What is infant formula or ‘Baby food’?
Infant formula, also known as ‘Baby Food’, is an artificial substitute for human breast milk. Formulas are designed for infant consumption and are usually based on cow’s milk.
Substitutes or complements to breast milk are as old as mankind. Indeed, when no or insufficient human milk was available, substitutes for human milk were used. The lactose and milk proteins are in specific formulations replaced partly or 100 % by other carbohydrates and soy proteins.
Animal milk - usually cow's milk - with the addition of 20 % sucrose on dry matter has often been reported as the replacement. Breastfeeding is, however, internationally recognised as the ideal form of infant feeding with multiple benefits associated with breastfeeding for child health.
If a decision to use an infant formula is taken, it is important to give instructions on correct preparation methods, emphasizing that un-boiled water, un-sterilized bottles, incorrect dilution and in-appropriate storage after reconstitution can lead to malnutrition and illness. |
What does infant formula / baby foods consist of?
The basic composition of any infant formula consists of:
•
Carbohydrates •
Proteins
•
Lipids
• Minerals
•
Vitamins
The proportion, the quality and the processing of these elements determine the overall quality of the food. Since an infant formula is the only source of nutrition of a new born infant, the choice of these criteria is vital.
All major infant formula producers developed their own brands with specific compositions; however, several legislations (Codex, USFDA, EU, FS Australia and New Zealand, China) provide the regulatory frame for the composition of infant formula and follow-up formula.
Carbohydrates
As in human milk, the bulk of an infant formula is composed of carbohydrates (usually about 55 % of the solids). In infant formula the lactose is often partially or completely replaced by hydrolysed starch (i.e. maltodextrin). Generally, the higher carbohydrate content, the higher the solids content can be fed to the dryer. The addition of cooked starch results in a thickening of the reconstituted formula. This will have an influence on the solids content that can be fed to the spray drying plant.
Proteins Protein is composed of many amino acids, 9 of which are indispensable, cannot be synthesised by the human body and have to be supplied in adequate proportions by the food. The amino acid profile and the energy supplied by proteins of human milk provide the “golden standard” for any formula. For an equal energy value, the infant formula must contain an available quantity of each indispensable amino acid at least equal to that of human breast milk.
Soya protein is, after cows’ milk protein, the most widely used protein for infant formula. The protein has to be isolated from the soy bean in order to get rid of undesirable components such as oli-gosaccharides, fibres, saponins and phytoestrogens. The amino acids profile of soy protein is deficient in Sulphur containing amino acids, and L-Methionine enrichment is therefore required.
Another aspect of proteins is their potential allergenicity. A growing proportion of infants show a certain degree of allergenicity to foreign protein, e.g. cow, goat, or soy. A Reduction of the risk of allergic reactions to cow’s milk protein can be achieved by hydrolysing the proteins to smaller peptides (e.g. Hypo-Allergenic formulae).
High total protein content will result in a high viscosity of the formulation to be dried. The total solids content will therefore have to be reduced.
Lipids
Lipids constitute the main energy supply of infant for mul a. In many infant formulas, the lipids are a mixture of milk fat and vegetable oils. The quality of the lipids is expressed by their fatty acid composition, the degree of saturation, and the content of trans fatty acids. In most countries the oils of vegetable origin are enriched with long-chain poly-unsaturated fatty acids (LC-PUFA) containing oils.
Due to the high degree of instauration of these oils, special care has to be taken in order to avoid fat oxidation and rancidity. Generally, high lipid content in the formula will result in a low viscosity of the feed to the dryer. The total solids content can thus be increased.
Minerals As for proteins, fats and carbohydrates, minerals also play an important role in the nutrition of infants. K, Na, Ca, Mg, P and Cl are referred to as minerals, whereas Fe, Cu, Zn, Se, Mn and I are referred to as micro- or trace elements. Minerals are generally referred to as having no influence on the subsequent drying.
Vitamins
• Water soluble vitamins: B1, B 2,
B 3, B5, B6, B12, C, Folic acid, Biotin.
• Fat soluble vitamins: A, D, E, K1
Fat soluble vitamins can be encapsulated, which makes them granular and Cold Water Soluble. In this way all vitamins can be blended and used as pre-blend with an analysis certificate allowing a simplified control for each batch to be spray dried. Vitamins have no influence on the operation of the spray dryer.
Ingredients in infant formulae / Baby food In general typical raw materials for standard infant formulae are:
•
Milk (skimmed or full fat, liquid or powder, cow or buffalo)
• Casein (acid or K / Ca neutralised)
•
Whey protein (concentrate / isolate, partially demineralised)
•
Carbohydrates: lactose, sucrose, maltodextrin and corn syrup (powder or syrup)
• Vegetable oils, anhydrous butter oil,
cream • Emulsifiers/Stabilizers: lecithin (soy), mono- and diglycerides
• Mineral salts (K, Na, Ca and Mg as carbonates, citrates, phosphates, chlorides)
• Micro-nutrients (e.g.
vitamins, amino acids, KI, FeSO4, ZnSO4, CuSO4)
Milk When the milk source is fresh milk, it should be cooled before standardisation of fat content, pasteurized and cold stored in silo tanks. From these tanks it will be pumped to the wet mixing with the dry ingredients.
Oils Oils are supplied either in drums or in bulk from insulated tank lorries. The oil is pumped to storage tanks. Depending on the melting point of the oil, the tanks can be provided with double jacketing. If milk, either liquid or in powder form, is not available, anhydrous butter oil can be used. In order to prevent oxidation of the (poly-unsaturated) oils, the oil tanks are usually equipped with an inert gas (N2) supply.
Production of Dried Infant Formulae
In general, dried infant formula can be produced using either
a “dry mix” or a
"wet mix" process. Each type of the processes has its specific advantages and disadvantages.
The “dry mix” process
Advantages:
• The lack of water involved in the process makes it safer from a microbiological point of view, as no growth can be expected. However, the microbiological quality of the final dry mixed powder will be no better than what was used to form the 'mix'.
• A much smaller investment, as less equipment and thereby, a smaller building is needed. The costs fo r en ergy and maintenance will also be considerably lower.
Disadvantages:
• It does not allow incorporating lipids, which means that the ingredients should already contain them.
• No heat treatment is included. Thereby the physical and microbiological quality is defined by the quality of the raw materials used, a nd h ow the actual dry mixing is performed.
• Physical powder properties such as wet ability and solubility will be defined by the properties of the single ingredients, unless a rewet agglomeration process follows the mixing and that adds to the investment and manufacturing costs.
• The different ingredients have different densities and will therefore se gregate during canning and transportation. In other words, the product can get an inhomogeneous appearance and composition, which can be vital for the end-user.
The wet mix process
In the 'wet mix' process the situation is different. All quality aspects during wet mixing, concentration by evaporation and spray drying can be controlled to a higher degree resulting in better quality of the powder in terms of microbiology, physical and chemical properties.
Especially the possibility of heat treatment of the premix, either before or after the evaporation, is extremely important. Obviously, the investment as well as production costs become higher with this process.
The 'wet mix' process is, however, the most widely used, sometimes combined by adding some of the dry nutrients (e.g. vitamins, trace elements or carbohydrates) after the drying process, and each one of the major producers has their own way of preparing the 'wet mix' before final evaporation and/or drying. |
Evaporation
The raw materials used in the different formulations are often mixed to lower solids content than optimal for spray drying. This is because the dissolving of the powdered materials is better at lower solids. Concentration by use of a falling film evaporator is usually done before the final drying, since it is cheaper to remove water by evaporation, as by spray drying.
Heat Treatment of Baby Food / Infant formula
The ever increasing focus on a hygienic production of an infant formula has made a high-heat heat-treatment of the concentrate necessary.
Depending on product composition, this heat treatment is done either before the evaporation or after. Direct steam injection is used up to 100-140 C in fractions of seconds, followed by a flash cooling to 80 C. The SANIHEAT™ equipment as developed by GEA Niro (patent pending), is used.
Spray Drying
The drying system typically consists of:
• one or several high pressure nozzles or a rotary atomiser/wheel for the atomisation of the concentrate
• a drying chamber/tower
• an integrated fluid bed for secondary drying
• an external VIBRO-FLUIDIZER®
• one or several cyclone(s) and/or bag filter(s) as an air/powder separation system
• a fines return system to improve the agglomeration
Powder Structure
Until few years ago, most infant formula were dried in a TALL FORM DRYER™ or a COMPACT DRYER™. Both dryers produce non-agglomerated and agglomerated powders. However, to a great extent infant formula sold today are marketed as agglomerated powders, since the agglomeration improves the reconstitution properties.
It is therefore important that the degree of agglomeration and the compactness of the agglomerates can be controlled. This is achieved in the Multi-Stage Dryer, MSD™. |
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Drying Parameters In order to improve the production efficiency the drying temperatures and solids content of the concentrate are selected to be as high as possible. The product composition, however, is a d ecisive factor as to what parameters can be selec ted. Generally it can be mentioned that:
• The drying efficiency and capacity of a spray dryer is increased by increasing the difference between the drying air and exhaust air temperature.
• High ambient air humidity requires a lower spray drying temperature or a dehumidification of the air, which obviously increases the production costs.
Finished Powder Conveying System The final product from the spray dryer is conveyed to a silo system via a
positive pressure dense phase conveying system. From the bottom of each silo, the product is conveyed to either a blending area for mixing with other powders or to the bag or can filling line by v acuum conveying. Normally the powder is packed in an N2 atmosphere to prevent oxidation of the milk fat or vegetable (polyunsaturated) oil.
To make things simpler the powder from the dryer can fall by gravity into a hopper and from the hopper direct to the bagging or can filling line. Which solution to chose, depends on the overall approach to logistics, capacity and investment.
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