Types of stabilizers used in Ice cream making

 Stabilizers in ice cream

       In ice cream, stabilizers, usually used in combination of 2-3 types are primarily used for the following purposes:

Uses of stabilizer 

    To increase the viscosity of the mix

    To stabilize the mix i.e. to prevent wheying off

      To help in suspension of flavouring particles

      To produce a stable foam with desired stiffness at the time of packaging

     To reduce or slow down the growth of lactose crystals during storage mainly during temperature fluctuations

     To reduce moisture migration from the product to the package or the air § To help prevent shrinkage of the product volume during storage

      To provide uniformity to the product and resistance to melting

     To produce smoothness in texture during consumption

      Reduce the rate of meltdown (i.e. the rate at which ice cream melts) § Prevent shrinkage and slow down moisture migration out of ice

Mask the detection of ice crystals in the mouth during eating.

       Allow easier pumping and more accurate filling during processing. 

       Facilitate the controlled incorporation of air in the freezer

Classification of stabilisers 

Stabilizers which are used in ice cream and frozen desserts mainly fall into the following categories 

1. Proteins- Gelatin

2. Plantexudates – Arabic, ghatti, karaya and tragacanth gums

3. Seed gums – Locust ( carob) bean, guar, psyllium, starch and modified starches

4. Microbialgums – xanthan

5. Seaweed extracts – agar, alginates, carageenan

6. Pectins– low and high methoxyl

7. Cellulose– sodium carboxymethyl cellulose, microcrystalline cellulose, methyl and methylethyl cellulose, hydroxypropyl and hydroxypropylmethyl cellulose.

Properties of individual stabilizer ingredients

a) Sodium Alginate

Sodium alginate (E401) is a polysaccharide of guluronic acid and mannuronic acid. It is extracted from brown seaweeds such asMacrocystispyrifera and Laminaria digitata.     

      It consists of a negatively charged polymer chain with ionic bonds to positively charged sodium ions (Na+). In aqueous solution, the sodium ions dissociate from the polymer so it becomes charged. Calcium ions (Ca+2) or other doubly charged cations can bind to negative charges on two different polymer molecules.

    interactions lead to the formation of a gel. In ice cream, alginates are blended with phosphate, citrate or tartrate ions to prevent premature gelation due to the calcium from the milk solids. 

          The major advantage of alginate is its resistance to acid conditions, particularly when heated, whereas other stabilizers would lose their functionality. Usually, it is used at a level of 0.18-0.25%.

         Alginic acid extracted from kelp is insoluble in cold water; hence salts of organic acid are prepared or the propylene glycol ester which is readily soluble in hot or cold water is prepared. This product is known as propylene glycol alginate.

b) Carrageenan

          Carrageenans (E407) are complex polysaccharides of esters of galactose and m-3,6- anhydrogalactose,found in red seaweeds(Rhodophycae), such as Chondrus crispus (IrishMoss), Kappaphycus alverezii and Eucheuma denticulaturn. 

          Carrageenancan have several structures, usually classified as one of three types that have different properties:kappa( k ), iota ( i ) and lambda ( l ) . Carrageenans can also form gels with both milk proteins and locust bean gum. 

          In ice cream applications, k -carrageenan fractions are frequently used not as a primary stabilizer but as a secondary hydrocolloid to prevent wheying off of mix, a condition promoted by the other stabilizers due to their incompatibility in solution with milk proteins. 

          Hence, it is included in most blended stabilizer formulations at a usage rate of 0.01-0.05%. At higher concentrations the carrageenan would begin to gel and fail to function well. k -carrageenan reduces phase separation of milk proteins and polysaccharides which could result in wheying off.

c) Locust Bean Gum

           Locust bean gum (E410), also known as LBG, carob gum or St Johns Bread, is extracted from the seeds of the MediterraneanCeratoniasiliqua tree. 

          These large, evenly sized seeds were the original carats used as a measure of weight. LBG is a polysaccharide consisting of a mannose backbone with galactose side branches on about a quarter of the mannose units.The side branches occur in blocks, giving LBG  ̳smooth‘ regions of free mannose backbone and  ̳hairy‘ regions of galactose side groups. In solution, strong hydrogen bonds can form between the large smooth backbone regions. 

          This leads to gel formation under certain conditions. LBG is the best stabilizer for many ice cream applications and its ability to gel is crucial to some aspects of its use. However, it is also expensive stabilizer.

d) Guar Gum

         Guar gum (E412) is extracted from the seeds of Cyamposistetragonolobus, an annual crop grown in the Indian subcontinent. Guar has a similar structure to LBG: it has a backbone of mannose units, about half of which have galactose side branches. 

         Guar has a higher molecular weight than LBG and the side groups are more evenly spaced. The larger proportion of galactose units makes guar cold water soluble. The regions of backbone that are free of side chains are smaller than in LBG. 

          Hydrogen bonding between them is therefore not strong enough to form permanent cross-links, but does result in ̳hyper-entanglements‘. These are stronger than purely topological entanglements and account for the high viscosity of guar gum solutions at low concentrations.Guar gum is significantly cheaper than LBG. 

        Both these gums at 0.1- 0.15% impart a chewy body to the product. While locust bean gum may cause a comparatively short body, guar gum may impart stickiness to the product.

e) Pectin

      Pectin (E440) is extracted from citrus peel and apple pomace. It is a polysaccharide consisting of linear chains of galacturonic acid and galacturonic acid methyl ester units

      Pectin is classified according to its degree of esterification. High methoxy ( >50% esterified)and low methoxy ( < 50%) pectins possess different properties. For example,low methoxy pectin requires calcium to gel whereas high methoxy pectin gels at low pH and in the presence of high concentrations of sugar. 

      Pectin is the setting agent used in jam making. It is used as an ingredient in syrups and fruits used in making rippled effects in ice cream and is also effectively used in sherbets and ices. All fruits contain some pectin. Some fruits,such as apples and gooseberries, usually contain enough natural pectin to form a gel, whereas pectin must usually be added to set the jam for other fruits,such as strawberries and cherries. It is not a very satisfactory stabilizer for ice cream.

 f) Xanthan gum

        Xanthan gum (E415) is produced by the bacterium Xanthomonascampestris. It is a polysaccharide consisting of a chain of glucoseresidues with charged trisaccharide side groups. Xanthan has excellent solubility and is suitable for use under acid conditions,e.g. in water ice. 

       Xanthan is a rod-like polymer. In solution, the rods are oriented indifferent directions and interact to form a weak network. When a small amount of shear is applied, the rods all line up and the network is broken. When the shear is removed, the network reforms. 

        As a result, the viscosity of xanthan solutions decreases dramatically with shear, but quickly recovers once the shear is removed. This property is useful in sauces for ice cream. During dispensing, the viscosity is low, but as soon as shear forces cease, the viscosity rises substantially. 

        These results in a sauce that remains fixed after dosing onto the product. Xanthan gum provides viscosity which is stable over wide range of pH and temperature. It is effective at low levels when used along with locust bean gum and guar gum, these vegetable gums act synergistically with it. However, xanthan is not widely used in ice cream because it is expensive.

g) Sodium Carboxymethyl Cellulose

        Sodium carboxymethyl cellulose (E466) is derived from purified cellulose from cotton and wood pulp. It is a sodium salt polymer of anhydroglucose residues. 

        For use in ice cream, an average of 0.7 of the 3 hydroxyl groups in each glucose unit is substituted with a sodium carboxymethyl group. The long, negatively charged molecules produce a stable thickener that can also reduce casein precipitation. 

       CMC hydrates at low temperatures. It has excellent water holding property but may cause wheying off. Usually used together with other gums, CMC at 0.1-0.2% performs excellently as an ice cream stabilizer. However, its perception as a  ̳chemical‘ has resulted in fairly low usage.

h) gelatin

       Gelatin is a mixture of high-molecular-weight polypeptides derived from collagen from animal connective tissues, and was commonly used as a gelling and thickening agent. 

       Gelatin disperses in cold water and forms a gel upon heating the dispersion. It is used at the rate of 0.2-0.3% and requires ageing for at least 4 hours; often a practice of overnight ageing is followed. 

        It is a good ice cream stabilizer since forms a weak gel that melts readily in the mouth giving no impression of gumminess. However, the so called  ̳instant gelatin‘ may not require such long ageing periods. The effectiveness of gelatin may be altered by interactions with other mix constituents at high temperatures. 

         It is not suitable for vegetarians, and has now generally been replaced by other stabilizers.

The most important property of gelatin is its ability to form thermo-reversible gels. At a few percent in water, gelatin‘s gel-melting temperature (<35 C) is below body temperature, which can provide gelatin products with a unique 'melt-in-mouth' quality. Gelatin‘s most important attribute is its gel strength and, when determined by the standard method, is called the 'Bloom strength' or 'Bloom value.' Commercial products normally have a Bloom value that falls between 50 to 280.

i) Other hydrocolloids

      Other hydrocolloids viz. agar agar, an extract from red algae and gums such as tragacanth, Arabic, karaya, etc have found use in sherbets and milk ices.