Accepted Manuscript Novel 2D and 3D Imaging of Internal Aerated Structure of Ultrasonically Treated Foams and Cakes using X-ray Tomography and X-ray Microtomography M.C. Tan, N.L. Chin, Y.A. Yusof, J. Abdullah PII: S0260-8774(16)30084-X DOI: 10.1016/j.jfoodeng.2016.03.008 Reference: JFOE 8506 To appear in: Journal of Food Engineering Received Date: 20 August 2015 Revised Date: 5 March 2016 Accepted Date: 20 March 2016 Please cite this article as: Tan, M.C., Chin, N.L., Yusof, Y.A., Abdullah, J., Novel 2D and 3D Imaging of Internal Aerated Structure of Ultrasonically Treated Foams and Cakes using X-ray Tomography and X- ray Microtomography, Journal of Food Engineering (2016), doi: 10.1016/j.jfoodeng.2016.03.008. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. 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ACCEPTED MANUSCRIPT 1 Novel 2D and 3D Imaging of Internal Aerated Structure of Ultrasonically Treated Foams 2 and Cakes using X-ray Tomography and X-ray Microtomography 3 4 1Tan, M.C., 1Chin, N.L.*, 1Yusof, Y.A., and 2Abdullah, J. 5 6 1Department of Process and Food Engineering, Faculty of Engineering, Universiti Putra 7 Malaysia, 43400 UPM Serdang, Selangor, Malaysia. 8 2Plant Assessment Technology Group, Malaysian Nuclear Agency (Nuclear Malaysia), Bangi, 9 43000 Kajang, Selangor, Malaysia. 10 11 *Corresponding author: Tel.: +603 89466353; fax: +603 89464440 12 Email address: [email protected] 13 14 15 16 17 18 19 20 21 22 23 MANUSCRIPT 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 ACCEPTED 40 41 42 43 44 45 1 ACCEPTED MANUSCRIPT 46 Abstract 47 The aerated structure of ultrasound treated foams and its resulted cake structures were examined 48 using X-ray tomography and X-ray microtomography, leading to highly contrasted two- 49 dimensional (2D) and three-dimensional (3D) images. Through these imaging techniques and 50 software approaches, the effect of ultrasound treatment on the bubble size distribution was 51 distinguished clearly. Microbubbles in foam which were in the size range of 0 to 0.00125 mm 3 52 and in cakes which were in the range of 0 to 1 mm 2 increased by 48% and 29% respectively after 53 ultrasonic treatment at a frequency of 20 kHz. 54 55 Keywords 56 X-ray microtomography; X-ray tomography; 2D image; 3D image; Aerated foam; Cake 57 58 1. Introduction 59 Imaging is one of the direct methods to visualize and analyze bubbles or cells matrix in food 60 products. Traditionally, bubble sizes in cake batter have been examined by taking photographs of 61 aerated batter spread out on a thin film using micrMANUSCRIPToscope-linked camera (Niranjan and Silva, 62 2008; Sahi and Alava, 2003) or tinted cross sections of cake samples at 5 mm thickness with 63 black oil-based ink delineating pore walls using a digital camera (Barrett and Ross, 1990; Kocer 64 et al., 2007; Lange et al., 1994; Smolarz et al., 1989). The photographs were analyzed using 65 imaging software. The three-dimensional structure was then drawn based on the assumed 66 symmetrical two-dimensional images. This imaging technique is a destructive method and it also 67 arises problems in generating a sharp image due to inaccurate measurement of the walls and 68 curvature effects (Niranjan and Sahu, 2009; Niranjan and Silva, 2007). As such, bubble size 69 distribution is difficult to be measured and analyzed (Niranjan and Silva, 2007), especially with 70 the traditional imaging method. The poorly understood aerated foods’ structures, however, did 71 not stop the evolutionaryACCEPTED food manufacturers from seeking to exploit the versatility of bubbles as 72 a food ingredient (Campbell and Mougeot, 1999). Air is an important ingredient in aerated foods 73 such as beverages, baked, dairy, egg and confectionery products to enhance the appearance, 74 texture, and digestibility of the food products (Campbell and Mougeot, 1999). For bakery 75 products, air attribution has a significant influence on the quality of the final product because the 2 ACCEPTED MANUSCRIPT 76 cells in the final products are originated as bubbles in the batter during the mixing stage, and that 77 integrity of air cells would determine the volume of the final products (Edoura-Gaena et al., 78 2007). 79 80 The rapid developments in technology have improved those traditional imaging methods into 81 more effective and accurate ones. Today, information about microstructure of food products and 82 ingredients can be obtained using various imaging techniques such as bright-field, polarizing and 83 fluorescence light microscopy, confocal scanning laser microscopy and electron microscopy. A 84 relatively new technique, X-ray tomography and more advanced X-ray microtomography can 85 probe the microstructure of samples non-invasively up to a few millimeters and down to few 86 micrometers of resolution, the advantages also include observations under environmental 87 conditions without sample-disturbing preparations which occur in the fluorescence light 88 microscopy and electron microscopy techniques (van Dalen et al., 2003). The X-ray tomography 89 and X-ray microtomography techniques have emerged as important and useful non-invasive 90 imaging tools to measure the internal microstructure of cellular food products. X-ray 91 microtomography has been attempted for use to generate the 3D images of porous rice kernels 92 and whipped cream (van Dalen et al., 2003), aeratedMANUSCRIPT chocolate, mousse, marshmallow and 93 muffins (Lim and Barigou, 2004), bread crumb (Falcone et al., 2005; Moussawi et al., 2014), 94 extruded rye bran (Alam et al., 2013), dough (Bellido et al., 2006), biscuit, breadstick, emulsion 95 and coffee (Laverse et al., 2012), biopolymer foams (Trater et al., 2005), ice crystal formation in 96 strawberry (Nurzahida et al., 2010), banana slices (Léonard et al., 2008), apple tissue (Mendoza 97 et al., 2007), mango during ripening (Cantre et al., 2014) and processed meat (Frisullo et al., 98 2009) while X-ray tomography has been used to generate images of extruded starch (Babin et al., 99 2007), bread crumbs (Lassoued et al., 2007), cornflakes (Chaunier et al., 2007) and fruits (Rogge 100 et al., 2013). 101 102 The objective ofACCEPTED this study is to investigate the effects of ultrasound treatment in protein 103 suspensions for making foams to be used in the baking of cake. The highly aerated foam and 104 baked cake structure were then assessed via imaging using X-ray microtomography and X-ray 105 tomography techniques. The collected X-ray microtomography and X-ray tomography images 3 ACCEPTED MANUSCRIPT 106 were then reconstructed into 2D and 3D images for a complete evaluation of the internal aerated 107 structures. 108 109 2. Materials and methods 110 2.1. Materials 111 The cake making process uses protein suspensions from protein powder, i.e. whey protein 112 concentrate (Textrion PROGEL 800, DMV International, BA Veghel, Netherlands) because it is 113 a protein with the highest nutritional value (García-Garibay et al., 2008) and contains all of the 114 essential amino acids in higher concentration compared to vegetable proteins such as soy, corn 115 and wheat gluten (Recio et al., 2008). The typical composition of the whey protein concentrate is 116 80% protein, 6.5% lactose, 6.3% fat, 4.4% ash and 4.9% moisture with 6.5 pH. 117 118 2.2. Cake preparation from ultrasonically treated foam 119 The aqueous suspensions of whey protein powder at 20% (w/w) concentration were prepared by 120 dispersing 50 g of dry matter into 200 g of distilled water in a 500 mL beaker and stirrer using a 121 mechanical stirrer (RW20 DZM.n S2, IKA WorksMANUSCRIPT (Asia) Sendirian Berhad, Malaysia) at 355 122 rpm for 20 min until homogenous suspensions were obtained. The solution was sonicated with 123 20 kHz - 400 W high intensity ultrasound probe (Digital Sonifier Model 450, Branson 124 Ultrasonics Corporation, Danbury, Connecticut, USA) at 60% amplitude for 25 min. The control 125 sample has no ultrasound treatment and is known as an untreated sample. 250 g of the treated or 126 untreated whey protein suspension was whipped into foam at room temperature in a mixer 127 (5K5SSS, Kitchen Aid Inc., St. Joseph, Michigan, USA) at 330 rpm for 15 min. 128 129 The whipped foam was used for cake making following the Angel food cake recipe with an 130 adapted formulation given in Table 1 (Yamazaki and Lord, 1971). Sugar was added into the 131 foam during the extendedACCEPTED mixing of time 4 min. Mixing continued for another 4 min at a reduced 132 speed of 160 rpm when pre-mixed salt with flour was added to obtain cake batter. The speed of 133 mixing the cake batter was increased to 330 rpm during the final 15 s. 450 g of cake batter was 134 poured into the cake tin with dimensions showed in Fig. 1 and baked at 170°C with oven heat 135 levels setting of 20% (top): 30% (side): 10% (bottom) for 40 min in an electronic baking oven 4 ACCEPTED MANUSCRIPT 136 (ST-02, Salva Industrial, Spain). The baked cakes were inverted on a wire rack immediately and 137 cooled for 5 min before removing them from the tins. The cakes were left in ambient for 1 hour 138 for further cooling (Gómez et al., 2008; Tan et al., 2011) before cake imaging analyses.