Chemistry of ice cream

Ice cream is a popular dairy product among consumers of all ages. Textural of ice are the key
factors of the product. It is a microcrystalline network of liquid and solid phases. It contains air
cells entrapped in liquid phase and various other components like proteins, fat globules,
stabilizers, sugar, soluble and insoluble salts are also present in this phase. It is a complex
physicochemical and colloidal system consisting on many complex ingredients that affect ice
cream structure both in positive and defective functionality. Both stabilizers and emulsifiers
improve the texture of ice cream by enhancing its viscosity and limiting the movement of free
water molecules but their excess may cause the lower melting and less whipping ability. As
sugar provides sweet taste, improves thickness as well as bulkiness but on other hand its
excessive use can turn ice cream into soggy structure. One of its compositional contents, fat, also
exerts good effects on body, texture, palatability, flavor intensity, emulsion formation and
maintenance of melting point. If fat contents exceed a specific usage concentration, they cause
faster meltdown of ice cream along with destabilization and agglomeration of fat droplets.
Higher overrun results in collapsing of air cells ultimately shrinkage of structure occurs.
Hardness might also reduce as a result of smaller ice crystals due to high overrun values. Fiber
addition causes the binding of free water hence flow rate gets reduced and consistency
coefficient as well as viscosity enhanced. Binding of water results in less availability of its
molecules; freezing point rises and melting point decreases. It is much critical to control the
balance ice cream properties by maintaining its structure, texture and body based on chemistry
of different ingredients and processing effects.

1. Ramani Akshay R. Dairy Chemistry Division Chemistry of Ice cream

2. Content Introduction FSSAI Standards Ice cream Microstructure Emulsifier HLB concept Stabilizer Effect of processing parameter on Ice-Cream Modern Approach Defects in ice cream related to emulsion conclusion

3. India is the largest producer and marketer of milk. Ice cream is a popular dairy product among consumers of all ages. Ice cream contributes energy of ~ 220 kcal/100 g and is a rich source of nutrients. The ice cream market in India is forecast to exhibit a CAGR of 17.03% during 2016-2021. India produced more than 200 million liters of ice cream in the financial year 2020. Introduction (Goff et al ., 2013)

4. According to FSSAI (2011) Ice Cream, Kulfi , Chocolate Ice Cream or Softy Ice Cream means the product obtained by freezing a pasteurized mix prepared from milk and /or other products derived from milk with or without the addition of nutritive sweetening agents, fruit/fruit products, eggs/egg products, coffee, cocoa, chocolate, condiments, spices, ginger and nuts. It may contain cake or cookies as a separate layer and/or coating. The product may be frozen hard or frozen to a soft consistency and shall possess a pleasant taste and smell free from off flavour and rancidity. - FSSAI (2011)

5. 7 Sr. No. Requirements Ice cream category Regular Medium fat Low fat 1. Milk fat (%), Min. 10.0 2.5-10 2.5 2. Milk protein (%), Min. 3.5 3.5 3.0 3. Total solids (%), Min. 36.0 30.0 26.0 4. Weight/volume (g/lit.), Min. 525 475 475 Food Safety and Standards for Ice cream - FSSAI (2011)

6. Emulsifiers act as surface active agents and reduce the energy required to maintain the integrity of the fat globules. Added emulsifiers are more effective than milk proteins due to their smaller molecular size and greater mobility. Function of emulsifiers is to destabilize the fat globule. This permits a degree of clustering and prevents too rapid melting. Emulsifier - ( Bahramparvar et al ., 2011)

7. - ( Bahramparvar et al ., 2011)

8. The HLB (hydrophilic–lipophilic balance) concept is used for describing the nature of the surfactant. It is based upon the relative percentage of hydrophilic to lipophilic groups within the emulsifier molecule. Griffin assigned values ranging from 0 to 20 ( Waginaire et al ., 1997). Glycerol Mono Stearate (GMS ) has got a HLB number of 3 whereas polysorbate 65 has got a HLB number of 13 . HLB concept Materials having an: HLB value (3-6) are lipophilic & produce W/O. HLB value (9-12) are hydrophilic and produce O/W

9. Promote nucleation of fat during aging thus reducing aging time Improve the whipping ability Produce a dry and stiff ice cream Increase resistance to shrinkage and rapid melt down Increase resistance to the development of coarse/icy texture. Provide smooth texture in the finished product Role of emulsifiers in ice cream - ( Bahramparvar et al ., 2011)

10. The stabilizers are a group of compounds, usually polysaccharides. The ice cream would become coarse and icy very quickly Without stabilizers. Good ice cream products can be made with only the natural stabilizing and emulsifying materials present in milk such as milk proteins and phosphates, additional stabilizers have potential benefits. Chemistry of stabilizer -(Goff et al., 2013)

11. Most stabilizers are polysaccharides of plant origin Alginates and carrageenans (from seaweeds) Locust bean gum and guar gum(from tree seeds) Pectin (from fruit) Sodium carboxymethyl cellulose (from cotton). Xanthan, (a bacterial polysaccharide) Gelatin , (a polypeptide of animal origin.)

12. To increase the viscosity of the mix. To stabilize the mix i.e. To prevent wheying off . 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 . Role of Stabilizers in ice cream -(Goff et al., 2013)

13. Stabilizers are functionally work as hydrocolloids. The most apparent effect of stabilizers is the increased viscosity of the continuous liquid phase. The effect of stabilizers on viscosity exhibits considerable interaction with milk constituents. During hardening, the water content of ice cream falls considerably with a associated increase in the concentration of stabilizer in the liquid phase (increases the viscosity) Mechanism of action

14. The movement of water is partly block by the ability of hydrocolloids to form hydrogen bonds. Thus, refreezing of water that originated from melting of ice due to temperature fluctuations would not permit the formation of large ice crystals.

15. Effect of processing parameter on Ice-Cream

16. Flow diagram for the production of ice cream

17. T he main role of pasteurization is to ensure the microbiological safety of the product, the heating also affects the physico - 00 chemical structure of the mix. The emulsifier is melted and heat-activated stabilizers brought into colloidal solution. The whey proteins present in the SNF are partially denatured and uncoil exposing the lipophilic portion of the molecule. Effect of pasteurization -( Varnam et a l., 1994)

18. Denaturation also increases the number of available binding sites for protein: hydrocolloid interactions and thus enhances the action of stabilizers such as carrageenan. Pasteurization is generally beneficial to ice cream quality, but excessive heat treatment leads to unacceptable organoleptic deterioration.

19. During ageing a number of important changes occur. Skim milk powder and stabilizers become fully hydrated and the emulsifier-induced desorption of proteins continues. Substantial crystallization of fat also occurs. Triacylglycerols of the highest melting point are the first to crystallize and are situated closest to the surface of the fat globules. The crystallization process continues successively with triacylglycerols of progressively lower melting points, creating multiple-shelled fat globules with a core of liquid fat. Effect of ageing Varnam -(Goff et al., 2013)

20. This process causes the emulsion to undergo partial coalescence or fat destabilization, during which clumps and clusters of the fat globules form. Whipping

21. Overrun is usually defined as the volume of ice cream obtained in excess of the volume of mix, and is expressed as percent overrun Overrun Packaged ice cream 70-75% bulk ice cream 90-100% Super premium ice cream 30-50% Sherbet 30-40% milk shakes 10-50%

22. Fat globules in ice cream mix are of two types, large globules ranging in size from 0.5 to 4 µm, but with most less than 2 µm diameter, the overall mean being ca. 1 µm. In addition very fine globules are also present which range in diameter from 0.04 to 3 µm with a mean diameter of 05 µm. Destabilization of the fat emulsion, initiated by the action of emulsifiers, continues as a result of the combined effects of freezing and mechanical agitation during the freezing process. freezing process -(Goff et al., 2013) - ( Bahramparvar et al ., 2011)

23. Destabilization of fat globules during freezing.

24. Internal structure of ice cream. Ice crystal (b) Ice crystals (c) Unfrozen material -( Varnam et a l., 1994)

25. Wall separating ice crystals -( Varnam et a l., 1994)

26. 41

27. Anti-freezing protein A nti-freeze blood proteins found in deep sea species, e.g. Arctic ocean pout fish, and this anti-freeze protein is grown in vats using GM yeast. At only 0.01% concentration, this synthetic protein lowers the temperature at which ice crystals form and also affect their shape and it allows Unilever to make a thick, creamy 'low-fat' ice cream and this such ice cream is already on sale in the USA. ( Kaleda et al., 2018)

28. conclusion It is better to see the future of ice cream. Unilever has used genetic modification (GM) technology to make synthetic analogues of naturally-occurring anti-freeze blood proteins found in deep sea species. Restructuring casein micelles in ice cream mix with HPP is an interesting technology for improving textural properties of ice cream. It is much critical to control the balance ice cream properties by maintaining its structure, texture and body based on chemistry of different ingredients and processing effects.

29. Thank you