توليد ﺷﮑﻼت ﺣﺒﺎﺑﺪار و اﺳﺘﻔﺎده از ﻣﻘﻄﻊﻧﮕﺎري اﺷﻌﻪ X و ﭘﺮدازش ﺗﺼﻮﯾﺮ در ﺑﺮرﺳﯽ وﯾﮋﮔﯽﻫﺎي ﺣﺒﺎبﻫﺎ

Production of aerated chocolate and application of X-ray computed tomography and image processing in evaluating the bubbles features

در اﯾــﻦ ﻣﻄﺎﻟﻌــﻪ، ﺷــﮑﺮ ﺑــﺎ ﻣﺨﻠــﻮط اﯾﻨــﻮﻟﯿﻦ: ﻣﺎﻟﺘﻮدﮐﺴــﺘﺮﯾﻦ در ﻧﺴــﺒﺖﻫــﺎي 75:25 )CH3) 50:50 ،(CH2( و 25:75 )CH4( ﺟــﺎﯾﮕﺰﯾﻦ ﺷــﺪ. ﺳــﭙﺲ ﮔﺎز دياﮐﺴﯿﺪ ﮐﺮﺑﻦ در ﻓﺸﺎر 6 ﺑﺎر ﺑﻪ اﯾﻦ ﺳﻪ ﺷﮑﻼت ﻋﻼوه ﺑﺮ ﺷـ ﮑﻼت ﺣـﺎوي ﺷـﮑﺮ )CH1( ﺗﺰرﯾـﻖ ﺷـﺪ ﺗـﺎ ﺷـﮑﻼت ﺣﺒﺎﺑـﺪار ﺗﻮﻟﯿـﺪ ﺷـﻮد . ﺑـﺎ اﺳـﺘﻔﺎده از ﻣﻘﻄﻊﻧﮕﺎري اﺷﻌﻪ X از ﺷﮑﻼتﻫـﺎي ﺣﺒﺎﺑـﺪار ﺗﺼـﻮﯾﺮﺑﺮداري ﺷـﺪ و ﭘـﺲ از ﭘـﺮدازش ، ﺗﺼـﺎوﯾﺮ ﺑـﻪ دﺳـﺖ آﻣـﺪه ﺑـﺎ اﺳـﺘﻔﺎده از روش ﭼـﺎن -وز ﺗﻘﻄﯿـﻊ ﺷـﺪﻧﺪ ؛ ﯾﻌﻨﯽ، ﺣﺒﺎبﻫﺎ از ﺳﺎﯾﺮ ﻗﺴﻤﺖﻫﺎي ﺗﺼﻮﯾﺮ ﺟﺪا ﺷﺪﻧﺪ. وﯾﮋﮔﯽﻫـﺎي ﺣﺒـﺎب ﻫـﺎ ﮐـﻪ در اﯾـﻦ ﺗﺤﻘﯿـﻖ ﻣـﻮرد ﺑﺮرﺳـﯽ ﻗـﺮار ﮔﺮ ﻓﺘﻨـﺪ ﻋﺒـﺎرت ﺑﻮدﻧـﺪ از: ﺣﺠـﻢ ﮐـﻞ، ﻗﻄﺮ و ﻧﺴﺒﺖ ﺳﻄﺢ ﺑﻪ ﺣﺠﻢ. ﻫﻤﭽﻨﯿﻦ، ﺑﻠﻮرﯾﻨﮕﯽ، ﭼﮕﺎﻟﯽ و ﺳﺨﺘﯽ ﺷـﮑﻼت ﻫـﺎ ﻧﯿـﺰ ﺑـﺎ ﻫـﻢ ﻣﻘﺎﯾﺴـﻪ ﺷـﺪﻧﺪ. ﻧﺘـﺎﯾﺞ ﻧﺸـﺎن دادﻧـﺪ ﮐـﻪ روش ﭼـﺎن -وز ﺗﻮاﻧﺴـﺖ ﻧﻮﯾﺰﻫﺎي ﻣﻮﺟﻮد در ﺗﺼﻮﯾﺮ را ﺣﺬف ﮐﻨـﺪ. ﻫﻤﭽﻨـﯿﻦ ، ﻧﺘـﺎﯾﺞ ﭘـﺮاش اﺷـﻌﻪ X ﻧﺸـﺎن داد ﮐـﻪ ﻧﻤـﻮدار CH3 ﻗﻠـﻪ ﻫـﺎي ﺗﯿﺰﺗـﺮي ﻧﺴـﺒﺖ ﺑـﻪ CH2 و CH4 دارد ﮐﻪ اﯾﻦ ﻧﺸﺎﻧﯽ از ﺑﻠﻮرﯾﻨﮕﯽ ﺑﯿﺸﺘﺮ آن ﺑﻮد. ﻣﯿﺎﻧﮕﯿﻦ ﻗﻄﺮ ﺣﺒـﺎب ﻫـﺎي CH1 ﺑﯿﺸـﺘﺮ از ﺳـﺎﯾﺮ ﻧﻤﻮﻧـﻪ ﻫـﺎ ﺑـﻮد ﮐـﻪ دﻟﯿـﻞ آن را ﻣـﯽ ﺗـﻮان ﺑـﻪ ﺑﻠـﻮرﯾﻨﮕﯽ ﺑﯿﺸـﺘﺮ آن در ﻣﻘﺎﯾﺴﻪ ﺑﺎ ﻧﻤﻮﻧﻪﻫﺎي ﺑﺪون ﺷﮑﺮ ﻧﺴﺒﺖ داد؛ زﯾﺮا ﺳـﺎﺧﺘﺎر ﻣﺘﺒﻠـﻮر CH1 از ﺧـﺮوج ﮔـﺎز ﺟﻠـﻮﮔﯿﺮي ﮐـﺮده و ﻣﻮﺟـﺐ ﺑـﻪ ﻫـﻢ ﭘﯿﻮﺳـﺘﻦ ﺣﺒـﺎب ﻫـﺎي ﮐﻮﭼـﮏ و ﺗﺸﮑﯿﻞ ﺣﺒﺎبﻫﺎي ﺑﺰرﮔﺘﺮ ﺷﺪه اﺳﺖ. ﻫﻤﭽﻨﯿﻦ، ﻣﺸﺎﻫﺪه ﺷﺪ ﮐﻪ در ﺗﻤـﺎم ﺷـﮑﻼت ﻫـﺎ، ﭼﮕـﺎﻟﯽ ﺷـﮑﻼت ﺣﺒﺎﺑـﺪار ﮐﻤﺘـﺮ از ﺷـﮑﻼت ﺑـﺪون ﺣﺒـﺎب اﺳـﺖ؛ زﯾـﺮا ﺑﺨﺸﯽ از ﻣﻮاد ﺟﺎﻣﺪ و ﭼﺮﺑـﯽ ﺑـﺎ ﮔـﺎز دي اﮐﺴـﯿﺪ ﮐـﺮﺑﻦ ﺟـﺎﯾﮕﺰﯾﻦ ﺷـﺪ. ﻧﺘـﺎﯾﺞ اﻧـﺪازه ﮔﯿـﺮي ﺳـﺨﺘﯽ ﻧﯿـﺰ ﻧﺸـﺎن داد ﮐـﻪ ﻧﻤﻮﻧـﻪ ﻫـﺎي ﺑـﺪون ﺷـﮑﺮ ﺣﺒﺎﺑـﺪار از ﻧﻤﻮﻧﻪﻫﺎي ﺑﺪون ﮔﺎز ﻧﺮﻣﺘﺮ ﺑﻮدﻧﺪ وﻟﯽ در ﻣﻮرد CH1 ﻋﮑﺲ اﯾﻦ ﭘﺪﯾـﺪه ﻣﺸـﺎﻫﺪه ﺷـﺪ ﮐـﻪ دﻟﯿـﻞ آن را ﻣـﯽ ﺗـﻮان ﺑـﻪ ﺣﻀـﻮر ﺷـﮑﺮ در اﯾـﻦ ﻧﻤﻮﻧـﻪ ﻧﺴـﺒﺖ داد؛ زﯾﺮا در ﻣﺤﺼﻮﻻت ﺣﺒﺎﺑﺪار، ذرات ﺟﺎﻣﺪ، ﺑﻪوﯾﮋه ﺷﮑﺮ، ﯾﮏ اﺳﮑﻠﺖ ﭘﯿﻮﺳـﺘﻪ را ﺗﺸـﮑﯿﻞ ﻣـﯽ دﻫﻨـﺪ و ﻫﻤـﺎن ﻧﻘﺸـﯽ را اﯾﻔـﺎ ﻣـﯽ ﮐﻨﻨـﺪ ﮐـﻪ ﭼﺮﺑـﯽ در ﻣﺤﺼـﻮﻻت بدون حباب بازي مي كند

13Introduction: Chocolate is a suspension of solid particles, including sugar, cocoa solids and milk powder (depending on the chocolate type) in a continuous fat phase, namely cocoa butter or its substitutes. The solid particles account for approximately 70% of chocolate with the fat constituting about 30%. Sugar takes up nearly 40–50% of the total solid particles of chocolate, thus influencing its sweetness, particle size distribution, rheological and sensory properties. It is also considered to be a bulking agent and a source of energy which produces 394 kcal/100 g of refined sugar. Therefore, consumers are increasingly becoming concerned with chocolate sugar and calorie content nowadays. This issue can be resolved by replacing sugar with bulk (nutritive) sweeteners and/or dietary fibers. Bubbles are found in many food products, including cakes, chocolates and beverages. Although they do not increase the food nutritional value, they change its textural properties and mouthfeel. Bubbles are normally visible to the naked eye and their mean diameter ranges from 0.05 to 3 mm. X-ray computed tomography is a 3D imaging technique which captures the images of a sample cross-sections. It is used for the non-destructive visualization and characterization of food microstructure. In this method, a series of radiographs of a sample are captured from different angles to be utilized for the 3D reconstruction of the material microstructure. Materials and methods: sugar was replaced with inulin: maltodextrin mixture at ratios of 25:75 (CH2), 50:50 (CH3) and 75:25 (CH4). Carbon dioxide was injected into the samples at 6 bar to produce aerated chocolate. Using X-ray computed tomography, the images of the samples were captured and after processing, the obtained images were segmented using the Chan-Vese method. The properties of bubbles included total volume, diameter and surface to volume ratio. The crystallinity of the samples was determined through X-ray diffraction. The hardness of the chocolate bars was measured using the puncture test. The density of the aerated chocolates was also compared with that of the nonaerated ones. Results and discussion: X-ray diffraction revealed that there were many strong peaks in the diffractogram of CH1, which can be ascribed to the high degree of sugar crystallinity in addition to the impurities present in the commercial sugar utilized in this study. In the case of the sugar-free samples, namely CH2, CH3 and CH4, two distinct peaks could be seen at 2θ of about 21° and 23.5°, both of which were much stronger and more defined in the scattering pattern of CH3, demonstrating the more crystalline structure of this sample. It seems that inulin and maltodextrin have physically interacted with each other or with the other ingredients of the chocolate, in particular CBS, which has been more pronounced at the ratio of 50:50. The results of image segmentation showed that the Chan-Vese method, compared with the adaptive thresholding one, was more able to segment the images, because this method does not depend on the image gradient and is especially suitable for the objects with vague edges. The mean bubble diameter of CH1 was bigger than that of the other samples, which could be due to its higher degree of crystallinity, because the crystalline structure of CH1 prevented the gas from being lost leading to the coalescence of smaller bubbles and the formation of bigger ones. In addition, it was observed that the density of the aerated chocolate was higher than that of the unaerated one in all the formulas as a portion of solid particles and fat was replaced with the gas. The results also demonstrated that the sugarfree aerated samples were softer than the corresponding nonaerated ones. However, it was reversed in the case of CH1 which could be ascribed to the presence of sugar in this sample, because in aerated products, solid particles, particularly sugar, form a continuous skeleton and play the same role as fat does in nonaerated products