6. The ovens are kept at a very high temperature,
between 800-900° F (426.6-482.2° C). The pita
loaves move quickly through the ovens where they
are exposed to the high heat for about one minute.
Whether sliced or left whole, the pita are conveyed
to the packaging area where they are stacked in a
pre-determined amount and inserted into pre-
printed plastic bags. Workers may close the bags
manually with twist ties. Alternately, the bag
openings may be fitted with a zipper tear-strip, in
which case the bag is mechanically heat-sealed.
7. The packaged pitas are loaded onto trays or into
cartons for shipment. If the pitas are not going to
be shipped immediately, they are flash-frozen
and kept in industrial freezers that are regulated
to a constant temperature of about 10° F (-12.2°C
for 3 months. You can keep pita bread tightly
closed in original plastic bag and store at room
temperature for 5-7 days. Refrigerator storage
isn’t recommended, as pita bread will quickly dry
out and become stale.
8. Physical spoilage includes: Moisture loss or gain.
Moisture loss or gain affects the texture and the firmness
of bakery products. This problem can be prevented by
using a high moisture barrier film e.g., low or high density
polyethylene.
Staling is considered as any change, short of
microbiological spoilage, that occurs in bread during the
post baking period, making it less acceptable to the
consumer
9. Sensory evaluation of Pita Bread
CRUST COLOR CRUMB COLOR TASTE AND AROMA
Creamish yellow color
with light brown patches
Whitish cream color Characteristic Pita aroma
and taste
Cream color with light
brown patches
Light yellowish cream
color
Light smell and taste from
additive
Light cream color with
light brown patches
Yellowish cream color Perceptible smell and
taste from additive
Lighter gray color with
pale or dark brown
patches
Light grayish cream color Definite undesirable taste
and smell from additive
Gray color with pale or
dark brown patches
gray color very definite
unacceptable smell and
taste
10. Because of its high moisture content, 38-40%,
bread is particularly subject to bacteria
growth. While the baking process destroys
most of the bacteria, bread is still susceptible
to re-inoculation of fungi after packages.
11. Flour contains approximately 8000 mould spores in 1 g, The
most common bread spoilage moulds are Penicillium spp
and Aspergillus spp. Both can produce mycotoxins
(Achratoxin A and Aflatoxin) , which are very resistance and
can survive heating process. Bacillus Subtilis and Bacillus
Licheniformis can cause ropiness, but rope is now rare ,
because of adding preservatives and good bakery hygiene
practice. Bacillus Cereus may survive baking process
because Bacillus species can form endospores. A major
reservoir of Staphylococcus Aureus are humans and some
outbreaks have been involved with bakery products.
That’s why microbial tests are very important in bacery.
12. I’ve chosen 5 microbial tests for pita bread.
•Yeasts and moulds.
•Bacillus Cereus.
•Bacillus Subtilis.
•Penicillium .
•Staphylococcus Aureus
The most important part in microbial testing is sampling and sample
preparation.
13. Sampling
If the quantity of food to be examined is large, take
representative samples of 50 g each from different parts of
the suspect food because contamination may be unevenly
distributed.( If the food is a powder or consists of small
discrete particles, then it should be thoroughly mixed before
taking sample).
Transporting and storage of samples
Transport samples promptly in insulated shipping containers
with enough gel-type refrigerant to maintain them at 6°C or
below. Upon receipt in the laboratory, store the samples at
4°C and analyze as soon as possible. If analysis cannot be
started within 4 days after collection, freeze samples
promptly and store at -20°C until examined.
14. Sample preparation
Using aseptic technique, weigh 50 g of sample
into sterile blender jar. Add 450 mL Butterfield's
phosphate-buffered dilution water (1:10 dilution)
and blend for 2 min at high speed (10,000-12,000
rpm). Prepare serial dilutions from 10-2 to 10-6 by
transferring 10 mL homogenized sample (1:10
dilution) to 90 mL dilution blank, mixing well with
vigorous shaking, and continuing until 10-
6 dilution is reached
17. 2.Penicillium is a genus of ascomycetous fungi of major importance in the
natural environment as well as food and drug production
We can use two medias, Czapek yeast autolysate agar and
malt extract agar, and incubate at 25 C for 7 days for the
growth of Penicillium spp. On a glycerol-nitrate salts agar of
0.93 water activity, and on Czapek yeast autolysate agar at 5
C and 37 C, extent of growth after 7 days provided
taxonomically valuable data; within-species variation is low,
while between-species variation is sufficiently marked to assist
in determinative classification. Moreover, water relations
shows a very high correlation with penicillus type in some
Sections of the genus.
20. Plate count of B. cereus
Inoculate duplicate Bacara or MYP (Mannitol-egg yolk-
polymyxin) agar plates with each dilution of sample
(including 1:10) by spreading 0.1 mL evenly onto surface
of each plate with sterile glass spreading rod. Incubate
plates 18-24 h at 30°C and observe for colonies
surrounded by precipitate zone, which indicates that
lecithinase is produced. B. cereus colonies are usually a
pink-orange color on Bacara or pink on MYP and may
become more intense after additional incubation
21.
22. Colonies of B. cereus grown on MYP are
pink and lecithinase positive, but other
bacteria are not inhibited and can interfere
with isolation of B. cereus. Colonies of B.
cereus grown on Bacara are pink-orange
and are lecithinase positive, but other
organisms are inhibited.
23. 4.Bacillus Subtilis
Optimum growth temperature 28-30 C.28-30 hours. Aerobic. Agar
media : colonies round or irregular, surface dull, become thick and
opaque, may be wrinkled may become cream colored or brown.
24. 5.Staphylococcus aureus is a Gram-positive coccal bacterium that is a
member of the Firmicutes, and is frequently found in the human
respiratory tract and on the skin. It is positive for catalase and nitrate
reduction. Although S. aureus is not always pathogenic, it is a common
cause of skin infections (e.g. boils), respiratory disease (e.g. sinusitis),
and food poisoning. Disease-associated strains often promote infections
by producing potent protein toxins, and expressing cell-surface proteins
that bind and inactivate antibodies. The emergence of antibiotic-
resistant forms of pathogenic S. aureus (e.g. MRSA) is a worldwide
problem in clinical medicine.
25. The 3M™ Petrifilm™ Staph Express Count Plate
provides confirmed Staphylococcus aureus results in
as few as 22 hours in 3 simple steps.
1) Inoculate - 3M™ Lift the top film and add
sample
2) Incubate
3) Enumerate - Distinctive red-violet colonies
appear in as few as 22 hours.
https://www.youtube.com/watch?v=VyGmOMkor
2g
26. Chemical spoilage of pita bread arises from lipid
degradation and production of off-flavors and off-odors
known as rancidity. Rancidity can be either oxidative or
hydrolytic.
Oxidative rancidity occurs in bakery products with a
water activity < 0.3. Products turn rancid when the fat is
oxidized and decomposed to short chain fatty acids,
aldehydes, and ketones through autolytic free radical
mechanism. These radicals can bleach pigments,
breakdown proteins, destroy fat-soluble vitamins, and
darken fat. Rancid products will produce a musty,
disagreeable odor and taste. The addition of commercial
anti-oxidants, such as butylate hydroxy toluene (BHT) and
butylate hydroxy anisole (BHA), in addition to natural
antioxidants, such as vitamin C, can extend the shelf-life
and protect essential nutrients
27. Hydrolytic rancidity
The Aw of pita bread is - 0.96 making it
more susceptible to hydrolytic rancidity.
Hydrolytic rancidity occurs mostly in the
absence of oxygen. It results in the
hydrolysis of triglycerides and the release
of glycerol and short-chain fatty acids.
Unless fat is added, hydrolytic rancidity will
not occur in pita bread.
