Modification mechanism of protein in rice adjuncts upon extrusion and its effects on nitrogen conversion during mashing.

The traditional production of wort with adjunct-introduced was achieved by double mashing procedure, which hindered the utilization of proteins in adjunct and led to a deficiency of nitrogen in wort. In this study, the modification mechanism of the extrusion pretreatment on the structure characterization of rice flour protein was investigated. The decoction mashing procedure was performed to enhance the nitrogen conversion of the extruded rice adjunct. Decreased solubility along with disrupted secondary and tertiary structures of rice protein were observed after extrusion. As a result, the total nitrogen, free amino nitrogen, and free amino acids content of wort with extruded rice adjunct-introduced were improved by 23.28 %, 34.67 %, and 7.33 %, respectively, which could be verified by the electrophoretic patterns of the wort protein. The application of extrusion as a pretreatment of adjuncts can promote the protein availability of adjuncts in the decoction mashing stage.

Microencapsulated procyanidins by extruding starch improved physicochemical properties, inhibited the protein and lipid oxidant of chicken sausages.

Microencapsulated procyanidins by extruding starch (MPS) were used in meat and meat products as an antioxidant for their simple production process and high stability. This study investigated the controlled released properties of MPS and their effect on antioxidant capacity, physicochemical properties, and sensory qualities of chicken sausages during 4°C storage within 28 days. Antioxidant capacity, particle size analysis, and simulated digestion in vitro demonstrated that microencapsulation by extruding starch delayed the procyanidins release. The reduced crystal structure of MPS was determined by the morphology observation (SEM) and the decrease of the typical diffraction peak at 2θ of 20.9° (XRD). The MPS-added sausage had a higher (p < 0.05) ABTS and DPPH radical scavenging ratio (97.6% and 67.3%) and sulfhydryl contents (114.69 nmol/g protein) than other groups. Moreover, lower (p < 0.05) thiobarbituric acid reactive substances (TBARS) (0.67 mg MDA/kg sausage) and carbonyl values (3.24 nmol/mg protein) were detected in MPS-added sausages than others at the end of storage. The MPS addition increased redness (a* value) and decreased the lightness (L* value). The sensory analysis suggested that the sausage with the increased redness was favorable. These results denominated that MPS was an alternative antioxidant in chicken sausages. Practical Application: In this study, microencapsulated procyanidins were prepared by extrusion technology, and the effect on the quality of chicken sausages was investigated, which provides an alternative natural antioxidant for meat and meat products.

Bioconversion of Apple Pomace into Microbial Protein Feed Based on Extrusion Pretreatment.

Apple pomace (AP) is often used directly as animal feed, while the value of feeding is limited by its low protein content. In this study, extrusion pretreatment was performed for AP, and further fermentation was carried out to improve its nutrition value. Strains suitable for extruded apple pomace (EAP) to produce high-quality microbial protein (MP) feed were screened from 12 different strains. Results showed that Aspergillus niger 3.324 (Asn), Candida utilis1314 (Cau), Geotrichum candidum 1315 (Gec), Bacillus subtilis A308 (Bas1), and Lactic acid bacteria (Lac) were screened as the dominant strains, which exhibited higher feeding value. Strong symbiotic effect was observed in fermentation with mixed strains of Asn, Cau, Gec, and Lac at the ratio of 1:1:1:1. Compared with AP, the pure protein content in the optimized fermented EAP (FEAP) was increased by 138% accompanying with a pleasant flavor and taste. And its pure protein content was increased by 19.20% in comparison to that of the fermented apple pomace. The nutrition value of FEAP was characterized by amino acid profiles; it found that FEAP was comparable to other commercial proteins with higher contents of histidine, phenylalanine, threonine, and valine. Combination of fermentation and extrusion technology significantly enhanced pure protein content and nutritional composition of apple pomace, which was revalorized as a nutritive animal feed rich in microbial protein.

Effect of ultrasound-assisted dough fermentation on the quality of dough and steamed bread with 50% sweet potato pulp.

Ultrasound at an intensity of 17.5, 20.0, 22.5, 25.0 and 27.5 W/L was used to assist dough fermentation to prepare steamed bread with 50% sweet potato pulp (SB-50% SPP), which was compared with SB-50% SPP without ultrasonic treatment. The dough rheology, starch-gluten network, texture characteristics and sensory quality of steamed bread with different ultrasonic power densities (UPDs) were investigated. Dough samples at UPD of 22.5 W/L showed optimal viscoelasticity. The microstructure images exhibited that the content of starch particles wrapped in the gluten network increased significantly after sonication. In addition, the reduction in free sulfhydryl (SH) content and increase in wet gluten content after ultrasonic treatment led to significantly improved dough extensibility (p < 0.05). Results exhibited that the specific volume of SB-50% SPP increased by 13.93% and the hardness decreased by 21.96% compared with the control under UPD of 22.5 W/L. This study suggested that the application of ultrasound as a green technology to dough fermentation could lead to SB-50% SPP with good quality and sensory characteristics.

Influence of emulsifiers and enzymes on dough rheological properties and quality characteristics of steamed bread enriched with potato pulp.

The aim of this study was to evaluate whether processing characteristics of steamed bread enriched with potato pulp could be improved through the addition of different emulsifiers (soy lecithin-Soy L, sodium stearoyl lactate and diacetyl tartaric esters of monoglyceride) and enzymes (glucose oxidase-GOX and transglutaminase). Results showed that separate addition of each emulsifier at 1% concentration or each enzyme at 1.5 U/g could increase the viscoelasticity and strength of potato pulp dough due to enhancement of gluten network. Fermentation properties of dough showed that Soy L and GOX significantly (P < 0.05) increased the maximum dough height and the gas retention capacity during fermentation which promoting dough expansion. Moreover, Soy L and GOX increased specific volume and improved crumb structure and softness of steamed bread, which were consistent with the results of sensory analysis. In conclusion, Soy L and GOX could be used as improvers of potato pulp steamed bread.