Fermented Dairy Ingredients 341effi ciency - particulate - air (HEPA) - fi ltered air
to keep out airborne yeast, mold, and other
contaminants (Nauth 2006 ). The containers
used must be free from possible contami-
nants in the fi nal stages of packaging and
storage. The yogurt must be stored at a refrig-
erated temperature as soon as the packaging
process is completed.Shelf Life of Yogurt
The shelf life of yogurt at a refrigerated tem-
perature is around 34 weeks, depending on
the standard hygiene observed during manu-
facture and the microbial quality of the ingre-
dients and the packaging material. Various
techniques have been used to extend yogurt ’ s
shelf life, including freezing and drying, gas
fl ushing, adding preservatives, using aseptic
equipment, applying multiple frequency
microwave, and sterilizing with heat (Tamime
and Robinson 2007 ).
The shelf life of Greek yogurt and/or
labneh is quite short. At refrigeration tem-
perature, a shelf life of seven to 10 days is
recommended (Yamani and Abu - jaber 1994 ).
The relatively short shelf life of cloth bag
labneh is largely responsible for the wide use
of benzoates and sorbates to control growth
of spoilage microorganisms (Mihyar et al.
1999 ) due to aerial contamination during sun
drying or pressing, although the latter can be
minimized. The shelf life of yogurt cheese is
similar to that of labneh anbaris, which is
longer than that of labneh due to a higher
total solids content and more concentrated
lactic acid. At ambient temperature, the shelf
life is about 12 to 18 months as long as the
product is kept submerged under olive oil
(Tamime and Robinson 2007 ).Application of Yogurt
The popularity of yogurt has increased over
time from simply plain fermented milk to
fruit - added and fl avored yogurts. At present,
fruit - added yogurts are the most popularQuality of Yogurt
The quality of yogurt, just as for any other
food, is essential to assure safety for human
consumption, comply with regulations, attain
a specifi c shelf life, and achieve high organo-
leptic standards within existing constraints of
manufacture and marketing. Therefore, it is
important to ensure the quality of all ingredi-
ents at the time of receiving, handling, and
manufacturing so the end product complies
with certain chemical, microbiological, and
organoleptic standards. In large scale manu-
facture, the hazard analysis and critical
control point (HACCP) concept is employed
to monitor all aspects of the raw material,
equipment, manufacturing process, and end
product.
The quality of liquid milk, whole or skim,
as a raw material is essential for yogurt man-
ufacture. Various tests to determine the total
solids, fat, protein, antibiotics, taints, organo-
chlorine, organophosphate, and dirt contents
are usually performed. If milk powder is the
raw material, then tests for its solubility are
also important, in addition to the microbio-
logical tests and moisture content of skim
milk (Tamime and Robinson 2007 ).
The starter culture added to the yogurt mix
is usually in a liquid form containing 1:1
(chain:chain) ratio of Str. thermophilus and
Lb. delbrueckii subsp. bulgaricus. In this
case, checking the balance before application
is required to confi rm that the culture is suit-
able for use (Tamime and Robinson 2007 ). If
the culture is for probiotic yogurt, the direct -
vat inoculation (DVI) of preserved cultures
is preferable due to diffi culties in maintaining
the correct ratio of the probiotic bacteria if
they are grown as a mixed culture prior to
inoculation (Tamime et al. 2005 ).
Fruit must be incorporated into yogurt
using sterile equipment to avoid yeast and
mold contamination. The blending and fi ller
areas are very crucial to the microbiological
quality of the yogurt with respect to yeast
and mold. These areas should have high -