The structural and physicochemical properties of pomelo peel powders with different particle sizes were investigated. The MasterSizer and scanning electron microscopy observations indicated that three pomelo peel powders with different particle sizes were successfully prepared via jet milling, of which the average diameters (d(90)) were 53.43 ± 0.49, 27.73 ± 0.13, and 20.15 ± 0.17 µm. Fourier‐transform infrared spectroscopy, X‐ray diffraction, and low field nuclear magnetic resonance analysis indicated that the functional groups of pomelo peel powders were not affected by particle size; while the crystal region, proportion of immobile water (A22) and free water (A23) decreased with reduced particle size. The decrease in the proportion of immobile water and free water resulted in reduced solubility and water‐holding capacity of pomelo peel powders with the smallest particle size. Our findings suggest that the desirable properties of pomelo peel powders can be designed by appropriate particle size. Practical application The study investigated the structural and physicochemical properties of pomelo peel powders with different particle sizes. The data indicated that the desirable properties of pomelo peel powders can be designed by appropriate particle size. The study may be useful for the utilization of pomelo peels as a raw food material.

Pomelo fruitlets have the potential for extracting cellulose. This study aimed to investigate characterization and functionality of cellulose extracted from pomelo fruitlets by different extraction methods. Cellulose extracted by acidic-alkaline hydrogen peroxide hydrolysis (CAA), alkaline hydrogen peroxide hydrolysis (CA), and ultrasonic assisted alkaline hydrogen peroxide hydrolysis (CUA) were prepared from pomelo fruitlets. The results showed that cellulose CUA had higher yield and purity with higher crystallinity and smaller particle size than those of CAA or CA (p < 0.05). Specifically, the yield of CUA was 82.75% higher than that of CAA, and purity was increased by 26.42%. Additionally, water- and oil-holding capacities of CUA were superior to those of CAA or CA, increasing by 13–23% and 10–18%, respectively. The improvement of water- and oil-holding capacities were highly related to its smaller particle size with increased surface area. The results suggested that ultrasonic assisted alkaline hydrogen peroxide hydrolysis is a promising and efficient method to prepare high-purity cellulose from pomelo fruitlets, and this cellulose is expected to be a food stabilizer and pharmaceutical additive.

Phosphate is widely used in surimi products to improve the gel properties. However, excess addition of phosphate occurs, which can harm the consumer's health. This study aimed to evaluate the effects of agar gum and fucoidan on maintaining the gel properties of surimi products instead of phosphate. Interestingly, our results showed that 0.125% of agar gum and fucoidan to replace phosphate could enhance water‐holding capacity and maintain gel strength and textual properties of surimi products well. Especially at frozen storage for 1 year, 0.125% of agar gum reduced the expressible moisture content of surimi products by around 10% (p < .05). Sensory evaluation showed that 0.125% of agar gum and fucoidan instead of phosphate can improve tissue and fondness of surimi products in refrigerated storage for 24 h but not in frozen storage for 1 year. The addition of agar gum and fucoidan at a high concentration >0.50% increased the WHC, but significantly decreased gel strength and springiness of surimi products (p < .05). Particularly, 1.00% of agar gum and fucoidan reduced gel strength by around 20% (p < .05). It might be due to the destruction of the gel network structure of surimi protein following the excess addition of these polysaccharides. It can be concluded that 0.125% of agar gum and fucoidan can replace phosphate to develop high‐quality surimi products, and excessive addition of them have negative effects.

The effect of black tea powder on the antioxidant activity and gel characteristics of fish balls from silver carp were investigated after freezing storage for 7 days. The results show that black tea powder with different concentrations of 0.1%, 0.2% and 0.3% (w/w) could significantly increase the antioxidant activity of fish balls (p < 0.05). In particular, at the concentration of 0.3%, the antioxidant activity was the strongest among these samples, where the reducing power, DPPH, ABTS and OH free radical scavenging rate were up to 0.33, 57.93%, 89.24% and 50.64%, respectively. In addition, black tea powder at the level of 0.3% significantly increased the gel strength, hardness and chewiness while greatly reducing the whiteness of the fish balls (p < 0.05). ESEM observation found that the addition of black tea powder could promote the crosslinking of proteins and reduced the pore size of the gel network structure of the fish balls. The results suggest that black tea powder could be used as a natural antioxidant and gel texture enhancer in fish balls, which we found to be much related to the phenolic compounds of black tea powder.

&lt;p&gt;CCN number concentration (N&lt;sub&gt;CCN&lt;/sub&gt;), particle size-resolved activation ratio at supersaturation (SS) of 0.10% and particle number size distribution (PNSD) in dry state of both ambient PM1 and PM10 particles were measured in the North China Plain in November in 2018. Two fog events were observed during nighttime of 12nd and 13rd Nov. During fog events, the dry particle concentrations sampled from the PM10 inlet were much higher than those from PM1 inlet for particles (particle size bins) with diameter larger than ~200 nm. Additional sub-micron particles sampled by PM10 inlet but not been sampled by PM1 inlet indicates that these particles have grown into droplets with diameter larger than 1um. The growth of particle size by over 5 times can be resulted from not only the activation to form fog droplets but also the hygroscopic growth at RH higher than 99%. There was no significant decrease of particle number concentration larger than ~200 nm during fog periods compared with those beyond the fog periods, suggesting that the fog droplets may be generally smaller than 10um and can be sampled by PM10 inlet. The size-resolved activation ratio curve showed that the critical diameter was about 160-180nm and there was significant difference (&gt;50%) of N&lt;sub&gt;CCN&lt;/sub&gt; at SS of 0.1% between PM1 and PM10, mainly due to the difference of PNSD between PM1 and PM10 in fogs. The measured PNSD and CCN-activity might be applied on the analysis of the relationship between fog droplets and the corresponding ambient supersaturations.&lt;/p&gt;