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A comparison of chestnut polysaccharide extraction using ultrasound-assisted extraction (UAE) and hot water extraction (HWE) demonstrated that UAE is superior to HWE due to its higher extraction efficiency. Scanning electron microscopy (SEM), thermogravimetric analysis-differential scanning calorimetry (TGA-DSC) and Fourier-transform infrared spectroscopy (FTIR) were used to characterize the ultrasound-assisted-extracted polysaccharide (UAEP) and hot water-extracted polysaccharide (HWEP). SEM images revealed that the UAEP and chestnut residue were crushed, with particle sizes that were smaller than those of the HWEP, which was related to the breakage of long-chain polysaccharides. TGA-DSC showed a higher transition temperature and enthalpy value for the UAEP than the HWEP, and the FTIR spectrum revealed typical characteristics of polysaccharides, with some differences between the UAEP and HWEP. The evaluation of antioxidant activities showed that the UAEP had stronger antioxidant capacities than the HWEP, regardless of the reducing power and DPPH-, ABTS- and hydroxyl radical-scavenging activities, suggesting that ultrasound is an optimal method to rapidly extract chestnut polysaccharide, a potential natural antioxidant.

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Carboxymethyl chestnut starch (CMCS) was synthesized by the reaction of chestnut starch and monosodium chloroacetate in an alkali environment. The hydroxyl groups of starch were etherized through carboxymethyl groups, and the crystallinity of starch was reduced after carboxymethylation. As degree of substitution (DS) increased from 0.22 to 0.63, the degree of amyloglucosidase hydrolysis decreased from 37.0 to 1.6%, which was markedly lower than that of native chestnut starch (NCS) (83.2%). The differential scanning calorimetry results revealed the absence of a transition peak in all CMCS samples. CMCS paste showed significant higher light transmittance and freeze‐thaw stability than those of NCS, and had no water release during storage at room temperature. CMCS with middle DS showed higher viscosity than NCS at high shear rate. The results demonstrated that CMCS can be applied in the industrial processing of paste foods and frozen food as a thickening agent. Practical applications Carboxymethylated starch can be used as an alternative thickener in a wide range of industrial applications. However, there is little information on the synthesis and physicochemical properties of carboxymethylated chestnut starch till now. In the present study, the carboxymethylated chestnut starch was synthesized by the optimization of process, and the microstructure, light transmittance, and freeze‐thaw stability of starch were studied. We believe that starch industry can utilize the results of this study in the synthesis and application of this modified starch.

The eating quality of cooked chestnut kernel depends on its nutritional components, which differ greatly among different cultivars. This study aimed to study the influence of nutritional components on the texture characteristics and sensory properties of cooked chestnut. After roasting or boiling, the content of moisture, crude protein, and water‐soluble protein all decreased and showed a significant positive correlation with springiness. Amylose content was significantly positive correlated with the cohesiveness, chewiness, and adhesiveness of cooked chestnut. The evaluation of the effect of total starch content on the sensory properties of cooked chestnut revealed a significant positive correlation between total starch content and color, aroma, sweetness, taste, and texture. Additionally, arginine, threonine, and methionine were positively related to the aroma formation of chestnut. The results indicated that changes in the nutritional components of chestnut, due to different cooking methods, can lead to variation in the sensory properties and texture characteristics of chestnut. Practical applications In a wide range of industrial applications, various cooking methods for chestnut processing have been developed. However, there is little information on the texture and sensory properties of chestnut kernel after thermal processing. In the present study, the effect of nutritional components on the texture characteristics and sensory properties of cooked chestnut was studied. We believe that related food factories can utilize the results of this study in the raw material selection for the thermal processing of chestnut kernels.

Long shelf life is important for industrially packaged cooked chestnut kernel. This study aims to investigate the physicochemical and digestive properties of starch in cooked chestnut stored for varying periods of up to 12 months. Apparent amylose content decreases significantly during the initial storage period of 2 months and then increases gradually in the succeeding 10 months. During storage, the degree of gelatinization decreases, whereas the degree of retrogradation (DR) increases. The relative crystallinity of cooked chestnut starch increases during storage and shows a significant positive correlation with DR. The content of rapidly digestible starch (RDS) decreases significantly during shelf life. Starch retrogradation and relative crystallinity exhibit a significant negative correlation with RDS content, and the short‐range molecular order of starch is negatively correlated with the content of slowly digestible starch. The results indicate that the digestibility of cooked chestnut kernel decreases during storage because of an increase in the crystallinity of starch.

The inhibitory effects of phytic acid (PA) on the browning of fresh-cut chestnuts and the associated mechanisms of PA on polyphenol oxidase (PPO) and peroxidase (POD) activities were investigated. The enzymatic browning of chestnut surfaces and interiors was suppressed by soaking shelled and sliced chestnuts in a PA solution. The specifi c activities of PPO and POD extracted from chestnuts declined due to inhibition by PA. PA was determined to be a competitive inhibitor of both PPO and POD by Lineweaver-Burk plots. The binding modes of PA with PPO and POD were analysed by AutoDock 4.2.Keywords: phytic acid, chestnut, enzymatic browning, polyphenol oxidase, peroxidaseChestnut has been a valuable food resource for centuries for the people living in East Asia, South Europe, and North Africa (GOUNGA et al., 2008). Chinese chestnut (Castanea mollissima Blume) is popular in East and Southeast Asia because of its delicious, sweet taste. Research on the chemical composition of chestnuts reveals the presence of various nutrients that are important for human health (DE VASCONCELOS et al., 2010;BLAIOTTA et al., 2012). In the processing of chestnut fruit, it will darken after peeling, mechanical damage, segmentation, grinding, and prolonged exposure due to enzymatic browning. The browning reaction decreases both the acceptability and nutritional quality of chestnuts (DE LA ROSA et al., 2011). Enzymatic browning involves the activities of polyphenol oxidase (PPO) and peroxidase (POD), which oxidize phenols found in fruit and vegetables to anthraquinones, which then become melanins by non-enzymatic polymerization. Controlling the activity of PPO and POD is a potential strategy for the inhibition of enzymatic browning (ZHOU et al., 2015). Effective inhibitors are necessary, because traditional methods, such as heating and adjusting pH value, are impractical in chestnut fruit pretreatment. Phytic acid (PA) is an antioxidant, chelating agent, and non-toxic food additive that has been used to inhibit enzymatic browning of apple juice and asparagus lettuce (CHEN et al., 2010;DU et al., 2012). The present study investigated the effects of PA on the enzymatic browning by inhibiting PPO and POD activities in fresh-cut Chinese chestnuts. Additionally, the inhibition modes and binding sites between PA and PPO and POD were determined.

Farmers’ perceptions of land value determine how land is used, which, in turn, can affect the ecological protection and sustainable development of land resources. This study constructed an index system of farmers’ perceptions of the sustainable development value of agricultural land in four aspects: economic value, security value, ecological value, and emotional value. Using data from 1652 farm households in Shaanxi Province, China, we empirically analyzed the influence of farmers’ perceptions of sustainable development value on their intention to obtain financing secured by agricultural land. Farmers’ perceptions of sustainable development value were found to have a significant negative effect on their willingness for agricultural land secured financing, and social capital played a negative moderating role in the relationship between the two. Further, we found differences between ordinary farmers and new management entities in their value perceptions of agricultural land; thus, there was heterogeneity in the effect on intention to obtain financing secured by agricultural land. Based on the findings, we suggested ways to promote the market development of agricultural land financing, including guiding farmers to form sustainable perceptions of agricultural land value, and innovating mortgages secured by agricultural land with new management entities as the main demanders.