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The use of chitosan aerogels as an adsorbent for the regeneration of frying oil

One of the most commonly used food preparation methods is deep-fat frying. The improvement of the quality of used frying oil (UFO) is important because the reuse of frying oil could provide significant savings to the food industry. This study aimed to enhance the quality of used sunflower oil by using chitosan aerogels (CA), which can be considered as novel adsorbents with an increased surface area compared to chitosan powder. Aerogels are novel nanostructured materials with high porosity and large surface area. In this study, CA were produced by drying the 2% (w/v) chitosan gels using supercritical drying. In the study, 32 consecutive deep-fat frying were performed using potato slices in sunflower oil at 180 ± 5 °C. The effect of the adsorbent concentration (0.5, 1, and 2% (w/w)) and different adsorption temperatures (90, 135, and 180 °C) were studied by examining the UFO before and after the adsorption treatments. The physicochemical properties of the oil were analyzed by determining free fatty acid (FFA) content, total polar compounds (TPC), smoke point, p-anisidine value (p-AnV), and color (CIE L*, a*, b*). Moreover, the structural changes of aerogels after the adsorption process were investigated by Fourier Transform Infrared spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR). CA could reduce the % FFA values from 0.44% to 0.18% due to the ionic interaction between CA and FFA. In addition, TPC value and the smoke point increased after the treatments. The p-AnV was compensated with CA, indicating that secondary oxidation products were adsorbed. Moreover, CA caused a darker color after the adsorption treatments. Additionally, compared with magnesium silicate, the same concentrations of CA were found more effective in improving all the quality parameters of oil except for the L* values.

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A feature extractor for temporal data of electronic nose based on parallel long short-term memory network in flavor discrimination of Chinese vinegars

Volatile flavor is a key indicator of food quality which can directly affect consumer preference and purchase intention. Electronic nose is considered as a promising intelligent sensory analysis tool for food flavor assessment, however, extracting effective features from the gas sensor array is still a major challenge, which largely determines the performance of subsequent classifiers. Here, a parallel long short-term memory (LSTM) network is proposed as a feature extractor for automatically extracting features from the whole time series of sensor responses in flavor discrimination of five Chinese vinegars. The network was trained by the temporal data from the sensor array and yielded different feature patterns corresponding to different vinegars, which were then fed to other conventional classifiers for pattern recognition. We also evaluated the influence of the extracted feature dimension that is related to the dimension of the hidden state of the LSTM layer on the classification performance. The results indicate that a larger dimension of extracted feature is unnecessary for promoting classification accuracy, instead, the optimum dimension 4 of the hidden state gives the highest accuracy of 95.8% in this application under the softmax evaluator. Moreover, much higher accuracies were obtained when combined with other sophisticated classifiers such as support vector machine. The results demonstrate that the proposed network is competent to extract features directly and automatically from the temporal data of the electronic nose.

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Fabrication of chitosan-based smart film by the O/W emulsion containing curcumin for monitoring pork freshness

In this research, curcumin (Cur) was encapsulated in succinylated soy protein isolate (SSPI) emulsion and combined with chitosan (CS) to prepare a smart film. The good adsorption ability of SSPI at the oil-water interface provides good physical stability for preparing Cur-loaded emulsion. These CS smart films containing SSPI emulsions with different curcumin content were evaluated on the structure, mechanical, barrier, antioxidant, antibacterial properties, and controlled release behavior. SEM and FT-IR results showed that the Cur-loaded emulsion was compatible with the CS matrix. By adding the emulsion, the film blocked 97.11% of ultraviolet radiation, reduced the water vapor transmission rate by 42%, and improved the swelling degree (32.26%), water solubility (12%), thermal stability and elongation at break (70.79 %) (p < 0.05). In addition, the film has a high antibacterial effect on Staphylococcus aureus and Escherichia coli (Bacterial inhibition zone diameter: 19.59 mm and 18.66 mm) and the release rate of curcumin in the film reaches 82.60%, mainly following the Fickian diffusion. The film gradually turns red under alkaline conditions, a property that makes the films successful in monitoring the deterioration of pork during storage. Adding SSPI emulsions and curcumin to films has great potential for food freshness monitoring and packaging.

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