Ultrasound Velocity to Measure Fillet Fat Content Abstract The objective of this research is to develop a reliable non invasive method to measure fat content in fillet using ultrasound A-Mode scan. The results of the fat measurement from this non invasive method were then compared to the results of fat measurement using a proven method. The Soxhlet method is a standard fat measurement procedure recommended by the Association of Official Analytical Chemist (AOAC). The samples used in this investigation are chicken, meat and fish fillets. The experimental results showed that there is correlation between fat content and the measured ultrasound velocity travelled in the sample. This indicates that fat measurement using the ultrasound A-Mode scan technique can be used to determine fat content in fillet with reasonable accuracy by using accurate tools for the measurement process and increasing the data acquisition during the experiment. Keywords Fillet, Ultrasound velocity, Fat content I. INTRODUCTION Fat is very important to our body but consuming it exceedingly, will contribute to health complication such as heart disease, high blood pressure and obesity [1]. One of the major fat sources is meat either chicken, beef or fish. However most of these methods, for example the Soxhlet Method, cause the destruction of the food itself. A number of researchers have attempted to develop non invasive techniques to measure fat in food. For example, Buniyamin [2, 3], used near infrared Radiation (NIR) technique to measure fat content in food products such as fish fillets and burgers with some success. The research presented in this paper attempts to develop a reliable non invasive method to measure fat in meat type fillet using ultrasound. A study by Sriyani Jayasooriya [4] stated that conventional application of ultrasound such as medical imaging; cleaning and measuring fat depth of carcasses are well established. That statement is well proved by a lot of researchers and application nowadays. Ultrasound velocity measurement itself is not new since there is a research that uses ultrasound technique for fluids characterization [7]. R.A. Shannon [6] in his research, used ultrasound velocity as a tool to measure and determine fat content in salmon fillet muscle. He used Panametric 500PR pulser-receiver to produce ultrasonic pulse and two 2.25 MHz single-element transducer to transmit and receive ultrasonic pulse. 12 numbers of samples from two difference supplier is used in her study. The result found that ultrasound velocity in a sample can be affected by the non-constant density due to the in-homogeneities of fat content in salmon muscle [6]. The research presented in this paper, attempts to measure fat in a natural non-homogenous substance; that is meat fillet from various type of animal; chicken, beef and fish. The sample is naturally nonhomogenous due to natural variations in the tissue itself. II. METHODS AND SAMPLE The meat fillet fat was first measured using the ultrasound A-Mode Scan method and then using the standard Soxhlet method. The Soxhlet method is a traditional method for the analysis of fat that was developed by a German chemist Franz von Soxhlet in 1879 [5]. The results from the Soxhlet measurement were used to validate the result from the ultrasound velocity measurement method. Ten (10) pieces of meat fillet each from chicken, beef and fish from a Malaysian supplier was used. The fat content of the meat fillet was measured at room temperatures. Since the samples were frozen during storage, they were left for thaw before being used for experiment. Samples reach the room temperature defined as 27 0 C after 5 hours of thawing process. Water content in frozen state will give a slight effect on the ultrasound velocity. It has been shown that ultrasound velocity increase approximately 8% after the sample is thawed [8]. Figure 1 shows the samples exposed to room temperature. 69
Figure 2: Fat measurement rig C B A Figure 1: Chicken, beef and fish fillet III. ULTRASOUND MEASUREMENT METHOD The fat measurement rig for velocity measurement experiment is shown in Figure 2. The rig is used to positioning the sample between the ultrasound transmitter and receiver ultrasound. It can hold the sample with maximum thickness of 60mm. Ultrasound Echoscope GAMPT-Scan is used to generate ultrasound pulse. 2MHz ultrasound transmitter is used to transmit the ultrasound wave and 4MHz receiver for receiving transmitted ultrasound wave. To increase the sound conductivity, ultrasound gel is applied to the sample before measurement is start. Computer was used to log the data collected. The complete connection for experiment is shown in Figure 3. With label, A is fat measurement rig, B is Ultrasound Echoscope GAMPT-Scan and C is the computer. Figure 3: Connection for ultrasound velocity measurement method The set-up was built to enable the ultrasonic pulse to enter and pass through the filet. Theoretically, ultrasonic pulse velocity travel through a medium depends on the density of the medium. Medium density is majorly influenced by its meat, fat and water content assuming that no bones exist in the fillet that is measured. For this experiment, it is assumed that the water content for all samples is same after undergoing the same thawing process and that only fat content will vary in the samples. The receiver will detect the ultrasonic pulse travelled through the samples. The time-of-flight of ultrasonic pulse is recorded to measure the ultrasound velocity in the samples. Equation {1} is used to measure the velocity. {1} 70
The ultrasound velocity for each sample, was measured 5 times, at 5 difference locations and was then averaged [4]. IV. VALIDATION The fat in all the samples were then extracted and measured using the Soxhlet method to investigate the accuracy of the fat detection using the ultrasound velocity measurement method. In the Soxhlet method, the samples were first dried, grinded, weighed; and the fat was then collected using a chemical reactant apparatus setup as in Figure 4. Fat percentage is calculated by using equation {2}. {2} using linear regression line, the value of coefficient of determination, R 2 was obtained. In order to find the correlation between percentage of fat and ultrasound velocity ms -1, the value of the correlation coefficient, R was first determined. Table 1 shows the rule of thumb that was used, where the relationship between both parameters was determined based on the value of R. The value of R shows how much the point fits the regression line. The closer to 1.0, the better fits the regression line and thus shows that the relationship between both parameters is strong. TABLE I RULE OF THUMB FOR CORRELATION COEFFICIENT. Value of correlation coefficient, R Strength of relationship -1.0 to -0.5 or 0.5 to 1.0 Strong -0.5 to -0.3 or 0.3 to 0.5 Moderate -0.3 to -0.1 or 0.1 to 0.3 Weak -0.1 to 0.1 None or very weak A. Results for Chicken fillet samples. Figure 5 shows the ultrasound velocity versus method for Chicken fillet. Figure 5: Graph of ms -1 versus %fat for Chicken fillet. Figure 4: Soxhlet Process V. RESULTS From the graph, there is the trend of decreasing in ultrasound velocity in increasing of fat content. By using linear regression, the value for R 2 is obtained. All data from ultrasound velocity measurement method were plotted in graphs that plot ultrasound velocity, ms -1 versus percentage of fat (%). By 71
By using the rule of thumb, with r=0.411 and n= 10, there is moderate linear correlation between ultrasound velocity and fat percentages in chicken fillet. B. Results for beef fillet samples. Figure 6 shows the ultrasound velocity versus method for Beef fillet. With value of r= 0.221 and n=10, the correlation between ultrasound velocity and fat content in fish fillet is weak. Figure 7: Graph of ms -1 versus %fat for Fish fillet. VI. DISCUSSION AND CONCLUSION Figure 6: Graph of ms -1 versus %fat for Beef fillet. From the graph, there is the trend of increasing in ultrasound velocity in increasing of fat content. This graph slightly does not satisfy the theory. For value R 2 = 0.079, With value of r= 0.281 and n= 10, the graph did not satisfy the theory and showed weak correlation between ultrasound velocity and fat percentages in meat fillet. C. Results for Fish fillet samples. Figure 7 shows the ultrasound velocity versus method for Fish fillet. From the graph, there is the trend of increasing in ultrasound velocity in increasing of fat content. This graph satisfies the theory. For value R 2 = 0.049, Result from the experiment can be said to be slightly inaccurate due to several measurement weaknesses during the experiment. The measurement weaknesses mention here are tools for thickness measuring and in-homogeneities of fat concentration in a sample. Tools used for thickness measurement is a standard ruler with only 0.1cm dimension. Since the ultrasound velocity in sample is higher than 1000m/s, more accurate tools is needed to measure the sample thickness. This problem can be solved by using micrometer. Inhomogeneities fat content will affect the measurement accuracy since variation in fat content in a sample will affect the ultrasound velocity. This problem can be solved by using more samples with more reading taken from each sample. This paper showed there is a trend of decreasing ultrasound velocity with increasing fat content in the sample. This trend can be seen on chicken fillet and fish fillet result. Although the results obtained satisfy the theory, the correlations between two variables are moderates and weak. For meat fillet, result obtained did not satisfy the theory. From early observation and analysis, it due to in-homogeneities of fat concentration is sample and inappropriate tools used to measure sample thickness. This phenomenon and action can contribute to the error during the experiment. Illustration below show how weakness in fat measurement occurs due to in-homogeneities of fat concentration in the sample. As shown in Figure 8, 72
on the fish fillet picture, the mark x indicates the position with high fat concentration and the circle marks the place where the transducer is placed. ACKNOWLEDGMENT The authors gratefully acknowledge and thank University Teknologi Mara (UiTM) for the Research Intensive Faculty Grant. In addition, the authors would also like to thank the medical laboratory technician, Mr. Mohamad Azhar Johari and the Food Technology Laboratory assistant, Mrs. Nor Suhadah Mohammad Samri for their support throughout this project. REFERENCES Figure 8: Fish fillet As shown, the transducer is placed at different 5 points and thus do not fully represent (or accurately) the fat content in the fish fillet as for this type of fish, the fat is concentrated at the edges. This will contribute the error when compared with Soxhlet method result. This weakness also occurs in measurement for meat fillet and chicken fillet. In order to minimize this weakness, more reading should be taken from the sample. The effect of variation in fat concentration in sample also can be minimized if a large number of samples used Proper tool for measuring sample thickness is necessary. Small error in measuring sample thickness will give huge effect to the ultrasound velocity since the time-of-flight is in s unit. Tools with high dimension and accuracy such as micrometer should be used. [1] CHOLESTEROLDATABASE.COM. Saturated Fat Source: List of Food High in Saturated Fat and Total Fatty Acids (beef, pork, chicken). Internet: http://www.dietaryfiberfood.com/fat-saturated.php, [December 1, 2011] [2] Norlida Buniyamin, Ringgau D., Mohamad Z., Murat Z. H., Non- Destructive Fish Fat Detection Using Infrared Sensor in 2011 International Conference on Food Engineering and Biotechnology (ICFEB 2011), Bangkok, Thailand. Vol. 9, pp 33-37, 7th 9th May 2011. [3] Norlida Buniyamin, M.A. Mohd Shari, M.H. Abdul Halim, R. Sam, Using Infrared Radiation to Measure Burger Fat Content, Proceedings of the 2012 International Conference on System Engineering and Technology (2012 ICSET), September 11-12, 2012, Bandung, Indonesia. [4] Sriyani Jayasooriya, Dr. Bhesh Bhandari, Dr. Peter Torley, Dr. Bruce D Arcy. Ultrasound in Meat Processing. Internet: http://www.mintrac.com.au/files/newsletter/sriyani%20jayasooriya.pd f, [December 2, 2011] [5] M. Hazwan Abdul Halim, Ultrasound velocity measurement to determine fat content in chicken, beef and fish fillet, in Faculty of Electrical Engineering, Thesis, Bachelor of Elec. Engineering. Shah Alam: University Teknologi MARA (UiTM), 2007, pp. 60. [6] R.A. Shannon, P.J. Probert-Smith, J.Lines, F. Mayia. Ultrasound Velocity Measurement to Determine Lipid Content in Salmon Muscle: the effect of mysepta. January 8, 2004 [ November 24, 2010] [7] Malcolm J.W. Povey. Ultrasound Techniques for Fluids Characterization, Internet: http://www.sciencedirect.com/science/article/pii/b9780125637305500 003#PDFExcerpt, October 18, 2007 [December 5, 2011] [8] REZA GHAEDIAN, ERIC ANDREW DECKER, DAVID JULIAN McCLEMENTS. Use of Ultrasound to Determine Cod Fillet Composition. Journal of Food Science, Internet: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2621.1997.tb04415.x/abstract, July 20, 2006 [December 5, 2011] 73