It should be noted that the design of infant formulas is highly complex due to the nature of the biological requirements of the developing child. What follows is a generalized description of some of the key areas of infant formulations and is not meant to be an exhaustive review of the relevant nutritional chemistry. The key to successful formula design is to match as closely as possible the physical and nutritional properties of breast milk. Milk is a natural emulsion, which means it is a fine dispersion of tiny droplets of fats and oils suspended in water. Milk also contains important components including proteins, sugars, minerals, salts, and trace elements. Formula is made by blending similar materials in an attempt to match the characteristics of true milk. Formula design typically falls into one of three categories:
Milk based formulas (containing milk components such as casein or whey protein)
These formulas typically start with cow milk as a base since most infants have no problem ingesting cow’s milk. This type of formula is fortified with extra nutritional elements.
Animal or vegetable fat based formulas (containing vegetable and/or milk components)
Some infants have a sensitivity, allergy, or potential allergy to formula based entirely on cow’s milk. Formula made with vegetable derived milk or a limited amount of cow’s milk derived components may be more suitable for these children. Most vegetable derived formulas are soybean based. However, allergies to soybean milk also exist, so this approach does not guarantee the product will be trouble free. In general, using hydrolyzed proteins can minimize allergy concerns. They are less likely to cause allergic reactions.
Non-milk based (containing no milk components at all)
There are expensive, specialty formulas for infants who have a strong sensitivity to both cow’s and soy milk, or other medical or digestive conditions that are formula related.
Formulas are available in three forms: powder, liquid concentrate, and ready-to-feed. Powder and liquid concentrate are less expensive but they require mixing/dilution prior to use. This may be a problem because they may be improperly mixed or mixed with water contaminated with bacteria. Ready-to-feed is the most expensive type but requires no mixing before use. This is an advantage because the mother can be sure the baby is getting the appropriate dose of nutrients and doesn’t have to worry about contamination problems.
As described above, protein used in formulas can come from a variety of sources such animal milk or soybeans. Soy milk is made by taking soybeans, soaking them in baking soda, draining them, grinding the beans, then diluting the mixture with water and homogenizing it. The proteins, which come from soybeans, may be in the form of protein concentrates or protein isolates. The latter helps eliminate or reduce carbohydrates that can cause flatulence and abnormal stools. Other useful proteins can be derived from nuts, fish, and cottonseed oil but these have limited application in infant formulas.
Fats and carbohydrates
Fats and oils are an important dietary requirement for infants. Therefore formulations attempt to match the serum fatty acid profile of real breast milk. These fatty acids include eicosapentaenoic acid (EPA) which may be derived from fish oil and other sources. In actual breast milk there is a significant amount of fatty compounds known as triglycerides. For example, docosahexaenoic acid (DHA) is believed to be an important triglycerides. Triglycerides which are similar to (but not biochemically identical to) those found in breast milk can be derived from egg yolk phospholipids. Alternatively, fatty acid precursors (molecules which react to form dietary fatty acids) may be added to infant formula. These precursors (e.g., alpha and gamma linolenic acid) allow the infants’ bodies to synthesize the necessary fatty acids. However, this method is not as efficient for delivering fatty acids as breast milk is.
The diluent is the carrier or bulk of the liquid of the formula. For milk based formulations, skim milk may be used as the primary diluent. In milk free formulations, purified water is used.
A number of essential minerals are added to infant formula. These include calcium, phosphate, sodium, potassium, chloride, magnesium, sulfur, copper, zinc, iodine, and iron. Iron is one of the most important components since all babies need a source of iron in their diet. Some parents are concerned that iron-fortified formulas cause intestinal problems in infants but this is a myth. In general parents can expect formula fed babies to experience more gastrointestinal problems than breastfed babies.
Vitamins are added to increase the nutritional value of formula. These include vitamins A, B12, C, D, and E as well as thiamine, riboflavin, niacin, pyridoxine, pantothenate, and folacin.
A variety of materials are added to ensure the formula stays homogenous and that the oil and water soluble components do not
separate. These include emulsifiers such as mono and di-glycerides as well as thickeners like natural starches and gums (e.g., such carrageenan.)
The Manufacturing Process
The method of manufacture depends on the type of formula being made. The following steps describe a general procedure for a ready-to-feed, milk-based formula.
- 1 The primary ingredients are blended in large stainless steel tanks. The skim milk is added and adjusted to 140° F (60° C). Fats, oils and emulsifiers are added next. Additional heating and mixing may be required to yield the proper consistency. Minerals, vitamins, and stabilizing gums may be added at various points in the process depending on their sensitivity to heat. Once mixing is complete, the batch can be temporarily stored or transported via pipeline to pasteurization equipment.
- 2 Pasteurization is a process that protects against spoilage by eliminating bacteria, yeasts, and molds. Pasteurization involves quickly heating and cooling the product under controlled conditions which microorganisms cannot survive. A temperature of 185-201.2° F (85-94° C), held for about 30 seconds, is necessary to adequately reduce microorganisms and prepare the formula for filling. Several pasteurization methods are commercially available—one common method warms the formula by sending it through a tube adjacent to heat plate heat exchanger. Thus the formula is heated indirectly. Another method heats formula directly and then uses the heated liquid to preheat the rest of the incoming formula. The preheated formula is further heated with steam or hot water to the pasteurization temperature. After pasteurization is complete, the batch may be processed further by homogenization.
- 3 Homogenization is a process which increases emulsion uniformity and stability by reducing the size of the fat and oil particles in the formula. This process can be done with a variety of mixing equipment, which applies high shear to the product. This type of mixing breaks the fat and oil particles into very small droplets.
- 4 The resulting composition is standardized to ensure key parameters, such as pH, fat concentration, and vitamin and mineral are correct. If any of these materials are at insufficient levels the batch can be reworked to achieve the appropriate levels. The batch is then ready to be packaged.
- 5 Packaging process depends on the manufacturer and type of equipment employed, but in general, the liquid formula is filled into metal cans which have lids crimped into place. These can be filled on conventional liquid filling equipment commonly used in the food and beverage industry.
- 6 The filled packages can be subsequently heated and cooled to destroy any additional microorganisms. The finished cans are then packed in cartons and stored for shipping.
Quality of infant formula is ensured at three levels, which have some degree of overlap. First, in the United States, there are governmental standards, which establish the nutritional quality of infant formulas and other dairy substitutes. Specific details of these standards can be found in the Code of Federal Regulations; more information is available from the Food and Drug Administration (FDA) which regulates infant formula as a special diet food. The FDA publishes a monograph detailing everything from the mandated nutrient list to label copy and artwork used on packaging. Second, the dairy industry sets its own industry-wide quality control standards. The industry is self-policing and has its own regulatory organization, the International Dairy Federation, which sets industry standards for manufacturing and quality control. Third, individual companies set their own standards for quality control. For example Martek, one producer of triglycerides used in formula, has microbiologists and engineers monitor 30 different checkpoints of triglyceride production, 24 hours a day.
Future developments in infant formula manufacturing techniques will be driven, in part, by business and marketing concerns. This dependence on the marketing climate may be a benefit to the industry because there is tremendous opportunity for expansion. It is estimated that the total worldwide market for infant formula could be as high as $80 billion. Therefore, the current estimated world sales of formula of $4 billion represents only 5% of the total potential sales. Should the market grow even close to $80 billion, it is likely to spur manufacturers to find better ways to simulate breast milk. One such future improvement is being developed by scientists who have recently identified an important fatty acid in breast milk that is not found in infant formulas. This particular fatty acid appears to be important for the development of cell membranes in eye, brain, and nerve tissue. Addition of this material could be a significant advance in formula technology. Formula manufacturers can continue to make their products better by incorporating breakthrough research findings such as this one. However, even though there is great potential for growth, there is no guarantee it will be realized. The industry is experiencing criticism from groups which claim that formula is unnecessary and, in fact, may be harmful to infants. Should this trend negatively impact formula sales, manufacturers may be less likely to make significant investments in product and process development.