Effects of hot-air microwave rolling blanching pretreatment on the drying of turmeric (Curcuma longa L.): Physiochemical properties and microstructure evaluation.

Blanching pretreatment can improve product quality and efficiency during food processing. Effects of hot-air microwave rolling blanching (HMRB) on physiochemical properties and microstructure of turmeric were investigated under various treatment times (0-10 min). Results showed that HMRB significantly changed weight, electrolyte leakage, texture, viscoelastic properties, pectin fractions content, thermal properties and drying quality of turmeric. Meanwhile, HMRB promoted the redistribution of water in turmeric and changed the cell structure, thus shortening drying time by 6.35-34.92 %. The polyphenol oxidase and peroxidase were entirely inactivated after blanching for 8 and 10 min, respectively. Compared with unblanched dried turmeric, the curcumin content, total phenolic, DPPH and ABTS were significantly increased by 20.76 %, 5.63 %, 7.54 % and 19.05 % at the optimal blanching time (8 min). Overall, HMRB can be used as a promising pretreatment technology to enhance the drying rate and improve the quality of dried turmeric.

Succeeded high-temperature acid hydrolysis of granular maize starch by introducing heat-moisture pre-treatment.

Acid hydrolysis is a crucial method for modifying granular starch, but it is often conducted at low temperatures (below 55 °C) for an extended period of time to prevent crystallinity loss. The high-temperature acid hydrolysis (HTAH) behavior of heat-moisture treated (HMT) starch at 69 °C was investigated for the first time. The crystalline structure of starch was enhanced by HMT, confirmed by its rheological, thermal, and infrared Fourier transform spectroscopy results. The amorphous structure of HMT starch was preferentially hydrolyzed with high reactivity, related to a fast hydrolysis stage (4.17 × 10-2 min-1). And the crystalline flakes were separated from starch granules, accompanied by strengthened molecular interactions. HMT starch was transformed from 16.98 µm granules to 158 nm thick and 2.57 µm broad flakes with a 6.40 % increase in crystallinity after 40 min of hydrolysis. For native starch, the HTAH destroyed the crystalline structure due to gelatinization, resulting mainly gelatinous aggregates. These evidenced that the hydrolysis of granular starch was successfully performed at a relatively high temperature by introducing heat-moisture pre-treatment. This study could provide a novel perspective on the combination of increasing temperature and pre-treatment for granular starch hydrolysis intensification design, as well as a strategy for efficiently preparing small-sized crystalline starch, which has promising applications in Pickering emulsion and material filler.

Factors affecting energy efficiency of microwave drying of foods: an updated understanding.

Microwave drying (MWD) is an efficient dielectric drying method in food, with advantages such as volumetric heating, fast drying, safety, and good product quality. As a key indicator of a dryer's market value, energy efficiency is of concern to sellers and dryer manufacturers. This paper systematically reviewed the quantification methods and influencing factors of energy efficiency of microwave drying in food application from different perspectives. Mechanisms and possible improvements of these factors are highlighted. Future trends in improving the energy efficiency of MWD are proposed. Energy consumption of MWD depends on a variety of factors such as equipment structure, drying conditions (microwave power, frequency, temperature, and air velocity), material properties, and combined/hybrid drying technologies. The drying system can be effectively improved if these parameters are adjusted appropriately and taking the processing cost into consideration. Although a good product can be obtained by pretreatment or combined/hybrid drying method, it may consume more energy. Future research should develop artificial intelligence, renewable energy, and computational fluid dynamics technology to pave the way for large-scale application of MWD and reduce energy consumption.

Effects of carboxymethyl cellulose/pectin coating combined with ultrasound pretreatment before drying on quality of turmeric (Curcuma longa L.).

Turmeric is an herb with multiple bioactive substances and health benefits. Drying is one of the most important steps of its processing and sales. In order to obtain high-quality turmeric products, we used five different pretreatment methods to treat turmeric prior to pulse-spouted microwave vacuum drying (PSMVD), including carboxymethyl cellulose coating (CMC), pectin coating (P), ultrasound (US) and their combination (CMCUS or PUS). The effect of different pretreatments on the drying kinetics, quality attributes and microstructure of turmeric were evaluated. Results showed that the US pretreatment had the shortest drying time (60 min), while coating treatment did not significantly affect drying rate. Dried turmeric with coating pretreatment had lower rehydration ratio and water adsorption capacity compared with individual ultrasound treatment. Carboxymethyl cellulose coating protected bioactive substances better than pectin coating. Moreover, CMCUS pretreatment showed significantly lower total color change, higher curcumin content, total phenols and flavonoid content as well as antioxidant capacity in all dried samples. Microstructure observation showed that the polysaccharide coating covering the surface of turmeric might reduce the degradation of bioactive compounds. Therefore, the CMCUS pretreatment before PSMVD of turmeric was recommended due to the efficiency and quality protections.

Hot-Air Flow Rolling Dry-Blanching Pretreatment Improves the Drying Quality of Acanthopanax sessiliflorus by Increasing the Drying Rate and Inactivating Enzymes.

The processing of Acanthopanax sessiliflorus has attracted interest due to its health benefits. In this work, an emerging blanching technology, called hot-air flow rolling dry-blanching (HMRDB), was employed to treat A. sessiliflorus before drying. The effects of varied blanching times (2-8 min) on enzyme inactivation, drying characteristics, bioactive compound retention, and microstructure were examined. The results demonstrated that blanching for 8 min rendered polyphenol oxidase and peroxidase nearly inactive. The blanching process reduced the drying time of samples by up to 57.89% compared to an unblanched sample. The Logarithmic model showed good fitting performance for the drying curves. The total phenolic and flavonoid content of the dried product increased as blanching time increased. The total anthocyanin content of the samples blanched for 6 min was 3.9 times higher than that of the unblanched samples, and 8 min of blanching produced the greatest DPPH• and ABTS• scavenging capabilities. The retention of active compounds in a dried product is a result of the inactivation of enzymes and a reduced drying period. Changes in the porous structure of the blanched samples would be responsible for the accelerated drying rate, according to microstructural analysis. These results indicate that HMRDB enhances the drying process and improves drying quality when applied to A. sessiliflorus before drying.

Effect of different drying techniques on drying kinetics, nutritional components, antioxidant capacity, physical properties and microstructure of edamame.

The present study aimed to investigate the effect of hot air drying (HD), microwave rolling-bed drying (MRD), hot air microwave rolling-bed drying (HMRD), pulse-spouted microwave vacuum drying (PSMVD) and freeze-drying (FD) on the drying characteristics, quality properties and microstructure of edamame. Six models were fitted the drying curves, and quality attributes were analyzed. Results indicated that Page model was the most suited model for edamame drying. Compared with HD, MRD and HMRD improved the quality of edamame and decreased the drying time by 45.59% and 36.03% respectively. The FD and PSMVD possessed higher rehydration ability, nutrient retention and antioxidant capacity compared with other methods. Moreover, PSMVD products showed a crunchy texture, the less color change and the shortest drying time (70 min). Microscopy images demonstrated a distinct porous structure in PSMVD, which facilitated the moisture transfer. Overall, PSMVD is a promising dehydration method for obtaining high value-added edamame products.

[Effects of different land-use types on soil organic carbon and its prediction in the mountainous areas in the middle reaches of Lancang River].

Based on the analysis of 210 surface soil samples (0-20 cm) according to field investigation in 2011, soil organic carbon (SOC) content and its distribution under four different land-use types in the middle reaches of Lancang River were studied. Combining with the correlation analysis, relationships among SOC content, land-use type, topographical factors and NDVI were revealed. Furthermore, multiple linear regression and Kriging method were used to predict the SOC contents distribution in the mountainous areas in the middle reaches of Lancang River. The results exhibited that the rank order of SOC content under the four land-use types was forestland > scrubland > grassland > farmland. The important factors influencing the SOC content were land-use type, aspect, slope and curvature. Comparing the accuracy of these two models, we found that the multiple regression model performed better than geo-statistics in prediction of the SOC content in the mountainous region.

[Dynamics of salinization land based on EVI series data and landscape pattern analysis in Songnen Plain: a case study in Da'an City].

The west part of Jilin Province is one of the most salinization regions in China and much attention has been paid to the dynamics and monitoring of the salinization land. Based on the land use data derived from TM images in 2000, 2005 and 2010 and the enhanced vegetation index (EVI) series data from 2000 to 2012 of Da'an City as a typical salinization region, we used landscape pattern analysis to elucidate the dynamics of salinization land, and used gray incidence method to analyze the main driving factors for the dynamics of land salinization. The results showed that the dominant land use types in Da'an City were cultivated land, grassland and salinization land. From 2000 to 2010, the area of salinization land and construction land showed an increasing trend, while that of grassland tended to decrease. Salinization land, which showed increased connectivity and integrity, was mainly transformed from grassland, swamp land and water area. Annual EVI values in Da'an City showed an overall increasing trend while the average values showed obvious spatial differences with the lowest EVI level in salinization land. From 2000 to 2012, the increment of vegetation cover area was larger than that of the degraded area. Landscape transformation affected the changing trends of EVI. Both natural factors and human activities affected the dynamics of salinization land, and human activities showed a greater impact on land salinization than climate factors.