Salted duck egg white contains many kinds of high quality protein, but it is often discarded as food factory waste because of high salinity and other reasons. The discarded salted duck egg white not only causes a waste of resources, but also causes environmental pollution. Using salted duck egg white as raw material, this study was completed to investigate the effects of three drying methods including freeze drying, vacuum drying, and spray drying on physicochemical and nutritional properties of protein powder from salted duck egg white. The results showed that the solubility, foaming and foaming stability, emulsification and emulsification stability of the protein peptide of salted duck egg white decreased to different degrees after drying. The scavenging rates of freeze-dried samples for superoxide anion, hydroxyl radical, and 1,1-Diphenyl-2-picrylhydrazyl (DPPH·) reached 48.76, 85.03, and 80.17%, respectively. Freeze drying had higher scavenging rates than vacuum drying and spray drying. The results of electron microscopy showed that freeze-drying had the least effect on the structure of protein peptide powder of salted duck egg white. The purpose of this experiment was to provide theoretical guidance and technical support for industrial drying of salted duck egg white protein solution.

Salted duck egg white (SDEW), as the main by-product in the production process of salted egg yolk, has not been effectively used as a food resource because of its high salt concentration. This study creatively used isoelectric point precipitation, ultrafiltration, and cation exchange to separate and purify lysozyme from SDEW and preliminarily explored the enzymatic properties of lysozyme. The results showed that the relative molecular weight of lysozyme was about 14 KDa, and the specific activity of lysozyme reached 18,300 U/mg. Lysozyme had good stability in the temperature range of 30 °C to 60 °C and pH of 4 to 7. Metal ions, Fe²⁺, Cu²⁺, and Zn²⁺, strongly inhibited lysozyme activity. Different surfactants showed certain inhibition effects on lysozyme from SDEW, among which glycerin had the strongest inhibitory effect. This study aimed to provide a theoretical reference for industrial purification and production of lysozyme from SDEW.

Nostoc sphaeroides is an edible Cyanobacterium which has high nutritional value and is widely used in dietary supplements and therapeutic products. N. sphaeroides contains protein, fatty acid, minerals and vitamins. Its polysaccharides, phycobilin, phycobiliproteins and some lipids are highly bioactive. Thus, N. sphaeroides possesses anti-oxidation, anti-inflammation and cholesterol reducing functions. This paper reviews and evaluates the literature on nutritionally and functionally important compounds of N. sphaeroides. It also reviews and evaluates the processing of technologies used to process N. sphaeroides from fresh harvest to dry particulates including pretreatment, sterilization and drying, including their impact on sensorial and nutritional values. This review shows that a suitable combination of ultrasound, radio frequency and pulse spouted microwave with traditional sterilization and drying technologies greatly improves the sensorial and nutritive quality of processed N. sphaeroides and improves their shelf life; however, further research is needed to evaluate these hybrid technologies. Once suitably processed, N. sphaeroides can be used in food, cosmetics and pharmaceutical drugs as an ingredient.