FAIRY OF DAIRY INDUSTRY - FLAVOURED MILK

Flavoured Milk???
Let's take a look at the video presented by Dennis Jonsson, President and CEO of Tetra Pak Group about the importance and future development of flavoured milk.

Source: https://www.youtube.com/watch?v=6rZ2eV18Hvg

Most people love flavoured milk, but what exactly is flavoured milk? Flavoured milk is a sweetened milk beverage, commonly manufactured by using milk or recombined milk, sugar, permitted flavourings as well as artificial or natural colourings. Flavoured milk is probably one of the most preferred type of beverages in terms of its high nutritional value which benefits people from all ages, especially children and the elderly. The popularity of flavoured milk in Australia was proven when The Sunday Times reported that Western Australia was the “flavoured milk capital” of Australia in 2013. How amusing! Flavoured milk is available in many different types of flavour such as chocolate, strawberry, vanilla, honeydew and green tea flavour. You can choose from a wide range of consistency and flavours to suit your taste and lifestyle. It is common to find the name of the flavour conjoined with the words “flavoured milk” on the label of the milk beverages since it complements with regulation 89 of Food Regulations 1985. 

A typical flavoured milk formulation consists of 95% milk, 5% sweetener, 0.10% flavouring and 0.01% colouring. The composition of flavoured milk may include milk fat and non-milk fat solids of more than 2 and 8%, respectively, sucralose as permitted sweetening substance of not more than 300 mg/kg, permitted colouring substance, permitted food conditioner, protein, mineral substances and organic acids. The fat content in flavoured milk is comparatively lower than whole milk, since flavoured milk is categorised as low-fat group of dairy products. Meanwhile, the carbohydrate content is significantly higher in flavoured milk than usual milk including low-fat milk and whole milk due to the addition of flavours which contributes to 3% of added sugar in the milk. However, the addition of flavouring agent does not affect protein, salt, calcium and phosphorus content in the final product.

                          Comparison of average composition of flavoured milk and whole milk

Source: Adapted from “Evaluation and comparison of the physicochemical properties of different commercial milk products” by Datgostar et al., 2013, European Journal of Experimental Biology.

Most milk flavourings are water soluble as the flavour should be dissolved in the aqueous phase of milk. However, there may be occurrence of partition effects due to the possible migration of lipophilic flavour ingredients into the oil globules whereby their palate effects are masked. Besides, the addition of sweetening agents such as sucralose in flavoured milk is necessary for sweetening, adding carbohydrate calories and mouthfeel as well as to disperse stabilisers and flavouring powders, for instance, cocoa powder. However, the amount of sucralose added should not exceed 300 mg/kg according to Food Regulations 1985 as high sucralose content may result in sugar crystallisation which gives an undesirable mouthfeel when drinking the flavoured milk. This will raise health concerns among the consumers as the acceptable daily intake (ADI) is set at 5 mg/kg of body weight per day.

Flavoured milk is efficiently heat-treated with methods such as pasteurisation, sterilisation or ultra-high temperature (UHT) processing. Both pasteurisation and UHT processing are heat treatments aimed at reducing the number of harmful organisms to a safe level for preventing health hazards. Pasteurisation of flavoured milk can be carried out either as a batch operation (batch pasteurisation) with the product heated at 63 °C for 30 min and held in an enclosed tank or as a continuous operation (High Temperature Short Time, HTST pasteurisation) with the product heated at 72 °C in a plate heat exchanger for 15 s. The flavoured milk is then cooled immediately to 4 °C. Meanwhile, UHT processing involves heating flavoured milk at 135 °C for at least 2 s whereas sterilised flavoured milk is usually produced in two steps consisting of a continuous heating step at 121 °C for 3 min to render them as commercially sterile.

Let's take a look at this video for better visualisation of automatic packing line for sterilised flavoured milk!

Automatic packing line for sterilised flavoured milk

Source: https://www.youtube.com/watch?v=mevoNw99bOQ

        As for the preparation of pasteurised flavoured milk, no other ingredients should be added to the milk used for the preparation of flavoured milk after pasteurisation. However, sterilised permitted colouring substance, namely Sunset Yellow and Allura Red, and flavouring substance may be added after pasteurisation provided that the flavoured milk is packed immediately into the final containers. This ensures the good quality of the flavoured milk by avoiding recontamination of milk after pasteurisation. This is because addition of unsterilised ingredients after pasteurisation results in reactions that cause rancidity due to chemical development which involves lipase and other enzymes to react with the milk fat to form free fatty acids.

Most of the flavours are stable during pasteurisation but not UHT processing of flavoured milk. This is due to the much higher working temperature (135 °C) required for UHT processing, although for only a short period, can result in undesirable reactions between many flavouring materials and the components of milk. Since UHT milk has a characteristic flavour of its own, the added permitted flavouring substances must be able to complement or mask the unique flavour. Alternatively, the risk of overheating, the distribution of heating and holding times should be minimised to ensure minimum temperature difference between the heating and heated flavoured milk.

                                Stability of flavour in flavoured milk processed by different heat treatment

        In general, heat treatment of flavoured milk causes the denaturation of whey proteins, namely serum albumin, immunoglobulin, α-lactalbumin and β-lactoglobulin. In particular, the denaturation of β-lactoglobulin results in production of high levels of reactive sulphydryl groups which undergo reactions to form hydrogen sulphide, mercaptans, sulphides and disulphides which are responsible for the cooked flavour in UHT and sterilised flavoured milk. Hence, the permitted flavouring substances used to produce flavoured milk must either contain minimal or no sulphur-containing flavouring materials.

           Denaturation of whey proteins in flavoured milk

Heat treatment of flavoured milk also results in enzyme inactivation which is a desired reaction due to their negative effect on the flavour of dairy product. Furthermore, the destruction level of microorganisms varies depending on the type of heat treatment used for flavoured milk. For instance, batch pasteurisation kills most microorganisms and inactivates some enzymes whereas HTST pasteurisation kills all vegetative microorganisms, inactivate most of the enzymes and causes insolubility of serum proteins. Meanwhile, UHT treatment of flavoured milk sterilises milk while minimising chemical changes. Sterilisation process kills pathogenic microorganisms while causing chemical changes, such as Maillard reaction, which leads to the production of brown pigments in heated milk.  

Well, flavoured milk is definitely here to stay and with demands increasing, more innovative flavours such as pistachio and pumpkin flavour are expected to hit the shelves in future. People who love dairy products from all walks of life, young or old, most probably would love drinking flavoured milk with abundance of nutrition and yumminess.

Different unique flavours of flavoured milk

Source: Google Image