This study selected peach, citrus and apple pectins to construct liquid composite systems consisting of pectin, anthocyanin and polyphenol, which were systematically analyzed for apparent color, spectral characteristics, anthocyanin content, polyphenol composition and content to elucidate the effects of different pectins on the coloration characteristics of the composite system. Results demonstrated that all three pectins at 0.1% concentration competed with polyphenols for binding to anthocyanin, enhancing the composite system’s apparent color and color stability after ultrasound treatment. The pectin-anthocyanin interaction was dependent on methyl ester groups. Peach pectin, characterized by broad molecular mass distribution (polydispersity index = 4.17) and short-chain dominance (m_n = 3.92 × 10⁴ g/mol), exhibited strong anthocyanin interaction, effectively stabilizing the anthocyanin content and altering the chromophore content, and finally causing the system to exhibit a stable deep pink color. Citrus pectin, with its large molecular mass (m_w = 30.85 × 10⁵ g/mol) and loose conformation (R_z = 170.60 nm), only weakly stabilized anthocyanins, primarily through physical encapsulation, having no significant impact on the apparent color. Apple pectin, featuring compact structure (R_z = 39.50 nm) and low molecular mass (m_w = 1.20 × 10⁵ g/mol), had a minor restricting effect on the molecular motion of free polyphenols after competitive binding to anthocyanins, leading to polyphenol oxidation and chromophore structural modifications, and finally imparting a dark brown color to the system. These findings provide theoretical and technical foundations for developing stable anthocyanin-based food systems through rational pectin selection and structural modulation.

Blueberry pulp can be prone to phase separation, flocculation, and stability deterioration during processing and storage, thus constraining its large-scale industry. It is an urgent need to develop naturally stabilized composites. Preliminary studies have revealed that the introduction of kiwifruit pulp can be expected to significantly modify the rheological properties of blueberry pulp, in order to improve the stability. In this study, a systematic investigation was made of the dynamic evolution patterns of the key quality attributes in kiwifruit during storage. The underlying mechanisms were determined to govern their impact on the quality of blueberry-kiwifruit pulp composites. The quality features of kiwifruit were first explored (including soluble solids, texture, electrical properties, microstructure, and flavor) during storage. And then, an analysis was implemented on the effects of kiwifruit under different storage conditions on the quality of blueberry-kiwifruit composite fruit (including pH, conductivity, rheological properties, particle size distribution, and PME activity). Results showed that the total soluble solids (TSS) of kiwifruit firstly increased and then decreased with the prolongation of the storage, due to the degradation of starch particles. And the highest TSS (14.7 %) was observed in the kiwifruit storage for 7 days. Additionally, the starch granules in kiwifruit pulp were first degraded, followed by the hydrolysis of cell wall polysaccharides (such as pectin), which were accompanied by the disruption of the pectin network structure during storage. Therefore, the two key quality indicators of kiwifruit gradually decreased, namely, hardness and cohesiveness, indicating the gradual softening in the macro-texture of kiwifruit. Specifically, both the W1W and W5S response values significantly increased as the storage of kiwifruit was prolonged. In detail, the highest W1W response value (18.255) and W5S response values (4.234) were observed in kiwifruit after 10-day storage. Furthermore, the W1W and W5S response values decreased by 80.89% and 41.99%, respectively, thus subjecting to mingling blueberry pulp with kiwifruit pulp. The reason was that the dilution of the kiwifruit pulp was used to inhibit the concentration of volatile flavor compounds in blueberry pulp. The integrity of the cell wall decreased gradually, while the impedance and reactance shared the downward trend, indicating the decreased hardness and viscoelasticity of kiwifruit. In the blueberry-kiwifruit compound pulp, the pH increased with the increase in storage time, while the conductivity firstly decreased and then increased. The layering and condensation in the compound pulp were significantly improved after the addition of the kiwifruit pulp. The lowest apparent viscosity (4 404.3 Pa·s) was obtained in the compound pulp with kiwifruit that had been kept in storage for 7 days. Particle distribution illustrated that there was a decrease in the Volume-average particle size（D [4,3]） and the Area-weighted average particle size (D [3,2]) of the compound pulp, compared with the single blueberry pulp. It implies that the pulp particles were intensely coated with each other and then formed smaller complexes. Additionally, due to the PME inhibitor (PMEI) from kiwifruit, the PME activity of compound pulp decreased by 38.14%, compared with blueberry pulp after thermal sterilization. This process contributed to the better rheological properties of the compound pulp. Taken together, the kiwifruit stored during the mid-storage period should be considered as the optimal material to improve the rheological quality of the compound pulp.

To investigate the effects of ultrasound-assisted sugar pretreatment on the quality and hygroscopicity of vacuum freeze-dried peach chips, we compared the moisture loss rate and solid yield of peach slices after ultrasound-assisted osmosis in four sugar solutions (sucrose, maltose, glucose and oligoisomaltose) as well as the microstructure, texture (hardness and brittleness), hygroscopicity and glass transition temperature of the resultant peach chips. The results showed that ultrasound-assisted osmosis increased the water loss rate and solid gain of peach slices, resulted in denser pores, cell rupture and structural collapse, and significantly increased the hardness of peach chips compared to the control group (P < 0.05). In addition, ultrasound-assisted osmosis reduced the hygroscopicity of peach chips, and the percentages of mass change after reaching the hygroscopic equilibrium with increasing relative humidity from 0 to 90% ranged from 55.16% to 59.63%, compared to 61.43% for the control group. Ultrasound-assisted osmosis increased the glass transition temperature to 64.27 ℃ compared to the control group (52.37 ℃). In conclusion, ultrasonic-assisted osmotic treatments with sugar solutions have significant influence on the product quality while reducing the hygroscopicity and changing the glass transition temperature of peach chips. The results of this study provide a technical reference for improving the quality of dried peach chips.

Color is an important factor affecting the sensory quality of fruit and vegetable (FV) products. The vibrant and stable color of FV products can give people a good visual enjoyment, which can in turn promote consumers’ appetite and increase the market value of the products. This paper summarizes the types and properties of natural colorants in FV, clarifies the effects of thermal and non-thermal drying technologies and their combination on the color of FV products, reveals the influence mechanism of colorant degradation products on the products’ quality, and reviews the color preservation technologies of dried FV. We hope that this review could provide a theoretical basis for the color preservation and quality enhancement of dried FV products.

In this study, experiments were conducted to investigate the effect of moisture distribution during pre-drying on the microstructure and textural quality of hot air-vacuum freeze dried peach slices. The moisture distribution during the hot air pre-drying process at different temperatures (40, 60 and 80 ℃) and the product temperature during heating were monitored. Three levels of dry-basis moisture content (7, 6 and 5 g/g) were selected as moisture conversion points for each temperature. The color, shrinkage rate, microstructure, pore distribution, textural properties and hygroscopicity of peach crisps were measured. The results showed that drying temperature had a great impact on the moisture distribution during the pre-drying process, but the overall trends of moisture mobility were consistent among the different drying temperatures. The lower the moisture content of the pre-dried sample, the closer the color of the final dried sample to that of the fresh sample. The color of the sample dried at 40 ℃ with a moisture conversion point of 5 g/g was the closest to that of the fresh sample. Drying time had a greater effect on the shrinkage rate than temperature. It took longer to dry peach slices to the same moisture conversion point at 40 ℃ than 60 and 80 ℃. The sample shrank distinctly during both pre-drying and combined drying. There was a significant difference in the pore structure between the freeze-dried and combined dried samples. The sample with a moisture conversion point of 5 g/g had the most heterogeneous pore structure. The average hardness value of the hot air-vacuum freeze dried sample increased by 52.11% compared with that of the freeze-dried sample. The lower the moisture content of the pre-dried sample, the higher the hardness value of the hot air-vacuum freeze dried sample. This study showed that hot air pre-drying can effectively control the crunchiness and hardness of peach crisps. The decrease in the hygroscopicity of the hot air-vacuum freeze dried sample compared with the vacuum freeze dried one may be related to the structure changes during the pre-drying process. In summary, hot air-vacuum freeze drying is conducive to improving the texture quality and storage stability of peach crisps than vacuum freeze drying.

This study was conducted to investigate the effects of blanching methods and freezing rates on the textural properties of processed broccoli. Low-field nuclear magnetic resonance (LF-NMR) spectroscopy and physicochemical analysis were used to evaluate the water distribution, water-holding capacity (WHC), electrical conductivity, and hardness of broccoli samples subjected to hot water or steam blanching followed by freezing at −20, −40, and −80 ℃. Besides, the microstructure was observed. The results indicated that the optimal process for maintaining the hardness of broccoli was steam blanching followed by freezing at −40 ℃. The treatment group exhibited the greatest increase in the peak area proportion (A₂₁) of bound water compared with the control group and the strongest water-holding capacity, the inflorescence and stem retaining 66.72% and 62.53% of the initial hardness, respectively, and the relative electrical conductivity increasing to 87.01%. Scanning electron microscopy (SEM) images showed that the integrity of the cellular structure was maintained after the treatment. This study provides theoretical and technical support for maintaining the quality of frozen prepared broccoli in actual production process.

In this study, using mixed solutions of sucrose (SUC) and fructo-oligosaccharides (FOS), isomaltooligosaccharides (IMO), or xylo-oligosaccharides (XOS) as the medium, pulsed ultrasound (US)-assisted osmotic dehydration (OD) of kiwifruit chunks was carried out. Changes in the properties of mixed sugar solutions were systematically analyzed during the dehydration process, the quality formation of kiwifruit chunks was examined, and the process of mass transfer during OD was evaluated from a multidimensional perspective. Results showed that US accelerated the mass transfer. Specifically, the content of total soluble solids (TSS), osmotic pressure and conductivity of the mixed sugar solutions significantly decreased and the turbidity increased. US-SUC-XOS group showed the highest TSS content (23.65 °Brix), osmotic pressure (1439.00 mOsm/L), conductivity (13316.87 μS/cm) and turbidity (12.50 NTU). During the OD process, the TSS content and osmotic pressure of the mixed sugar solutions decreased, the turbidity increased, and the conductivity decreased first and then increased, indicating that mass transfer took place. Analysis of the quality changes of kiwifruit chunks demonstrated that the TSS content continued to increase. The highest TSS content (15.35 °Brix) was observed in the 12 h US-SUC-XOS group. Additionally, the infiltration of sugars could support cells, resulting in obvious plasmolysis, which in turn contributed to decreased texture properties. Analysis of electrical characteristics demonstrated that US-assisted OD facilitated the movement of charged particles, which was reflected in a decrease in the impedance and reactance values of kiwifruit chunks. Notably, in the US-SUC-XOS group, the adhesion effect slowed down the particle movement, leading to the highest impedance and reactance values. X-ray spectroscopy analysis confirmed the mass transfer of elements. The highest proportion of K (67.08%) and the lowest proportion of Ca (28.61%) were obtained in the 12 h US-SUC-XOS group. Additionally, ¹H nuclear magnetic resonance (NMR) spectroscopy confirmed the mass transfer of sugar molecules between the mixed sugar solution and kiwifruit chunks. The moisture distribution results highlighted that the infiltration of sugar molecules could induce a large amount of free water to escape from kiwifruit chunks and reduce the mobility of water molecules. The 12 h US-SUC-XOS group showed the lowest peak area of free water and the highest peak area of immobile water and bound water. In summary, different mixed sugar solutions mediate different degrees of mass transfer. In particular, SUC-XOS solution can retard the degradation of kiwifruit tissues, in turn contributing to the formation of good quality in kiwifruit chunks.