In order to determine the effect of trehalose as a total or partial replacement of sucrose in osmotic dehydration on the quality of candied strawberry, the changes in the solid growth rate, water loss rate, water activity, free sugar content, water state, texture and color of candied strawberry were studied when the osmotic dehydration was performed using a mixture of trehalose at varying levels ranging from 0% to 40% and sucrose (the total mass was 40% of that of strawberry). The results showed that with increasing trehalose proportion, the solid gain rate decreased linearly while the water activity and the trehalose content increased linearly. However, the relationships of trehalose levels with the transverse relaxation times and peak areas for three water states and color parameters were all fitted to a quadratic function, indicating that the interaction between trehalose and sucrose is mainly manifested in the freedom of water and color. In addition, excessive addition of trehalose increased the individual differences in the texture of candied strawberry. At addition levels of 35% and 40%, the variation coefficients of viscous force were 174% and 67%, respectively, which were higher than those at the other addition levels (17%–46%). The research results provide a reference for the application of trehalose in candied strawberry.

In order to illustrate the chemical pathway of the browning of preserved strawberry during storage, commercial preserved strawberries were stored at 37, 25 or 4 ℃ and evaluated for color parameters and the contents of ascorbic acid, total phenol, three free sugars, five free amino acids and 5-hydroxymethyl furfural (5-HMF), and correlation and cluster analyses were performed as well. The results showed that for each temperature, the color parameters L*, a*, and b* of preserved strawberry all decreased with storage time, and the total color difference ΔE was 11.42–33.33 after 90 days of storage, suggesting that the color of preserved strawberry changed obviously during storage. Additionally, the contents of ascorbic acid, total phenol, free sugars, and free amino acids decreased in varying degrees, while 5-HMF content increased linearly. The correlation analysis showed that ΔE was significantly correlated with all color and chemical parameters except glutamine content (P < 0.05, P < 0.01, P < 0.001), indicating that the browning may result from a combination of ascorbic acid degradation, polyphenol oxidation and Maillard reaction. Using cluster analysis, the samples stored at higher temperature and for a longer period of time were distinguished from others, suggesting that the influence of storage temperature and period on the browning degree cannot be neglected. In conclusion, during storage, ascorbic acid, total phenol, free sugars and free amino acids are involved in the browning of preserved strawberry, despite the asynchrony. The results of this study provide a rationale for browning control of preserved strawberry.

Explosion puffing drying is well known as one of the most novel processing of food products. The raw materials are also required to be pre-dried at the given moisture content. A preferred combination of vacuum freeze-drying and explosion puffing drying can be utilized to produce the crispy products of fruit and vegetable with better color and higher brittleness. Among them, vacuum freeze-drying can be used to maintain a better shape, and then form a more loose porous structure in the dried samples. This study aims to explore the effect of pre-drying treatment on the structural and textural properties of different fruit and vegetable crisps after vacuum freeze-drying combined with explosion puffing drying. Three moisture conversion points were also selected (60 %, 45 %, and 30 % moisture content in wet base). The moisture status, cell structure, shrinkage, porosity, stress-relaxation properties, and texture profile analysis (TPA) were analyzed for the pre-dried samples. The drying time, energy consumption, and texture properties were determined for the dried crisp samples. The results showed that the moisture content gradually decreased, and the free water gradually disappeared with the pre-drying, while the immobilized water was the main component of water in the samples. The decreased degree of free water content presented a significant difference among different fruit and vegetable slices, when the vacuum freeze-drying to 60 % moisture content. The free water contents of apples, peaches, pears, and potatoes decreased by 94.94%, 89.76%, 91.53%, and 99.49%, respectively. A large amount of free water was removed from the pre-dried samples during the early drying stage. The shrinkage rate of dried crisps decreased gradually, as the water conversion point continued to decrease, whereas, there was an increase in the porosity, hardness, chewiness, and elastic modulus. The higher shrinkage ratios were found in the crisps of apple, peach, and pear, compared with the rest. The higher hardness was found in the crisps of potato and yam. Green radish crisps shared the more severe fractures of the cell wall and the highest porosity. There was a significant difference in the texture properties of fruit and vegetable crisps with the different moisture conversion points (P<0.05). Once the water conversion point was 60%, the hardness and brittleness of the fruit and vegetable crisps were relatively higher, with the potato and yam crisps having the highest hardness, whereas, the peach and pear crisps had the highest brittleness. The dried crisps presented a too-soft texture and poor taste at the lower water conversion point. The reason was that the fruits and vegetables with the higher moisture easily formed the dry layer on the surface of the samples during expansion, resulting in a higher hardness of the chips. Once the moisture content was lower, the skeleton structure in the samples were basically formed after vacuum freeze-drying, while the subsequent explosion puffing drying then resulted in insufficient expansion force and minimal impact on the texture of the samples. The porosity of green radish crisps was significantly higher than that of the rest when the water conversion point was 30%. The skeleton in the samples was basically formed at the later stage of drying. The lower shrinkage ratio resulted in a larger internal porosity. The higher the water conversion point was, the shorter the combined drying time was, particularly for the fruits and vegetables, except for peach and pear, and the lower the energy consumption for all fruits and vegetables was. The statistical analysis revealed that the moisture conversion point and porosity played a crucial role in the texture properties of the fruit and vegetable crisps during vacuum freeze-drying. The finding can provide a significant implication on the drying time and energy consumption.

In order to improve the bioavailability of lutein (LUT), a novel lutein-stevioside nanoparticle (LUT-STE) were prepared previously, but the information about LUT-STE on protecting of eye health was limited. This study investigated the effect of LUT-STE on antioxidant activity of H₂O₂-induced human retinal pigment epithelial (ARPE) cells. LUT and LUT-STE (final concentration of 5 μg/mL) significantly enhanced cell viability from (74.84 ± 5.10)% to (81.92 ± 10.01)% (LUT) and (89.33 ± 4.34)% (LUT-STE), and inhibited the cell apoptosis (P < 0.05). After pretreatment with LUT-STE in ARPE cells, the levels of superoxide dismutase (SOD), catalase (CAT) and glutathion peroxidase (GSH-Px) in ARPE cells were significantly increased (P < 0.05), the contents of reactive oxygen species (ROS) and malondialdehyde (MDA) were decreased. In addition, the vascular endothelial growth factor (VEGF) levels were inhibited by 13.61% and 17.39%, respectively, pretreatment with LUT and LUT-STE. Western blotting results showed that the pretreatment with LUT-STE inhibited the expression of caspase-9 and caspase-3 and up-regulated Bcl-2/Bax pathway to inhibit H₂O₂-induced apoptosis. In summary, the novel delivery LUT-STE had more pronounced inhibitory effect on H₂O₂-induced damage in human ARPE cells.

β-Carotene, a typical non-oxygenated carotenoid, is the most efficient source of retinol (VA). The low bio-availability of β-carotene lead to large accumulation in colon; however, the relationship between β-carotene and gut microflora remains unclear. This study intends to explore the interaction between β-carotene and gut microflora using an in vitro fermentation model. After 24 h fermentation, the degradation rate of β-carotene was (64.28 ± 6.23)%, which was 1.46 times that of the group without gut microflora. Meanwhile, the production of VA was nearly 2 times that of the group without gut microflora, indicating that the gut microflora can metabolize β-carotene into VA. β-Carotene also influences the production of short-chain fatty acids (SCFAs), the production of total SCFAs in 0.5 mg/mL β-carotene (BCM) group was (44.00 ± 1.16) mmol/L, which was 2.26 times that of the blank control (BLK) group. Among them, the production of acetic acid in BCM group was (19.06 ± 0.82) mmol/L, which was 2.64 time that of the BLK group. Furthermore, β-carotene significantly affected the structure and composition of gut microflora, increasing the abundance of Roseburia, Parasutterella and Lachnospiraceae, and decreasing the abundance of Dialister, Collinsella and Enterobacter (P < 0.05). This study provides a new way to understand how β-carotene works in human body with gut microflora.