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The water status, texture properties, sugars, and total carotenoid of dehydrated yellow peach slices pretreated with or without osmotic dehydration (OD) combined with heat pump drying were studied. In this study, different osmotic agents were used, namely, sucrose and isomaltooligosaccharide (IMO) with 30 °Brix for 1, 3, and 5 h. Results showed that the dehydrated samples pretreated by sucrose-OD with the best shape and cell structure showed lower hardness compared to the dehydrated yellow peach slices with IMO-OD pretreatment and without OD pretreatment. Notably, the highest total carotenoid content was found in dehydrated yellow peach slices pretreated by IMO-OD, followed by samples without OD, and samples with sucrose-OD pretreatment. In addition, the lowest a

Background High carotenoid content always lead to a yellower/redder color in carrots, while a puzzling phenomenon still exists that freeze-dried carrots (FDC) have a higher carotenoid content but a lighter color compared with thermal-dried carrots. It seems that carotenoid is not the only main factor affecting sample color. Hence the discoloration characteristics of freeze-dried carrots were comprehensively analyzed from physical structure and color-related chemical composition profile. Results Outcomes of low-field nuclear magnetic resonance and scanning electron microscopy showed that sublimation of immobilized water preserved the intact porous structure of FDC, which kept the volume shrinkage below 30% and led to less accumulations of color-related compositions. Besides, results of correlation and principal component analysis-X model proved that lutein and caffeic acid mainly affected a* value (r = 0.917) and b* value (r = 0.836) of FDC, respectively. Moreover, lipoxygenase indirectly affected sample color by degrading carotenoids, and the lutein content loss for fresh and blanching FDC was 41.56% and 47.14%, respectively. Conclusions The discoloration of FDC was significantly affected by both physical structure and color-related chemical compositions. © 2021 Society of Chemical Industry.

Background Polyphenol oxidase (PPO) is considered a problem in the food industry because it starts browning reactions during fruit and vegetable processing. Ultrasonic treatment is a technology used to inactivate the enzyme; however, the mechanism behind PPO inactivation is still unclear. For this reason, the inactivation, aggregation, and structural changes in PPO from quince juice subjected to ultrasonic treatments were investigated. Different intensities and times of ultrasonic treatment were used. Changes in the activity, aggregation, conformation, and structure of PPO were investigated through different structural analyses. Results Compared to untreated juice, the PPO activity in treated juice was reduced to 35% at a high ultrasonic intensity of 400 W for 20 min. The structure of PPO determined from particle size distribution (PSD) analysis showed that ultrasound treatment caused initial dissociation and subsequent aggregation leading to structural modification. The spectra of circular dichroism (CD) analysis of ultrasonic treated PPO protein showed a significant loss of α-helix, and reorganization of secondary structure. Fluorescence analysis showed a significant increase in fluorescence intensity of PPO after ultrasound treatment with evident blue shift, revealing disruption in the tertiary structure. Conclusion In summary, ultrasonic treatment triggered protein aggregation, distortion of tertiary structure, and loss of α-helix conformation of secondary structure causing inactivation of the PPO enzyme. Hence, ultrasound processing at high intensity and duration could cause the inactivation of the PPO enzyme by inducing aggregation and structural modifications. © 2019 Society of Chemical Industry.

Background Recently, consumers' demand on high quality dried fruit or vegetable products have increased dramatically. The instant controlled pressure drop (DIC) dried products have attracted consumers' attention due to its unique sensory characteristics. The product quality, especially the appearance quality of the DIC products, is influenced closely by water status and water distribution in the material, which is rarely reported in the literatures. In this study, a comparison system for the apple cubes with or without the moisture equilibrium process (MEP) was established to explain the effect of the MEP on the expansion behavior of the DIC dried apple cube. Results The results showed that the MEP could induce a more homogenous spatial distribution of water in the semi-dried apple cube after pre-drying. Meanwhile, the MEP treated and DIC dried apple cubes showed better quality in terms of the appearance and texture properties including high porosity (71.77%), large pores (maximum pore size of 1.55 mm), and thin pore walls (pore wall thickness of 0.079 mm). Conclusion The MEP was approved to be a compulsory treatment to achieve the DIC dried apple cubes with good expansion behavior. © 2019 Society of Chemical Industry.

White-flesh guava is widely planted in tropical or subtropical areas of Southeast Asia. Despite of folk statements on specific function, few researches are focused on the description of its plant secondary metabolites. In the present work, contents of total phenolics and flavonoids as well as antioxidant activity from different parts (peel, flesh, and seed) were determined. The constituents of ethanol extracts were characterized by HPLC-QTOF-MS. A total of 69 phenolic compounds as well as nine polar compounds were detected, with flavonoids, hydrolyzable tannins, phenolic acid derivatives, and benzophenones of the four predominant phenolic compounds. Moreover, the presence of other phenolics (lignan, phenylethanoid, stilbenoid, and dihydrochalcones) was revealed. Simultaneously, the polar compounds, such as triterpenoids, iridoid were identified. Benzophenones and triterpenoids were proved to be marked constitutes of peel and flesh, respectively. The existence of isoflavonoids, lignan, phenylethanoid were firstly reported for edible parts or by-products of guava. The results showed that white-flesh guavas, particularly peel parts, were superior resources of antioxidant compounds, with exploitation value.

The effect of freeze drying (FD), far‐infrared radiation drying (FIRD), heat pump drying (HPD), hot air drying (HAD), and hot air combined instant controlled pressure drop drying (DIC) were compared on the drying efficiency and quality attributes of dried shiitake mushrooms. The results showed that in comparison with the HPD, HAD, and DIC, the FIRD shiitake mushroom exhibited better appearance with less shrinkage and lower ΔE (6.10), lower hardness (34.82 N), and higher rehydration ratio (7.55), which were more resemble to those of the FD sample. Besides, a significantly higher (p

BACKGROUND Computer vision-based image analysis system is widely used in food processing to evaluate the quality changes recently. It could objectively measure surface colour of various products since it provide some obvious advantages with its objectivity and quantitative capabilities. In this study, computer vision-based image analysis system was used to investigate the colour changes of apple slices dried by instant controlled pressure drop-assisted hot air drying (AD-DIC). RESULTS The CIE L* value and PPO activity in apple slices decreased during entire drying process, while other color indexes including CIE a*, b*, △E, C* value increased. The browning ratio calculated by image analysis increased during drying process, and sharply increment was observed for DIC process. The change of 5-hydroxymethylfurfural (5-HMF) and Fluorescent compounds (FIC) showed the same trend with browning ratio due to Maillard reaction. Moreover, the concentration of 5-HMF and FIC both had a good quadratic correlation (R2>0.998) with the browning ratio. CONCLUSION Thus, browning ratio was a reliable indicator of 5-HMF and FIC changes in apple slices during drying. The image analysis system could be used to monitor color changes, 5-HMF and FIC in dehydrated apple slices during AD-DIC process.

Summary The effect of instant controlled pressure drop-assisted hot air drying (AD-DIC) on browning-related components in apple slices was studied. Results showed the AD temperature had no significant effect on colour index of final apple slices. The aspartic acid, glutamic acid, lysine, histidine, arginine, sucrose and dehydroascorbic acid (DHAA) in apple slices increased firstly during the AD process and then decreased during DIC process. The fructose, glucose, reduced ascorbic acid and major phenolic compounds reduced with the abrupt increase of 5-hydroxymethylfurfural (5-HMF) during AD-DIC. There were significant correlations (P

Summary Degradation kinetics of total phenolic compounds, capsaicinoids and antioxidant activity in red pepper during both hot air drying and infrared drying were investigated, as well as the correlation between antioxidant compounds and antioxidant capacity was discussed in current study. The fractional conversion kinetic and first order kinetic models were proved to describe the changes of total phenolic compounds vs. drying time and moisture content, respectively. Degradation of capsaicinoids and antioxidant capacity vs. drying time and moisture content both followed fractional conversion kinetic model. Infrared drying accelerated the degradation rate of total phenolic compounds and capsaicinoids vs. drying time as compared with hot air drying at the same temperature; however, a contrary result was found that infrared drying decreased the degradation rate of both total phenolic compounds and capsaicinoids vs. moisture content. Total phenolic compounds exhibited a stronger relationship with antioxidant capacity of red pepper analysed by multiple linear regression analysis.

The ability of excipient nanoemulsions to increase the bioaccessibility of different kinds of nutraceuticals (phenolics and carotenoids) in mangoes was studied. Oil-in-water excipient nanoemulsions containing small digestible lipid nanoparticles (d200 nm) were prepared using different oil phases: medium chain triglycerides (MCT) and long-chain triglycerides (LCT). These nanoemulsions were then mixed with pureed mango and passed through a simulated gastrointestinal tract (GIT): mouth, stomach, and small intestine. Carotenoid bioaccessibility decreased in the following order: LCT nanoemulsionsMCT nanoemulsionsbuffer solution, which was attributed to differences in the solubilization capacity of the mixed micelles generated in the intestinal fluids. The digestion products of LCT formed mixed micelles with hydrophobic domains large enough to accommodate the carotenoids, whereas those of MCT did not. Excipient emulsions had much less effect on phenolic bioaccessibility, which may be because phenolics are smaller more polar molecules and are therefore more easily solubilized in aqueous intestinal fluids. These results highlight the potential of excipient nanoemulsions in boosting the bioavailability of lipophilic bioactive agents in fruits and vegetables.

Background Hot air drying and sun drying are traditional drying technologies widely used in the drying of agricultural products for a long time, but usually recognized as time-consuming or producing lower-quality products. Infrared drying is a rather effective drying technology that has advantages over traditional drying technologies. Thus, in order to investigate the application of infrared drying in the dehydration of red pepper, the drying characteristics and quality of infrared-dried red pepper were compared with those of sun-dried and hot air-dried red pepper. Results The infrared drying technology significantly enhanced the drying rate when compared with hot air drying and sun drying. Temperature was the most important factor affecting the moisture transfer during the process of infrared drying as well as hot air drying. Effective moisture diffusivity (Deff ) values of infrared drying ranged from 1.58 × 10(-9) to 3.78 × 10(-9) m(2) s(-1) . The Ea values of infrared drying and hot air drying were 42.67 and 44.48 kJ mol(-1) respectively. Infrared drying and hot air drying produced color loss to a similar extent. Relatively higher crispness values were observed for infrared-dried samples. Conclusion Sun drying produced dried red pepper with the best color when compared with hot air drying and infrared drying. Meanwhile, infrared drying markedly improved the drying rate at the same drying temperature level of hot air drying, and the products obtained had relatively better quality with higher crispness values. © 2015 Society of Chemical Industry.

BACKGROUND Dehydration has been considered as one of the traditional but most effective techniques for perishable fruits. Raspberry powders obtained after dehydration can be added as ingredients into food formulations such as bakery and dairy products. In this study, raspberry powders obtained by hot air drying (HAD), infrared radiation drying (IRD), hot air and explosion puffing drying (HA-EPD), infrared radiation and microwave vacuum drying (IR-MVD) and freeze drying (FD) were compared on physical properties, bioactive compounds and antioxidant activity. RESULTS Drying techniques affected the physical properties, bioactive compounds and antioxidant activity of raspberry powders greatly. FD led to significantly higher (P < 0.05) values of water solubility (45.26%), soluble solid (63.46%), hygroscopicity (18.06%), color parameters and anthocyanin retention (60.70%) of raspberry powder compared with other drying methods. However, thermal drying techniques, especially combined drying methods, were superior to FD in final total polyphenol content, total flavonoid content and antioxidant activity. The combined drying methods, especially IR-MVD, showed the highest total polyphenol content (123.22 g GAE kg−1 dw) and total flavonoid content (0.30 g CAE kg−1 dw). Additionally, IR-MVD performed better in antioxidant activity retention. CONCLUSION Overall, combined drying methods, especially IR-MVD, were found to result in better quality of raspberry powders among the thermal drying techniques. IR-MVD could be recommended for use in the drying industry because of its advantages in time saving and nutrient retention. © 2015 Society of Chemical Industry