Volume 13, Issue 5 -

The paper aims to study the change of protein denaturation in whole quail egg during heating using in situ nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) techniques. The NMR relaxometry demonstrated that the protein denaturation occurred within 64–66 °C. The quail eggs after 8 min heating at 65 °C were successfully recognized by NMR combined with principal component analysis due to protein denaturation. The protein denaturation dynamics study revealed that the protein denaturation occurred at 8, 6, 4, 2 min for the quail eggs heated at 65, 70, 75, 100 °C, respectively. In addition, the protein denaturation of quail egg was also detected by the T 1 weighted MRI imaging, confirming that the dramatic changes occurred at 8 min when the eggs were heated at 65 °C. All these results showed that the NMR with MRI provided an effective way to assess the protein denaturation of quail eggs.

This study presents the non-linear viscoelastic properties of soy protein isolate (SPI) dispersions and acid-induced gels to considerable detail. The storage ( G′ ) and loss ( G′′ ) moduli of SPI dispersions showed Type III (week strain overshoot) and Type IV (strong strain overshoot) networks when the strain amplitudes varied between 0.01 and 1.00 and 1.00 to 100.00, respectively. In the case of acid-induced SPI gels the rheological parameters showed the characteristics of Type I (strain thinning) network. Fourier transform rheological experiments showed that the higher harmonic curves obtained u strain sweep test showed quite different shapes for SPI dispersions and gels. In the case of dispersions, the highest I 3 / 1 (0.101) occurred at the strain amplitude of 0.40 and then decreased to below 0.02. In the case of acid-induced SPI gels, the I 3 / 1 value began to be appreciable at the strain amplitude of 0.1 increased rapidly to its highest value ( I 3 / 1 =0.05).

Finite element (FE) models of uniaxial loading of pumpkin peel and flesh tissues were developed and validated using experimental results. The tensile model was developed for both linear elastic and plastic material models, the compression model was developed only with the plastic material model. The outcomes of force versus time curves obtained from FE models followed similar pattern to the experimental curves; however the curve resulted with linear elastic material properties had a higher difference with the experimental curves. The values of predicted forces were determined and compared with the experimental curve. An error indicator was introduced and computed for each case and compared. Additionally, Root Mean Square Error (RMSE) values were also calculated for each model and compared. The results of modeling were used to develop material model for peel and flesh tissues in FE modeling of mechanical peeling of tough skin vegetables. The results presented in this paper are a part of a study on mechanical properties of agricultural tissues focusing on mechanical peeling methods using mathematical, experimental and computational modeling.

Determining the natural frequency of watermelon is important to reduce loss by vibration during transportation. The purpose of frequency sweep test is to determine the tolerance of watermelon to vibration within a certain frequency range and to search the resonant frequency of watermelon in a certain frequency range. Frequency sweep test of Xinong No.8 watermelon cultivar was conducted, and the acceleration transmissibility curve was obtained. Furthermore, the 1st and 2nd order natural frequencies of watermelon were determined as 35.125 Hz and 71.034 Hz respectively from the acceleration transmissibility curve. Based on Geometric and mechanical parameters of Xinong No.8 watermelon cultivar, a finite element analysis model was developed and modal analysis of watermelon was carried out to obtain its natural frequencies and mode shapes. Since the value of 1st and 2nd order resonance frequency were the same or similar to the value of 3rd, 4th, and 5th order resonance frequency, this study only focused on 1st and 2nd order modes. The 1st order and 2nd order natural frequency test data fit to the corresponding simulation data well which validated the FEA model. This study demonstrated the feasibility of detecting the resonant frequency of watermelon vibration during transportation using FEA methods and provided a theoretical basis for watermelon transportation device design to reduce damage by avoiding resonant frequency.

Due to variation in economic value of different varieties of rice, reports indicating the possibility of mixing different varieties on the market. Applying machine vision techniques to classify rice varieties is a method which can increase the accuracy of classification process in real applications. In this study, several morphological and textural features of rice seeds’ images were examined to evaluate their efficacy in identification of three Iranian rice varieties (Tarom, Fajr, Shiroodi) in their mixed samples. On the whole, 666 images of rice seeds (222 images of each variety) were acquired at a stable illumination condition and totally, 17 morphological and 41 textural features were extracted from seeds images. Principal component analysis (PCA) method was employed to select and rank the most significant features for the classification. Subsequently, the MLP neural network classifier was employed for classification of rice varieties in the mixed bulks of three and two varieties, using top selected features. The network was three-layered feed forward type and trained using two training algorithms (BB and BDLRF). The classification accuracy of 55.93, 84.62 and 82.86 % for Fajr, Tarom and Shiroodi, 86.96 and 93.02 % for Fajr and Shiroodi, 86.84 and 96.08 % for Tarom and Shiroodi and 91.49 and 95.24 % for Fajr and Tarom were obtained in test phase, respectively.

Starch isolated from sweet potato was subjected to different levels of HMT at 15, 20, 25, 30, and 35 %. HMT showed negligible effect on the swelling power of starch. The swelling power was decreased with the increasing of the initial moisture content of the starch. The apparent amylose contents of HMT starches decreased from 24.11 % to 20.56 % with the initial moisture content increasing from 15 % to 35 %. The pasting temperatures enhanced from 73.1 to 81°C ( p < 0.05) with the rapidly digestible starch (RDS) contents decreasing from 86.97 to 70.24 % ( p < 0.05). Avrami equation analysis showed that HMT reduced the rate of starch retrogradation. The Avrami exponents of native and HMT-35 starches were 0.70 and 0.98 with the recrystallization rates 0.22 and 0.10, respectively. HMT could restrain the starch retrogradation and these results could provide theoretical guidance on sweet potato starch modification.

The effect of osmotic dehydration (OD) and ultrasound-assisted osmotic dehydration (ULOD) on drying kinetics and quality of peach cylinders by infrared radiation drying were investigated. The moisture state and redistribution after osmotic pretreatments and subsequent drying process were also studied by low field nuclear magnetic resonance. The water loss and solute gain increased with osmotic time, and ULOD could promote water transfer. The signal amplitude of free water and immobile water diminished and shifted to the left for samples pretreated by both ULOD and OD. The brightness in T 2 -weighted images appeared a declining trend with increasing osmotic time of ULOD and OD, indicating the moisture content reduced gradually. During dying process, the free water of all samples was removed completely after drying for 120 min. ULOD and OD could increase water activity and decrease shrinkage of samples. Long pretreatment of ULOD and OD improved the color of dried peach cylinders.

Acidulant encapsulation is used to prevent the unwanted acid hydrolysis of other ingredients in food industry. It is preferred to efficiently solidify the molten coatings on acidulant particles. In this article, a molten lipid was atomized in a fluidized bed of cold citric acid powder for the production of encapsulated acidulant. The effect of lipid-to-citric acid mass ratio and atomization pressure on the size distribution of encapsulated particles was investigated. The median particle size ( D 50 ) increases with lipid content, and fine particles were reduced with lipid encapsulation. The surface morphology of lipid-encapsulated citric acid particles was studied by scanning electron micrograph to gain insight into the possible encapsulation mechanism. The encapsulation efficiency increases with the lipid-to-citric acid mass ratio.

Response surface methodology (RSM) with a Box–Behnken design (BBD) was used to optimize the extraction conditions of carotenoid antioxidants from Cordyceps militaris . An enzyme-assisted extraction (EAE) method was developed and optimized to enhance 2,2-diphenyl-1-picrylhydrazil (DPPH) radical-scavenging activity of carotenoid antioxidants from C. militaris . The optimum conditions were as follows: a pH of 4.1, an extraction time of 40.4 min, an extraction temperature of 48.7 °C and 0.43 % enzyme (cellulose: pectinase, 1:1, w/w) concentration. Under these conditions, the DDPH radical-scavenging activity of C. militaris extracts was 81.62±2.26 %, indicating that the BBD is an efficient approach to develop mathematical models for predictingcarotenoids antioxidant extraction from C. militaris . The successful extraction of carotenoid antioxidants from C. militaris provides a basis for the development and utilization of C. militaris resources.

In this study, the ultrasound-assisted extraction (UAE) was used for extraction of pinocembrin from Flos populi . Based on the results of the single-factor experiment, four independent parameters, including ethanol concentration (40–80 %), extraction temperature (50–70 °C), extraction time (25–45 min) and electrical acoustic intensity (40.8–81.5 W/m 2 ) were further investigated using response surface methodology (RSM) coupled with Box-Behnken design. The experimental data were fitted to the quadratic response surface model using multiple regression analysis with high adjusted determination coefficient value ( R 2 ) of 0.9697. The highest yield (134.2 ± 1.53 mg/g) of pinocembrin was obtained under the optimal conditions (ethanol concentration of 68 %, extraction temperature of 69 °C, extraction time of 42 min and electrical acoustic intensity of 66.81 W/cm 2 ), which agreed to the predicted value of 132.9 mg/g. Moreover, the comparison between the UAE and reflux extraction also showed the suitability of UAE for pinocembrin from Flos populi .