The following patent states that sterilized infant formula has a shelf life
of 1 1/2 years.  I believe I have also seen 2 years but have no reference for
that.  One of my posts was written rather poorly and the impression seems to be
that I am saying that genetic engineering increases shelf life.  I wasn't
saying that.  The following patent is worth reading.  Valerie W. McClain, IBCLC

http://www.uspto.gov/patft/index.html
patent # 6194009
"Refrigeration-shelf-stable ultra-pasteruized or pasteruized infant formula"
inventor:  Kamarel
assignee:  Princeton Nutrition, LLC

"An infant formula which contains all the essential macronutrients and
micronutrients, have heretofore been available only in shelf-stable sterilized
products. Sterilized products are generally sold in hermetically sealed containers
such as cans and are intended to have a long room temperature shelf-life.
Table 2 lists several commercially available shelf-stable sterilized infant
formulas. As will be discussed further herein, sterilization processes, due to the
severity of the heat treatment can cause undesirable physical, chemical,
enzymatic and microbial changes which deleteriously affect the final product.

Moreover, although such sterilized products are often marketed as
"ready-to-feed" (RTF), they are typically stored at room temperature, and enzymatic
reactions still occur, albeit slower, during room temperature storage of sterilized
products. Such reactions can result in a host of undesirable defects, such as
the destruction of vitamins which are necessary to the integrity of the
overall product. Since sterilized products are designed to have up to one and a
half (11/2) year of room temperature shelf-life, such products will have a
different actual content of degradable micro nutrients (vitamins) in the early part
of its shelf-life as compared to the latter part. Thus, an infant will obtain
a different and unknown amount of vitamins depending on when the sterilized
product is consumed.

To account for this degradative process during long-term shelf-life,
manufacturers of sterilized infant formulas often include up to 50% to 70% more of a
given vitamin than would normally be included to account for the inherent
degradation loss and to ensure the product is likely to contain at least the
labeled amount of nutrients at the end of its shelf-life. Such large overdosing
results in an imbalance in the taste of the product, particularly if consumed in
the early stages of its shelf-life. Moreover, the cost factor of including such
large overdoses is considerable. In addition to the high cost of
sterilization, and increased overdosing of vitamins, sterilization processes require high
cost packaging, such as in metal cans.

Like milk, liquid infant formulas (usually containing milk proteins and
sometimes soy protein) are heated for a variety of reasons, the main reasons being:
to remove potential pathogenic organisms and to increase shelf-life. The
major concerns about the resulting products of thermal process are safety and
quality. Like milk, heat-treated infant formulas should not be a public heath
risk. They should have a good keeping quality, provide an intended balance of
nutrients, and be of desirable sensory characteristics, i.e., appearance, color,
flavor, and mouth feel. When milk or infant formulas are heated at a constant
temperature, all their constituents and components will be affected, but to
different extents. Increasing the temperature will accelerate reaction rates. But
different reactions will be affected to different extents. Physical,
chemical, enzymatic and microbial changes will depend principally upon the
time-temperature conditions, but will also be influenced by other factors, such as
composition, pH, and oxygen content. The wide range of reactions taking place when
infant formulas are heated will influence the safety and quality of the
product. Upon heating of products at higher temperatures for longer times, some
undesirable changes can also take place (e.g., decrease in pH, Maillard browning,
cooked caramel flavor, denaturation of whey proteins and interaction with
casein). The changes that take place during heating and subsequent storage, can
affect the nutritional value and sensory characteristics.

In thermal processing, the most important parameter is the level of microbial
inactivation achieved. For safety reasons, the minimum holding time
(residence time) should be considered for microbial inactivation, although this will
give an underestimate of the true level of microbial inactivation."



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