ReferencesBarron , 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 and Technology: 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.

EXERCISE 1:

OBJECTIVE EVALUATION OF FOOD: DISCUSSION

*red yung flow ng discussion para makuha nyo ang train of thought ko habang ginagawa ito. Delete these red comments.

Why it is important to evaluate foods objectively

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 of these evaluations are mostly numerical and can be compared to scientific standards that have already been established.

Introduce products in the exercise

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 impact on the quality of the product will be conducted. In this exercise, the products that were objectively evaluated were cheese and cultured milk.

What were the experiments conducted for each product and the rationale for conducting them

For cheese, the tests that were conducted included: weight, color, firmness, pH and salinity determination. Weight measurement was applicable because cheese is solid. Color determination 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 product’s quality and consumer acceptance.

What were the experiments you did in this class? Explain each one - what it is, what’s its principle, what’s its purpose and the findings or the result in the experiment? What does this imply? What recommendations do you have?

WEIGHT and VOLUME

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.

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 absolutely no 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.

COLOR MEASUREMENT

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 milk’s 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 cheese’s 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.

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).

TEXTURE

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 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 the texture 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).

ACIDITY

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 product’s flavor than pH (Nielsen, 2010). pH, however, describes how much 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 solution’s 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.

SOLUBLE SOLIDS

Lastly, soluble solids concentration was taken for both products. The refractometer was 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 refractometer’s reference temperature is set at 200C. Thus, for temperatures higher or lower than 200C, 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.