Ex1 Final Paper

8/12/2019 Ex1 Final Paper

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FN 112 Group 1 Date Submitted: July 5, 2013

Gaa, Joshua

Go, Lindsley

Micu, Hanna

Pagatpatan, Leonard

Vano, Olana

Introduction

Pre-lab, Compilation

Methods

Results

Discussion

EXERCISE 1 - OBJECTIVE EVALUATION OF FOODS

INTRODUCTION

In food processing, various scientific techniques are employed, making enough surplus to

be sold outside the household. As technology advances, food technology also geared up to meet

the productivity, quality, safety, and economic requirements of different foods. In order to keep

pace with quality requirements and regulations from the government, most food industries have a

quantity control and quality assurance that can able to monitor the different stages of food

starting from the raw material up to its finished product.

In order to achieve assurance, food evaluation is conducted wherein food quality testing

personnel perform numerous standardized physical and chemical tests on different food products.

It includes checking physical properties such as sizes, weight, colour, texture, density, etc. and

chemical properties such as pH, vitamin content, fat content, etc. Food evaluation has two major

types of methods, namely subjective and objective evaluation.

Present day technology continues to develop and use various modern tools for both

monitoring and controlling the parameters of food quality. In this laboratory exercise, objective

evaluation (physical and chemical properties) will be conducted. It uses various methods which

require the use of standardized instruments such as penetrometer, pH meter electrode,

colorimeter, etc. These instruments will further enhance the accuracy of the results, thus making

the data reliable. Furthermore, this exercise also aims on teaching the proper way of handling

and cleaning these instruments since it would also lead to a more reliable results.


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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:

[ ]

[ ]

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 form the 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

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


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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 wasdipped 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.

Cultu red Mi lk 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:

[ ]

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 first

followed by another symbol in fraction form the 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

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

instrument. Results were recorded by the investigators.


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

80 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 120 oC 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:

[ ]

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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[ ] ( )

Where: N = normality of NaOH

V = the volume of NaOH used in mLF = is the factor of predominant acid presentW = 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 C 76 H 52 O 6 (coffee)Ascorbic Acid C 6 H 8 O 6 (preserved food items)

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

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

calibrated refractometer. Results were recorded.

Results

In this exercise, the group used a cheese (Eden) and cultured milk (Yakult) as

samples for objective evaluation of foods. There were three samples for each type of food with

the same brand. Their weights are shown in table 1. The actual net weight was obtained through

the subtraction of the container weight with the gross weight (inclusive of the

wrapper/container). Thus net weight stands for the actual weight of the product that the

consumers get. There were only small deviations in the weight of the products.


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Table 1. Sample weights (Gross and Net)

Sample

Weight in grams

Mean Gross SD Container(Mean) SDMeanActual

Net

SD

Cheese a 36.16333 0.005774 1.606667 0.005774 34.55667 0.005774Cheese b 36.77667 0.005774 1.55 0.01 35.22667 0.005774Cheese c 36.15333 0.005774 1.5 0 34.65333 0.005774Milk a 89.99333 0.015275 9.9933 0 80 0Milk b 89.87333 0.005774 9.8733 0 80 0Milk c 90.38333 0.005774 10.3833 0 80 0

Manufacturers label their own product with the net weight table 2 shows the deviation of

the actual net weight with the manu facturers declared net weight.

Table 2. % Deviation of the actual product

Declared Net Weight Actual Net Weight % Deviation (mean)Cheese a 35 34.55667 1.266667Cheese b 35 35.22667 0.647617Cheese c 35 34.65333 0.990476Milk a 80 80 0Milk b 80 80 0Milk c 80 80 0

In the experiment in determining the colors of foods, the Munsell book of colors and

HunterLab colorimeter were used. The results were as follows. The three cheeses served as

different trials. The same procedures were applied for the cultured milk sample.


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Table 3. Determination of Color of Foods

SampleMunsells book

of colorsHunterLabs Colorimeter

L a bCheese a 2.5y 8/6 76.17 1.66 29.49

Cheese b 2.5y 8/6 76.29 1.85 29.78Cheese c 2.5y 8/6 76.34 2 29.97Mean 76.26667 1.836667 29.74667

SD 0.087369 0.170392 0.24173Milk a 10yr 8/4 69.91 0.28 17.41Milk b 10yr 8/4 69.97 0.28 17.41Milk c 10yr 8/4 69.83 0.21 17.24

Mean 69.90333 0.256667 0.040415SD 0.070238 17.35333 0.09815

The cheese was the only subject sample thus this was the only sample for the test of

firmness. The test was done using a needle and how much it could penetrate for 5 seconds. The

results are shown in table 4. It shows that the same brand of cheese may have different firmness

but this can also be attributed to human errors especially in handling the penetrometer.

Table 4. Test for firmness

SampleDepth of penetration in millimeters

Mean SDTrial 1 Trial 2 Trial 3

cheese a 20.7 22.6 23.1 22.13333 1.266228cheese b 24.6 24.8 24.9 24.76667 0.152753cheese c 23.6 23.4 20.5 22.5 1.734935

The pH of foods and its temperature are also necessary to determine whether it is

potentially hazardous or not. The experiment on pH and temperature subjected both milk and

cheese and the results are as follows. The milk has a pH within the PHF range while the cheese

was below 4.5. The milk was warmer than cheese and it can be attributed to its state which is

liquid.


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Table 5.1. pH and temperature test for cheese

TrialMean SD1 2 3

pH 3.21 3.22 3.26 3.23 0.026458Temp ( C) 20.6 25 23 22.86667 2.203028

Table 5.2. pH and temperature test for cultured milk

TrialMean SD1 2 3

pH 5.86 5.9 5.89 5.883333 0.020817Temp( C) 27.4 26 24.5 25.96667 1.450287

To test the titratable acidity of liquid foods, a titrant (NaOH) was first standardized since

it was only prepared in the laboratory using NaOH pellets. It was standardized using a known

concentration and weight of analyte (KHP) and was titrated. The results are as follows:

Table 6.1 Standardization of the Titrant

Standardization Trial

1 2 3 Mean SDWeight of KHP (g) 0.2544 0.2601 0.2568 0.2571 0.002862Volume of NaOH used (mL) 13.5 13.9 13.8 13.73333 0.208167Normality of NaOH 0.092271 0.091624 0.092181 0.092025 0.000351

After the concentration of the titrant was identified, it was used in the diluted form of the

cultured milk. The milk was found to have 0.49% titratable acidity.

Table 6.2. Titratable Acidity of cultured milk

Trial 1 Trial 2 Mean SDWeight of sample (g) 10 10 10 0

Volume of NaOH used (mL) 6 6.4 6.2 0.282843%Titratable Acidity 0.49778 0.53006 0.51003 0.028327


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The last experiment of this exercise was to determine the sucrose and salt levels which

are th soluble solids in food. The cheese was subjected to test using the salinometer to determine

the salt concentration while the cultured milk was subjected for sucrose concentration test. The

cheeses had different levels of salt concentration with nearly the same deviation each trial.

Table 7.1. Total soluble solid test for cheese

Temp( C)

Trial Mean(Bx) SD

CorrectedTss

Reading

%TSS

1 2 3cheese a 24 10.5 11.5 11 11 0.5 11.29 Bx 124.19

cheese b 26 17.5 17 17 17.16667 0.288675 17.62 Bx 193.82cheese c 25 21 21 20 20.66667 0.57735 21.05 Bx 231.55

Table 7.2. Total soluble solid test for cultured milk

Temp( C)

Trial Mean(Bx) SD

CorrectedTss

Reading

%TSS

1 2 3

Milk a 28 14 14.5 14.5 14.33333 0.288675 14.93 Bx 14.93

DISCUSSION

Objective evaluation is an essential method in the food industry in maintaining the

quality and consistency of food products and also for the development and improvement of new

products. It describes the characteristics of food in an index that does not rely on the very

variable human senses through the use of instruments and physical and chemical techniques.

This characteristic then makes objective evaluation desirable for routine tests. Data or results ofthese evaluations are mostly numerical and can be compared to scientific standards that have

already been established.

However, one of the limitations of objective evaluation is that it can only measure up to

one specific attribute of a product. Thus, only tests of characteristics that have a significant


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impact on the quality of the product will be conducted. In this exercise, the products that were

objectively evaluated were cheese and cultured milk.

For cheese, the tests that were conducted included: weight, color, firmness, pH and

salinity determination. Weight measurement was applicable because cheese is solid. Colordetermination defined very specifically the yellow color trait of cheese. Firmness measurement

was also necessary to know precisely how soft or how hard the cheese is. pH determination was

conducted to find out how acidic or how basic the cheese was. Lastly, salinity was also

determined considering that cheese has a particular salty flavor. All these attributes - weight,

color, softness or hardness and salinity or saltiness describe cheese and the combination of

these attributes is a reflection of the quality of the cheese and, with sensory evaluation, is also a

reflection for consumer preference or acceptability.

For cultured milk, the tests that were conducted included the following: Volume, color,

pH, titratable acidity and soluble solids determination. Volume was determined, and not weight,

because milk is liquid. The creamy white color of the product was also quantified through color

determination. pH and titratable acidity tests were also determined to find out how acidic the

product is, considering that all milk products are acidic because of lactic acid. Lastly, the soluble

solids concentration was also conducted to find out how much sugar is dissolved in the product,

considering that it has a particular sweet flavor. Similar to what was mentioned earlier, all these

attributes- volume, color, acidity and soluble solids concentration - define milk and these

attributes altogether say something about the products quality an d consumer acceptance.

First, the products weight and volume measurements were taken. The purpose of these

tests is to measure or describe quantity. Both cheese and milk have characteristics for weight and

volume. However, weight measurement is more applicable for cheese and volume measurement

is more applicable for milk because cheese is solid and milk is liquid.

It is more accurate, and also convenient, to measure the quantity of liquids in terms of

volume because of the physical property of liquids wherein they take the shape of their container.

On the other hand, it is more accurate and practical to describe the quantity of solids in terms of

weight because they have fixed dimensions and volume measurement presents difficulties during

the process because solids come in different and irregular shapes.


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To support this, the packaging of the products also declare their contents in terms of

weight in grams for the cheese and volume in ml for the milk.

The results of the comparison of the declared quantity of the products with their actual

quantities show that there is very little percent deviation for the cheese at 0.97% and absolutelyno deviation for the cultured milk. This implies that the declared quantity value is accurate and

that the portion control for both the cheese and milk product is effective.

Next, the products colors were quantified. It is important to measure color of foods since

it has been established that, along with appearance, flavor and texture, this is a quality that

determines food acceptance (Nielsen, 2010). Thus, it is important to control the color of food

products during mass production to achieve the same desired effect on the consumers when they

visually assess the food.

In this exercise, two methods for color measurement were used. The first method was the

manual use of the Munsell Book of Colors while the second one used a more advanced device -

the Hunter Lab. Using the Munsell Book of Colors , color is further described in terms of hue,

value and chroma. Hue is instinctively the main color of the product; value is the lightness or

darkness of the color; while chroma or saturation, indicates the intensity of the color (Nielsen,

2010) . In this exercise, the milks color was described to be 10 YR 8/4. This shows that the

product has a Yellow-Red hue. Its value being 8 implies that it is very light and is very close to

be completely white at 10. Its chroma at 4 suggests that the product is dull in terms of color and

is closer to neutral gray at 0.

The HunterLab Colorimeter makes use of the concept of the Hunter L,a,b Color Space

wherein all colors are being uniformly spaced in 3 dimensions with L denoting lightness, a

representing the red(+) and green(-) coordinates and b representing the yellow(+) and blue(-)

coordinates (Nielsen, 2010) . In the exercise, the cheeses mean L value is 76.3. This implies that

its color is light because it is closer to 100 which is white and far from 0 which is black. The

mean a coordinate of the cheese is 1.8, which shows that the color has a red characteristic

because it is positive. However, the coordinate shows that the color has only a hint of red

because the value at 1.8 is very small. The mean b coordinate, on the other hand, is 29.7 and this

implies that the color has a strong yellow characteristic.


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Other methods for color measurements include the use of the CIELab and CIE LCH color

scale. These two color-order systems are widely adopted in the food industry. CIELab is

basically the same as the HunterLab but it has been improved to have a more accurate and

uniform spacing between colors (Nielsen, 2010). CIE LCH is quite parallel to the Munsell

system where L is the value or the lightness, C is the chroma or the intensity of the color and H is

the hue or the instinctive color of the item (Nielsen, 2010). Using these color scales, several

colorimeters with varying features and specifications are now available for industrial and

research application (Nielsen, 2010).

Next, the texture of the products were also described using a stand-model penetrometer.

The penetrometer aims to describe the firmness or tenderness of food items. Thus, between

cheese and cultured milk, only cheese was tested because it was only applicable to it. However,

this test measures only one of the many attributes that comprise texture. Texture also includes

cohesiveness, springiness, resilience, and these attributes of foods are being scientifically studied

under rheology. However, rheological properties should only be considered to be a subset of

textural properties of food since sensory detection of texture encompasses factors beyond the

scope of rheology (Nielsen, 2010).

Textural properties of food are influenced by several factors including homogeneity of

the item or the extent of its particles to be suspended uniformly across the space or the extent of

it being well-mixed. The isotropic property, or the consistency of the item to respond to a

specific load or force regardless of direction, is another factor (Nielsen, 2010). Another factor is

temperature. A concrete example on how T affects texture is how typical viscosity of most food

items decrease as T increases (Nielsen, 2010). The addition of products that are dilatents, such as

cornstarch, also affect viscosity and texture (Nielsen, 2010). In this experiment, temperature also

played a role in the evaluation of the firmness of the cheese. At lower temperatures, cheese

would be harder, while in higher temperatures it would be softer.

In this exercise, the penetrometer was the only gadget used to determine the texture of the

solid product, cheese, in the form of its firmness. The penetrometer measures the depth of

penetration of a cone-shaped weight or the plunger inside a food product in a given time period,

which is 5 seconds. The plunger used for cheese was that with the larger diameter because

cheese is quite soft. The results show that the product is soft as it could penetrate deeply at an


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average of 23.13 mm. However, the SD values show inconsistencies between trials. This may be

because different people handled the instrument per trial which may have caused differences in

estimation of the 5s time frame.

Other tests that can be done to objectively evaluate the texture of solid foods include thetexture analyzer from Stable MicroSystems which is primarily used for solid and semi-solid

foods (IFST, 2013). For liquid foods, viscometers or rheometers may be used (IFST, 2013).

Next, the acidity of the food items were described through measuring the pH and

titratable acidity. Titratable acidity deals with measuring the total acid concentration contained in

food. Titration is used to find out this value and this process involves exhausting the intrinsic

acids in the product with a standard base (Nielsen, 2010). This test is a better predictor of the

effect of the acidity on the products flavor than pH (Nielsen, 2010). pH, however, describes howmuch hydronium ions are present in the solution and this is significant in food science because

microorganisms need these ions to proliferate (Nielsen, 2010).

In the experiment, the pH of the cultured milk was 5.9 and its titratable acidity was 0.5%.

The pH of regular milk is around 6.8 and the reason why the cultured milk has a lower pH value

is because suitable microorganisms had been added and as a result of fermentation, these

microorganisms synthesize acids that lower the pH of the milk. This decrease in pH increases the

shelf life of the milk (MBHES, 2008). The titratable acidity Codex standard for fermented milk

should be at a minimum of 0.3%. The cultured milk in question is then within this specification.

Since titratable acidity is expressed in terms of the predominant acid, the results show that the

cultured milk is 0.5% lactic acid by weight.

In measuring the pH of the products, it was also crucial to note the temperature because

an increase or decrease in any solutions temperature will affect the viscosity which, in turn, will

affect the mobility of the ions in the solution (Barron , Ashton, & Geary, 2006). For example, a

higher T will lead to a decrease in viscosity and an increase in the mobility of the ions. A higher

T may also lead to an increase in the numbers of ions in the solution because of the dissociation

of molecules, especially for weak acids and weak bases (Barron , Ashton, & Geary, 2006). These

effects will then reflect in the pH value readings.

Lastly, soluble solids concentration was taken for both products. The refractometer was


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used for the cultured milk because it has a sweet taste, thus, it has a significant sugar content that

the refractometer can determine. The refractometer works on the ability of the sugars to deviate

light. The device actually measures the refractive index of the solution and reads it as degrees

Brix. In the experiment, a hand-held model was used and temperature was taken during the

process for correcting the reading. Temperature correction is necessary when reporting the

soluble solids concentration because the refractometers reference temperature is set at 20 0C.

Thus, for temperatures higher or lower than 20 0C, the reading is not accurate, thus, must be

corrected. The corrected %TSS for cultured milk was found to be 14.9%.

For solid foods packed in liquid, it was necessary to homogenize the sample first before

determining the soluble solids concentration so that the large chunk of solid would come in

smaller and finer particles and so light could pass through it since this is the method of how the

refractometer works. Also, it needs to be homogenized so that it can be spread and can be

correctly placed into the refractometer.

The salinometer was used to measure the soluble solids in the cheese mixture because

cheese has a salty taste, thus, a significant amount of salt that can be quantified using the

salinometer. This test for soluble solids is an objective method for describing flavor. Other

compounds that can be determined by percent soluble solids include alkaloids and these

determine the bitter taste.

REFERENCES

Bark, Z. (2009). Food Processing (First Edition ed.). NY, USA: Elseviers Science andTechnology

Barron , J. J., Ashton, C., & Geary, L. (2006). The Effects of Temperature on pH Measurement. Reagecon Diagnostics, Technical Services Department . Reagecon Diagnostics.

IFST. (2013). Food Texture . Retrieved July 1, 2013, from Institute of Food Science andTechnology:

http://www.ifst.org/learninghome/helpforteachers/lessonplantopics/foodtexture/MBHES. (2008, October 29). The Importance of pH in Food Quality and Production . Retrieved

July 1, 2013, from MBH Engineering Systems: http://www.mbhes.com/ph_&_food.htm Nielsen, S. S. (Ed.). (2010). Food Analysis (Fourth Edition ed.). NY, USA: Springer.Scott S.J. (2004). Food Processing. Prnciples and Application. Iowa, USA: Blackwell

Publishing


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APPENDIX

Cheese - Gross WeightTrial

Mean SD1 2 3

cheese a 36.16 36.16 36.17 36.16333 0.005774cheese b 36.78 36.78 36.77 36.77667 0.005774cheese c 36.16 36.15 36.15 36.15333 0.005774

Cheese - Container WeightTrial

1 2 3 Mean SDcheese a 1.61 1.6 1.61 1.606667 0.005774cheese b 1.56 1.55 1.54 1.55 0.01

cheese c 1.5 1.5 1.5 1.5 0

Cheese - Actual Net WeightTrial

Mean SD1 2 3cheese a 34.55 34.56 34.56 34.55667 0.005774cheese b 35.22 35.23 35.23 35.22667 0.005774cheese c 34.66 34.65 34.65 34.65333 0.005774

Cheese - Percent DeviationTrial

1 2 3cheese a 1.285714 1.257143 1.257143cheese b 0.62857 0.65714 0.65714cheese c 0.971429 1.000000 1.000000

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