INTRODUCTION:
Egg
freshness identification is a fascinating and significant topic in food safety
research, owing to the close association of eggs with everyday life and the
ease with which egg composition can alter during storage. Over the last decade,
many studies have focused on detecting egg freshness.
The
yolk, albumen, and air chamber are the three primary components of an egg.
Between the yolk and the albumen is a layer of yolk membrane. Albumen moisture
eventually evaporates from the shell pores and penetrates the yolk as storage
time passes. Because of the reduced membrane flexibility, this process
continues until the yolk membrane is fully split up.
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The new egg has no space for air. When the egg starts to cool, its egg's actual content contracts, resulting in the creation of an air cavity. Due to water evaporation, CO2 dissipation, and shrinkage of egg contents, the dimension of the air chamber can rise. The larger the air chamber size is, at the similar temperature and humidity, the longer the storage time is. As a result, the yolk index and air chamber elevation could be used as primary indicators of egg freshness. (Jeffrey, 1945)
1.
CHECK
THE EXPIRATION DATE
Checking the date on
the carton is one of the simplest methods to know if your eggs are still okay.
However, if you discard your refrigerated eggs as soon as the expiration date
approaches, you may be squandering perfectly good eggs.
A "sell by"
date defines how long a store should sell eggs for, usually no more than 30
days after packing, but it does not mean the eggs are bad. An expiration date,
on the other hand, indicates when the eggs are no longer regarded fresh.
The "pack
date," which is the day the eggs were graded, washed, and packaged, is
required to be displayed on the carton of eggs that have been graded by the
USDA. However, if you don't know what to look for, you can miss it.
The "pack
date" is printed as a Julian date, which means that each day of the year
is assigned a numerical value. As a result, the numbers 001 and 365 are used to
represent January 1st and December 31st, respectively.
You may be relatively sure your eggs are still fresh if they are still within the expiration or "sell by" date on the carton, or 21–30 days after the "pack date."
2.
CONDUCT
A SNIFF TEST
The
sniff test is the earliest, easiest, and most accurate technique of determining
whether or not an egg is spoiled. You can detect if your eggs are still good
with a simple sniff if they are past their "sell-by" or expiration
date.
Bad
eggs, whether raw or cooked, emit a distinct odor. Break the egg onto a clean
surface or bowl and simply give it a sniff if you can't tell while it's still
in the shell. Toss the egg and wash the bowl or plate with warm, soapy water if
anything smells off. It's a positive sign that the egg is still safe to use if
everything smells normal, or if there's no odor at all.
1.
COMPLETE
A VISUAL INSPECTION
Your
eyes, in addition to your nose, are an important element for determining if an
egg is excellent or poor. Check whether the egg's shell isn't cracked, slimy,
or powdery while it's still in its shell. Bacteria can be detected by sliminess
or fissures, whereas mold can be detected by a dusty look on the shell. Before
usage, crack the egg onto a clean, white bowl or plate if the shell appears dry
and unbroken. Check the yolk and whites for any pink, blue, green, or black
coloration, as this could signify the growth of bacteria.
You
may even observe if the egg whites or yolk are still runny. This signifies that
the egg is aged and its freshness has deteriorated. However, this does not
always imply that it has turned rotten; it may still be entirely safe to use.
2.
SHAKE
IT.
Holding
an egg up to your ear and shaking it is another approach that isn't as
effective as the float trick. It's gone rotten if you hear liquid swishing
around within. No sound, on the other hand, equals good news. The sound of a
sloshing yolk usually indicates an old, watery yolk.
3.
PERFORM
A FLOAT TEST
One
of the most common methods for determining if an egg is okay or rotten is to do
the float test. This is also a frequent way to figure out how old a fertilized
egg is as it develops into a chick. It can also be used to determine whether or
not an unfertilized table egg is fresh. Set your egg gently in a bowl or pail
of water to perform the float test. The egg is fresh if it sinks. It is old if
it tilts upwards or perhaps floats. This is because the little air pocket
inside an egg develops larger when water is removed and replaced by air as the
egg ages. The egg may float if the air pocket is large enough.
This
approach can tell you whether an egg is fresh or old, but it can't tell you if
it's good or awful. Even though an egg sinks, it can still be bad, but an egg
that floats may be OK to eat.
1.
CANDLE
YOUR EGGS
Candling
is a method used either to assess the quality of a table egg or to assess the
development of the chick in a fertilized egg. This is done industrially using
specialized equipment to ensure the proper grading of table eggs before they
are packaged. But it can also be done on your eggs at home. You’ll need a dark
room and a small, bright source of light. In the past, candles were used, hence
the name “candling.” Yet it is probably more effective to use a small flashlight
or reading light instead. Hold the light source up to the large end of the egg.
Then, tilt the egg and turn it quickly from left to right. If done correctly,
the contents of the egg should be illuminated.
This
enables you to determine if the air cell in the egg is small or large. The air
cell in a very fresh egg should be thinner than 1/8 inch (3.175 mm). Gases
replace water lost through evaporation as the egg ages, and the air pocket
grows larger. You should be able to tell how firm the egg white and yolk are by
moving the egg from side to side. A fresher egg will have less movement.
Candling may take some experience, but it is a reliable way to tell if an egg is
fresh or old. However, it, like the float test, is unable to determine whether
an egg has gone bad.(Kouame, Voemesse, Lin, Onagbesan, & Tona, 2021)
1.
SPECTROSCOPY
METHODS
· The old way of handling and processing eggs, which is centered on handling, is no longer satisfactory to the current poultry industry. As a result, automating egg quality control is a difficult problem to solve. Non-destructive ways for assessing egg freshness have been proposed in response to this requirement. In the measurement of egg freshness, spectroscopic approaches in combination with multivariate statistical methods have a wide range of applications.
·
Infrared
spectroscopy:
Infrared radiation (IR) or simply infrared refers to energy in the electromagnetic radiation spectrum with wavelengths greater than visible light but shorter than radio waves. The determination of organic contents in feeds, foods, pharmaceutical items, and related materials is commonly done using near-infrared (NIR) spectroscopy. The NIR is based on electromagnetic radiation absorption in the wavelength range of 800–2500 nm.
·
Front-face
fluorescence spectroscopy:
In
the field of dairy products, front-face fluorescence spectroscopy has been
extensively used. However, only basic research in the literature looked into
the use of front-face fluorescence to determine egg freshness. This could be
explained by the fact that eggs are complex products containing several
fluorescent chemicals, making molecular information from their spectra
difficult to deduce. It has been discovered that front-face fluorescence
spectroscopy can be used to evaluate the freshness of eggs. Ultraviolet
radiation was used to assess the quality of eggs with various levels of
pigmentation. Two maxima were found in the emission spectra of various eggs.
These excitation wavelengths are linked to porphyrin pigments and porphyrin derivatives such as florin and oxoflorin. The results revealed that the intensity at 672 nm is dependent on the freshness of the egg. Because of the presence of porphyrin on an eggshell, UV energy causes it to generate a brilliant red autofluorescence. Because the strength of autofluorescence is dependent on the amount of porphyrin on the shell surface, the autofluorescence of a fresh egg is stronger than that of an old egg. These findings led to the conclusion that fluorescence spectroscopy could be a promising method for quantifying porphyrin in eggs and hence determining egg freshness.
2.
PHYSIOCHEMICAL
METHODS
·
Fresh egg characteristics alter as they
age, influenced by both storage temperature and environmental variables
(concentrations of O2 and CO2, relative humidity). The albumen has a
significant impact on the overall quality of the inside egg.
·
Thinning
of albumen:
Albumen
thinning indicates a deterioration of quality. The spherical yolk is in a
central position surrounded by thick albumen when a fresh egg is delicately
cracked out onto a smooth flat surface. When a stale egg is broken open, the
yolk is flattened and typically moved to one side, and the thick albumen
surrounding it has thinned, resulting in a huge region of albumen collapsing
and flattening, resulting in a wide arc of liquid. The Haugh Units method,
which is based on assessing both the intact weight and the albumen height of a
cracked egg, is the most extensively used method for determining albumen
quality.
The height of albumen is said to be affected by strain and age, with albumen height decreasing as the hen's age rises, even as the egg weight and total amount of albumen rises.
·
Height
of air cell:
Air cell height, which is determined by egg weight and storage relative humidity, is another metric used to assess egg freshness. The only quantitative egg freshness parameter evaluated by the European Union rule is air cell height, which is determined by egg weight. In theory, a grade is equivalent to a letter grade. Up until the expiration date, an egg must maintain the features of its grade (air cell height 6 mm). However, because the air cell height is so strongly influenced by external relative humidity and temperature, it's difficult to ensure quality without tight control of these two variables during the entire egg marketing cycle.
·
Ph.
Of Egg Albumen:
The pH was utilized to determine the freshness of the eggs. As a result, the pH of albumen from a recently laid egg ranges from 7.6 to 8.5. The pH of albumen increases at a temperature-dependent pace during shell egg storage, reaching a high of about 9.7. The loss of carbon dioxide from the egg through the pores in the shell causes the albumen pH to rise. The balance between dissolved carbon dioxide, bicarbonate ions, carbonate ions, and proteins determines the pH of albumen.
·
Albumen
refractive index:
The albumen refraction index, which uses the refraction phenomenon of light at the boundary plane between the lanes of a small prism exposed at a part of the detection section of the refractometer and the liquid to be assessed to measure the liquid concentration of albumen (index of refraction), has also been used as an indicator of egg freshness. However, when compared to readings established by pH and Haugh Units, this technique is very time-consuming.
CONCLUSION:
When eggs spoil, they
begin to smell bad, and the yolk and egg white may become discolored. Cracked
or slimy eggshells can also be a sign of bacterial contamination.
Easy ways to determine
an egg’s freshness include checking the expiration date, visually inspecting
the eggshell, and cracking the egg open to smell the inside.
If a person has any
doubt about whether an egg has gone bad, they should throw it out.
The main risk of
eating bad eggs is Salmonella infection, which can cause
diarrhea, vomiting, and fever. A person can reduce the risk of Salmonella by
keeping eggs refrigerated, discarding eggs with cracked shells, and cooking
eggs thoroughly before eating them.
The article is
contributed by Rashmeen Rashid, one
of the writers at the School of Literature.
