Determination of Different Factors That Affect the Rigidity of Starch Gels - Research Proposal Example

DETERMINE DIFFERENT FACTORS THAT AFFECT THE RIGIDITY OF STARCH GELS (name) (tutor) (course) (institution) (date) Introduction / background information Starch is a form of carbohydrate in which plants store their energy. After plants make their own energy from sunlight via photosynthesis, it is converted into starch which is then stored in plant tissues. There are various plant tissues where starch is stored in plant depending on the type of plant for instance seeds in wheat and maize, roots for instance in cassava, arrowroots and sweet potatoes, fruits for example banana and in sago palm in the pith (Schenck & Hebeda 1992). Starch from different plant sources gelation properties. Starch is the most available diet on earth. It has various different functions that include gelling, thickening, mouth feel enhancing and also emulsification. An example of application of starch in food industries includes frozen foods, canned foods, beverage emulsification, baked foods, encapsulation, snacks, confections amongst others (Mason, 2009). Various types of starch will impact on the characteristics of viscosity of the starch paste and the strength of the gel that will form. It is worth noting that in native starches, the greater the amount of amylopectin, the more the starch viscosity while higher amylase content makes the paste firmer i.e. with greater strength (Johnson, Davis, & Gordon, 1990 p.290). Amylose and Amylopectin In natural form, starch occurs as an insoluble polysaccharide made up of glucose monomers as building blocks. Glucose is processed via photosynthetic process from water and Carbon Dioxide in presence of sunlight and Chlorophyll. Amylose is made up of linear (un-branched) glucose monomers joined via α(1-4) linkages. For instance 1/5 starch from potatoes is made up of amylase while the 4/5 is made up of amylopectin. Amylopectin refers to starch which is made up glucose monomers joined by α(1-4) glycosidic linkages but with D- glucan branch linked at α(1-6) linkages( Mason at el 2011). The properties of starch for instance gelatization viscosity; retrogradation, temperature and solubility are highly impacted by the intensity of the branching found in amylopectin starch. This is evident from the fact that waxy starches have about 1/10 amylose while the remaining potion is made up amylopectin while regular starch have amylase composition ranging between 20-30% while the rest is amylopectin. The disparity in the characteristics of both can be explained the impact of gelation. Gelation in hot water is the most remarkable characteristic of starch. Starch absorbs about 30% their own weigh of water. As the temperature increases to about 55 ℃ most of the starch starts losing their native structure which allows it to imbibe more water as it tenderises and then swells. After this, partial separation of amylase and amylopectin occurs resulting to gel formation as the starch in water thickens. Modified starch and native starch Native starch refers to the starch that is generally prepared in food via cooking in most of the homes and then consumed after shot-time cooking. Native starches have been known for their properties for instance susceptibility to acidity, lower stability, susceptibility to heating and so on. Therefore on industrial scale, modified starch is the most preferable form of starch owing its stability. Starch can be modified through two ways that is physical modification and chemical modification all aimed at improving starch stability. Chemical modification of starches entails: oxidation, cross-linking, conversion and stabilization. Stabilized starches have gels that exhibit less firming once it ages, less temperature of gelatinization, good stability and clarity. Aim The aims of this experiment are to determine the effect of the following on the rigidity of starch gels: Amount of starch Type of starch Addition of sugar Addition of salt Incorporation of air Effect of blending and agitation Effect of incomplete gelatinisation Effect of dextrinisation Effect of storage Effect of freezing Interactions On addition of different ingredients on starch for instance acid, sugar or salt, the properties of starch are greatly impacted upon. Adding acid The pH of most acidic foods ranges between 4-7. As long as the pH is within this range, it has little or no effect on the starch in the food. Acid hydrolysis occurs when pH level goes below this range. As the acidity increases, the amylase content and the power to swell decreases while the solubility of starch increases. From this then one can conclude that acid results to less gel formation process and production of jelly that exhibit. The increased solubility here can be attributed to fragmentation due to acidic hydrolysis. Addition of sugar The addition of sugar to starch increases the temperature of gelatinization, inhibits the granular swelling and also reduces the viscosity. The hike in the temperature of gelatinization is attributed to binding of sugar molecules to the starch chains. Sugar presence also reduces the activity of water and hence the water that is available for the process of geltinization. When sugar is introduced to starch after boiling it hikes the viscoelaticity of the starch gel. Retrogradation of starch is also reduced on sugar addition. Method Control or reference sample 1 Tablespoon corn flour) C.P.= control proportions ½ cup water) Method: 1. Blend starch with half the measured water 2. Add remaining water and bring to the boil, stirring constantly. 3. Simmer for 1 minute. 4. Pour into wetted jelly mould (dariole) Variables Experimental Procedure 1. Amount of starch a) Cornflour Use ½ cup water and 2 teaspoons, 1 b) Arrowroot tabs,1 ½ tabs and 2 tabs of starches a, b, c c) Medium wheaten flour 2. Blending C.P. and method except add dry ingredients to boiling water. 3. Effect of agitation a) None C.P. but do not stir once on the heat b) Constantly C.P. stir vigorously 4. Types of Starch a) Soften wheaten flour C.P. b) Medium wheaten flour ½ cup water plus 1 Tab of each of the c) Hard wheaten flour Starches listed d) Cornflour e) Arrowroot f) Rye flour g) Rice flour h) Potato starch i) Custard powder 5. Effect of incomplete gelatinisation on starch gels C.P. Cook until sauce begins to thicken. Do not bring to the boiling point. Record temperature at which mixture begins to thicken. 6. Incorporation of air into starch gels a) Cornflour C.P. and method. Prior to pouring mixture into Mould, beat with hand held beaters On high speed 3 minutes. 7. Effect of sugar on starch gels a) Cornflour C.P. and Method. a) Add 1 tab, 2 tabs and 3 tabs sugar to starch b) Add 1 tab, 2 tabs, 3 tabs sugar after boiling 8. Effect of acid on starch gels a) Cornflour C.P. and method a) Add 1 tab, 2tabs, 3 tabs vinegar to starch when Blending. b) Add 1 tab, 2tabs, 3tabs vinegar to gelatinised Starch mixture. N.B. Keep water and vinegar to equal ½ cup 9. Effect of sugar and acid on starch gels C.P. and method a) Cornflour a) Add 1 tab, 2 tabs and 3 tabs sugar and vinegar to starch when blending b) Add 1tab, 2tabs and tabs sugar and vinegar to mix after boiling 10. Effect of dextrinisation a) Use of moist heat cooking: a) Make up C.P. and method. (i) cornflour Use a fitting lid and simmer 10 minutes. b) Use of dry heat cooking: Dextrinise starch by: Frying roux of equal parts oil and starch medium wheaten flour Until golden in colour then make up C.P. and method Heat dry starch until dextrinised Then make up C.P. and method 11. Effect of freezing As for control, cool, cover and freeze for 1 week. Thaw gel prior to evaluating for gel quality Results   1tab blend sag% 2tab blend sag% 3tab blend sag% 1 tab boiled sag% 2tab boiled sag% 3tab boiled sag% Sugar 2.5 3 3.8 3.3 3.8 3 Acid 3.8 4.2 3.3 4 4.2 3 Sugar + acid 5.2 5.5 5.5 4.5 4.7　 4.9               Control 4.5           Table1, Sugar, Acid and Sugar+Acid of sag %. Variables were added when blending and after boiled. Terms and definitions Amylose: is a straight chain type of starch made up of glucose polymers. Amylopectin: these are starch molecules with the main branch made up of alpha 1,4 glucose links and alpha-1,6 at branch points. Gelatinization- this refers to the process of formation of gels in starch. It involves absorption of water and disruption of the starch structure. Sugar- Sugar in this case refers to monosaccharide or disaccharides that when added to the starch gel reduces the viscosity and firmness of gel due to their high competitively for sugar when compared with the starch (Bean, & Yamazaki, 1978). Dextrinization is a process in which dextrins are formed. Dextrins: refer to a mixture of soluble substances that result from partial decomposition of starch by acid, enzyme or heat. Freezing: Subject the gel to temperatures below zero degree (melting point of water). Thawing: This is the process in which frozen gel is subjected to temperature above the melting point of water to observe the difference. Agitation: This refers to stirring or physically stirring a great speed. Incomplete gelatinisation: partial formation of gel from some of the starch. Discussion and Conclusion In the gel that was made up of potato, the microstructure was affected by the freezing process while that of wheat was impacted upon by both the thawing and freezing processes. It was noted that the pore size that increased as a result of the ice molecules hiked with higher rates of freezing on both samples. On heating, the gels regained their structures owing to the modification of the structure as the ice molecules melted hence restructuring and reversing to their actual forms (Sinitsyn, et al., 2010 p.1888). The incorporation of air on dough mixture inhibits the process of gelatinization. This leads to a less viscous and stiff starch mould. In the gel that was made up of potato, the microstructure was affected by the freezing process while that of wheat was impacted upon by both the thawing and freezing processes. It was noted that the pore size that increased as a result of the ice molecules hiked with higher rates of freezing on both samples. On heating, the gels regained their structures owing to the modification of the structure as the ice molecules melted hence restructuring and reversing to their actual forms (Sinitsyn, et al., 2010 p.1888). Amylose starch molecules are the ones that are involved in gel formation process. This is due to orientation of their linear molecules parallel to one another after which they move close to one another hence bonding to form gels. Due to their ability to sleep alongside one another, these gels can be cooked in paste form for instance pancake. Amylase does not contribute to the viscosity of the gel to a greater effect. This explains why the wheat flour formed paste with lot of ease while the corn flour and arrowroots which are mainly made up of amylopectin with bulk of side chain formed a rigid but gel-less material (Johnson, Davis, & Gordon, 1990 p.292). The addition of sugar to a typical gelatine made of starch, the gel strength and viscosity decreases because sugar (monosaccharide/ disaccharides) competes for water with starch. Since sugar has high affinity for water than starch, there will be no water for gelatinization hence reduction in viscosity and strength of the gel (Johnson, Davis, & Gordon, 1990 p.293). Dextrinization may result after addition of acid to the starch gels. After addition of vinegar (an organicacid) o a starch gel in early periods of gelatinization process, starch will dextrinize. This means that there will be formation of dextrins from partial degradation of amylopectin therefore it would be as branched as before. Also, the amylase will break into small pieces of less length. This finally results to less gel strength and decreased starch paste viscosity (Perry et al., 2007). As mentioned earlier on, acid leads to dextrinization while sugar competes for the water with the starch in the gel therefore reducing its stiffness and viscosity. Acid hydrolysis increases with increase in temperature (on heating). This results to less think starch mixture in comparison with the one made with the same amount of starch with no or one of these ingredients i.e. sugar or acid. Freezing the gels translates to formation of ice from the water molecules trapped between the starch molecules in the gel. The thawing process reverses the physical state of the water molecule to liquid and hence regaining of the structure. Freezing the gels translates to formation of ice from the water molecules trapped between the starch molecules in the gel. The thawing process reverses the physical state of the water molecule to liquid and hence regaining of the structure. Incomplete/ partial gelatilization refers to the situation were the total starch in the mixture is not in the gel state due to partial process of gelatization. This means that some of the starch in the mixture is in the particulate form and not in the whole gel. This affects the viscosity of the gel and also its stiffness since all the starch in not bound giving the dough a rough texture (Nugent, 2005, p 50). Implications / Relevance to food preparation Excessive addition of sugar in the starch solution makes it to thicken. Therefore as one requires more sugar, it is advisable to do it after the gelatinization process has occurred. Acid is added to starch as a tenderizer but excessive addition of acid results to reduction of water holding capacity that might result to leaking of liquid therefore acid addition should be done after complete gelatinization. In source preparation therefore, acid sugar mixture should be introduced in the process of blending since adding after boiling hardens the gel to the extreme levels. Problems in Design There were breakages that occurred after heating and this affected the measured result therefore it is recommendable to employ another method when such experiments are carried out in future. The pH of acidity was not determined and this cannot be ignored in impacting on the starch properties. The time of heating was non-uniform and therefore there might have been incidences of under heating or overheating and this subsequently affected the results. The importance of rigidity was exaggerated at expense of other parameters in respect to addition of sugar and acid for instance variables like aging, time of heating, gelation temperatures and various pH should be put in consideration in future for more objective results. In the course of conducting these experiments, various challenges manifested and it is these challenges that we can attribute the results disparity between the expected results and the ones that were got. References 1. Johnson, J.M., E.A. Davis, and J. Gordon. 1990. Interactions of starch and sugar water measured by electron spin resonance and differential scanning calorimetry. Cereal Chemistry 67(3): 286-291. 2. Bean, M.M. and W.T. Yamazaki. 1978. Wheat starch gelatinization in sugar soutions. I. Scurose: Microscopy and viscosity effects. Cereal Chemistry 55(6): 936-944. 3. Brown, W. H.; Poon, T. (2005). Introduction to organic chemistry (3rd ed.). Wiley. 4. Sinitsyn, A. et al. (2010). "Thirty thousand-year-old evidence of plant food processing". Proceedings of the National Academy of Sciences 107 (44): 1885–9 5. Mason, WR 2011,’ Starch use in food’, in BeMiller,J and Whistler, R(ed.), Starch chemistry and technology , Academic press, Viewed 10 October 2013. 6. 7. Perry, George H; Dominy, Nathaniel J; Claw, Katrina G; Lee, Arthur S; Fiegler, Heike; Redon, Richard; Werner, John; Villanea, Fernando A et al. (2007). "Diet and the evolution of human amylase gene copy number variation". Nature Genetics 39 (10): 1256–60. 8. Nugent, A. P. (2005). "Health properties of resistant starch". Nutrition Bulletin 30: 27–54 Read More