. The two most popular variations that I have come across in the food industry are categorized by their alcohol precipitation content used in manufacturing (low acyl, high acyl). These two variations of the gum can help to produce a wide variety of textures. Low acyl gellan gum is characterized by forming firmer gels with a more brittle texture, similar to the gels formed by agar and/or Kappa Carrageenan. On the other hand high acyl gellan gum is characterized by forming gels that are softer and more elastic. Another major difference between the two varietals is that the low acyl gels are thermoirreversible meaning that once the gel is dispersed, hydrated, and set it will not melt. High acyl gellan gum is thermoreversible meaning it can be melted and re gelled after the gel has been set. Gellan gum is a fairly young hydrocolloid in the food industry. I am sure further advances in studies of this hydrocolloid will provide the food industry with continued usages for the product.
Iota Carrageenan is a phycocolloid meaning a hydrocolloid that is derived from seaweed. In this case red seaweed. It is one of three Carrageenans, the others being Kappa and Lambda. Some of the main advantages of using Iota as a thickening or a gelling compound is that it yields more elastic or softer gels, as opposed to one of its brothers Kappa that produces more rigid or brittle gels. When constructing formulas using iota it is important to note that it reacts best with the presence of calcium (ie milk, cream, etc). It is also important to note that gels made using iota have the ability to be frozen and then thawed before use. This makes it possible to make a base and to mold it and freeze it or keep it frozen and to take it out before service, thus prolonging the shelf life of the gel. I have found that there is a wide range of ratios in weight of iota:rest of ingredients that you could use depending on what your desired end result will be. You also have to take into consideration the formula you are using; whether or not your using milk instead of cream or other dairy products (fat concentration), are you using an acid in your base, how much sugar are you going to add, how much salt your going to add. There are many factors that will determine the final outcome of your finished product. I have seen and made gels that eat like cooked custards using a ratio of 1K of base:2-3g of iota (.002-.003). I have also used iota in combination with other stabilizers in ice cream formulas. I have found that by using iota in my base it promotes a creamier mouth feel to the finished frozen dessert. When it comes down to it Iota Carrageenan is a very versatile hydrocolloid, with a vast array of uses in a modern kitchen.