Dairy beverages: Balancing function and nutrition

Dairy drinks are becoming popular delivery systems for functional ingredients — through simple nutrient fortification, modification of viscosities, or new and novel forms. L Steven Young, PhD, reports

To integrate nutrients into dairy beverages, they need not be milk-derived. But to do this successfully, it is necessary to carefully consider the complex chemistry and physics of these products to ensure formulas and ingredients remain compatible with sensory, marketing, manufacturing, packaging and distribution needs.

Dairy beverages are made entirely or in part with milk or milk-derived ingredients, such as milk, milk fat, lactose and milk proteins. Further, beverages may (eg, milk) or may not (eg, smoothies) have a standard of identity that defines their composition and restricts terminologies. Different viscosities can also be applied depending on the concept. Table 1 classifies dairy beverages based on processes and/or packaging used to render the beverage commercially sterile.

Product developers need to understand packaging and distribution options when formulating dairy beverages. This, in turn, determines how a product should be processed and, thus, how the product needs to be formulated. Formulas must tolerate whatever conditions need to be applied, be they variations in packaging (glass, paper, flexible, plastic), processing (culturing, physical and thermal stress), or formula (acidity, pH, solids, sweetener systems, amount and type of protein).

Packaging
Package selection can be a challenge. Many times this is a balance between marketing needs such as size, shape, appearance, labelling or shelf-life expectations, and operational concerns — what can or cannot be executed, production rates, etc. In addition, the package must be compatible with the overall product concept and product formulation specifics.

Processing
Once distribution and packaging needs are determined, general process conditions and considerations are pretty much known. If refrigerated distribution is necessary, simple pasteurisation with refrigerated packaging and distribution may suffice. If room-temperature distribution or extended refrigerated shelf life is needed, other processing and packaging strategies will be necessary. If a cultured beverage is desired, it may be necessary to ensure that nutraceutical ingredients are not themselves fermented during the process.

Nutritional targets and claims
Formulation objectives need to be considered. This includes desirable nutrient content claims, structure/function claims and any available health claims. These would include any and all claims related to total fat, calories, protein, carbohydrates, vitamins, minerals and other components such as plant sterols. Of course, local and/or federal regulatory authorities can determine what can or cannot be said about the finished food. These may differ market to market, so care must be taken to formulate for the specific market to be serviced.

Fat: Milk fat can be totally or partially replaced with standard or more novel vegetable oils such as soy, corn, cottonseed, canola or sunflower. The amount and type of fat/oil to use depends on what is to be said about the finished beverage. Further, the fat/oil selected needs to be compatible with all aspects of the finished beverage including appearance, viscosity, mouthfeel and flavour. In fat-free formulas, of course, little or no added fat may be allowed. Besides the nutritional issues related to fat, fat contributes direct and indirect, positive and negative effects on flavour and colour. Proper selection and use of any fat/oil source is critical to success.

Table 1. Classification of Milk Ingredient-Based Beverages by Process

  • Pasteurised, refrigerated
  • UHT pasteurised, refrigerated
  • UHT pasteurised, aseptically packaged
  • Retorted
  • Co-dried dry mixes
  • Dry-blended dry mixes
  • Hot-fillable high acid (? pH 4.5) beverages
  • Liquid concentrates
Protein: Milk contains basically two types of protein — insoluble casein and soluble whey proteins. Each type has several sub-types that can affect beverages in differing ways. Caseins are not stable to some thermal processes and can precipitate at pH's consistent with high-acid beverages. Whey proteins, although stable to pH, may tend to increase in viscosity and denature with high thermal processes. Again, care is necessary when considering either whole milk protein, casein and/or whey ingredients in any given beverage.

It is possible to separate casein and whey proteins from milk in nearly undenatured states. Therefore, sources of milk protein are available such as skim milk, ultra-filtered skim milks, milk protein concentrates, milk protein isolates, whey protein concentrates and whey protein isolates. This can be both good and bad depending on the amount and type of protein desired; form, colour, and flavour of the beverage; and thermal processing conditions to be considered.

Nondairy proteins such as soy can also be used. Soy performs differently than casein and whey functionally, as well as in properties based on its manufacturing history and supplier. If proteins are not selected properly for the intended purpose, serious defects can occur such as precipitation, oiling-off, off-flavours and discolouration. Sometimes, this can be accomplished via formulation and processing. Other times, the use of select and appropriate hydrocolloids such as carrageenan and pectin may be necessary to prevent the destabilisation of proteins in beverages, and not only dairy-based beverages.

Carbohydrates: Carbs in dairy beverages can come from milk (naturally occurring lactose) and added sweeteners, bulking agents and/or stabilisers. Depending on what needs to be claimed, more or less simple 'sugars' can be used. Further, depending on manufacturing, packaging and distribution conditions, nonreducing sugars may be necessary to deliver desired sensory attributes without discolouration during processing and storage. A wide variety of novel, new carbohydrate ingredients can make for extremely innovative dairy beverages.

Table 2. Select Dairy Nutraceuticals
Whey proteins
Whey protein fractions
Butryic acid
Conjugated linoleic acid (CLA)
Sphingolipids
Sialic acid
Lactulose
Lactitol
Lactobionic acid
Galacto-oligosaccharides
Calcium
Various cultured (probiotic)components

(Courtesy of Steven Young Worldwide)

High-intensity sweeteners: Other than naturally derived sweeteners, formulators can use a variety of high-intensity sweeteners. Depending on the sensory characteristics desired and processing conditions, typically a blend of two or more high-intensity sweeteners may be desirable. When blended, high-intensity sweeteners can be used at levels below which off-flavors and tastes develop. In addition, when used in blends, synergies between sweeteners can produce more sweetness than would be expected. This allows use of lower levels of the specific blend and typically a more 'natural' sugar-like sweetness with fewer lingering off-tastes. Finally, when blended and used at lower levels, increased stability to thermal processes may also occur.

Vitamins and minerals: Milk and milk-derived ingredients can be sources of a variety of naturally occurring vitamins and minerals. However, the vitamins and minerals are not always compatible with marketing, formulation and processing needs. Therefore, it may be necessary to add a specific vitamin/mineral premix to achieve nutrient targets. When this is done, it is also necessary to ensure that vitamins and minerals do not negatively affect sensory properties of the mix, and are stable throughout the entire intended shelf life of the product. This can be a daunting task and overages of certain vitamins may be necessary.

Probiotics: Beverages are near-perfect systems to deliver probiotic microbiological cultures to foster good intestinal health. It is relatively easy to see that delivering live and active probiotic bacterial cultures in a dairy beverage can be both appropriate and daunting. Not only is it necessary to select the most appropriate 'cocktail' of bacterial strains, but the amount of the cocktail should be stable across the full intended shelf life of the beverage and compatible with all sensory attributes of the finished food.

Further, the cocktail must be compatible with the specific formula, processing conditions, packaging and distribution options. Some new technologies are available but typically dairy beverages with probiotic cultures can be simply pasteurised, cultured, packed and distributed under refrigerated conditions. The addition of probiotic cultures without culturing — so called 'sweet' dairy beverages — can also be considered. Doing this in a shelf-stable format for room-temperature distribution has not yet been commercially achievable.

Prebiotics: Unlike probiotics, the addition of prebiotic ingredients such as water-soluble dietary fibres is fairly straightforward. However, each prebiotic ingredient needs to be used at the rate recommended by the manufacturer and may not be compatible with other characteristics of the beverage such as flavour, colour and viscosity. It is critical to make sure the prebiotic ingredient is stable to the thermal and acid conditions of formulation and processing. If the ingredient is not stable, you can expect serious quality changes during processing and distribution, including development of off-colours, off-flavours, differing sweetnesses, solid-liquid separation, oil-off, etc. Having said all this, prebiotic dairy beverages are relatively easy to execute under virtually all process conditions.

Dairy nutraceuticals: Table 2 lists a number of evolving and novel nutraceutical components of milk. As more is learned and as more become commercially available, they will increasingly become more desirable as viable ingredients in dairy-based beverages.

Preservatives: It may, or may not, be necessary to use appropriate preservatives to prevent the growth of yeast, mold and, eventually, more deleterious micro-organisms. The amount and type of any given preservative is dictated by conditions and needs.

Formulation: A variety of dairy-based beverages can be contemplated. Tables 3, 4, 5 and 6 show some basic approaches.

Again, care is necessary in each specific case to select and use each ingredient in an appropriate and effective way. Balancing nutritional guidelines and needs with issues related to shelf stability is the key to success. Not all elements can be balanced out at the same time. It may be neither desirable nor possible to deliver multiple product features.

Final tips
For dairy beverages, not all rules apply in each given application. Care must be taken when considering what to formulate and how. Further, consideration of marketing, processing, packaging, and distribution options and needs also play a role. Finally, no formula can be created without consideration of economics along the way. Each and every beverage concept needs to deliver nutritional efficacy, functional performance and economic opportunity.

L Steven Young, PhD, is principal of Steven Young Worldwide in Houston, Texas, a technical and nontechnical consulting firm specialising in the development and use of novel new food ingredients.
www.stevenyoung.net
Respond: [email protected]
All correspondence will be forwarded to the author.

Table 3. Fortified Milk
Control Prebiotic milk drink*
Skim milk 100.0% 85.0%
Digestion-resistant maltodextrin 2.5%**
Vitamin/mineral premix to suit***
Water to 100%
Per 240ml serving:
Dietary fibre None 5.10g*
Net glycaemic carbs 13.5g 10.2g
* Further fortification with dairy and non-dairy proteins possible
** Provides 'excellent source' of dietary fibre and prebiotic influence
*** Vitamin/mineral premix up to 20% daily value of each essential nutrient
(Courtesy of Matsutani America, 2005)

Table 4. Dairy-Based Liquid "Meal Replacement"

Option A

Option B

Nonfat dry milk

8.30%

Milk protein isolate

3.32%

Soy protein isolate

2.70%

Digestion-resistant maltodextrin

2.50%;

2.50%

Soy phytosterols

0.30%

Sucralose

0.015%

0.015%

Acesulfame-K

0.030%

0.030%

Flavour, colour, vitamins, minerals

to suit

to suit

Stabiliser

to suit

to suit

Water

to 100%

to 100%

Per 240ml serving:

Total fat

0.92g*

0.2g**

Dietary fibre

5.1g***

5.1g***

Lactose

11.2g

0.08g***

Net glycaemic carbs

11.2g

0.9g

Total protein

6.9g

13.0g

Soy protein

none

6.5g****

Phytosterols

none

650mg****

Calories

105

140

* 99% Fat-free
** Fat-free
*** Excellent source of dietary fibre; available structure/function claims
**** Lactose-free
**** Soy protein and phytosterol health claims available

(Courtesy of Matsutani America, 2005)


Table 5. Yoghurt Beverages

Option A

Option B

Option A

Option B

Cultured base*

Whole milk

57.10%

57.10%

Nonfat dry milk

3.00%

2.50%

Whey protein concentrate (35%)

3.00%

Whey protein concentrate (80%)

1.50%

Gelatin

0.50%**

0.50%**

Water

to 100%

to 100%

Pasteurised sugar/stabiliser base

Sugar

74.00%

74.00%

Pectin

1.00%**

1.00%**

Water

to 100%

to 100%

Blend

Cultured base

60%**

60%**

Pasteurized sugar/stabilizer base

40%**

40%**

Flavour, colour, vitamin, mineral premix

to suit

to suit

Per 100 g serving

Total fat

2.1g

2.1g

Total milk protein

2.5g

2.5g

Sugar

10.0g***

10.0g***

* Culture per need; fortify per need
** By modifying these elements, more or less viscosity can be achieved
*** Partially or totally replace with high-intensity sweetener(s)

(Courtesy, US Dairy Export Council, 2005)


Table 6. Directly Acidified Dairy-Juice Drink

Skim milk powder

1.00 - 20.0%*

Pectin

to suit**

Sugar, flavour, colour

to suit

Fruit juice

to suit

Edible acid

to suit***

Vitamin, mineral fortification

to suit***

* Will determine viscosity and type of beverage to be made
** Required to stabilise milk proteins to process and acidity
*** Amount and type of acid depends on flavour and buffering capacity of mix and added acid.Typically, **** Amount and type will vary based on stability and solubility

(Courtesy of Steven Young Worldwide, 2005)


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