•Freeze–thaw (F–T) cycles decreased chicken in vitro digestibility.•Protein aggregation induced by F–T cycles reduce chicken digestibility.•Hydrogen bonds destruction and β-sheet contents increase ...caused protein aggregation.•F–T cycles obviously affected the digestive capacity of pepsin for chicken.
The effect of freeze–thaw (F–T) cycles on the digestive and protein structural properties of chicken breasts during in vitro digestion was investigated. With F–T cycles increased, the hardiness, chewiness, and shear force of chicken breasts increased, whereas the digestibility decreased, and particle size of digestive samples increased was evidenced by laser particle size analyzer and confocal fluorescence microscopy. The digestibility of the fifth F–T cycle samples in pepsin and pepsin/trypsin decreased by 25.99% and 11.82% compared to fresh samples, respectively. During F–T cycles, the disruption of protein structure was confirmed by the α-Helix decrease, β-sheet increase, the intrinsic tryptophan intensities decrease and a redshift in the maximum value. Therefore, F–T cycles destroyed protein structure and induced the protein aggregation, resulting in chicken that was difficult to digest in the simulated digestion. The phenomenon became more acute as the number of F–T cycles increased.
Vocabulary is the basis of language, but memorizing new words has always been a hard job for all English learners. This paper was written based on the theories on lexical chunk by Lewis and other ...scholars, and the experiment conducted on my own teaching class. The paper explored the function of lexical chunks, types of lexical chunk, high frequency lexical chunks, the differences between lexical chunks in English and Chinese, and how to implement the method of lexical chunk teaching.
The effects of different frying temperatures (150, 175, 200, 225 and 250 °C) and times (0.5, 1.0, 1.5, 2.0 and 2.5 min) on yield, shear force, color and sensory characteristics, and heterocyclic ...aromatic amine (HAA) contents of roasted pork were investigated. The results showed significant decreases in yield, shear force and L* and increases in a*, b* and the amounts of HAA of roasted pork with increased frying temperature and time (P < 0.05). The highest score of overall acceptability in crispy and darker roast pork fried at 225 °C for 1 min was obtained. However, the principal component analysis demonstrated that higher HAA contents of roasted pork under high frying temperature (225–250 °C) and long frying time (2–2.5 min) occurred. Considering the various qualities and the amounts of HAA, frying roasted pork at 175 °C for 1.5–2 min was the most suitable condition for preparing roasted pork.
•Effect of frying condition on qualities and HAAs of roasted pork was analyzed.•Change in qualities was significant with increased frying temperatures and times.•Roasted pork fried at high temperature (225–250 °C) and long time (2–2.5 min) were correlated with high HAAs level.•Heat treatment at a temperature below 175 °C and within 1.5–2 min is recommended.
The goal of this study was to explore the cryoprotective effect of ice structuring protein (ISP) on the aggregation behaviour and structural changes of myofibrillar protein (MP) from quick-frozen ...pork patties during frozen storage. Frozen storage causes the formation of large protein aggregates and weakens MP structures. After adding ISP into patties, MP had a more stable aggregation system, which was manifested by a uniform particle size distribution and significantly higher absolute zeta potential (11.71 mV) than the control (9.56 mV) (P < 0.05). Atomic force microscopy results showed that the surface roughness of MP aggregation decreased by 9.78% with ISP after freezing for 180 d. Additionally, compared to patties without ISP, the MP carbonyl content from the ISP-treated patty decreased by 32%, and the free amino content increased by 14.99% during frozen storage. Results from circular dichroism spectroscopy and fluorescence spectroscopy showed that MP secondary and tertiary structure stability in patties improved with ISP. Overall, ISP has the potential to improve MP aggregation and structural stability during frozen storage.
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•Frozen storage led to unfolding of the myofibrillar protein (MP) structure and aggregation.•ISP (ice structuring protein) reduced MP aggregation during frozen storage.•ISP enhanced the structural stability of MP during frozen storage.•ISP added into patty improved the cryoprotection ability of MP.
This study evaluated the physicochemical and antioxidant properties of clove essential oil (0, 0.2, 0.4, 0.6, 0.8, 1.0 % v/v) nanoemulsion (CEON) loaded chitosan-based films. With the increasing ...concentrations of the CEON, the thickness, b* and ΔE values of the films increased significantly (P < 0.05), while L* and light transmission dropped noticeably (P < 0.05). The hydrogen bonds formed between the CEON and chitosan could be demonstrated through Fourier-transform infrared spectra, indicating their good compatibility and intermolecular interactions. Furthermore, the added CEON considerably reduced the crystallinity and resulted in a porous structure of the films, as observed through X-ray diffraction plots and scanning electron microscopy images, respectively. This eventually led to a drop in both tensile strength and moisture content of the films. Moreover, the antioxidant properties were significantly enhanced (P < 0.05) with the increase in the amount of clove essential oil (CEO) due to the encapsulation of CEO by the nanoemulsion. Films containing 0.6 % CEO had higher elongation at break, higher water contact angle, lower water solubility, lower water vapor permeability, and lower oxygen permeability than the other films; therefore, such films are promising for application in meat preservation.
•Clove essential oil nanoemulsion (CEON) with small particle size was prepared.•Chitosan-based films containing CEON were successfully developed.•Chitosan films with CEON exhibited excellent mechanical and barrier properties.•CEON improved the antioxidant property of chitosan films.
The cryoprotective effect of ice structuring protein (ISP) on the microstructure and myofibrillar protein (MP) structure of mirror carp induced by freeze-thaw (F-T) processes was surveyed. The ...average diameter of ice crystals of those without ISP increased (from 130 to 220 μm), and the carbonyl content and 2θ value were also increased, meanwhile, the sulfhydryl, free amine, α-helix content, fluorescence intensity (FI) and peak intensity were significantly decreased after five F-T processes (P < 0.05). When the addition of ISP, the size of ice crystal and the change in MP structure of ISP-treated sample was smaller than those without ISP in a single F-T period. The average diameter of ice crystals of ISP-treated sample was 17.5% lower than those without ISP after three F-T processes. The carbonyl content of ISP-treated sample was 16.5% lower than those without ISP after five F-T processes. The α-helix and FI of ISP-treated sample were 58.2% and 816 A.U., higher than those without ISP. The physical stability of the MP was increased after ISP treated. Hence, ISP could protect muscle fibers by inhibiting the extension of ice crystals, and improve the stability of the MP structure.
•Freeze-thaw damaged the muscle tissue and protein structure of mirror carp.•Ice structuring protein minimized the freeze-thaw damage to fish microstructure.•Ice structuring protein curbed freeze-thaw induced changes in myofibrillar protein structure.•Ice structuring protein enhanced the physical structure stability of myofibrillar protein.
The impacts of freeze–thaw (F–T) cycles and cooking on the basic composition, protein and lipid oxidation, and advanced glycation end products (AGEs) of chicken breasts were studied. During F–T ...cycles, the moisture and protein contents of raw and cooked chicken breasts decreased, and protein and lipid oxidation occurred, increasing carbonyl and TBARS contents. Meanwhile, the contents of methylglyoxal, glyoxal, and hydroxymethylfurfural in raw meat increased by 2.27, 2.27, and 5 times, respectively, whereas glyoxal and hydroxymethylfurfural contents increased by 2.73 and 3 times, respectively, after cooking as F–T cycles increased. The formation of carboxymethyl lysine, pentosidine, and fluorescent AGEs in cooked samples was confirmed using an ELISA kit and fluorescent intensity. The study also revealed that AGEs contents of chicken meat were negatively correlated with moisture contents and positively correlated with carbonyl and TBARS levels. Therefore, F–T cycles and subsequent cooking promoted AGEs formation in cooked meat.
The influence of drying methods on the quality of beef jerky from Inner Mongolia was discussed. Beef jerky processed by traditional natural freeze-drying from Huhhot (HT) and Bayan Nur (BT) was ...tough, chewy, red and lustrous, while that processed by modern hot air drying from Huhhot (HM) and Bayan Nur (BM) was cohesive, hard, brown and dark, as observed by the moisture content (MC), shear force and colour. HT and BT had high free fatty acid (FFA) contents. And HM and BM had high free amino acid (FAA) contents. HT and BT had high hydrocarbon, aldehyde and ketone contents, while HM and BM had high nitrogen-containing compound contents. The higher hydrocarbon, acid and ester contents were observed in BT and BM, and higher nitrogen-containing compound contents were observed in HT and HM. The traditional method was related to a typical green grassy, fatty, meaty and sweet odour. The modern method increased nitrogen-containing compound contents, generating a roasted beef odour.
•The quality of beef jerky from different drying methods and districts in Inner Mongolia was compared.•The varieties and quantities of flavour compounds from four beef jerky samples were detected.•High aldehyde and ketone contents with a fatty, meaty and sweet odour were observed in HT and BT.•A high content of nitrogen-containing compounds with a roasted beef odour was observed in HM and BM.
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The present study established an eco-friendly extraction method for adsorbed proteins from the interfacial layers of oil-in-water (O/W) emulsions which stabilized by whey protein ...isolate. Tween 20, a typical food-grade low molecular weight surfactant, could sufficiently extract adsorbed proteins. Then, ultra-filtered centrifugation was applied to purify the adsorbed proteins. The results showed that the concentration of Tween 20 solution was a crucial factor impacting extraction efficiency, and concentration of Tween 20 from 0.5 % (v/v) could efficiently extract the adsorbed proteins from the oil-water interface. Moreover, when compared with the traditional isopropyl alcohol precipitation method, our developed method could efficiently extract, as well as maintain the unaltered structure of adsorbed proteins from different emulsions prepared with different concentrations of protein solution and different homogenization methods. Our method could substantially decrease the use of organic solvent within the laboratory setting, thereby minimizing the potential risks to the environment and human health.
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