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Obesity is caused by a prolonged positive energy balance1,2. Whether reduced energy expenditure stemming from reduced activity levels contributes is debated3,4. Here we show that in both sexes, total energy expenditure (TEE) adjusted for body composition and age declined since the late 1980s, while adjusted activity energy expenditure increased over time. We use the International Atomic Energy Agency Doubly Labelled Water database on energy expenditure of adults in the United States and Europe (n = 4,799) to explore patterns in total (TEE: n = 4,799), basal (BEE: n = 1,432) and physical activity energy expenditure (n = 1,432) over time. In males, adjusted BEE decreased significantly, but in females this did not reach significance. A larger dataset of basal metabolic rate (equivalent to BEE) measurements of 9,912 adults across 163 studies spanning 100 years replicates the decline in BEE in both sexes. We conclude that increasing obesity in the United States/Europe has probably not been fuelled by reduced physical activity leading to lowered TEE. We identify here a decline in adjusted BEE as a previously unrecognized factor.

Dietary choices have a profound impact on the aging process. In addition to the total amount of energy intake, macronutrient composition influences both health and lifespan. However, the exact mechanisms by which dietary macronutrients influence onset and progression of age-associated features remain poorly understood. Cellular senescence is a state of stable growth arrest characterized by the secretion of numerous bioactive molecules with pro-inflammatory properties. Accumulation of senescent cells is considered one of the basic mechanisms of aging and an important contributor to chronic inflammation and tissue degeneration. Whether dietary macronutrients affect the accumulation and the phenotype of senescent cells with age is still unknown. Here, we show that feeding on diets with varying ratios of dietary macronutrients for 3 months has a significant effect on different senescence-associated markers in the mouse liver. High protein intake is associated with higher expression levels of the two classical senescence-associated growth arrest genes, p21 and p16. Furthermore, the expression of many pro-inflammatory secretory markers was increased in diets enriched in protein and further enhanced by increases in fat content. These results provide preliminary evidence that dietary macronutrients have a significant influence on senescence markers and merit further investigation.

Total daily energy expenditure (“total expenditure”, MJ/d) reflects daily energy needs and is a critical variable in human health and physiology, yet it is unclear how daily expenditure changes over the life course. Here, we analyze a large, globally diverse database of total expenditure measured by the doubly labeled water method for males and females aged 8 days to 95 yr. We show that total expenditure is strongly related to fat free mass in a power-law manner and identify four distinct metabolic life stages. Fat free mass-adjusted daily expenditure accelerates rapidly in neonates (0-1yr) to ~46% above adult values at ~1 yr, declines slowly throughout childhood and adolescence (1-20 yr) to adult levels at ~20 yr, remains stable in adulthood (20-60 yr) even during pregnancy, and declines in older adults (60+ yr). These changes in total expenditure shed new light on human development and aging and should help shape nutrition and health strategies across the lifespan.

With lifestyle changes, chronic diseases have become a public health problem worldwide, causing a huge burden on the global economy. Risk factors associated with chronic diseases mainly include abdominal obesity, insulin resistance, hypertension, dyslipidemia, elevated triglycerides, cancer, and other characteristics. Plant-sourced proteins have received more and more attention in the treatment and prevention of chronic diseases in recent years. Soybean is a low-cost, high-quality protein resource that contains 40% protein. Soybean peptides have been widely studied in the regulation of chronic diseases. In this review, the structure, function, absorption, and metabolism of soybean peptides are introduced briefly. The regulatory effects of soybean peptides on a few main chronic diseases were also reviewed, including obesity, diabetes mellitus, cardiovascular diseases (CVD), and cancer. We also addressed the shortcomings of functional research on soybean proteins and peptides in chronic diseases and the possible directions in the future.

Dietary macronutrient composition influences both hepatic function and aging. Previous work suggested that longevity and hepatic gene expression levels were highly responsive to dietary protein, but almost unaffected by other macronutrients. In contrast, we found expression of 4005, 4232, and 4292 genes in the livers of mice were significantly associated with changes in dietary protein (5%-30%), fat (20%-60%), and carbohydrate (10%-75%), respectively. More genes in aging-related pathways (notably mTOR, IGF-1, and NF-kappaB) had significant correlations with dietary fat intake than protein and carbohydrate intake, and the pattern of gene expression changes in relation to dietary fat intake was in the opposite direction to the effect of graded levels of caloric restriction consistent with dietary fat having a negative impact on aging. We found 732, 808, and 995 serum metabolites were significantly correlated with dietary protein (5%-30%), fat (8.3%-80%), and carbohydrate (10%-80%) contents, respectively. Metabolomics pathway analysis revealed sphingosine-1-phosphate signaling was the significantly affected pathway by dietary fat content which has also been identified as significant changed metabolic pathway in the previous caloric restriction study. Our results suggest dietary fat has major impact on aging-related gene and metabolic pathways compared with other macronutrients.

In mammals, trait variation is often reported to be greater among males than females. However, to date, mainly only morphological traits have been studied. Energy expenditure represents the metabolic costs of multiple physical, physiological, and behavioral traits. Energy expenditure could exhibit particularly high greater male variation through a cumulative effect if those traits mostly exhibit greater male variation, or a lack of greater male variation if many of them do not. Sex differences in energy expenditure variation have been little explored. We analyzed a large database on energy expenditure in adult humans (1494 males and 3108 females) to investigate whether humans have evolved sex differences in the degree of interindividual variation in energy expenditure. We found that, even when statistically comparing males and females of the same age, height, and body composition, there is much more variation in total, activity, and basal energy expenditure among males. However, with aging, variation in total energy expenditure decreases, and because this happens more rapidly in males, the magnitude of greater male variation, though still large, is attenuated in older age groups. Considerably greater male variation in both total and activity energy expenditure could be explained by greater male variation in levels of daily activity. The considerably greater male variation in basal energy expenditure is remarkable and may be explained, at least in part, by greater male variation in the size of energy-demanding organs. If energy expenditure is a trait that is of indirect interest to females when choosing a sexual partner, this would suggest that energy expenditure is under sexual selection. However, we present a novel energetics model demonstrating that it is also possible that females have been under stabilizing selection pressure for an intermediate basal energy expenditure to maximize energy available for reproduction. (C) 2022 The Author(s). Published by Elsevier Ltd.

A variety of inbred mouse strains have been used for research in metabolic disorders. Despite being inbred, they display large inter-individual variability for many traits like food intake and body weight. However, the relationship between dietary macronutrients and inter-individual variation in body weight and food intake of different mouse strains is still unclear. We investigated the association between macronutrient content of the diet and variations in food intake, body composition, and glucose tolerance by exposing five different mouse strains (C57BL/6, BALB/c, C3H, DBA/2, and FVB) to 24 different diets with variable protein, fat, and carbohydrate contents. We found only increasing dietary fat, but not protein or carbohydrate had a significant association (positive) with variation in both food intake and body weight. The highest variation in both body weight and food intake occurred with 50% dietary fat. However, there were no significant relationships between the variation in fat and lean mass with dietary protein, fat, or carbohydrate levels. In addition, none of the dietary macronutrients had significant impacts on the variation in glucose tolerance ability in C57BL/6 mice. In conclusion, the variations in food intake and body weight changes increased with the elevation of dietary fat levels.

Contrary to popular opinion that lean individuals "eat what they want" and exercise more, Hu et al. study a cohort of healthy underweight volunteers and reveal them to have reduced physical activity relative to normal BMI controls and lower food intake. This cohort is also shown to have higher than expected resting energy expenditure, which is associated with elevations in thyroid hormones.

Publisher Copyright: © 2021 The Authors Understanding the impacts of activity on energy balance is crucial. Increasing levels of activity may bring diminishing returns in energy expenditure because of compensatory responses in non-activity energy expenditures.1–3 This suggestion has profound implications for both the evolution of metabolism and human health. It implies that a long-term increase in activity does not directly translate into an increase in total energy expenditure (TEE) because other components of TEE may decrease in response—energy compensation. We used the largest dataset compiled on adult TEE and basal energy expenditure (BEE) (n = 1,754) of people living normal lives to find that energy compensation by a typical human averages 28% due to reduced BEE; this suggests that only 72% of the extra calories we burn from additional activity translates into extra calories burned that day. Moreover, the degree of energy compensation varied considerably between people of different body compositions. This association between compensation and adiposity could be due to among-individual differences in compensation: people who compensate more may be more likely to accumulate body fat. Alternatively, the process might occur within individuals: as we get fatter, our body might compensate more strongly for the calories burned during activity, making losing fat progressively more difficult. Determining the causality of the relationship between energy compensation and adiposity will be key to improving public health strategies regarding obesity.

Summary The doubly labeled water (DLW) method measures total energy expenditure (TEE) in free-living subjects. Several equations are used to convert isotopic data into TEE. Using the International Atomic Energy Agency (IAEA) DLW database (5,756 measurements of adults and children), we show considerable variability is introduced by different equations. The estimated rCO2 is sensitive to the dilution space ratio (DSR) of the two isotopes. Based on performance in validation studies, we propose a new equation based on a new estimate of the mean DSR. The DSR is lower at low body masses (, Graphical Abstract, Highlights 5,756 doubly labeled water (DLW) measures highlight variation from calculation equation We derive here new equations for calculating CO2 production when using DLW These equations outperform previous equations in validation studies We recommend these equations should be adopted in future studies using DLW in humans, Speakman et al. use a large database of doubly labeled water measurements to show the choice of equation for the calculation of energy expenditure introduces significant variation into the final estimate. They then derive new equations that outperform previous equations in validation studies against chamber calorimetry.

As a major health issue, obesity is linked with elevated risk of type 2 diabetes. However, whether disrupted glucose homeostasis is due to altered body composition alone, or whether dietary macronutrients play an additional role, independent of their impact on body composition, remains unclear. We investigated the associations between macronutrients, body composition, blood hormones and glucose homeostasis. We fed C57BL/6N mice 29 different diets with variable macronutrients for 12 weeks. After 10 weeks, intraperitoneal glucose tolerance tests were performed. Generalized linear models were generated to evaluate the impacts of macronutrients, body composition and blood hormones on glucose homeostasis. The area under the glucose curve (AUC) was strongly associated with body fat mass, but not dietary macronutrients. AUC was significantly associated with fasting insulin levels. Six genes from transcriptomic analysis of epididymal white adipose tissue and subcutaneous white adipose tissue were significantly associated with AUC. These genes may encode secreted proteins that play important previously unanticipated roles in glucose homeostasis., Hu et al. found that disrupted glucose homeostasis in obese mice is mainly due to high body fatness, and dietary fat plays an additional role on fasting glucose levels.

The modulation of exciton recombination is one of the core issues for the electronic/optoelectronic devices. Here, we investigate the exciton recombination and surface depletion of ZnO nanowires under various interface conditions in terms of continuum medium mechanics and bond relaxation method. We find that the enhancement of donor concentration, nanowire dimension and external temperature can modify the carrier recombination, surface barrier height and surface depletion depth. Moreover, coated a thin epitaxial layer on the nanowires is of great benefit to reduce the surface state for suppression of recombination rate. The related mechanism on the interface confinement has also been clarified. Our predictions agree well with the experimental measurements, which provide an effective guidance for the organization of electronic device design.

The heat dissipation limit theory predicts lactating female mice consuming diets with lower specific dynamic action (SDA) should have enhanced lactation performance. Dietary fat has lower SDA than other macronutrients. Here we tested the effects of graded dietary fat levels on lactating Swiss mice. We fed females five diets varying in fat content from 8.3 to 66.6%. Offspring of mothers fed diets of 41.7% fat and above were heavier and fatter at weaning compared to those of 8.3% and 25% fat diets. Mice on dietary fat contents of 41.7% and above had greater metabolizable energy intake at peak lactation (8.3%: 229.4±39.6, 25%: 278.8±25.8, 41.7%: 359.6±51.5, 58.3%: 353.7±43.6, 66.6%: 346±44.7 kJ day−1), lower daily energy expenditure (8.3%: 128.5±16, 25%: 131.6±8.4, 41.7%: 124.4±10.8, 58.3%: 115.1±10.5, 66.6%: 111.2±11.5 kJ day−1) and thus delivered more milk energy to their offspring (8.3%: 100.8±27.3, 25%: 147.2±25.1, 41.7%: 225.1±49.6, 58.3%: 238.6±40.1, 66.6%: 234.8±41.1 kJ day−1). Milk fat content (%) was unrelated to dietary fat content, indicating females on higher fat diets (> 41.7%) produced more rather than richer milk. Mothers consuming diets with 41.7% fat or above enhanced their lactation performance compared to those on 25% or less, probably by diverting dietary fat directly into the milk, thereby avoiding the costs of lipogenesis. At dietary fat contents above 41.7% they were either unable to transfer more dietary fat to the milk, or they chose not to do so, potentially because of a lack of benefit to the offspring that were increasingly fatter as maternal dietary fat increased.

Objectives The carbohydrate-insulin model (CIM) predicts that increases in fasting and post-prandial insulin in response to dietary carbohydrates stimulate energy intake and lower energy expenditures, leading to positive energy balance and weight gain. The objective of the present study was to directly test the CIM's predictions using C57BL/6 mice. Methods Diets were designed by altering dietary carbohydrates with either fixed protein or fat content and were fed to C57BL/6 mice acutely or chronically for 12 weeks. The body weight, body composition, food intake, and energy expenditures of the mice were measured. Their fasting and post-prandial glucose and insulin levels were also measured. RNA-seq was performed on RNA from the hypothalamus and subcutaneous white adipose tissue. Pathway analysis was conducted using IPA. Results Only the post-prandial insulin and fasting glucose levels followed the CIM's predictions. The lipolysis and leptin signaling pathways in the sWAT were inhibited in relation to the elevated fasting insulin, supporting the CIM's predicted impact of high insulin. However, because higher fasting insulin was unrelated to carbohydrate intake, the overall pattern did not support the model. Moreover, the hypothalamic hunger pathways were inhibited in relation to the increased fasting insulin, and the energy intake was not increased. The browning pathway in the sWAT was inhibited at higher insulin levels, but the daily energy expenditure was not altered. Conclusions Two of the predictions were partially supported (and hence also partially not supported) and the other three predictions were not supported. We conclude that the CIM does not explain the impact of dietary macronutrients on adiposity in mice., Highlights • Higher fasting insulin related to inhibited lipolysis and leptin pathways in sWAT, supporting CIM. • Higher fasting insulin related to inhibited hypothalamic hunger pathway, contrasting CIM. • Fasting insulin decreased with higher dietary carbohydrate, overall contrasting CIM. • Higher dietary carbohydrate did not lead to greater EI/adiposity, or lowered EE.

We investigate the Auger recombination (AR) rate in CdSe/CdS core/shell nanocrystals (NCs) under different interface confinements in terms of the interface bond relaxation mechanism and Fermi’s golden rule. We find that the epitaxial layer of CdS can not only depress the influence of the Coulomb interaction between electrons and holes, but can also change the wave function and quantum confinement, resulting in the reduction of the AR rate. Moreover, the AR lifetime of CdSe/CdS core/shell NCs at a fixed entire dimension is lower than that of bare CdSe because of interface confinement of the wave function. A great drop of the AR rate can be achieved by adding an alloying layer that depresses the interface effect. Our predictions are in agreement with the available evidence, suggesting that the proposed approach could provide a general method to explore the AR process in core/shell NCs.

We investigate the properties in two-dimensional (2D) special parity–time (PT) symmetric complex potentials. The linear case of this special 2D PT-symmetric complex potential and self-focusing nonlinear cases are discussed. For linear case, the eigenvalues and eigenfunction for different loss or gain level of the PT-symmetric complex potentials are obtained numerically. For nonlinear cases, the existence of asymmetric solitons and PT-symmetric solitons is studied in this PT symmetric system. The eigenvalue for linear case is equal to the critical propagation constant b c of existing PT-symmetric solitons. When the PT-symmetric soliton's propagation constant reaches a certain threshold b c 1 , a branch of asymmetric solitons can bifurcate out from the branch of PT-symmetric solitons.

We are grateful to Dr Kevin Hall of the NIH for comments on an earlier draft of this paper, and Dr Stephan Guyenet for his informative blog posts on the CIM. Our study of mouse diets was funded by the strategic research program of the Chinese Academy of Sciences (XDB13030100).

We study the optical properties of two-dimensional linear modes and solitons in parity-time (PT) symmetry Bessel complex-valued potential. The PT-breaking points, the eigenvalues and eigenfunction for different modulated depths of two-dimensional PT symmetry Bessel complex potential are obtained numerically. The PT-breaking points increase linearly with increasing the real part of the modulated depths of PT potential. The existence of fundamental and dipole solitons are studied in self-focusing and self-defocusing media. The eigenvalue for linear case is equal to the critical propagation constant b c of the existing soliton. The fundamental solitons are stable in both the self-focusing and self-defocusing media, and the dipole solitons are stable in the self-defocusing media but unstable in the self-focusing media.

The optical solitons in parity-time (PT) symmetric mixed Bessel linear potential and modulated nonlinear lattices are studied, including linear case, and self-focusing modulated nonlinear lattices׳ cases. For linear case, the PT-breaking points, the eigenvalues and eigenfunction for different modulated depths of PT symmetry Bessel complex potential, are obtained numerically. The eigenvalue for linear case is equal to the critical propagation constant bc of soliton existence. With increasing of the depth of the nonlinear lattices, the power of fundamental solitons decreases and the beam width changes little, but the power of multipole solitons increases and the beam width decreases. Fundamental solitons are stable in the whole region and multipole solitons are stable with the propagation constants close to bc. The range of multipole solitons stability decreases with increasing of the depth of the nonlinear lattices.

A variational technique is established to study the fundamental solitons in parity-time symmetric optical lattices. The variational results show that the fundamental solitons can exist in the semi-infinite gap. The variational method can be fit for the solitons whose real part of field is symmetrical or antisymmetrical. Following numerical simulations, the variational results are in good agreement with the numerical results.

We investigate the existence and stability of solitons in parity-time (PT) symmetric Scarff complex potentials, including linear case, and self-focusing and self-defocusing nonlinear cases. For linear case, the PT-breaking points, the eigenvalues and eigenfunction for different modulated depths of PT symmetry Scarff complex potential are obtained numerically. For nonlinear cases, the existence and stability of fundamental and multipole solitons are studied in self-focusing and self-defocusing media. For a fixed modulated depth, the eigenvalue for fundamental or multipole linear modes is equal to the critical propagation constant b c of fundamental and multipole solitons existence. Fundamental solitons are stable in the self-defocusing nonlinear media and low power region for the self-focusing nonlinear case. Multipole solitons are stable with the propagation constants close to b c both for self-focusing and self-defocusing nonlinearities.

To investigate the role of extracellular signal-regulated kinases (ERKs) in sevoflurane post-conditioning induced cardioprotection in vitro.Isolated rat hearts were subjected to 30 min ischemia followed by 120 min reperfusion (I/R). Sevoflurane post-conditioning was carried out by administration of O2-enriched gas mixture with 3% sevoflurane (SEVO) for 15 min from the onset of reperfusion. Cardiac functions, myocardial infarct size, myocardial ATP and NAD(+) contents, mitochondrial ultrastructure, and anti-apototic and anti-oncosis protein levels were measured.Sevoflurane post-conditioning significantly improved the heart function, decreased infarct size and mitochondria damage, and increased myocardial ATP and NAD(+) content in the I/R hearts. Furthermore, sevoflurane post-conditioning significantly increased the levels of p-ERK and p-p70S6K, decreased the levels of porimin, caspase-8, cleaved caspase-3, and cytosolic cytochrome c in the I/R hearts. Co-administration of the ERK1/2 inhibitor PD98059 (20 μmol/L) abolished the sevoflurane-induced protective effects against myocardial I/R.Sevoflurane post-conditioning protects isolated rat hearts against myocardial I/R injury and inhibits cell oncosis and apoptosis via activation of the ERK1/2 pathway.

We put forward the existence and stability of defect surface gap solitons at the interface between uniform media and an superlattice with self-defocusing nonlinearity. We reveal that the defect plays the significant role in controlling the region of solitons existing. Various solitons are found to be existed in different gaps for different defects. For positive defects, fundamental solitons can exist stably in the semi-infinite gap, and dipole solitons can exist stably in the first gap but they are unstable in the second gap. For zero or negative defects, fundamental and dipole solitons can exist stably in the first gap and the second gap, respectively.

The existence and stability of solitons in one-dimensional multilayer photonic crystals potentials are reported. For all of the solitons, there exist cutoff points of the propagation constant below which the solitons vanish in the semi-infinite gap. The fundamental solitons are stable in the whole range where solitons exist. The antisymmetric dipole solitons can be stable when the propagation constant closes to the cutoff point. The range of stability for symmetric tripole solitons is changed with modulation depth and width of the multilayer photonic crystals potentials. The power of solitons increases with increasing of propagation constant and modulation width or decreasing of modulation depth of the potentials.

We investigate the optical properties with two-dimensional (2D) Scarff parity–time (PT) symmetric potentials, including linear case, and self-focusing and self-defocussing nonlinear cases. For linear case, the PT-breaking points, the eigenvalues and eigenfunction for different modulated depths of 2D Scarff PT symmetry complex potential are obtained numerically. The PT-breaking points increase linearly with increasing the real part of the modulated depths of PT potential. Below the PT-breaking points, the eigenvalues of linear modes are real, however, eigenvalues of linear modes are complex above the PT-breaking points. For nonlinear cases, the existence of fundamental and multipole solitons is studied in self-focusing and self-defocussing media. The eigenvalue for linear case is equal to the critical propagation constant b c of soliton existing.

A variational technique is developed to study the defect solitons in defect lattices. The variational results show that the fundamental solitons can only exist in the semi-infinite gap for positive and zero defects, however, fundamental solitons can exist in both the semi-infinite gap and the first gap for negative defect. There exists a critical propagation constant b c of fundamental solitons, below which the solitons vanish. For zero defect, the value of b c is associated with the edge of the first band. The value of b c increases with the depth of defect, and b c locate in the semi-infinite gap and the first gap for the positive and the negative defect. Following numerical simulations, the variational results are in good agreement with the numerical results.

We reported the existence and stability of defect solitons in saturable nonlinearity media with parity-time (PT) symmetric optical lattices. Families of fundamental and dipole solitons are found in the semi-infinite gap and the first gap. The power of solitons increases with the increasing of the propagation constant and saturation parameter. The existence areas of fundamental and dipole solitons shrink with the growth of saturation parameter. The instability of dipole solitons for positive and no defect induced by the imaginary part of PT symmetric potentials can be suppressed by the saturation nonlinearity, but for negative defect it cannot be suppressed by the saturation nonlinearity.

In order to understand the relationship between electric conductivity and quality parameters of common carp during storage, the electric impedances in the frequencies ranging from 1 to 20 kHz, total viable count (TVC), total volatile basic nitrogen (TVB-N), and K values of gutted and ungutted common carp were determined during 4°C storage. The result showed that the change ratio of electric impedance (Q value) of both gutted and ungutted common carp decreased with increasing storage time, while TVC, TVB-N, and K values increased gradually. There was a good correlation between Q values and TVC, TVB-N, and K values of gutted and ungutted common carp, and their correlation coefficients were 0.952, 0.965, 0.928, and 0.956, 0.975, and 0.938, respectively. This result demonstrated that Q value is valid to predict some quality parameters of common carp during 4°C storage.

The existence and stability of defect solitons in parity-time (PT) symmetric optical lattices with self-defocusing nonlinearity are reported. It is found that various solitons can exist in different gaps for different defects. All of the solitons have real and imaginary parts of opposite parities. For positive defects, fundamental and multipole solitons can exist stably in the semi-infinite gap and the first gap, respectively. For zero or negative defects, fundamental and multipole solitons can exist stably in the first gap and the second gap, respectively. For solitons with positive and negative defects, there exists a cutoff point of the propagation constant above which the defect solitons vanish. The relation with the cutoff point and the depth of PT potentials is studied. The influence of the imaginary part of the PT-symmetric potentials on soliton stability is given.

To investigate the effects of chitosan composite coatings for maintaining the quality of grass carp portions, indictors of microbiology (total bacteria count, TBC), chemistry (pH; total volatile basic nitrogen, TVB-N; 2-thiobarbituric acid, TBA; K-value), and sensory characteristics were analyzed periodically. The results showed that chitosan (1.5%, w/v) + acetic acid (1.0%, v/v) + tea polyphenol (TP, 0.5%, w/v) coating significantly (p ≤ 0.05) reduced growth of microorganisms as reflected in TBC, lipid oxidation as displayed in TBA, chemical spoilage as reflected in pH, TVB-N, K-value, and sensory characteristic scores compared to the control samples. The effect of chitosan (1.5%, w/v) + acetic acid (1.0%, v/v) + vitamin C (VC, 0.5%, w/v) coating was better than chitosan (1.5%, w/v) + acetic acid (1.0%, v/v) coating. Chitosan together with acetic acid and TP can be used as a type of preservative coating for grass carp portions under chilled storage.

Summary Silver carp (Hypophthalmichthys molitrix) skin and muscle were hydrolysed, respectively, and then used as part of an edible coating to preserve fish. The effects of muscle and skin hydrolysates as edible coatings for shelf life extension of common carp (Cyprinus carpio) were evaluated over 18 days at 4 °C, by comparing these two treatments, a chitosan coating with muscle hydrolysate, chitosan alone, and an untreated control. All coatings were made up with 5% glycerol. The quality of the carp was assessed by using total volatile basic nitrogen (TVB-N), total viable counts (TVC), thiobarbituric acid (TBA) and K value. Compared with the control group, the rate of increase in TVB-N, TVC, TBA and K value of carp coated with fish skin hydrolysates, fish muscle hydrolysates and chitosan added to fish muscle hydrolysates were lower. According to the total viable counts, the storage life of fish with fish skin hydrolysates coatings and chitosan added fish muscle hydrolysates coatings were 16 days, 2 days longer than those with the chitosan coatings and twice as long as the control group.