Pectic oligosaccharides (POS), small molecular polymers, can be prepared from pectin by different methods. Compared with natural pectin, POS have lower molecular mass, better water solubility, higher bioavailability, and more diverse biological activities. A series of POS with different molecular masses and structures can be obtained under different preparation conditions. In addition, the biological activities of POS are closely related to their molecular mass and structures. This review aims to comprehensively summarize the preparation, purification, structure analysis, and biological activity of POS, in order toprovide some references for their applications as natural active substances in the fields of food, medicine, and health products.

As an emerging nanoparticle, carbon dots (CDs) have been widely used in the fields of chemical sensing, biological imaging, drug delivery, photocatalyst and food detection due to its superior biocompatibility and photoluminescence. Food processing by-products come from a wide range of sources and are easy to obtain. Moreover, the surface of CDs prepared from food processing by-products is usually rich in functional groups and miscellaneous elements, imparting excellent photocatalytic, antioxidant and antibacterial properties to CDs. In recent years, CDs have been used as food packaging additives to enhance the ultraviolet (UV) shielding, mechanical, antioxidant and antibacterial properties of food packaging. In this paper, the types of food processing by-products that can be used to prepare CDs and natural polymer-based films added with CDs and the application of CDs in active and intelligent packaging are reviewed in order to provide guidance for the preparation of CDs from food processing by-products and its application in food packaging.

In order to explore the effect of heat shock treatment (HT) on the storage quality of fresh-cut lily bulbs, changes in the quality characteristics of lily bulb slices (Lilium davidii var. unicolor Cotton) exposed to heat shock treatment (hot water at 55 ℃, 2 min) were examined during storage at 4 ℃. The results demonstrated that HT effectively maintained the color of fresh-cut lily bulbs during storage and preserved the cell wall structure. The activities of peroxidase (POD), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL) were suppressed by HT. Meanwhile, the accumulation of total phenolics (TP) and malondialdehyde (MDA) and the increase of relative electric conductivity (REC) were delayed, which led to reduced mass loss, decay rate, and browning degree. Comparison with the control group, the activities of POD, PPO and PAL in the HT group decreased by 95.26%, 21.74% and 41.65%, respectively. The decay rate, browning degree, MDA content, REC and TP content in the HT group were 10.56%, 1.55, 0.13 μmol/g, 19.71% and 3.51 mg/g, respectively, which were all significantly lower than those in the control group (P < 0.05), and the hardness, whiteness and soluble protein content were 1 848.09 g, 79.65 and 7.62 mg/g, respectively, which were all significantly higher than those in the control group (P < 0.05). After 40 days of storage, mass loss rates of 0.85% and 0.66% and soluble sugar contents of 14.04% and 14.78% were observed respectively for the control and HT groups, with no significant difference being found between the groups (P < 0.05). Furthermore, plasma membrane dissolution did not appear in the HT group until the 40th day, which was 30 days later than the control group. Therefore, HT effectively delayed the quality deterioration of fresh-cut lily bulbs during storage and prolonged the storage time.