Quality standards in food products such as fresh vegetables must be paid attention to maintain the presence of foreign matter, like rodent hairs, insects, sharp materials or any other impurities of other origin. The most suitable method for determining the foreign materials and separating them from vegetable matter is by light filth method. Light filth includes rodent hairs, insects, etc. which is present in the non aqueous phase and is separated from aqueous phase. Thus this method being convenient and simple is widely used. Broccoli as a sample of weighed quantity was boiled in water for particular time. Another sample of broccoli was boiled in water containing fixed amount of Lead acetate (25g) and Acetic acid (10ml).
To both of these samples add measured hexane solution which leads to separation of hexane and water layer along with vegetable matter and impurities. Hexane is added slowly to not create any bubbles. Organic liquid is filtered through the Buchner funnel and the presence of foreign materials is seen through microscope. Thrips and hairy material are observed for the sample treated with only water, while foreign material or insects observed in other sample treated with lead acetate and acetic acid are more in amount. Thus, referring to standard permissible limits of thrips in fresh broccoli, the samples observed were in the limits and are acceptable for human consumption.
Analysis for foreign matter is required as to know the quality of the food manufactured and to determine the raw material change if necessary. High amount of foreign materials present such as metals, chemicals, etc. can be injurious to health of consumer and society as whole. The appropriate reason of analysis is done to ensure the food product is in pure form and is not harmful for consumers. Analysis of food includes detection of impurities such as solid impurities, minerals present, metals or chemicals present example lead, mercury, rodent hairs and insects. The light filth method allows identification of the materials from which they have usually developed such as plant, animal, soil, etc.
There are large numbers of cases where insects are found in fruits and vegetables. People trust in farmers and industries thinking precautions are taken to prepare insect free vegetables and fruits and most of the time they are betrayed. FDA tolerates more insects than it should do for example in US they tolerate up to 60 insects per 100 gram of broccoli. Even though farmers use pesticides to limit insect infestation on crops, the effects are often not up to the mark. Various pesticides and insecticides are banned due to their strong action and harmful effects on the human beings. Various types of insects are now resistant to pesticides and insecticides. Vegetables with cracks and holes are more likely to suffer from infestation, since these are areas for insects to nourish and hide.
North America has most of the fresh and frozen broccoli eaters, thus tests should be performed to determine the amount of foreign materials present and if they exceed the limit determined by FDA or not. So, the aim of the experiment is to examine the light filth analysis of fresh broccoli using Wildman method for aphids and thrips. Lead acetate is used to kill the insects as it acts as poison for most of the insects while acetic acid is used to lower the ph of the solution, thus making it difficult for insects to survive. Heptane being lighter than water enters the crevices of broccoli and thus carries all the light filth on top of the water.
20x-30x wide-field microscope
For part 1A:
Take 100gm fresh broccoli in 500ml water in Erlenmeyer flask. Add small amount of anti-foaming agent into it if found foaming. Boil for 15 minutes.
For part 1B:
Take 100gm of fresh broccoli in 500ml water in Erlenmeyer flask containing 25gm Lead acetate and 10ml Acetic acid. Add small amount of anti-foaming agent and boil for 15 minutes.
Add 35ml heptane by tilting the flask at 45-degree angle. Mix the mixture using plunger by dipping it below the liquid surface and rotate with caution that no air enters the solution. Add water slowly to bring level up to the neck of flask. Allow the mixture to stand for 30 minutes. Slowly move the plunger in a clockwise direction to remove the debris from interface of heptane-water.
Remove the heptane layer into beaker. Filter the heptane layer using Buchner funnel and use ruled filter paper to filter. Observe the filtered heptane for insects or rodent hair using wide field microscope.
When Broccoli was treated with water and heptane separation of foreign material took place when filtered. There was presence of thrip (picture 1) and 2 rodent hairs were seen using microscope (picture 2). The group that followed the procedure involving treatment with Lead acetate and Acetic acid has found aphids (picture 3) and worm (picture 4) observed in that particular sample.
The insects and the rodent material found are widely due to the following reasons.
Raw materials used
From the soil when grown
During the storage condition
While transferring broccoli from one place to other.
However, it is impossible to restrict the infestation of insects and rodents in vegetative matter. There must be steps taken to prevent the infestation of insect by using pesticides and insecticides.
It is necessary to test the vegetative matter for foreign materials to prevent the consumer from the toxic and poisonous effects of the foreign materials.
The results obtain should be under the limit decided by the FDA. These limits must be strictly adhered to and followed.
There are various ways to reduce the foreign materials present in the vegetative matter. They are as follows.
Physical hazards must be properly defined and must be taken seriously.
Sources of foreign materials should be checked and verified.
Inspection of foreign materials present inside and tests performed regularly.
Storage conditions must be adequate
Proper use of insecticides and pesticides must be done.
Regular cleaning and sanitisation must be done.
There are few questions that comes to mind when performing these tests such as
Are these foreign materials very harmful?
Answer 1) Sometimes the foreign materials can be harmful such as sharp objects and large number of rodents and insects can cause food poison too. These objects can be lethal.
Can these materials be washed easily at home?
Answer2) Some of the foreign materials can be washed such as worms and larger objects, but few objects such as rodent hairs may or may not be washed.
Thus the results obtained were under the limit and were very low in number, thus passing the test.
Lab manual World Academy of Science, Engineering and Technology International Journal of Biological, Biomolecular, Agricultural, Food and Biotechnological Engineering Vol:10, No:3, 2016. Canadian Food Inspection Agency, Physical Hazard,2017.Available at http://active.inspection.gc.ca/rdhi-bdrid/english/rdhi-bdrid/introe.aspx?i=8
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