In Situ Monitoring of the Effect of Ultrasound on the Sulfhydryl Groups and Disulfide Bonds of Wheat Gluten

The role of biospectroscopy and chemometrics as enabling technologies for upcycling of raw materials from the food industry

It is important to utilize the entire animal in meat and fish production to ensure sustainability. Rest raw materials, such as bones, heads, trimmings, and skin, contain essential nutrients that can be transformed into high-value products. Enzymatic protein hydrolysis (EPH) is a bioprocess that can upcycle these materials to create valuable proteins and fats. This paper focuses on the role of spectroscopy and chemometrics in characterizing the quality of the resulting protein product and understanding how raw material quality and processing affect it. The article presents recent developments in chemical characterisation and process modelling, with a focus on rest raw materials from poultry and salmon production. Even if some of the technology is relatively mature and implemented in many laboratories and industries, there are still open challenges and research questions. The main challenges are related to the transition of technology and insights from laboratory to industrial scale, and the link between peptide composition and critical product quality attributes.

Effect of Steam Flash-Explosion on Physicochemical Properties and Structure of High-Temperature Denatured Defatted Rice Bran Protein Isolate

The effects of Steam Flash-Explosion (SFE) on the physicochemical properties and molecular structure of high-temperature denatured defatted rice bran protein isolate (RBPI) were investigated. The mechanism of SFE treatment on high-temperature denatured defatted RBPI was revealed. The analysis of the physical and chemical properties of RBPI showed that the surface hydrophobicity, characteristic viscosity, and thermal stability of rice bran protein isolate were significantly affected by the pressure of saturated steam and pressure holding time. Under the conditions of 2.1 MPa and 210 s, the surface hydrophobicity index decreased significantly from 137.5 to 17.5, and the characteristic viscosity increased significantly. The peak temperature of denaturation decreases from 114.2 to 106.7 °C, and the enthalpy of denaturation decreases from 356.3 to 231.4 J/g. The higher structure (circular dichroic spectrum and endogenous fluorescence spectrum) of rice bran protein isolate was analyzed by volume rejection chromatography (SEC). The results showed that steam flash treatment could depolymerize and aggregate RBPI, and the relative molecular weight distribution changed greatly. The decrease in small molecules with poor solubility was accompanied by the increase in macromolecules (>550 kDa) soluble aggregates, which were the products of a Maillard reaction. The contents of free sulfhydryl and disulfide bonds in high-temperature rice bran meal protein isolate were significantly increased, which resulted in the increase in soluble aggregates containing disulfide bonds. Circular dichroism (CD) analysis showed that the α-helix content of the isolated protein was significantly decreased, the random curl content was increased, and the secondary structure of the isolated protein changed from order to disorder. The results of endogenous fluorescence spectroscopy showed that the high-temperature rice bran meal protein isolate was more extended, tryptophan was in a more hydrophilic microenvironment, the fluorescence intensity was reduced, and the tertiary structure was changed. In addition, the mean particle size and net surface charge of protein isolate increased in the aqueous solution, which was conducive to the development of the functional properties of the protein.

Multi-mode S-type ultrasound-assisted protein extraction from walnut dregs and in situ real-time process monitoring

This study aimed to investigate the impact of multi-mode S-type ultrasound treatment on the protein extraction level of walnut dregs. The structural properties of the walnut protein (WP) were characterized, and the correlation between protein structure and extraction level was analyzed. The in situ real-time monitoring model for the ultrasound-assisted WP extraction process was established by a miniature fiber near-infrared (NIR) spectrometer. Results showed that the protein yield, purity, and comprehensive extraction index (CEI) of extracted WP were 71.07 %, 72.69 %, and 71.72, respectively, under optimal conditions (dual-frequency 20/28 kHz, ultrasonic treatment duration 30 min, and ultrasound power density 120 W/L). The secondary structure of extracted WP displayed that the proportion of α-helix and β-sheet reduced, while the contents of β-turn and random coil increased after ultrasonic treatment. Besides, sonication decreased the disulfide bond content and increased free sulfhydryl (-SH) and surface hydrophobicity compared to the control. The microstructures of WP confirmed that appropriate sonication could unfold the protein aggregates and reduce the particle size. The extraction level of WP is positively correlated with the -SH content (p < 0.01). The quantitative prediction model of Si-PLS for -SH content in the ultrasound-assisted WP extraction process was established and performed a good correction and prediction performance (Rc = 0.9736; RMSECV = 0.446 μmol/L; Rp = 0.9342; RMSEP = 0.807 μmol/L). This study exploited a high-efficiency way for the WP extraction industry, and provided theoretical support for the development of the intelligent system in industrial protein extraction process.

Structure characterization and antioxidant activity analysis of polysaccharides from Lanzhou Lily

Lanzhou Lily (Lilium davidii var. unicolor) is a traditional medicinal plant and popular edible vegetable bulb in China. In this study, the polysaccharides of Lanzhou Lily (LLPs) were extracted by polyethylene glycol-based ultrasonic-assisted enzymatic extraction method (PEG-UAEE). The optimum process conditions were obtained by single-factor experiments and response surface methodology (RSM). Then, the preliminarily structure of LLPs was characterized by HPLC, FT-IR, and SEM, and its antioxidant activities were evaluated. The results showed that LLPs yield reached 14.75% under the optimized conditions: E/S ratio 1,400 U/g; pH 5.0, ultrasonic time 30 min; and ultrasonic temperature 50 °C. The LLPs has pyranoid ring, uronic acid, and the characteristic absorption peaks of -OH, C = O, and C-H. The results of scanning electron microscope indicated that the LLPs had irregular distribution, dispersed structure, and many holes. The HPLC analysis showed that the LLPs were heteropolysaccharide containing galactose (6.36%), glucose (76.03%), rhamnose (2.02%), and arabinose (7.09%). Moreover, the LLPs showed obvious antioxidant effect in vitro.

Impact of low-frequency ultrasound technology on physical, chemical and technological properties of cereals and pseudocereals

Cereals (CE) and pseudocereals (PSCE) play a pivotal role in nourishing the human population. Low-frequency ultrasound (LFUS) modifies the structure of CE and PSCE macromolecules such as starch and proteins, often improving their technological, functional and bioactive properties. Hence, it is employed for enhancing the traditional processes utilized for the preparation of CE- and PSCE-based foods as well as for the upcycling of their by-products. We report recent advances in LFUS treatments for hydration, germination, extraction of bioactive compounds from by-products, and fortification of CEs and PSCE, including kinetic modelling and underlying action mechanisms. Meta-analyses of LFUS influence on compounds extraction and starch gelatinization are also presented. LFUS enhances hydration rate and time lag phase of CE and PSCE, essential for germination, extraction, fermentation and cooking. The germination is improved by increasing hydration, releasing promoters and eliminating inhibitors. Furthermore, LFUS boosts the extraction of phenolic compounds, polysaccharides and other food components; modifies starch structure, affecting pasting properties; causes partial denaturation of proteins, improving their interfacial properties and their peptides availability. Overall, LFUS has an outstanding potential to improve transformation processes and functionalities of CE and PSCE.

Effects of sonication on the in vitro digestibility and structural properties of buckwheat protein isolates

The present work investigated the effects of sonication at different amplitudes and durations on the in vitro digestibility of buckwheat protein isolates (BPIs). The conformation, particle size and microstructures of the BPIs were also studied to explicate the possible mechanisms of the sonication-induced changes. The results showed that sonication conditions of 20 kHz, pulsed on-time 10 s, off-time 5 s, amplitude of 60% and duration of 10 min (SA6T10) improved the digestibility of BPIs from 41.4% (control) to 58.2%. The tertiary structure analysis showed that sonication exposed the hydrophobic core buried inside the protein molecules and broke the intramolecular crosslinks, based on the increase in the surface hydrophobicity and intrinsic fluorescence and the decrease in the disulphide content. The secondary structure analysis showed that SA6T10 decreased the content of β-turn and β-sheet by 40.9% and 22.4%, respectively, and increased the content of anti-parallel β-sheet, random coil, and α-helix by 40.9%, 30.6%, and 25.5%, respectively. The particle size of the control BPIs (427.7 ± 76.7 nm) increased to 2130.8 ± 356.2 nm in the SA6T10 sonicated sample with a corresponding decrease in the polydispersity index from 0.97 ± 0.04 to 0.51 ± 0.13. Moreover, scanning electron microscopy indicated that sonication broke the macroparticles into smaller fragments and changed the surface state of the proteins. Taken together, sonication has proven to be a promising approach for improving the digestibility of buckwheat proteins, which can be explored as a source of plant-based alternative protein for food applications.

Advances in infrared spectroscopy combined with artificial neural network for the authentication and traceability of food

The authentication and traceability of food attract more attention due to the increasing consumer awareness regarding nutrition and health, being a new hotspot of food science. Infrared spectroscopy (IRS) combined with shallow neural network has been widely proven to be an effective food analysis technology. As an advanced deep learning technology, deep neural network has also been explored to analyze and solve food-related IRS problems in recent years. The present review begins with brief introductions to IRS and artificial neural network (ANN), including shallow neural network and deep neural network. More notably, it emphasizes the comprehensive overview of the advances of the technology combined IRS with ANN for the authentication and traceability of food, based on relevant literature from 2014 to early 2020. In detail, the types of IRS and ANN, modeling processes, experimental results, and model comparisons in related studies are described to set forth the usage and performance of the combined technology for food analysis. The combined technology shows excellent ability to authenticate food quality and safety, involving chemical components, freshness, microorganisms, damages, toxic substances, and adulteration. As well, it shows excellent performance in the traceability of food variety and origin. The advantages, current limitations, and future trends of the combined technology are further discussed to provide a thoughtful viewpoint on the challenges and expectations of online applications for the authentication and traceability of food.

Effect of ultrasound-assisted freezing on the textural characteristics of dough and the structural characterization of wheat gluten

To better understand the effects of ultrasonic treatment in the whole freezing process (UWF) and the maximum ice crystal formation zone (UMF) on the quality of frozen dough, the textural properties of dough and the structure of gluten were investigated. The results showed that the UWF and UMF treatments improved the textural properties of frozen dough and obtain the best effect at the 60 W/L power densities. Ultrasound-assisted freezing reduced the destructive effect of disulfide bonds on dough, and led to a state of dynamic equilibrium of hydrophobic groups. UWF treatment at 80 W/L and UMF treatment at 40 W/L had positive effects prevented the secondary structure from destruction by freezing. The network of gluten treated by ultrasound-assisted freezing was more uniform and smaller than that of traditional freezing samples, which was similar to the network structure of fresh protein. According to Pearson's correlation analysis, there was a high correlation between SH, α-helix content and springiness. There was a significant positive correlation between β-turn and G', G″, and there was a significant negative correlation between β-turn and hardness. These results suggest that ultrasound-assisted freezing improved the process quality of dough though reducing the damage to gluten structure caused by freezing.