Excessive fructose intake is associated with the increased risk of mental illness, such as depression, but the underlying mechanisms are poorly understood. Our previous study found that high fructose diet (FruD)-fed mice exhibited neuroinflammation, hippocampal neurogenesis decline and blood–brain barrier (BBB) damage, accompanied by the reduction of gut microbiome-derived short-chain fatty acids (SCFAs). Here, we found that chronic stress aggravated these pathological changes and promoted the development of depressive-like behaviors in FruD mice. In detail, the decreased number of newborn neurons, mature neurons and neural stem cells (NSCs) in the hippocampus of FruD mice was worsened by chronic stress. Furthermore, chronic stress exacerbated the damage of BBB integrity with the decreased expression of zonula occludens-1 (ZO-1), claudin-5 and occludin in brain vasculature, overactivated microglia and increased neuroinflammation in FruD mice. These results suggest that high fructose intake combined with chronic stress leads to cumulative negative effects that promote the development of depressive-like behaviors in mice. Of note, SCFAs could rescue hippocampal neurogenesis decline, improve BBB damage and suppress microglia activation and neuroinflammation, thereby ameliorate depressive-like behaviors of FruD mice exposed to chronic stress. These results could be used to develop dietary interventions to prevent depression.

The effect of hot-water blanching (HWB) on drying characteristics and product qualities of dried apple slices with the novel integrated freeze-drying (NIFD) process was investigated by comparing with 3 different FD methods. Compared with the NIFD process without HWB pretreatment (VF-FD), the NIFD process with HWB pretreatment (HWB-VF-FD) resulted in a significantly higher mass loss and more sufficient freezing in vacuum-frozen samples, significantly higher rehydration ratio (RR), higher shrinkage ratio (SR), smaller Vitamin C (VC) content and lower hardness and better apparent shape in freeze-dried samples, and fewer change to the color of the dried or rehydrated samples (p<0.05). Compared with the conventional FD process with HWB pretreatment (HWB-PF-FD), HWB-VF-FD cost significantly less processing time and FD time and obtained significantly higher RR (p<0.05), almost the equivalent SR, VC content, and hardness, and similar appearance in dried samples. The microstructure of apple cell tissues was analyzed by transmission electron microscopy and scanning electron microscopy to interpret the above differences in drying characteristics and product qualities. The results suggested that the NIFD process of apple slices with HWB pretreatment was a promising alternative method to decrease drying time, achieve similar product quality, and simplify the process steps of the conventional FD technology.

Lemon fruits have a non-uniform histological structure, and are characterized by abundant volatile compounds. However, the distribution of volatile compounds in different tissues remain unknown. Herein, electronic nose (E-nose) and headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) were employed to qualitatively and quantitatively analyze the volatile compound content in different tissues of fresh lemon fruits, while their microstructures were observed using several microscopy methods. The numbers of volatile compounds detected in the flavedo, albedo, juice vesicles, and segment wall were 41, 23, 29, and 19, respectively. The volatile compounds detected in the four tissues were mainly alkenes, alcohols, aldehydes, esters, and ketones, with a significant descending order in the total content (p < .05). The measurements of E-nose and HS-SPME-GC-MS both showed that the highest total content of volatile compounds was in the flavedo, followed by albedo, juice vesicles, and segment wall (p < .05). Furthermore, oil sacs and oil droplets were only observed in the flavedo by microstructure observation, where more essential oils (mainly volatile compounds) were distributed. The microstructure observation results also verified the measurement results of the E-nose and HS-SPME-GC-MS. These findings provide basic data for sensory evaluation and the comprehensive processing and utilization of lemon fruits.

• Volatiles’ total content showed a first fast and then slow decrease during drying. • The IFD samples preserved higher content of volatiles, free amino acids, and soluble sugars. • Most volatile compounds showed negative correlations with amino acids. • Most volatile compounds showed positive correlations with soluble sugars.