This work investigated the effects of low-frequency ultrasound (US) induced conformational variation of duck liver globular proteins (DLGPs) on the binding behavior of n-alkenals based on multi-spectroscopic analysis combined with headspace solid phase microextraction technique. Results suggested that US-treatments, with the frequency of 40 kHz and the power density of 26.7 W/L, induced obvious tertiary and quaternary structure changes of DLGPs, as revealed by fluorescence and ultraviolet–visible absorption spectroscopy, whereas the secondary and primary structures of DLGPs remained almost unaffected, suggesting the presence of molten-globule (MG) intermediates due to US-treatment. Meanwhile, the particles size and absolute values of ζ-potential exhibited significant increases as the functions of ultrasonic durations. According to multivariate results, the conformational variations, involving natural, MG and post-MG states, could be differentiated successfully. The US-induced conformational changes of DGLPs allowed it easier to interact with volatile n-alkenals, attributed to the enhanced hydrophobic interaction and covalent binding. Correspondingly, the headspace fractions of n-alkenals were greatly reduced after ultrasound pretreatments, with different degrees ranging from 5.61 to 59.39%, depending on chemical structures and processing conditions. This work suggests the great potential of specific conformational variations of DLGPs induced by ultrasonic pretreatments to modulate flavor features of protein-based products.

Kinetic response of conformational variation of duck liver globular protein to ultrasonic stimulation and its impact on the binding behavior of n-alkenals

Historically, the study of food quality changes during processing, preservation, and storage has evolved from targeted, single-response studies towards studies relying on both targeted and untargeted approaches analyzing multiple responses. In our opinion, future studies should be based on a zoom-in approach in which fingerprinting is used as a multivariate, hypothesis-free starting point to screen for key quality differences in food extracts of differently processed, preserved, and stored foods. By interpreting the identity of selected fingerprint markers in terms of their relevance and consequences for application or connecting the markers to particular food reactions, in a subsequent kinetic study mechanistic as well as quantitative insight into the effect of extrinsic processing variables on quality changes can be obtained.

FROM FINGERPRINTING TO KINETICS IN EVALUATING FOOD QUALITY CHANGES: Process impact comparison after processing and during storage

Egg and egg products are a rich source of highly bioavailable animal proteins. Several processing technologies can affect the structural and functional properties of these proteins differently and can influence their fate inside the gastrointestinal tract. The present review examines some of the processing technologies for improving egg protein digestibility and discusses how different processing conditions affect the digestibility of egg proteins under gastrointestinal digestion environments. To provide up-to-date information, most of the studies included in this review have been published in the last 5 years on different aspects of egg protein digestibility. Digestibility of egg proteins can be improved by employing some processing technologies that are able to improve the susceptibility of egg proteins to gastrointestinal proteases. Processing technologies, such as pulsed electric field, high-pressure, and ultrasound, can induce conformational and microstructural changes that lead to unfolding of the polypeptides and expose active sites for further interactions. These changes can enhance the accessibility of digestive proteases to cleavage sites. Some of these technologies may inactivate some egg proteins that are enzyme inhibitors, such as trypsin inhibitors. The underlying mechanisms of how different technologies mediate the egg protein digestibility have been discussed in detail. The proteolysis patterns and digestibility of the processed egg proteins are not always predictable and depends on the processing conditions. Empirical input is required to tailor the optimization of processing conditions for favorable effects on protein digestibility.

Effect of processing technologies on the digestibility of egg proteins.

Comparison of oil-in-water emulsions prepared by ultrasound, high-pressure homogenization and high-speed homogenization

Phenolic modification of myofibrillar protein enhanced by ultrasound: The structure of phenol matters.

Background The adoption of innovative nonthermal processing as alternatives to conventional heating techniques in the food industry is mainly relied on their tremendous potential to simultaneously achieve preservation purposes and the maintenance of fresh-like characteristics and health benefits of final products. With increasing evaluation for the applicability of nonthermal processing, there remains, however, a great challenge for keeping the balance between the efficiency of microbial/enzymatic inactivation and the maintenance of sensory and nutritional characteristics. Accordingly, a timely summarization and elucidation of the response pattern and mechanism of related quality parameters under nonthermal conditions is of great importance. Scope and approach In this review, the nonthermal effects of high pressure processing (HPP) on volatilome evolution are discussed, considering its close relationship with food flavor quality. It starts with elucidating the pressurization principles linked to volatilome evolution. Then, the general volatile fingerprinting features responding to HPP in major food items are summarized, followed by the analysis of the response mechanisms behind. Finally, the potential of innovative applications based on HPP-induced volatilome evolution is discussed. Key findings and conclusions A critical examination of newly updated findings has suggested the non-negligible spatiotemporal HPP effects on the headspace volatile fingerprinting and flavor perception of pressurized foods. HPP-induced volatilome evolution results from the biochemical, physical, and chemical as well as metabolic effects of high pressure, and specific mechanisms depend on the features and manufacturing crafts of sample matrices, process variables and processing patterns. HPP shows its great potential as an aroma modification and flavor-tailoring technique, based on a comprehensive understanding of the mechanistic and quantitative relationship between volatilome evolution and process parameters.

Yuanrong Zheng

Papers

Kinetic response of conformational variation of duck liver globular protein to ultrasonic stimulation and its impact on the binding behavior of n-alkenals

Nonthermally driven volatilome evolution of food matrices: The case of high pressure processing