ex1 methods

8/12/2019 Ex1 Methods

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METHODS

Cheese sample

Three sachets of Kraft Eden cheese were weighed three times each using the top-loading

balance to obtain the gross weight. The packaging of the samples were removed (the three blocks

of shelled cheese were placed on a plate and were set aside) and cleaned thoroughly such that no

cheese particles were left. The washed packaging of the samples were air dried and once again

weighed using the top-loading balance having three trials each. All results were recorded and the

net weight and percent weight deviation were computed using the following formula:

Net Weight = gross weightweight of dry empty container EQUATION 1

% Weight Deviation = declared net wt.actual net wt. X 100 EQUATION 2

declared net wt.

Afterwards, the color of the cheese was measured using the Munsell Book of Colors. One

block of cheese was covered using white tissue paper with only a portion exposed. The exposed

part of the cheese was matched with the nearest color from the standard color chart avoiding

contact between the two, under appropriate illumination. The hue, value and chroma of the

cheese was, then, estimated and recorded by writing the symbol of the hue first followed by

another symbol in fraction formthe numerator representing the value and the denominator

representing the chroma.

Another color test was accomplished with the use of HunterLab Colorimeter. Enough

amount of cheese was mashed and spread over a clean petri dish such that no area of the dish

was visible. The petri dish was delivered to the Food Pilot Plant and the lab personnel managed

running the instrument. Results were recorded by the investigators.

For the firmness of cheese, the penetrometer was used. Each block of cheese samples

were divided into two placing the half on top of the other. The samples were placed on a small

plate. Afterwards, the needle of the penetrometer was changed to a thicker size because the

samples were perceived to be too soft. For each trial, the height of the mechanism head was

adjusted by releasing the lock screw and adjusting the course adjusting screw. This must bring


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the point of the penetrating instrument exactly into contact with the surface of the sample. Then

the thumb release lever was pressed for five seconds and released to end the test. Before taking

the penetration reading, the depth gauge rod was slowly pushed down to as far it would go.

To check the cheeses pH level, 5 grams of the sample was placed inside a beaker and

was diluted with 20 ml distilled water. Then, the electrodes of the calibrated pH meter was

dipped into the sample solution. Until the reading was constant, the investigator could only

record the pH value and temperature. Three trials were done for this evaluation.

The last objective evaluation done was the measure of the cheeses saltiness. Ten grams

cheese was thoroughly blended with ten millilitre of distilled water. To minimize undissolved

solids, mixture was filtered using cheesecloth. A drop of the cheese liquid was placed on the

prism of the calibrated salinometer. Results were recorded.

Cultured Milk Sample

The gross weight of three bottles of cultured milk was measured using the top-loading

balance. For each bottle, three trials were completed and results were recorded. Subsequently,

the volume of the three cultured milk were measured using the graduated cylinder. Again, results

were recorded while taking note of the declared volume of each sample. Lastly, The percent

deviation was determined using the equation below:

% Deviation = declared volumeactual volume x 100

Declared volume

In determining the samples color, a portion of it was transferred into a clear test tube.

Then it was matched with the nearest color from the standard color chart of Munsell Book of

Colors avoiding contact between the two, under appropriate illumination. The hue, value and

chroma of the milk was, then, measured and recorded by writing the symbol of the hue firstfollowed by another symbol in fraction formthe numerator representing the value and the

denominator representing the chroma.

Another color test was accomplished with the use of HunterLab Colorimeter. Enough

amount of milk was poured over a clean petri dish such that no area of the dish was visible. The


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petri dish was delivered to the Food Pilot Plant and the lab personnel managed running the

instrument. Results were recorded by the investigators.

The next to evaluate was the pH content of the milk sample measured by the pH meter. A

____ml beaker was half filled with the milk sample while the electrode tip of the pH meter was

cleaned using distilled water and gently wiping using soft tissue. The calibrated pH meter was

dipped into the milk sample. Three trials were done and pH value and corresponding temperature

were recorded making sure that readings are constant before taking down.

The next procedure done was titration. In preparing the 0.1 NaOH solution, the weight of

the reagent-grade NaOH pellets was calculated such that the weight is enough to prepare 500 mL

of 0.1 NaOH. This was placed inside the beaker and weighed using the top-loading balance.

Sufficient CO2-free distilled water, which was boiled for 20 minutes and cooled before use, was

added. The solution was stirred to the point where solids are dissolved. It was then transferred

into a 500 mL volumetric flask while the beaker was rinsed twice using distilled water.

Afterwards, it was diluted to 500 mL mark and was transferred to a clean labelled PET bottle.

Next was to standardize the NaOH solution. A 0.2500 g potassium acid phthalate, KHP

(previously dried for 2 hours at 120oC and cooled in a dessicator for 30 minutes) to at least 4

decimal places was weighed and transferred quantitatively into a 250 mL Erlenmeyer Flask. The

primary standard was dissolved into about 50 mL distilled water and 3 drops of phenolphthalein

indicator was added. The KHP solution was titrated with NaOH solution to a faint pink end point

that persisted for about 15 seconds. The normality of NaOH was calculated using the formula:

Normality of NaOH Weight of KHP in g

Volume of NaOH in L used x 204.229

The next step was to prepare the sample. The cultured milk was mixed thoroughly before the

analysis. Afterwards the titratable acidity was determined. 10 grams of the prepared sample was

weighed into a 250-mL Erlenmeyer Flask and 50 mL distilled water was added as well as 3

drops of phenolphthalein indicator. It was titrated with 0.1 NaOH solution until a faint pink color

persists for 10 seconds.

The percent titratable acidity (TA) was computed using the equation and factors given below: ( 2

to 3 determinations per sample were made and the average was reported)


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%TA (NV) NaOH x F x 100

W

Where: N = normality of NaOHV = the volume of NaOH used in mL

F = is the factor of predominant acid present

W = is the weight of the sample in g

Factors (F):

Citric Acid 0.06404 (most local fruits)

Mallic Acid 0.06750 (peaches, apricots, plums)

Tartaric Acid 0.07505 (grapes)

Acetic Acid 0.06005 (vinegar and pickles)

Lactic Acid 0.090000(milk and dairy products)

For computation:

Tannic Acid C76H52 O6 (coffee)

Ascorbic Acid C6H8O6 (preserved food items)

For the last objective evaluation, the sugar content of the milk was measured with the use

of refractometer. Using a dropper, a drop of the milk sample was placed on the prism of the

calibrated refractometer. Results were recorded.

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