Research On Porosity And Texture Characterics Of Berry Chips

In recent years, puffed food as a kind of new foods, is accepted widely by the consumer. Theresearch chooses raspberry as the material studied, and propose a way to quantitatively analyze theporosity of berry chip. The textural properties of berry chip related to the internal pore structurewere deterimined by using single factor and response curve method. Porosity of puffed chip maybe evaluated according to the differential spectral values of near-infrared spectrum, the mainresearch results are as follows.(1) By means of machine vision technology, feature extraction method for the pore structureof the raspberry puffed chip was carry out by the edge detection of chip’s image using Sobelalgorithm and Roberts algorithm. Linear filtering and median filtering ways were selected toprocess noise of images. Threshold values of0.4binary images met the test requirements, theobvious fractal characteristics were observed in the chip internal pore structure, chip with perfectself-similarity. This result supported that the void structure at middle cross-section may representof the whole chip.(2) By means of single factor experimental method, hardness and crispness of berry chip werestudied under micrwaove vacuum puffing conditions. the results were as follows.1) With puffedtime increases, the hardness prior increases and then decreases, and crispness reduced, andporosity firstly increases and then decreases.2) With the vacuum pressure increases, the hardnessfirstly decreases and then increases, while crispness and porosity firstly increase and then decrease.3) With the increases of the initial moisture content, hardness decreases and then increases, butcrispness and porosity firstly increase and then decrease.(3) The interaction of factors, in terms of microwave intensity, vacuum pressure, initialmoisture content, on the texture characteristics of berry chip, named as hardness, crispness,porosity, were studied under microwave vacuum conditions by using response surface method. Theresult showed that.1) Improtance order of each factor on chips hardness order is as puffed time,vacuum pressure, initial moisture content and microwave intensity. Monomial items of the puffedtime, and quadratic item of the vacuum pressure have the significant effect on the hardness. Thequadratic items of the initial moisture content have significant effect on the hardness. The othersare not significant.2) Improtance order of each factor on chips expansion ratio is as puffed time,microwave intensity, vacuum pressure and initial moisture content. Monomial items of the initialmoisture content and monomial items of the puffed time have the significant effect on thecrispness. And the interaction terms of the initial moisture content and puffed time, initial moisturecontent and vacuum pressure have significant effect on the crispness.(4) Stepwise regression algorithm was adopted based on multiple linear regressions method to establish the porosity of the quantitative analysis of the mathematical model. The mathematicalmodel of the porosity and puffed time was high significant with R~2of0.984, predicted correlationcoefficient of0.999. The mathematical model of the porosity and vacuum pressure wsa highsignificant with R~2of0.959and predicted correlation coefficient of0.983. The mathematicalmodel of the porosity and initial moisture content was high significant with R~2of0.996, predictedcorrelation coefficient of0.996. Therefore, this model could accurately forecast the porosity.