Application and Functions of Stabilizers in Ice Cream

MARYAM BAHRAMPARVAR AND MOSTAFA MAZAHERI TEHRANI

Department of Food Science and Technology, Ferdowsi University of Mashhad(FUM)

Introduction

Ice cream is a frozen dairy product consumed in the frozen state where the freezing and whipping processes are important unit operations for the development of the desired structure, texture, and palatability.

There are many formulation and processing factors that influence the texture and acceptability of ice cream. Stabilizers are one such ingredient, which, in spite of the low level in the formulation, impart specific and important functions to the finished product.

In 1915, the word stabilizer was assigned to a group of substances that, at that time, were known as holders, colloids, binders, and fillers. They were also referred to as improvers, a term used to refer to enzymes or blends of enzymes and gums. Colloids, hydrocolloids, and gums are other names of these substances, which indicate that these materials are macromolecules, mostly polysaccharides, that are capable of interacting with water.

Interaction with water also allows some of these compounds to interact with proteins and lipids in the mix. Stabilizers normally contain ∼l03 monomer units and have molecular weights of ∼105–10. The primary purposes for using stabilizers in ice cream are to produce smoothness in body and texture; retard or reduce ice and lactose crystal growth during storage, especially during periods of temperature fluctuation; provide uniformity to the product; and provide some degree of shape retention during melting. They also contribute to mix viscosity, stabilize the protein in the mix to avoid wheying off, help in suspension of flavoring particles, create a stable foam with easy cut off and stiffness at the barrel freezer for packaging, slow down moisture migration from the product to the package or the air, and assist in preventing shrinkage of the product volume during storage.

Stabilizers must also have a clean, neutral flavor, not bind to other ice cream flavors, contribute to acceptable meltdown of the ice cream, and provide desirable texture upon consumption. Despite their natural sources, under European law they are considered food additives and, therefore, they have associated E numbers. A good stabilizer should be nontoxic, readily disperse in the mix, not produce excessive viscosity or separation or foam in the mix, not clog strainers and filters, provide ice cream with desirable meltdown, be economical, and not impart off flavor to the mix.

The amount and kind of stabilizer required in ice cream depend on its properties, mix composition, and ingredients used; processing times, temperatures, and pressures; storage temperature and time; and many other factors. Usually 0.1–0.5% stabilizer is utilized in the ice cream mix. Mixes high in fat or total solids (40%), chocolate mixes, or ultra-high temperature

pasteurized mixes require less stabilizer than do mixes that are low in total solids (37%), are high-temperature, short-time (HTST) pasteurized, or are to be stored for extended periods of time.

Many valuable studies have been published about ice cream stabilizers, with review articles, books, and book chapters relating various aspects of ice cream. For example,Hartel reviewed ice crystallization during manufacturing of ice cream and stated the

effects of different factors in this phenomenon. Mechanisms and kinetics of recrystallization in ice cream were also reviewed by this author.  Milk protein and food hydrocolloid interactions and protein–polysaccharide incompatibility has been investigated by Sybre et al. and Doublier et al., respectively. In a review article, Adapa et al. discussed the mechanisms of ice crystallization and recrystallization in ice cream and factors influencing them, especially stabilizers. Goff discussed the formation and stabilization of structure in ice cream and related products with an emphasis on colloidal aspects.

Dickinson reviewed hydrocolloids at interfaces and the roles of these materials on properties of dispersed systems, emulsifying capacity of some hydrocolloids, and protein– polysaccharide complexes at interfaces. Goff discussed the roles of hydrocolloids in frozen foods. The freezing process, structure formation, and physicochemical changes in frozen foods and the influence of polysaccharide stabilizers on these phenomena were also discussed in this book chapter.

However, there is no comprehensive review available in the literature concerning various aspects of stabilizers in ice cream. So, the aim of this review was to investigate the different kinds of stabilizers and their specific characteristics and the varied functions of these substances in ice cream, including the effects on rheological properties of ice cream and ice cream mix, phase separation, overrun, crystallization and recrystallization, melting behavior, and sensory characteristics. Finally, limitations on the excessive use of stabilizers in ice cream are mentioned.

Types and Characteristics of Individual Stabilizers in Ice Cream

A variety of substances have been used as stabilizers. Gelatin, an animal protein derivative, was one of the first materials used as an ice cream stabilizer, although it has largely been replaced by polysaccharide hydrocolloids in modern ice cream manufacture. Some of the common stabilizers and their characteristics are listed below.

• Gelatin (E441): This relatively expensive stabilizer is effective at concentrations of 0.3–0.5%; however, it may not prevent the effects of heat shock. (4) It is also not acceptable to certain religious and vegetarian populations. The use of gelatin as a stabilizer produces thin mixes that require a long aging period. Gelatin disperses easily and does not cause wheying off or foaming.

• Guar gum (E412): Guar gum is extracted from the seeds of a tropical legume, Cyamoposis tetragonolba, called guar. It has been grown in India and Pakistan for centuries and, for a short time and to a limited extent, in the United States. It is the least expensive stabilizer and effectively decreases the undesirable effects of heat shock in ice cream. It readily disperses and does not cause excessive viscosity in the mix. Generally, 0.1–0.2% is required in a mix and, therefore, this substance is considered to be a strong stabilizer.

• Sodium carboxymethyl cellulose (CMC) (E466): This chemically modified natural gum is a linear, long-chain, water-soluble, and anionic polysaccharide. Purified sodium carboxymethyl cellulose is a white-to-cream–colored, tasteless, odorless, free-flowing powder. CMC forms weak gels by itself but gels well in combination with carrageenan, locust bean gum, or guar gum. It is a strong stabilizer and only 0.1–0.2% is needed in a mix. It imparts body and chewiness to ice cream.

• Locust bean gum (carob bean gum) (LBG) (E410): Locust bean gum is obtained from the beans of the tree Ceratonia siliqua, grown mostly in the Mediterranean area. This strong stabilizer is used at 0.1–0.2% levels and causes phase separation in ice cream mixes. LBG is only partially soluble in cold water and it must be heated above 85◦C to hydrate fully. For the following reasons it was reported to be an ideal gum in stabilization of ice cream:
• It creates a uniform, medium, and reproducible viscosity that is not destroyed by agitation.

• It cools uniformly and allows easy incorporation of air into the mix.
• It provides superior heat-shock resistance.
• It does not produce any taste or flavor-masking properties to the mix.
• It forms a cryo-gel, which can be effective in cryo-protection.
• Carrageenan (Irish moss) (E407): This stabilizer was originally derived from red algae called Chondus crispus. The major sources of this gum are now the two tropical red seaweeds, Eucheuma cottonii (now called Kappaphycus alarezii) and E. spinosum (now E. denticulatum), which are commercially farmed in the Philippines, Indonesia, and Tanzania. The extract of Kappaphycus alarezii is almost pure kappa carrageenan (with less than 10% iota), whereas the extract of E. denticulatum is a relatively pure iota carrageenan (less than 15% kappa).

The extracts of Gigartinacean algae (Chilean carrageenophytes), Gigartina skottsbergii, Sarcothalia crispate, and Mazzaella laminarioides, however, are gelling carrageenans that are weaker and less interactive with kappa casein in milk than C. crispus extracts. These gelling carrageenans have been found to be copolymers of kappa and iota carrageenan, which the industry refers to as kappa-2 carrageenan,kappa/iota hybrids, or weak-gelling kappas. Carrageenan is used in many stabilizers blends at levels of 0.01–0.02% to prevent phase separation (wheying off) through its interaction with milk protein.

• Xanthan (E415): This bacterial exopolysaccharide is obtained by the growth of Xanthomonas campestris in culture. Its blend with guar gum and/or locust bean gum makes an effective stabilizer for ice cream, ice milk, sherbet, and water ices.

A combination of xanthan gum with sodium alginate is reported to serve as a milk shake stabilizer.

• Alginates: Alginates, or algin, is a generic term for the salts and derivatives of alginic acid. This acidic polysaccharide occurs as the insoluble mixed calcium, sodium, potassium, and magnesium salt in the Phaeophyceae, brown seaweeds.

Alginates dissolve in cold water and gel in the presence of calcium and acid. However, because of their price, they are not widely used. Sodium alginate, a member of this group, has an E number of 401.

• Microcrystalline cellulose (Cellulose gel) (MCC) (E460): MCC has effective application in foam stabilization and overrun control. The addition of 0.4% and higher levels of MCC to ice cream mix results in the formation of a gel, which preserves the original texture of frozen dessert products during storage and distribution by increasing their resistance to heat shock and by maintaining the three-phase system of air–fat–water in these products. MCC also allows for reduction of fat and solids content by 2 to 4% with minimal loss of texture. Like carrageenan, cellulose gel has the capability to prevent whey separation in mixes, thereby countering the destabilizing effects of some soluble gums.

In addition to these above-mentioned common substances, other, more local, hydrocolloids have been used as ice cream stabilizers. Salep, for example, is obtained by milling dried tubers of wild orchids and is applied as an essential ingredient for the production of traditional ice cream in Iran and Turkey. This kind of ice cream, which is called kahramanmaras or maras in Turkey, differs from common ice cream in its high sugar content, natural flavor, and sticky gummy body, especially due to salep addition. Marastype ice cream is served hard and a knife should be used during consumption, due to its unique textural properties. Compared to other stabilizers, salep is used in higher content, generally, 0.78–1%, in ice cream formulation. In addition to stabilizing properties, salep has health benefits. Salep contains approximately 11–44% high polysaccharides (glucomannan). Glucomannan is classified as a hydrocolloid; it absorbs 200 mL of water per gram. According to Farshoosh and Riazi, salep varieties grown in Iran come in two forms, one with branched or palmate tubers and the other with rounded or unbranched tubers. The palmate-tuber salep (PTS), at similar concentrations to rounded-tuber salep (RTS), produces solutions with more pseudoplasticity and higher consistency. For this reason, BahramParvar et al. concluded that PTS is a better ice cream stabilizer compared to RTS. These authors used this kind of salep and another Iranian local gum (Lallemantia royleana seed gum) compared to CMC, which is a well-known commercial gum, in ice cream formulation. Although products prepared using only salep (PTS) showed greater differences compared to ice cream containing CMC, all variations were not significant.

Lallemantia royleana, with the vernacular name of Balangu or Balangu Shirazi, is a member of the Labiatae family and has an extensive distribution in different regions of European and Middle East countries, especially Iran. Balangu seed is a good source of polysaccharides, fiber, oil, and protein and has some medicinal, nutritional, and human health properties.It adsorbs water quickly when soaked in water and produces a sticky, turbid, and tasteless liquid. (37) In comparison with CMC, Balangu seed gum (BSG) did not have a significant effect (P > 0.05) on most characteristics of ice cream and could serve as a suitable stabilizer. BahramParvar et al. also studied the effects of different levels of substitution of CMC and PTS by BSG. They found a synergistic effect between CMC and BGS in elevation of ice cream mix viscosity. However, such a regular trend was not observed in the case of BSG and PTS. Often, different levels of this replacement (0–100%) improved sensory characteristics of ice cream, although most differences were not significant.

Other local gums have also been studied. For instance, Uzomah and Ahiligwo(22) investigated the effects of the water-soluble gums extracted from seeds of achi (Brachystegea eurycoma) and Ogbono (Irvingia gabonesis; commonly found in Nigeria) on quality characteristics of an ice cream mix and ice cream. These characteristics were compared to those of similar products made with commercial food gums. Only values of achi seed gum ice cream fell within the ranges of values obtained for the ice cream containing commercial gums. Moreover, Rincon et al. examined a mixture of gums from Acacia glomerosa, Enterolobium cyclocarpum, and Hymenaea courbaril (species grown in Venezuela) as stabilizers in the preparation of ice cream. Quality characteristics of the product (viscosity, overrun, meltdown, shape factor, and sensory properties) were determined and compared to ice creams made with a mixture of commercial gums. The mixture of Venezuelan hydrocolloids provided suitable viscosity for ice creams with the corresponding overrun and texture. It gave better foaming properties and air incorporation than the commercial gums tested and had the highest score of flavor, creaminess, overall acceptability, and lowest score of iciness. Based on these studies, local gums can be successfully used in preparation of ice cream.

It could be concluded that each stabilizer has own characteristics, and to gain synergism in function and improve their overall effectiveness, individual stabilizers are usually mixed. For example, because of the higher solubility of guar compared to locust bean gum at cold temperatures, guar gum is used more in HTST pasteurization systems.

Carrageenan is a secondary hydrocolloid used to prevent phase separation of a mix and also generally improves protein stability in the presence of such negative influences as shear, low pH, change in salt balance, among others. Hence, it is included in most blended stabilizer formulations. Multiple stabilizer ingredients are also used to reduce the overall cost of the stabilizer system. For example, Guven et al. produced ice creams containing four different combinations of LBG, CMC, guar gum, and sodium alginate and a control sample using only salep extract. They concluded that the use of combinations of suitable stabilizers instead of only one led to better results.

Effects of Stabilizers on Melting Rate

When ice cream is in the form of a cone or stick novelty, melting rate is of greatest importance to the consumer. The slow meltdown, slow serum drainage, good shape retention, and slower foam collapse is some of the desired important quality parameters of ice cream.

If the product melts too fast, a messy situation can occur. A fast-melting product is undesirable also because it tends to become heat shocked readily. However, a very slow rate of melting can also be indicative of defective ice cream.

Application and Functions of Stabilizers in Ice Cream

As the ice cream melts, heat transfers from the warm air surrounding the product into the ice cream to melt the ice crystals. Initially the ice melts at the exterior of the ice cream and there is a local cooling effect. The water from the melting ice must diffuse into the viscous unfrozen serum phase, and this diluted solution then flows downwards (due to gravity) through the structural elements (destabilized fat globules, air cells, and remaining ice crystals) to drip. Fat destabilization, ice crystal size, and consistency coefficient of ice cream mix were found to affect the melting rate of ice cream. Emulsifiers that promote destabilization and partial coalescence of fat globules greatly decrease the melting rate of ice cream and promote shape retention.

One function of stabilizers in ice cream is to increase the melting resistance, as reported in numerous studies.  Hydrocolloids, due to their water-holding and micro viscosity enhancement ability, significantly affect melting quality of ice cream. Moreover, it seems that the influence of stabilizers on thermal properties of ice cream such as thermal conductivity, melting onset, and heat of fusion could affect the melting rate.

Ice Cream Defects Caused by Stabilizers

Although stabilizers have very beneficial functions in ice cream, their excessive use may create problems. These limitations include undesirable melting characteristics, excessive mix viscosity, and contribution to a heavy, soggy body. Stabilizer/emulsifier components may also impart off-flavors, because they are prone to oxidation if not kept in a dry and cool environment. Baer et al. and Schaller-Povolny and Smith distinguished ice cream containing hydroxy propyl methyl cellulose and inulin gums as being gummier and chewy than other samples, respectively.

Conclusion

Because ice cream is a complex colloidal system, many factors should be taken into account in producing high-quality ice cream. Stabilizers, despite being used in very small amounts in ice cream, have been claimed to have one or more of the following functions:

Increase viscosity of ice cream mix, improve aeration and body, control meltdown, and restrict growth of crystals of ice during storage. In addition, stabilizers improve the sensory characteristics of ice cream by retarding iciness, enhancing creaminess, and decreasing wateriness. However, many polysaccharides of commercial interest are incompatible with milk proteins in solution, and phase separation often occurs, resulting in a change of functional behavior of the proteins and polysaccharides, a visual separation of a clear serum, and a loss of pleasing quality in the product.

Despite numerous studies, the exact mechanism of stabilizer action in ice cream is not clear. However, it seems that the effects of hydrocolloids in frozen desserts cannot be attributed to one particular factor but to several interaction effects. Because individual stabilizers have specific roles and seldom perform all of the desired functions, synergistic mixtures are often used. Often, trial and error is required to determine the right combination and concentrations of the available hydrocolloids to perform the functions desired for a given formula and market niche.

Acknowledgment

The authors are especially indebted to Professor Bruce Tharp, who read and commented on a draft of manuscript. We also thank Professor Douglas Goff, Professor Richard Hartel, Professor David Smith, and Professor Alan Muhr for sending some of their valuable articles.