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Material Type: Lab; Class: FOOD CHEMISTRY; Subject: FOOD SCIENCE; University: University of Florida; Term: Unknown 1989;
Typology: Lab Reports
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Laboratory 5 Carbohydrate chemistry - pectin and gelation Introduction Carbohydrates in foods are important for their structural, functional and nutritional properties as well as for their participation in many types of chemical reactions. Polysaccharide exist in foods as a diverse array of naturally occurring polymers and a wide variety of chemically modified forms. The physical state and chemical nature of polysaccharide influence the texture, appearance and mouth feel of foods. Gels are semi-rigid, elastic colloidal solutions which entrap large amounts of water. They are important in the food industry for such products like jellies, jams, puddings, etc. Jelly texture is influenced by a number of ingredients and conditions such as pectin - type and concentration; sugar - type and concentration; acid - influences charges of the molecules in the system; and water. The purpose of this exercise is to learn how to make jelly and to explain how the ingredients function in a pectin gel system. Also to compare and contrast product with different treatment variables and evaluate the difference between sensory and physical evaluation techniques. Jelly Formulation and Procedures Materials
64 oBrix. ( Note : some jelly formulations may not reach the desired Brix.)Brix.) h. Remove from heat and skim foam with a spoon. Add lemon juice or aspartame at this time; mix well. I. Take 25 mL in a beaker, allow to cool to 40C, and then measure the pH of the mixture (should be between 2.8 - 3.5). Record the pH measurements. j. Ladle the hot mixture into the jars, leaving Brix.)½” space at the top. Place lids on jars and seal by tightening. k. Invert jars for 1 min and then wipe jar of any spills with a damp cloth. l. Re-invert the jars and label each jar according to the treatment being performed. m. Store jars in a cool, dry area for the next lab section. Variables
1. Sugar - (Control) - Basic formulation using 1,400 g sugar. 2. Aspartame - Basic formulation without sugar; substitute 168 g aspartame for sugar at “step h” 3. Pectin - Low - Follow basic formulation but use 90 mL pectin instead of 180 mL. 4. Pectin - High - Follow basic formulation but use 270 mL pectin instead of 180 mL. 5. Acid - Low - Follow basic formulation but add 20 mL lemon juice with apple juice. 6. Acid - High - Follow basic formulation but add 100 mL lemon juice with apple juice. You may wish to set-up your lab notebook page with the following headings for data entry.
Variables pH Penetration Penetration Average Standard deviation Force #1 Force #
You may wish to set-up your lab notebook page with the following headings for data entry.
_____________________Sensory Scale_____________________ Variables Tenderness Flavor
Sensory Scale:
Descriptors Characteristics 1 2 3 4 5
Flavor very bitter/ mod. bitter/ sl. sweet, moderately very sweet metallic metallic bitter/metallic sweet Tenderness very tender moderately sl. tough/ moderately very tough tender tender tough
Calculations and discussion 1] Using the Instron, determine the force deformation curves for the various jelly products. Each lab group will get a copy of these so make sure you make copies for your lab report. 2] Report the force of penetration. This data will be given to you 3] Rate each product numerically using the sensory analysis scale above for the following: a) Tenderness Report the averages of all values recorded for each sample Calculate the standard deviation for each average value and comment on the variation b) Flavor Report the averages of all values recorded for each sample Calculate the standard deviation for each average value and comment on the variation 4] Plot the average tenderness (x-axis) vs. the average Instron force (y-axis). Force values will be determined using the Instron and data will be distributed to the class. Draw a trend line through the data and report the correlation coefficient, and comment on how good the variation was between the sensory and instrument data. Questions for discussion and conclusion