The test can be regarded as slightly positive when there is a gradual appearance of pink color but this appearance is due to the incomplete peroxidase inactivation. In order to complete the reaction, few drops of 1% guaiacol solution and 0.3% hydrogen peroxide solution can be added, which therefore pertains to a positive reaction wherein the enzyme peroxidase decomposed hydrogen peroxide . This will yield a rapid and intensive brown-reddish color indicating a high peroxidase activity. A negative result is characterized when there is no change in color after 5 minutes which indicates that peroxidase have been inactivated (Chapter 9 - Vegetable specific processing technologies).
1.5 Invertase
Inversion is promoted when sugar is cooked in a solution to which an aid has been added (McWilliams M., 2009). Invertase breaks down sucrose to glucose and fructose (McWilliams M., 2009).
Benedict's solution is a test reagent that reacts positively with simple reducing sugars. All monosaccharides and most disaccharides are reducing sugars, possessing a free carbonyl group (=C=O). Sucrose is an exception in that it is not a reducing sugar. A positive Benedict's test is observed as the formation of a brownish-red cuprous oxide precipitate. A weaker positive test will be yellow to orange. Both glucose and fructose test positive with benedict's solution, sucrose does not (Massengale, 2011).
Invertase is the common name of the enzyme that catalyzes the hydrolysis of table sugar (i.e.sucrose) into a much sweeter, equimolar mixture of glucose and fructose called “invert” sugar. Because invert sugar is a key ingredient in a number of sweets and confectionary products, the bakery industry provides one of the most important commercial applications of this enzyme reaction. For this reason, the enzyme has been extensively characterized and commercial sources of pure invertase are readily available.
While aqueous solutions of either pure sucrose or glucose display weakly dextrorotatory behavior, meaning they cause a slight right-handed rotation of plane polarized light, solutions of pure fructose are strongly levorotatory and cause a much greater left-handed rotation of the light. The enzyme reaction, therefore, catalyzes the inversion of the right-handed rotation of polarized light observed through sucrose solutions to the left-handed rotation observed for solutions of “invert” sugar, hence the enzyme’s common name of “invertase”. For similar reasons, the common monosaccharides glucose and fructose are also known as dextrose and levulose, respectively (Timmerman, 2011).
1.6 Pectin Methyl Esterase
The enzyme pectin methyl esterase’s (PME) action comprises the demethylation of the carboxymethyl groups of pectic polysaccharide chains. When the degree of methylation decreases, it may trigger different processes related to its texture and firmness. Blanching a fruit or vegetable at 60oC will result in a higher PE activity (Tijskens, 1998).
During blanching, rapid loss of turgor and membrane integrity occurs, mainly because the pectic polymers of the cell wall and middle lamella during processing changes. The loss of membrane selective permeability is due to low temperature treatments; this promotes diffusions of cations of the cell wall, causing activation of pectin esterase (PE) and enhancing the de-esterification of the pectins. This facilitates the formation of divalent bridges between bridges of galacuturonic acid attached to adjacent pectin chains. The divalent ion-pectin complexes formed in this way provide intercellular cementation, lending firmness to the tissues (Canet, 2004).
1.7 Proteases
A. Action on Meat
Tenderizing
Because of the lower cost of certain less tender cuts of meat in comparison with more tender pieces, attempts have been made to tenderize the less tender cuts. Grinding and cubing break up the connective tissue and make meat more tender. Tenderizing compounds containing various enzymes, usually proteases may be used to hydrolyze some of the proteins in meat. The enzymes include papain and mopapain from the green papaya fruit, bromelain from pineapple, ficin from figs, and actinidin from kiwifruit. The compounds are applied to the surface of meats prior cooking. A fork can be used to pierce the meet and how the materials to penetrate a little further. Most of these enzymes act primarily on the collagen of connective tissue. Care must be taken to control excessive action on the meat fibers and prevent the development of a mealy or mushy texture. Little enzymatic action occurs at room temperature, the optimal temperature for papaya enzyme activity being 140° to 160°F (60° to 70°C). This temperature is reached during cooking (Bennion & Scheule, Introductory Foods, 2010).
Meat Tenderizers
Certain proteolytic enzymes can increase the tenderness of less tender cuts of meat. The most common of these is a commercial blend of enzymes from papaya and salt, a blend that is referred to simply as papain. The three enzymes in these substances are chymopapain, papain, and a peptidase. Papain is applied to the surface of the meat, and then the meat is pierced repeatedly with a fork to help carry the enzymes into the interior. Unless piercing is done, the enzymes will tenderize only the surface of the meat and a very short distance (no more than 2 millimeters) into the muscle because of the limited penetrating capability of enzymes (McWilliams, 2012).
As stated by McWilliams (2012), Papain has little effect at room temperature, but it becomes active when the temperature of the meat reaches 55°C (131°F) and increases in activity with additional heating to even 80°C (176°F). Activity ceases when the enzymes is denatured by heat; it is definitely inactive at 85°C (185°F).
Much of the tenderizing effect is the result of the enzyme destroying the sarcolemma surrounding the myofibrils in the fibers, hydrolyzing actomyosin, and then continuing hydrolytic breakdown of various proteins in the fiber. Collagen also may be hydrolyzed to contribute still further to the tenderizing effect. The result of this enzymatic action often is the development of a somewhat mushy texture in regions where the enzymes has acted. This is true whether or not the enzyme has been allowed to stand on the meat for a period before cooking, because the enzyme exhibits its major action in the hot meat (McWilliams, 2012).
Although papain is the principal enzyme used for tenderizing meats, other proteolytic enzymes also can be utilized for this purpose. For example, bromelain is an enzyme found in fresh pineapple, its action sometimes occurs when the fresh fruit is an ingredient in recipes such as those for kabobs of stir-fried chicken. Bromelain is inactivated between 77° and 82°C (170° and 180°F). ficin, a proteolytic enzyme in figs, is another possible enzyme for tenderizing meat (McWilliams, 2012).
B. Action on Egg Albumin
Albumin
The albumen, usually called the egg white, consists of thin and thick portions. The portions of thin and thick white vary widely in different eggs and change during storage under varying conditions (Bennion & Scheule, Introductory Foods, 2010).
Enzymatic Hydrolysis and its Effect on the Viscosity of Proteins
Protein molecules may undergo hydrolysis to form shorter chains. This chemical change occurs at the peptide linkage between amino acids in the primary structure when the hydrogen of a molecule of water joins with the nitrogen in one amino acid moiety to form an amino group and the OH joins with the carbonyl of the adjoining amino acid to form a carbonyl group (McWilliams, 2012). The protease catalyzed reaction cleaves a peptide bond in the protein (van Oort & Whitehurst, 2010). Normally the hydrolysis of proteins causes a decrease in the viscosity of the protein solution (van Oort & Whitehurst, 2010).
Papain in Meat Tenderizer
Certain proteolytic enzymes can increase the tenderness of less tender cuts of meat. The most common of these is a commercial blend of enzymes from papaya and salt, a blend that is referred to simply as papain (McWilliams, 2012).
C. Action on Gelatin
Gelatin and its Structure
Gelatin is a protein made from collagen. Collagen is a structural protein found in all animals, meaning that it helps give animals their structure, or shape (Science Buddies, 2012). Gelatin is extracted from dead animal skins and bones as collagenous material, which is then treated to produce the final gelatin. This cholesterol-free protein has a unique sequence of amino acids; gelatin’s high content of the amino acids glycine, proline, and hydroxyproline frequently bind to form a repeating sequence of the triplet glycineproline- hydroxyproline, which gives gelatin its triple helical structure. This helical structure is responsible for trapping water molecules and forming gels (Bullerwell and Hagar,2012). Each amino acid chain is basically a hydrocarbon chain but may contain an amino group or a carboxylic acid group. Hydrogen bonding may take place either between the water molecules and the peptide links or between the water molecules and the amino and carboxyl groups on the side chain (Gaman and Sherrington, 1989).
The Action of Proteases on Gelatin
Gelatin is an important protein nutrient that can be broken down by the proteases. Various proteolytic enzymes are able to cleave the long gelatin molecules into shorter polypeptides. This change in molecular length quickly eliminates the usual ability of gelatin to form gels. If ingredients containing enzymes capable of catalyzing this proteolysis are incorporated into gelatin mixtures, a satisfactory gel cannot form. Among the foods containing these enzymes are papaya, which contains papain; pineapple, which contains bromelain; figs, which contain ficin; and kiwi fruit which contains actinidin (McWilliams, 2008).
There could be quite a marked difference between the use of fresh juice extract and canned juice. The fresh juice contains the proteases which attack proteins and break it down to smaller molecules. The effect of this on the gelatin solution, which is a protein, is that it is unlikely ever to set, as the enzyme would have weakened the gel forming properties of the gelatin. If canned juice is used, the heat used in canning would have destroyed the enzyme, so that the gelatin gel would have set in the normal way (Birch et al, 1977).
III. Materials and Methods-
1.1 Effect of Heat on Enzyme
In this experiment, apples (purchased at SM supermarket), beakers, distilled water, thermometer, Bunsen burner and tripod set up and paper towels are used.
Distilled water (500ml) was heated to 100°C. Apples bought from Supermarket were cut into cubes 0.5 inches at all sides then 25 slices of apple cubes was submerged into the heated water and samples were removed after 0, 10, 20, 30, 40, 50, 60 and 70 seconds respectively. After heating, apples were submerged in cold water to cool. And then apples were placed in paper towels. Time of browning was noted, and then heating time versus time of browning was plotted.
1.2 Catalase
The materials used for this experiment are: One potato (bought in SM Supermarket), two test tubes, distilled water (bought in SM Supermarket), knife, ruler, chopping board, beaker, bunsen burner and tripod setup, and 3% Hydrogen Peroxide solution.
The first step in conducting the experiment was the cutting of potato in uniform sizes. The dimensions of the potato were 0.5 inches, thus making a cube, having equal measurements at all sides. This was done until a total of ten potato cubes were cut. The next step was the submersion of 5 slices in boiling water for five minutes. This was considered as Lot A. The rest of the potato cubes were left unheated. Afterwards, the two test tubes were filled approximately 1/3 full with fresh Hydrogen Peroxide solution. Lastly, Lot A and Lot B were then placed inside the two test tubes separately. Results and observations were taken down respectively after completion.
1.3 Polyphenoloxidase
The materials used include one potato, test tubes, distilled water, cheesecloth, thermometer, Bunsen burner and tripod, 0.1% Catechol solution, and beakers.
Fifteen grams of potatoes were cut and blended with 100 ml distilled water. Then, filter was extracted through the cheesecloth. The collected filtrate was divided into two lots. Lot A was boiled for 3 minutes while Lot B was leave unheated. Each of 3 test tubes were filled with ¼ full distilled water and ten drops of catechol were added into each tube. Ten drops of heated potato extract was added to Lot A then ten drops of unheated potato extract was added to Lot B and another ten drops of distilled water was added to the third test tube which is controlled. Then each test tube were mixed. Lastly, the color of each tube was noted every 1 minute interval for 5 minutes.
1.4 Peroxidase
The materials used in this experiment include potato, which was purchased at SM Supermarket, distilled water, bought from the UST Multimedia car park, 1% guaiacol in ethanol & 0.3% hydrogen peroxide, which was prepared in the laboratory prior to use, Bunsen burner, beaker, tripod set-up, pipettes, test tubes, knife and chopping board, which were provided by the laboratory and pantry personnel.
To perform this experiment, distilled water was subjected to heat just to boil while potatoes were cut into 10 cubes with 0.5” specification on each side. The first 5 cubes were submerged into the beaker with boiling water for 5 minutes, labeled as Lot A, while the other 5 cubes were left unheated, identified as Lot B. After which, 10g of each lot was transferred into 2 separate test tubes. Into each test tube, 20ml of distilled water, 1ml of 1% guaiacol solution and 1.6ml of hydrogen peroxide were added and mixed very well. Observation was noted after 5 minutes.
1.5 Invertase
The materials used in this experiment were 0.25M Sucrose solution that was prepared by group 3, dry yeast bought at the grocery store, Benedict’s solution, test tubes, beakers, Bunsen burner and tripod set-up, stirring rods, pipettes and dropper that were issued to each of the group.
In the experiment, the yeast was prepared by mixing 3 grams of dry yeast with 20 ml of distilled water and was stand for 20 minutes. A 1/3 full with sucrose solution was filled in each of the two test tubes. The two test tubes were named Lot A and the other is Lot B. In lot A, 3 ml of the yeast suspension was filled and mixed while in Lot B, 3 ml of distilled water was filled and then mixed. After 10 minutes, each test tube was tested with Benedict’s Solution. Two millilitres of the solution was removed and was placed in another test tube. Then, 10 drops of Benedict’s Solution was added and heated in boiling water for 3 minutes. Note the color changes/precipitation after 3 minutes.
1.6 Pectin Methyl Esterase
The materials used in this experiment were ripe tomatoes, salt, cheese cloth and SOLA bottles with caps, bought at Landmark. The blender and thermometer were borrowed from the FT Lab. Sauce pan, bowl, plates and wooden spoon were borrowed from the pantry.
1.7 Proteases
A. Action on Meat
The materials used in this experiment include thin slices of lean meat, fresh pineapple, cooking oil and meat tenderizer (with Papain), which were all bought at SM Supermarket, and a frying pan that was borrowed from the pantry.
3g of tenderizing powder was applied and rubbed on one side of a thin slice of meat, which was then incubated for 30 min. Another sample was submerged in freshly extracted pineapple juice for 1 hr. Another slice of meat was allotted as control. The samples were then fried, taking care not to burn them, until golden brown. Texture was then evaluated in terms of tenderness using the 5-pt. scale with 1 being very tough, and 5 being moderately soft. ANOVA was the used to determine if there is significant difference among the samples.
B. Action on Egg Albumin
The materials used include meat tenderizer (with Papain) and egg white, which was bought from SM Supermarket, ruler, a test tube, and an incubator set at 35°C.
1 ml of egg white was placed in a test tube. The viscosity was determined by laying the tube on its side and measuring the distance travelled by albumin. This was recorded as the data for the control albumin. 0.05g of Papain was added and mixed with the egg white. The mixture was then incubated at 35°C and the change in viscosity was observed after 30, 60, 90, and 120 min intervals. Distance traveled by albumin was recorded in millimeters (mm). distance traveled versus time of incubation was plotted.
C. Action on Gelatin
The materials used include four transparent plastic cups, one gelatin envelope (Ferna), and fruits (papaya, kiwi, and pineapple) from SM supermarket, marbles, ice cubes, graduated cylinder, pan, and cheesecloth.
The fruits were chopped finely. Juices were extracted from the three samples using blender and cheesecloth. The gelatin dessert was prepared according to the package directions. 90 ml of gelatin was poured into each of four plastic cups. The cups were placed in a pan filled with ice cubes. It was then placed in a refrigerator until it was set. After the gel was formed, 10 ml of papaya juice was added to the first cup (Lot A); 10 ml of pineapple juice to the second cup (Lot B); 10 ml of kiwi juice to the third cup (Lot C). Nothing was added on the fourth cup (Lot D). A marble was placed on top of each gelatin and was allowed to stand at room temperature. Observations were noted at the end of the laboratory period.
IV. Results and Discussion
1.1 Effect of Heat on Enzyme
After submerging cubes of apple into hot and then cold water time when browning occurred was noted which is shown in the table below.
Table 1. Effect of Heat on Enzyme
Fig. 1 – Effect of Heat on Enzymes. The rate or speed of enzymatic reaction increases as the temperature increases until a critical level is reached, at which point denaturation or coagulation of the enzyme by heat stops the activity (Bennion & Scheule, Introductory Foods, 2010).
At its optimum temperature, enzymatic activity is greatest, and denature does not occur according to Bennion and Scheule (2010). Base on the table and graph, the longer the time of submerging into hot water, the longer the time when browning occurred. It is simply because at higher temperatures, denaturation dominates, and markedly reduced enzyme activity.
1.2 Catalase
Based on our results (Table 2), Lot B formed bubbles while Lot A did not. This is due to the aerobic bacteria still present on the food samples. Catalase is an enzyme that converts hydrogen peroxide into water and oxygen. The bacteria that contains this enzyme is usually aerobic (need oxygen) or a facultative anaerobe (can live with or without oxygen). A positive reaction is indicated by a continuous bubble formation when the catalase is introduced to bacterial colonies. (Anonymous) With those statements said, Lot A could not have formed bubbles since the potatoes were heated in a boiling medium, thus killing the bacteria that contains catalase in the process.
Table 2. Catalase Test
1.3 Polyphenoloxidase
The effect of potato extract was dependent on heating and the time it is allowed to stand for 5 minutes or more. Based on the table 3, the controlled sample does not change its clear, colorless state for 5 minutes. Lot A (heated potato extract) becomes slightly turbid after a minute and Lot B (unheated potato extract) changes its color from cream white to yellow to light orange. The action of polyphenoloxidase is undesirable because it causes the browning, off-flavor development and loss of vitamins of the fruit or vegetable which affects the nutritional quality and appearance of fruits and vegetables and therefore causes significant economic impact, both to food producers and to food processing industry (Queiroz, 2010).
Table 3. Color Changes Observed on Heated and Unheated Potato Extract
According to Bennion (1980), heating of fruits and vegetables denatures enzyme proteins so that heat treatment is used for stabilizing foods because of its capacity to destroy microorganisms and to inactivate enzymes. The improvement of methods to control browning is an important key to enhance product value and minimize post harvest losses.
1.4 Peroxidase
The most common way to determine the activity of peroxidase is the use of peroxidase test. On this experiment, the heated and unheated potatoes were subjected to peroxidase test which yielded the results shown below:
Table 4. Color Observation on the Heated and Unheated Potatoes
As seen on the table, the heated potatoes or Lot A gave a brownish yellow color which indicates a positive reaction. This is due to the utilization of the hydrogen peroxide by the peroxidase as a hydrogen acceptor to catalyze the oxidation (Whitaker, 2003). Also, the hydrogen peroxide decomposed the potato due to its exposure in high temperature for a certain period of time which caused the proteins to denature and damage the molecules inside the cell causing some parts of potato to detach from it. (Chachana, 2011). While as compared to Lot B, or unheated potatoes, it has retained its color but subsequent production of bubbles were evident as it attached on the sides of the test tube.
1.5 Invertase
Benedict’s solution is a test reagent that reacts positively with simple reducing sugars. A positive Benedict’s test is observed as the formation of a brownish-red cuprous oxide precipitate. On the results obtained, Lot B formed a white, cloudy formed precipitate while Lot A remained in its turbid blue-greenish solution after being added with Benedict’s solution and heated for 3 minutes. Invertase breaks down sucrose into glucose and fructose. Since there are no reducing sugars produced, Benedict’s test would be negative.
In Lot A where yeast cells were in, invertase is classified as an extra-cellular, glycoprotein which is localized to the thin volume of space that exists between the yeast’s plasma membrane and its outer cell wall (this peripheral volume is often called the periplasmic space). The enzyme serves the important biological function of cleaving sucrose on the outside of the cell into monosaccharides that can be transported (and subsequently metabolized) in the cytoplasm. That is, in the absence of invertase, yeast would have a difficult time utilizing table sugar as an energy source. Kinetic studies indicate that this extracellular form of invertase has a pH and temperature optima of about 4.8 and 40° C, respectively, and the Km for its substrate is about 5 mM sucrose. The enzyme’s native mass of about 270 kiloDaltons is constructed from two identical and heavily glycosylated subunits with a molecular weight of about 135 kiloDaltons. Because extracellular proteins are typically conjugated with oligosaccharide chains (i.e. glycosides) by post-translational modification before they are exported from eukaryotic cells, it is not surprising that the periplasmic form of yeast invertase is indeed a glycoprotein. However, invertase is unusual in that the numerous oligosaccharide chains attached to the two identical subunits account for nearly 50% of enzyme’s native mass (Lampen, 1971).
Table 5. Results of Benedict’s Test
1.6 Pectin Methyl Esterase
Two lots of tomatoes were processed where one lot was blanched and the other was unblanched. The blanched lot of tomatoes was processed at 60oC of boiling water, where the pectin esterase (PE) has higher activity level. During this process, demethylation of the carboxymethyl groups of pectic polysaccharide chains of the tomatoes changed (Tijskens, 1998).
Blanched tomatoes showed better texture and firmness due to the activation of PE and de-esterification of the pectins of the fruit. Also, the formation of the ion-pectin complexes in the cell wall occurred during the processing (Canet, 2004).
30 minutes of processing the blanched lot under boiling water were made, then storaging for 3 days. The final observations were made from the figure below:
Fig. 2 – Final Products After Processing of Tomatoes. (Blanched and unblanched respectively).
In this figure, blanched tomatoes were more pleasant in the eye than the other lot (unblanched). This figure proved that blanching process affects the appearance, firmness and texture of the product. Observations and ratings, based on the following attributes, were listed on the table 6.
Table 6. Mean Scores and Observations of Blanched and Unblanched Tomatoes
The following attributes were evaluated using the 9-point Hedonic scale, 1 = dislike extremely, 9 = like extremely.
Mean scores followed by different letters are significantly different at α<0.05.
Observations of the two lots of tomatoes were made after storage. In appearance, blanched sample appeared more agreeable than the unblanched sample due to the formation of ion-pectin complexes (Canet, 2004). In texture, it has the same reason as in appearance. In aroma, they have almost the same aroma but still blanched sample has more pleasant aroma than the other.
T-test was used to determine if there is significant difference between the two lot samples.After conducting the t-test it was determined that there is a significant difference between the blanched and unblanched tomatoes in all three attributes, as can be seen on table 6. Also based on the mean scores of the samples, it can be said that the blanched tomatoes are preferred in terms of appearance, texture, and aroma.
1.7 Proteases
A. Action on Meat
As can be seen in table 7, all meat samples are significantly different from each other with sample B being the most tender and the control being the least tender based on their mean scores.
Table 7. Mean Scores of 3 Meat Samples in Terms of Tenderness
Tenderness was evaluated using a 5-poin scale, 1 = very tough, 9 = very soft.
Mean scores followed by different letters are significantly different at α<0.05.
The difference in tenderness can be attributed to the enzymes present in pineapple juice and meat tenderizer. As stated by McWilliams (2012), certain proteolytic enzymes can increase the tenderness of less tender cuts of meat. Also according to Bennion and Scheule (2010), Tenderizing compounds containing various enzymes, usually proteases may be used to hydrolyze some of the proteins in meat. Papain is the enzyme present in meat tenderizer (McWilliams, 2012), and Bromelain is the enzyme present in Pineapple juice (Bennion & Scheule, Introductory Foods, 2010). Much of the tenderizing effect is the result of the enzyme destroying the sarcolemma surrounding the myofibrils in the fibers, hydrolyzing actomyosin, and then continuing hydrolytic breakdown of various proteins in the fiber (McWilliams, 2012).
B. Action on Egg Albumin
As can be seen in table # as the time of incubation increases, the distance travelled by albumin also increases. This relationship is evidently illustrated in figure 2.
Table 8. Viscosity of Albumin After 30 Minute Intervals
Fig. 3 – Plot of Incubation Time Versus Distance Traveled. The line represents the direct relationship between the time of incubation and the distance traveled by albumin.
As stated by McWilliams (2012) the enzyme present in meat tenderizers is Papain. Based on the results shown, it can be said that the protease papain in the meat tenderizer is responsible for the change in viscosity of the egg white. The change in viscosity is the result of the enzymatic hydrolysis of the albumin by the protease papain since albumin in egg white is a protein (Bennion & Scheule, 2010). As a result of the hydrolysis of the albumin, peptide bonds were cleaved from the protein (van Oort & Whitehurst, 2010) forming shorter chains (McWilliams, 2012) which resulted in the decreased viscosity of the egg white. This is confirmed by the statement of van Oort and Whitehurst (2010) that normally the hydrolysis of proteins causes a decrease in the viscosity of the protein solution.
C. Action on Gelatin
Lots A – C have the same results because the three of them contain high amount of enzymes called proteases specifically papain in papaya, bromelain in pineapple, and actinidin in kiwi (McWilliams, 2008). The reason why the marbles placed on top of the gelatin slowly moved in through the gelatin is that these proteases already acted upon the gelatin which is a protein made from collagen (Science Buddies, 2012).
The gelatin couldn’t completely hold its shape anymore and resist the force from the marble because the proteases were able to cleave the long gelatin molecules into shorter polypeptides (McWilliams, 2008). The helical structure, which is responsible for trapping water molecules and forming gels, was partially broken down into simpler molecules (Bullerwell and Hagar,2012). The hydrogen bonding that took place between the water molecules and the peptide links or the amino and carboxyl groups on the side chain, started to be chopped into pieces which are far too short to tangle (Gaman and Sherrington, 1989). The gel forming properties of the gelatin were already weakened by the enzymes present in fresh juice (Birch et al, 1977). Nothing happened in Lot D considering no enzymes acted upon the protein substrate.
Table 9. Effect of Proteases on Gelatin
V. Conclusion and Recommendations
It can be concluded that enzymes are a major consideration when dealing with food. The rate of enzyme activity is generally affected by temperature, pH, and amount and type of substrate. Specific enzymes act on specific substrates. The effects of enzyme on food may be desirable, such as the tenderizing of meat, or undesirable, such as the hydrolyzation of gelatin.
When dealing with enzymes, certain precautions must be taken. It is recommended to soak the apples in water to prevent enzymatic browning from occurring. It is also recommended to closely monitor pH and temperature since some enzymes are easily inactivated at low pH, like peroxidase, and at high pH, such as Papain.
VII. References
Books:
Aurand, L. (1973). Food Chemistry.
Bayndirli, A. (2010). Enzymes in Fruit and Vegetable Processing, Chemistry and Engineering Applications. CRC Press: Taylor and Francis Group.
Becket, S. (1995). Physico-Chemical Aspects of Food Processing. Springer.
Bennion, M. (1980). The Science of Food. New York: Harper and Row Publishers, inc.
Bennion, M., & Scheule, B. (2010). Introductory Foods. Upper Saddle Rive, N.J.: Pearson.
Bewley, D. J. (2006). Th eEncyclopedia of Seeds: Science, Technology and Uses. London, UK: Cromwell Press, Trowbidge.
Birch, G. e. (1977). Food Science. UK: Pergamon Press.
Brown, A. (2010). Understanding Food: Principles and Preparation. Cengage Learning.
Canet, W. (2004). European Food Research & Technology. Europe: Springer-Verlag.
Cichoke, A. J. (2002). Enzymes: The Sparks of Life. Book Publishing Company.
deMan, J. M. (1999). Principles of Food Chemistry. Maryland: Aspen Publishers, Inc.
Gaman, P., & Sherrington, K. (1989). The Science of Food. UK: Pregamon Press.
Jackson, R. S. (2008). Wine Science: Principles and Applications. Academic Press.
Lampen, J. (1971). Yeast and Neurospora Invertases, In the Enzymes. New York: Academic Press.
McWilliams M., P. R. (2009). Food Fundamentals, Tenth Edition. Upper Saddle River, New Jersey: Pearson Education, Inc.
Mcwilliams, M. (1997). Foods Experimental Perspectives. California: Prentice Hall, Inc.
McWilliams, M. (2008). Foods: Experimental Perspectives. New Jersey: Pearson Prentice Hall.
McWilliams, M. (2012). Foods: Experimental Perspectives 8th Ed. Upper Saddle River, N.J.: Pearson Prentice Hall.
Queiroz, C. (2010). Polyphenol Oxidase: Characteristics and Mechanisms of Browning Control. Food Reviews International , 361 — 375.
Tijskens, e. a. (1998). Activity of Pectin Methyl Esterase during Blanching of Peaches. Journal of Food Enginnering , 161-177.
Tijskens, L., Rodis, P., Hertog, A., Proxenia, N., & van Dijk, C. (1998). Activity of Pectin Methyl Esterase during Blanching of Peaches. Journal of Food Enginnering , 161-177.
Timmerman, A. (2011). The Isolation of Invertase from Baker's Yeast: An Introduction to Protein Purification Strategies. Wisconsin, USA: Wisconsin Press.
van Oort, M., & Whitehurst, R. J. (2010). Enzymes in Food Technology. Ames, Iowa: Blackwell Publishing Ltd.
Veira, E. (1999). Elementary Food Science 4th Edition. New York: Chapman & Hall.
Whitaker, J. R. (2003). Handbook of Food Enzymology. New York: Marcel Dekker, Inc.
Websites:
Anonymous. (n.d.). Retrieved June 30, 2012, from Catalase and Oxidase Testing: http://www.haspi.org/curriculum-library/A-P-Core-Labs/17%20Lymphatic%20System/Labs%20&%20Activities/Lab%20-%20Catalase%20&%20Oxidase%20Testing.pdf
Anonymous. (n.d.). Ohio University Department of Biological Sciences. Retrieved July 1, 2012, from http://www.biosci.ohiou.edu/introbioslab/
Bullerwell, W. G. (2003). The Science Teacher. Retrieved June 29, 2012, from university of Georgia: http://devacaf.caes.uga.edu/main/lessonPlan/supermarket.pdf
Chapter 9 - Vegetable specific processing technologies. (n.d.). Retrieved June 30, 2012, from FAO Corporate Document Repository: http://www.fao.org/docrep/V5030E/V5030E0q.htm
Chelikani, P., Ramana, T., & Radhakrishnan, T. (n.d.). Retrieved June 30, 2012, from Catalase: A repertoire of Unusual Features: http://medind.nic.in/iaf/t05/i2/iaft05i2p131.pdf
Doe, G. (2010). The Effects of pH on Peroxidse. Retrieved June 30, 2012, from eHow food: http://www.ehow.com/info_8440237_effects-ph-peroxidase.html
Massengale, C. (2011). Biology Activities. Retrieved July 1, 2012, from Cmassengale Web site: http://www.biologyjunction.com/biology_projects.htm
VIII. Appendix
1.6 Pectin Methyl
Esterase
Appearance
Computations:
Tabular value at 95% level of significance = 2.31
6.42 > 2.31 (α = 0.05)
Conclusion: Since the computed t-value is greater than the tabulated value at 95% level of significance, then there is a significant difference between Lots A and B n terms of appearance.
TEXTURE
Computations:
Tabular value at 95% level of significance = 2.31
6.81 > 2.31 (α = 0.05)
Conclusion: Since the computed t-value is greater than the tabulated value at 95% level of significance, then there is a significant difference between Lots A and B n terms of texture.
AROMA
Computations:
Tabular value at 95% level of significance = 2.31
11.86 > 2.31 (α = 0.05)
Conclusion: Since the computed t-value is greater than the tabulated value at 95% level of significance, then there is a significant difference between Lots A and B n terms of aroma.
1.7 Proteases
A. Action on Meat
ANOVA
Ho: There is no significant difference among the 3 samples.
Ha: Atleast one sample is significantly different from the others.
Computations:
a.)
b.)
c.)
d.)
e.)
f.) Degree of Freedom
g.) Mean Square (MS) = SS/df
h.)
i.)
Analysis: Since Fc is greater than Ft, then reject Ho and accept Ha.
Conclusion: At least one of the samples is significantly different from the others.
DMRT
B C A
B-A = 4.44 - 1.78 = 2.66 > 0.68* (k3)
B-C = 4.44 - 3.22 = 1.24 > 0.66* (k2)
C-A = 3.22 - 1.78 = 1.44 > 0.66* (k2)
Conclusion: There is a significant difference among all the samples at 95% level of significance.
Experiment 1: Enzymes
3F1
Group 3
Mañago, Alexis
Orencia, Claudine
Ortazo, Jhonna
Paz, Aujen
Pineda, Jacklyn
Rillo, Rebecca
Rogelio, Rhea
Roldan, Nikka
Roxas, Jeremiah
July 2, 2012
by
jacklynpineda (student)
