Ultrafine grinding is an important pretreatment to achieve the physical modification of dietary fiber. In this study, ultrafine grinding treatments were performed for different times to give pea insoluble dietary fiber (PIDF) samples with varied particle sizes (D₅₀). The correlations and quantitative relationships between the microstructures of multi-scales PIDF and its in vitro glucose adsorption and diffusion behaviors were comprehensively evaluated. The results indicated that the specific surface area (SSA), pore volume (PV) and oxygen-to-carbon surface ratio (O/C) of PIDF were significantly increased by ultrafine grinding at the cellular scale, while D₅₀ and cellulose crystallinity (CrI) were significantly decreased. These changes significantly improved the glucose adsorption capacity (GAC) of PIDF. The order of importance of microstructural changes on GAC was O/C > PV > SSA > CrI > D₅₀. GAC showed positive exponential relationships with SSA, PV, and O/C and showed a negative linear relationship with CrI. The ability to retard glucose diffusion increased significantly with decreased fiber particle size because of improved adsorption and interception of glucose and the dense physical barrier effect of PIDF. The quantitative equation of maximum glucose dialysis retardation index was GDRI_max = −1.65 ln(D₅₀) + 16.82 ln(GAC) − 68.22 (R² = 0.99). The results could provide theoretical support for quantitative and targeted intervention of dietary fiber structure for blood glucose control.

The effects of hot air drying (HAD), microwave-assisted hot air drying (MHAD) and vacuum freeze drying (VFD) on the antioxidant and volatile profiles of blueberry pomace (BP) were investigated. The dried BP produced by VFD showed the highest content of antioxidant components and strongest antioxidant activity. MHAD shortened the drying time by 62.5 % with weakened antioxidant profiles. A total of 14 anthocyanin monomers were monitored by UPLC-ESI-MS while 49 typical volatile compounds (VOCs) were identified by HS-GC-IMS. According to orthogonal partial least squares-discriminant analysis (OPLS-DA) and variable influence in projection (VIP) models, 21 VOCs were selected as key marker compounds. High temperature (≥ 50 °C) was beneficial to produce characteristic VOCs. The dried BP exhibited enhanced antioxidant profiles and pleasant aroma compared with the whole blueberry fruit. Overall, concerning the cost, antioxidant and aroma profiles, HAD at 60 °C is a suitable technique for the drying of BP.

Black tea leaves were pulverized at an organ-scale (~mm), tissue-scale (500–100 μm) and cell-scale (<50–10 μm) to investigate their physicochemical and functional properties. The results showed that cell-scale powders exhibited a bright brown color compared with organ- or tissue-scale powders with the highest total color difference (∆E) of 39.63 and an L value of 55.78. There was no obvious difference in the oil-holding capacity (OHC) of the organ- and tissue-scale powders (3.71–3.74 g/g), while the OHC increased significantly to 4.08 g/g in cell-scale powders. The soluble dietary fiber (SDF) content of cell-scale powders increased remarkably to 10.41%, indicating a potential application as a high-SDF food. Further, cell-scale pulverization of black tea enhanced its DPPH scavenging activity and ferric-ion-reducing antioxidant power (FRAP). However, the polyphenol content (13.18–13.88%) and the protein content (27.63–28.09%), as well as the Pb²⁺ adsorption capacity (1.97–1.99 mg/g) were not affected by multiscale pulverizations. The mean particle size (D₅₀) correlated linearly with tap density (TD), color parameters of L and b, SDF content, DPPH scavenging activity and FRAP. The results indicate that black tea powders pulverized at a cell-scale can be used as a soluble fiber-rich functional food additive with a bright color, enhanced OHC and antioxidant capacity.

Blueberry pomace (BP) powders are rich in bioactive compounds and possesses a fruity aroma, making them promising food ingredients. Micronization can improve their microstructure, phenolic release, aroma, and color. This study applied coarse grinding and superfine grinding to produce BP powders with five distinct particle sizes at three scales: plant scale (>500 μm), tissue scale (100–500 μm) and cellular scale (10–100 μm). The results and a correlation analysis indicated that at an intermediate grinding between the tissue and cellular scale, the microstructural changes of the increasing particle porosity and decreasing particle size enhanced the phenolic release capacity. However, the phenolic contents in particles at the cellular scale decreased, attributable to thermal degradation from grinding. Furthermore, a total of 45 volatile organic compounds (VOCs) were identified. Notably, cellular grinding scale enriched both fruity and roasted aroma associated with the increasing pore volume (PV) and the specific surface area (SSA) and the decreasing particle size. In addition, grinding enhanced powder lightness and redness with the control. In conclusion, considering the microstructures, functional components, aroma and color, grinding at 20 min with the particle size mostly between 10 and 100 μm, with a small portion between 100 and 200 μm, is the preferred method for blueberry pomace.