Effects of cooking methods on the Maillard reaction products, digestibility, and mineral bioaccessibility of Pacific oysters (Crassostrea gigas)

Effects of deep, air and vacuum frying on oyster quality and protein-mediated mechanism analysis via TMT quantitative proteomics

Fried oyster is a popular aquatic food product in East Asia, but nutrient loss during thermal processing become a significant concern. The goal of this research was to examine the impact of distinct frying techniques, including deep frying (DF), air frying (AF), and vacuum frying (VF), on the nutritional, textural and flavor characteristics of oysters. The VF method demonstrated superior retention of beneficial properties and flavor, and reduced protein and lipid oxidation compared to the DF and AF methods. Furthermore, proteomic analysis of oysters was attempted to explain the molecular mechanisms governing the influence of key differential proteins. 20 major differential proteins, including actin-2 protein, tryptophan 2,3-dioxygenase and 1-alph, involved in oyster protein oxidation were identified, annotated and analyzed to elucidate their influence mechanisms. This research provides a deeper understanding of intricate interactions between frying techniques and oyster biochemistry, which offers valuable implications for enhancing food quality in seafood industry.

Glycogen and zinc-enriched ferritin as bioavailable nanoparticulate nutrients released from gastrointestinal digestion of pacific oyster (Crassostrea gigas)

Oyster is a low-carbon animal food enriched with protein, glycogen, and trace minerals. Nano-nutrients are increasingly perceived as an unignorable part of foods. Here, simulated gastrointestinal digestion released a considerable amount of nanoparticulate nutrients from raw and cooked oysters. They were identified as glycogen monomers with size of 20-40 nm and their aggregates, as well as 6 nm-sized bare cores of ferritin containing iron and zinc (4:1, w/w). FITC-labeling and flow cytometry unveiled the efficient uptake of oyster glycogen by polarized Caco-2 cells via macropinocytosis and receptor-mediated endocytosis. Calcein-fluorescence-quenching assay revealed divalent-metal-transporter-1- and macropinocytosis-mediated enterocyte iron absorption from oyster ferritin. Zinquin-fluorescence flow cytometry and ex-vivo mouse ileal loop experiments demonstrated the ready intestinal zinc absorption from oyster ferritin via macropinocytosis, as well as the good resistance of oyster ferritin to phytate's inhibition on zinc absorption. Overall, our results offer a new insight into the digestive and chemical properties of oysters.

Effect of baking on the structure and bioavailability of protein-binding zinc from oyster (Crassoetrea hongkongensis)

To compare the bioavailability of protein-binding zinc, we investigated the impact of baking on the structure of zinc-binding proteins. The results showed that zinc-binding proteins enriched in zinc with relative molecular weights distributed at 6 kDa and 3 kDa. Protein-binding zinc is predisposed to separate from proteins' interiors and converge on proteins' surface after being baked, and its structure tends to be crystalline. Especially -COO, -C-O, and -C-N played vital roles in the sites of zinc-binding proteins. However, baking did not affect protein-binding zinc's bioavailability which was superior to that of ZnSO4 and C12H22O14Zn. They were digested in the intestine, zinc-binding complexes that were easily transported and uptaken by Caco-2 cells, with transport and uptake rates as high as 62.15% and 15.85%. Consequently, baking can alter the conformation of zinc-binding proteins without any impact on protein-binding zinc's bioavailability which is superior to that of ZnSO4 and C12H22O14Zn.

Cooking-Induced Oxidation and Structural Changes in Chicken Protein: Their Impact on In Vitro Gastrointestinal Digestion and Intestinal Flora Fermentation Characteristics

Meat digestion and intestinal flora fermentation characteristics are closely related to human dietary health. The present study investigated the effect of different cooking treatments, including boiling, roasting, microwaving, stir-frying, and deep-frying, on the oxidation of chicken protein as well as its structural and digestion characteristics. The results revealed that deep-fried and roasted chicken exhibited a relatively higher degree of protein oxidation, while that of boiled chicken was the lowest (p < 0.05). Both stir-frying and deep-frying led to a greater conversion of the α-helix structure of chicken protein into a β-sheet structure and resulted in lower protein gastrointestinal digestibility (p < 0.05), whereas roasted chicken exhibited moderate digestibility. Further, the impact of residual undigested chicken protein on the intestinal flora fermentation was assessed. During the fermentation process, roasted chicken generated the highest number of new intestinal flora species (49 species), exhibiting the highest Chao 1 index (356.20) and a relatively low Simpson index (0.88). Its relative abundance of Fusobacterium was the highest (33.33%), while the total production of six short-chain fatty acids was the lowest (50.76 mM). Although stir-fried and deep-fried chicken exhibited lower digestibility, their adverse impact on intestinal flora was not greater than that of roasted chicken. Therefore, roasting is the least recommended method for the daily cooking of chicken. The present work provides practical advice for choosing cooking methods for chicken in daily life, which is useful for human dietary health.

An Intelligent Method for Predicting Pacific Oyster (Crassostrea gigas) Freshness Using Deep Learning Fused with Malondialdehyde and Total Sulfhydryl Groups Information

To achieve a non-destructive and rapid detection of oyster freshness, an intelligent method using deep learning fused with malondialdehyde (MDA) and total sulfhydryl groups (SH) information was proposed. In this study, an "MDA-SH-storage days" polynomial fitting model and oyster meat image dataset were first built. AleNet-MDA and AlxNet-SH classification models were then constructed to automatically identify and classify four levels of oyster meat images with overall accuracies of 92.72% and 94.06%, respectively. Next, the outputs of the two models were used as the inputs to "MDA-SH-storage days" model, which ultimately succeeded in predicting the corresponding MDA content, SH content and storage day for an oyster image within 0.03 ms. Furthermore, the interpretability of the two models for oyster meat image were also investigated by feature visualization and strongest activations techniques. Thus, this study brings new thoughts on oyster freshness prediction from the perspective of computer vision and artificial intelligence.

The Effect of Heat Treatment on the Digestion and Absorption Properties of Protein in Sea Cucumber Body Wall

This study was designed, for the first time, to investigate the effect of oxidation on the digestion and absorption properties of protein in boiled sea cucumber body wall (BSCBW) via simulated digestion combined with everted-rat-gut-sac models. Boiling heat treatments led to protein oxidation in SCBW, manifested by increases in free radical intensity, thiobarbituric acid reactive substances, carbonyl groups, disulfide bonds, dityrosine bonds, advanced glycation end products, protein hydrophobicity and aggregation, and declines in both free sulfhydryl groups and secondary structure transition from α-helix to β-sheet. Boiling for 2 h caused anti-digestion collagen unfolding, provided the action site for protease and improved protein digestion and absorption levels. On the contrary, excessive oxidative modification of 4 h BSCBW resulted in decreased protein digestion and absorption levels. From the perspective of texture, digestion and absorption properties, boiling for 2 h can obtain sea cucumber products with better edible and digestible properties, which is considered to be a better processing condition.

Evaluation of heavy metals, mycotoxins and mineral bioaccessibility through in vitro static digestion models of rainbow trout (Oncorhynchus mykiss) and sole (Dover sole) side stream extracts obtained by Pressurized Liquid Extraction

The recovery of antioxidants and minerals as well as the content of contaminants of rainbow trout and sole side streams (head, skin and viscera) extracts obtained by pressurized liquid extraction (PLE) were evaluated. Then, the effect of the gastrointestinal digestion was tested. No mycotoxins were detected in the extracts, while heavy metals contents (mg/kg) were up to 2.9 (As), 0.054 (Cd), 0.16 (Hg) and 0.073 (Pb), being below maximum legislated limits. A positive effect of PLE was found for the antioxidant capacity recovery, being the oxygen radical capacity of sole head and skin extracts significantly enhanced after digestion (∼3.8 times). PLE significantly increased Mg, Fe, Zn, Se and P (K_PLE > 1) contents of rainbow trout side streams, Zn (K_PLE5.97) and Fe (K_PLE 2.80) of head sole and Mg, Se and P of all samples. Moreover, Mg, Ca and Fe bioaccessibility was lower in all sole extracts compared to rainbow trout.

Effect of glycation degree on the structure and digestion properties of ovalbumin: A study of amino acids and peptides release after in vitro gastrointestinal simulated digestion

Glycation can improve the functional properties of protein. However, in vitro and animal studies have shown that glycation induced lysine blockage and impaired protein digestibility. This study aimed to explore the effects of different glycation degree on the structure and digestive characteristics of ovalbumin. The results showed that glycation decreased the turbidity and hydrophobicity of the protein and changed the protein structure. Moreover, the results of in vitro simulated digestion revealed that glycation reduced the contents of essential amino acids and total amino acids after digestion. Glycation changed the amino acids and peptides release from the protein by resisting the digestion of digestive enzymes, especially trypsin. In conclusion, this work links glycation, protein digestibility, and the release of amino acids and peptides. This emphasizes the importance of the balance between improving properties and ensuring the digestibility of proteins during food processing.

The Effect of Vacuum Deep Frying Technology and Raphanus sativus on the Quality of Surimi Cubes

This study uses a response surface methodology to optimize the vacuum deep frying process of surimi cubes. The effects of vacuum deep frying temperature, frying time, and thickness on the hardness and color difference of surimi cubes with Raphanus sativus were studied. Further, the manuscript explored the quality changes of surimi cubes under different frying processes (vacuum deep frying, atmospheric deep frying, and shallow frying). Moreover, the Chinese Min-Cantonese cuisine-Raphanus sativus was utilized as auxiliary raw material to change the hardness and reduce the oil content. The optimal parameters of response surface methodology determined were: vacuum deep frying temperature 130 °C, frying time 900 s, and thickness 0.75 cm. Additionally, under this process condition, the hardness of the surimi chunks was 2015 ± 48.17 g, and the color difference was 23.27 ± 1.86. Surimi cubes without Raphanus sativus have superior elasticity and low hardness, and surimi cubes with Raphanus sativus have little color difference and high chewability. After the vacuum deep frying process, there was a high protein content and superior crispness. Shallow frying and adding Raphanus sativus effectively reduced the product's oil content. Therefore, Raphanus sativus is suitable as a potential nutritional supplement to broaden its application in fried surimi foods.