Rheological Properties Of Food And Agricultural Products b4f5b

Date : Friday, May 27th 2016 Place : Food Process Laboratorium Time : 09.30 – 11.00

Assistant : 1. M. Khoirur Rozikin (F14120017) 2. Putri Layla Andini (F14120079) 3. Hendi Okta K. (F14120100) 4. Sri Ichfana H. (F14120114)

REPORT FOOD PROCESS ENGINEERING “Rheological Properties of Food and Agricultural Products”

Arranged by : Farhandhika Akbar F14130046

Supervised by: Dr. Nanik Purwanti, S.TP, M.Sc

DEPARTMENT OF MECHANICAL AND BIOSYSTEM ENGINEERING FACULTY OF AGRICULTURAL ENGINEERING BOGOR AGRICULTURAL UNIVERSITY BOGOR 2016

INTRODUCTION Background Rheology is the branch of science that deals with the flow and deformation of materials. Rheological instrumentation and rheological measurements have become essential tools in the analytical laboratories of food companies for characterizing ingredients and final products, as well as for predicting product performance and consumer acceptance. The materials under investigation can range from low-viscosity fluids to semisolids and gels to hard, solid-like food products. A knowledge of the rheological and mechanical properties of various food systems is important in the design of flow processes for quality control, in predicting storage and stability measurements, and in understanding and deg texture. Quality attributes such as spread-ability and creaminess are extremely important to the acceptance of semisolid food products by consumers. In the case of food materials, texture is a key quality factor. Rheological behavior is associated directly with textural qualities such as mouth feel, taste, and shelf-life stability. As an example, rheological measurements are useful in storage stability predictions of emulsion-based products such as mayonnaise and salad dressings (Peter 2000). Objectives The objectives of this experiment are to measure large deformation (uniaxial compression) of a food product and an agricultural productand find some rheological properties of food and agricultural products. METHODS Time and Place This practice held on Friday, May 27th, 2016 at 09:30 to 11:00 am in Food Process Laboratorium, Faculty of Agricultural Technology, Bogor Agricultural University. Material Tools 1. Universal Testing Machine 2. Calipers Ingredient 1. Jicama

Procedure Start Prepare the jicama

Cut jicama into cylinder form with the ratio of diameter and heigh at 1-2.5 range, 2 specimen Make the UTM ready for measurement and set the safety level Set the maximum load of 0.5 kN and choose filename P. Compression

Set the maximum load of 0.5 kN and choose filename P. Relaxation

Put a little bit paraffin oil on the plate before placing the specimen

Put a little bit paraffin oil on the plate before placing the specimen

Set the upper plate above the surface of specimen

Set the upper plate above the surface of specimen

Make sure that the load deform and crosshead are zero

Make sure that the load deform and crosshead are zero

Press the start button

Press the start button, wait until the program end

Stop button when the specimen is broken

Save the data

Save the data

END

RESULT AND DISCUSSION

Picture 1 Graph of Uniaxial Compression Test

Picture 2 Graph of Uniaxial Compression Stress

Picture 3 Graph of Modulus Young

Picture 4 Graph of Secant Modulus

Picture 5 Graph of Tangen Modulus

Picture 6 Graph of Relaxation Test

DISCUSSION This practice is learned about engineering stress, true stress, engineering strain. Engineering stress is the applied load divided by the original crosssectional area of a material. True stress is the applied load divided by the actual cross-sectional area (the changing area with respect to time) of the specimen at that load. Definition of engineering strain is the amount that material deforms per unit length in a tensile test, also known as nominal strain. True strain equals the natural log of the quotient of current length over the original length. Engineering stress-strain would be the force divided by the original area for the duration of the test. True stress-strain would be the force divided by the actual areal, at every time that a measurement is taken. Jicama belongs to agricultural products which contains 75-80% water (Sahin 2006). This practice aims to find some rheological properties of food and agricultural products. The materials (jicama) are viscoelastic so the stress-strain curve is nonlinear. The parameters used in this lab include the relationship between stress-strain, young’s modulus, secant modulus, tangent modulus, and the relation between the stress and relaxation time. Secant modulus is the slope of a line connecting the origin of the stressstrain curve and any point (example 5% strain) on the curve. Secant modulus depending on the strain at the which it is evaluated. The value of the secant modulus can be seen in fig 4. In fig 5 can be seen the results of tangen modulus, tangen modulus is the slope of a line drawn tangent to the stress-strain curve at a particular stress (or strain level) when this point falls within the linear part of the stress-strain curve, the tangent modulus is equal to young’s modulus. Fig 6 shows the behavior of a material under stress relaxation. The relaxation test consists of two steps the straining step and relaxation step. The time to apply the step strain is namely the rise time. Relaxation time is the rate of stress decay which is the quantification of a material characteristic time. CONCLUSION In this practice, we can determine the rheological properties of food and agricultural products. Materials used in this lab is jicama. Every type of consumable food products has some rheological characteristics. Today, rheological instrumentation is considered a required analytical tool utilized by food scientist on a daily basis. Parameters used include the Young’s Modulus, secant modulus, tangent modulus, relation between stress-strain, and the relation between the true stress-strain and engineering stress-strain. REFERENCES Peter KW. 2000. Rheology of foods: New techniques, capabilities, and instruments. [internet] http://www.atsrheosystems.com/articles/food_paper.php. (June 2nd 2016). Sahin S. 2006. Rheological properties of food. [internet] http://linkspringer.com. (June 2nd 2016).

ATTACHMENT

Picture 7 Jicama

Picture 9 Calipers

Picture 8 Universal Testing Machine