Effects of curcumin-based photodynamic method on protein degradation of oysters

Photodynamic treatment (PDT) is a novel cold-sterilisation technology, but the evaluation of the protein quality of shellfish was scarce. In this study, the effects of curcumin (CUR)-mediated PDT on delaying protein degradation of oysters during cold storage at 4 ℃ and the mechanisms were investigated. The protein-degradation indexes and related enzymes were determined every 2 days. The results showed that the content of total volatile basic nitrogen (TVB-N), polypeptide nitrogen (PeN), amino acid nitrogen (AN) and free amino acid (FAA) in photodynamic group was significantly different from the control group since the first 2 days (P < 0.05). The pH value was significantly changed by PDT at the 4th and 8th day (P < 0.05). Interestingly, the activities of serine and aspartic protease were significantly inhibited by PDT during the whole cold storage (P < 0.05). Therefore, the study indicated that PDT has a positive effect on preventing protein degradation.     

风干肠加工和贮藏过程中蛋白质的降解规律

以总氮、非蛋白氮、氨基酸态氮、挥发性盐基氮、游离氨基酸以及不同种类蛋白质（肌浆蛋白、肌原纤维蛋白、碱溶蛋白和碱不溶蛋白）为指标,分析研究风干肠加工和贮藏过程中蛋白质的降解规律。结果表明：风干肠加工和贮藏过程中总氮含量没有显著变化;非蛋白氮含量持续升高,从原料肉的469.4 mg/100 g增加到成品肠的786.4 mg/100 g,贮藏240 d后增加至1 256.1 mg/100 g;多肽氮和氨基酸态氮含量在加工和贮藏过程中均持续增加,挥发性盐基氮含量在风干过程中没有显著变化,在贮藏180 d后迅速增加;大部分游离氨基酸含量经过加工和贮藏均有所提高,只有半胱氨酸含量明显降低;在加工过程中,肌浆蛋白和肌原纤维蛋白含量均因降解而减少,基质蛋白含量明显增加;在贮藏过程中,肌浆蛋白含量持续降低,肌原纤维蛋白含量在贮藏前180 d无明显变化,贮藏至240 d明显减少,基质蛋白含量没有显著变化。     

Evaluation of antibacterial protein with antioxidant activity from Rahnella aquatilis L103 and its effect on beef during refrigerated storage

A strain, Rahnella aquatilis L103, which was isolated from the soil around the roots of mushrooms, produced antibacterial protein though fermentation. This protein has broad antibacterial spectrum towards gram-positive and gram-negative bacteria. The protein has a significant antioxidant capacity on scavenging ABTS^+· (82.5%, 120 μg mL⁻¹), DPPH^· (64.1%, 600 μg mL⁻¹) and OH^· (60.1%, 750 μg mL⁻¹) as well. The protein was considered to be safe within concentration of 150 μg mL⁻¹ as shown by MTT results and was applied to beef refrigerated preservation. The treatment group presented lower total viable counts (TVC), total volatile basic nitrogen (TVB-N), 2-thiobarbituric acid (TBA), meanwhile, higher sensory score and longer shelf life (2 days) compared with the control group (P < 0.05). The results indicated that the protein under safe concentration was beneficial to beef preservation.     

Impact of Radio Frequency,Microwaving, and High Hydrostatic Pressure at Elevated Temperature on the Nutritional and Antinutritional Components in Black Soybeans

In this study, the effects of high hydrostatic pressure (HHP) at elevated temperature (60 °C) and 2 dielectric heating (DH) methods (radio frequency [RF], and microwaving [MW]) on the nutritional compositions and removal of antinutritional factors in black soybeans were studied. Each treatment caused <2% reduction in protein, and 3.3% to 7.0% decline in total amino acid content. However, the proportion of essential amino acid slightly increased in DH treated samples. The treatment decreased fat content (14.0% to 35.7%), but had small influence on fatty acid proportion. Antinutritional factors including trypsin inhibitor, tannins, saponins, and phytic acid were all declined by the 3 treatments, and DH treatment was generally more efficient. The most abundant saponins was decreased >22% in DH treated samples. MW and HHP led to higher in vitro protein digestibility, RF and MW promoted protein aggregation from atomic force microscope topography, but HHP caused more damages on protein subunits as seen from SDS‐PAGE image.     

Alcalase蛋白酶降解大豆胰蛋白酶抑制剂的研究

研究了不同酶解条件下 (pH值、温度、时间、加酶量和添加巯基还原剂 ) ,碱性内切蛋白酶Alcalase对大豆蛋白和大豆胰蛋白酶抑制剂的降解作用。研究结果表明 ,Alcalase可同时降解大豆蛋白和胰蛋白酶抑制剂。该酶解反应的最适条件为 :pH 8 0、温度 6 0℃、最适加酶量 10 μL/g蛋白 (约 0 0 2 832AU/ g蛋白 ) ,添加Na2 SO3为ω(Na2 SO3) =0 3% ,水解时间 4h。在此条件下 ,残留胰蛋白酶抑制活性为对照的 2 0 % ,可溶性蛋白含量可达 2 7mg/mL ,游离氨基酸含量为 7 1mg/mL ,大豆蛋白的水解度为 8 9%。还讨论了Alcalase蛋白酶降解大豆蛋白生成小肽的最佳反应条件     

Phenolics and in-vitro degradability of protein and fibre in West African Browse

Relationships among soluble phenolics, soluble and insoluble proanthocyanidins (PAC), lignin, N, neutral-detergent fibre (NDF), and in-vitro degradability of protein and NDF were determined in 72 West African fodder trees and shrubs. Species were collected in the semi-arid (Niger), sub-humid (Nigeria) and humid/sub-humid (Benin) zones. Variation among species in chemical composition and in-vitro degradability of protein and NDF was large. Zones did not differ in mean content of phenolic compounds. Protein degradability was negatively correlated with soluble phenolics (r = ?0.34, P < 0.01) and soluble PAC (r = ?0.47, P < 0.001). NDF was positively correlated with soluble PAC (r = 0.44, P < 0.001), insoluble PAC (r = 0.28, P < 0.05) and lignin (r = 0.76, P < 0.001). NDF degradability was negatively correlated with soluble PAC (r = ?0.40, P < 0.001) and lignin (r = ?0.59, P < 0.001). Chemical composition and in-vitro degradability along with field observations can provide useful criteria for determining the nutritive value of browse species.     

The Correlation Between In Vitro Antioxidant Activity and Immunomodulatory Activity of Enzymatic Hydrolysates from Selenium‐Enriched Rice Protein

The antioxidant and immunomodulatory activities of selenium‐enriched rice protein hydrolysates (Se‐PH) were evaluated by a cellular antioxidant activity test and macrophage proliferation and phagocytosis assays, respectively. The results showed that trypsin hydrolysate provided the highest proliferation rate of 60.91% at a concentration of 100 μg/mL. Moreover, a remarkable rise in the phagocytosis rates for trypsin hydrolysate (64.1%) and pepsin–trypsin hydrolysate (54.5%) was observed when the sample concentrations were increased to 50 μg/mL. A positive correlation was found between the phagocytic ability of macrophages and both the selenium concentration and the degree of hydrolysis of Se‐PH, and the correlation coefficients R obtained were 0.792 and 0.930 (P < 0.05), respectively. The capacity of Se‐PH to inhibit the oxidation of dichlorodihydrofluorescein had a significant negative correlation with the phagocytic ability of macrophages (R = –0.840, P < 0.05). In conclusion, a positive correlation was found between the antioxidant activity and the immunomodulatory activity of Se‐PH, which could be used as potential functional food additives for improving human health.     

Physical,chemical and oxidative changes in raw peanuts: Effect of relative humidity

Peanuts are susceptible to oxidative deterioration due to various factors during storage. This research studied the proximate composition (lipid, protein, total sugar, moisture and ash.), composition and content of amino acids and fatty acids, peroxide value (PV), carbonyl value (CV), malondialdehyde content (MDA), protein composition and structure changes in the peanuts stored for 320 days under different relative humidity (RH; 50%, 65% and 80%) conditions. Lipid oxidation was delayed at low RH (50% and 65%) storage conditions. At high RH (80%), the contents of unsaturated fatty acids, amino acids, protein and lipids decreased significantly during storage (P < 0.05), whereas the PV, CV and MDA contents increased significantly (P < 0.05). The CV values of YH-9326 and YH-22 increased by 14.46 and 17.48 times respectively. In addition, the protein structure changed throughout the whole storage period (P < 0.05). This research provides a theoretical reference for maintaining storage quality and extending shelf life.     

Effects of ε-Polylysine on Physicochemical Characteristics of Chilled Pork

The aim of this paper was to research effects of ε-polylysine (ε-PL) on physicochemical characteristics of chilled pork during storage. Chilled pork was treated with different concentrations of ε-PL. Sensory properties, total bacterial counts (TBC), pH, total volatile base nitrogen (TVB-N), metmyoglobin (MetMb) content, and α-thiobarbituric acid (TBA) of treated and control samples were analyzed periodically during refrigerated storage. Compared to control, significant reductions (p?<?0.05) for TBC, pH, TVB-N, and MetMb content of chilled pork treated with ε-PL during storage were found in this study. However, there were significant increments in sensory scores, and TBA almost did not change. TVB-N, pH, and log₁₀CFU/g showed a positive linear relationship among them. These results indicated that 1.25 % ε-PL could effectively inhibit the growth and reproduction of bacteria and enhance preservative effects of chilled pork. Thus, ε-PL has good potential to be a preservative and extends shelf life of chilled pork.     

乳清分离蛋白水解物对冷藏鱼糜的保鲜作用

通过测定不同贮藏时间内(0 d、1 d、3 d、5 d、7 d、9 d)草鱼鱼糜的羰基含量、硫代巴比妥酸反应物(thiobarbituric acid-reactive substances,TBARS)、细菌总数、挥发性盐基氮(total volatile basic nitrogen,TVB-N)值、三甲胺(trimethylamine,TMA)值、K值等指标的变化,并分析各指标之间的相关性,研究冷藏(4℃)条件下乳清分离蛋白(WPI)水解物对草鱼鱼糜的抗氧化及保鲜效果。实验分为5组,第1组为对照组,第2~4组中分别加入2%、4%和6%的水解物,第5组中加入0.02%的BHA。结果表明:随着WPI水解物添加量的增加,鱼糜的蛋白和脂肪氧化抑制显著(p0.05),保鲜效果明显改善,其中6%WPI水解物处理组效果最明显,在贮藏9 d内,与对照组相比,羰基含量、TBARS值、TVB-N值和K值分别降低了1.54 nmo L/mg蛋白、0.21 mg/kg、5.84×10~(-2) mg/g和11.7%,此时鱼糜仍处于二级鲜度。各指标间存在显著正相关(p0.05)。因此,WPI水解物可以起到很好的抗氧化和保鲜作用,未来可以考虑把乳清蛋白水解物作为天然保鲜剂用于鱼糜制品生产中。     

Effect of radiation and soaking on trypsin inhibitor and protein content of chickpea (Cicer arientinum L.)

Composition of Ascochyta-blight resistant chickpea for proximate components, vitamins, energy and trypsin inhibitor, was determined. The influence of irradiation and soaking at ambient temperatures (25–35°C) on trypsin inhibitor activity (TIA) and protein content of chickpea, was investigated. A significant linear relation (r = ?0.960 to ?0.987) was found between the loss of TIA and soaking time of irradiated and unirradiated seeds (p < 0.05) and the rate of loss increased with increasing radiation dose (0.25–1.00 kGy). However, effect of radiation alone was negligible. Maximum decrease (30.7%) in TIA (from 330.0 to 228.6 TIU/g) occurred during soaking for 12 h of 1.00 kGy sample. The protein contents increased from an initial value of 21.7% to 23.4% and 22.7% as a result of soaking for 12 h in tap and distilled waters respectively. Radiation treatment exhibited little or no effect.     

The effect of myofibrillar/sarcoplasmic protein ratios on the properties of round scad muscle protein based film

The effect of the ratios of myofibrillar protein (MP) to sarcoplasmic protein (SP) from round scad (Decapterus maruadsi) muscle on the properties of the resulting films was investigated. Tensile strength (TS) of films decreased with increasing SP content (p < 0.05). Films prepared from MP/SP ratio of 10:0 (w/w) exhibited the highest TS (p < 0.05). Elongation at break (EAB) of films prepared with SP content greater than 30% had the decreased EAB (p < 0.05). Water vapor permeability (WVP) of films increased when SP content increased up to 20% and decreased with increasing SP content up to 30% (p < 0.05). Solubility of films decreased but protein solubility increased with increasing SP contents (p < 0.05). The a*-value and ΔE* of film increased with increasing SP content. Films with all MP/SP ratios exhibited the negligible transmission to the light in UV range. Therefore, it is suggested that the type and ratio of proteins in fish muscle, both SP and MP, influenced the properties of film from round scad muscle. Results suggested that the removal of sarcoplasmic protein from fish muscle by thorough washing was an effective means to improve the mechanical properties as well as color of the fish muscle protein-based film.     

Fermentation of Allium chinense Bulbs With Lactobacillus plantarum ZDY 2013 Shows Enhanced Biofunctionalities,and Nutritional and Chemical Properties

In this study, fermentation of Allium chinense bulbs was carried out with Lactobacillus plantarum ZDY 2013. A decrease in pH from 6.8 to 3.5 and a stable lactic acid bacteria population were observed during 7‐d fermentation. The total phenolic content increased by 2.7‐fold in the aqueous and ethanol extracts of A. chinense bulbs after fermentation. Antioxidant capacity including 2,2‐diphenyl‐1‐picrylhydrazyl radical‐scavenging effect and reducing power of both extracts was significantly (P < 0.05) improved after fermentation. Antagonistic test against 6 pathogens showed that fermentation significantly (P < 0.05) enhanced the antimicrobial activity in both extracts of fermented bulbs, especially in the ethanol extracts of fermented bulbs against L. monocytogenes. Analysis of the free amino acid (FAA) profile by ion‐exchange chromatography revealed that fermentation significantly (P < 0.05) increased total FAA content. In addition, among 27 kinds of volatile components analyzed by headspace–solid phase microextraction–gas chromatography–tandem mass spectrometry, sulfur‐containing compounds accounted for 65.23%, but decreased to 43.65% after fermentation. Our results suggested that fermentation of A. chinense bulbs with L. plantarum could improve their biofunctionalities, and nutritional and chemical properties.     

Protein–protein interactions of a whey–pea protein co-precipitate

The aim of this study was to investigate the mechanisms behind protein–protein interactions in a co-precipitate of whey protein isolate (WPI) and pea protein isolate (PPI). A co-precipitate and blend, consisting of 80% WPI and 20% PPI, were compared. Covalent disulphide interactions were studied by blocking of free thiols with N-Ethylmaleimide (NEM), while electrostatic interactions were studied in systems with 0.5 m NaCl and hydrophobic interactions with 0.2% SDS. Protein solubility, stability and secondary, tertiary and quaternary protein structures were analysed. Co-precipitation did not introduce different protein–protein interactions than the direct blending of proteins. SDS affected solubility (P < 0.05), secondary and tertiary structure. However, the effects of NEM and NaCl were significant greater (P < 0.05) on the same parameters and thermal stability, especially when combined (P < 0.01). Thus, the protein–protein interactions in a whey–pea co-precipitate and protein blend consisted of disulphide bonds and electrostatic interactions.     

特定致腐菌对冷却猪肉的致腐作用机制

为研究特定致腐菌在冷却猪肉中的致腐作用机制,将韩国假单胞菌PS1（Pseudomonas koreensis PS1）和梭状芽孢杆菌J4（Bacillus fusiformis J4）分别接种到新鲜冷却猪肉中进行致腐实验,以不接种致腐菌的猪肉为对照,于4℃条件下贮藏,每隔1 d测定各组肉样的细菌总数、总挥发性盐基氮（total volatile basic nitrogen,TVB-N）含量、蛋白质含量以及脂肪酶、弹性蛋白酶、胰蛋白酶和胶原蛋白酶活力。结果表明：各组肉样细菌总数均呈现先上升后稳定的趋势,贮藏第5天,接种P. koreensis PS1、B. fusiformis J4的肉样细菌总数均超过8.0（lg（CFU/g））,明显大于对照组;接种特定致腐菌的2组肉样脂肪酶、弹性蛋白酶、胰蛋白酶和胶原蛋白酶活力均高于对照组,且呈现先上升后降低趋势,至贮藏第7天,弹性蛋白酶、胰蛋白酶和胶原蛋白酶活力均达到峰值,而脂肪酶活力在贮藏第5天达到峰值;同时,各组肉样蛋白质含量不断降低,产物TVB-N含量明显增加,贮藏第5天,接种特定致腐菌的2组肉样TVB-N含量均超出15mg/100g,明显高于对照组。     

Changes in quality of rainbow trout (Oncorhynchus mykiss) fillets preserved with salt and sugar at low concentrations and stored at 4°C

The effects of dry-curing with low concentrations of salt and sugar on the quality of rainbow trout (Oncorhynchus mykiss) fillets were studied over a 16-day storage period at 4°C. Physicochemical characteristics (total volatile base nitrogen (TVB-N), biogenic amines (BAs), ATP-related compounds and K value), microbial populations (total aerobic counts (TAC), H₂S-producing bacteria, Pseudomonas, Aeromonas, and lactic acid bacteria) and sensory (SA) indicators were analyzed. Fish samples were subjected to the following treatments: untreated (control), dry-cured with 1.3% salt (T1), and dry-cured with 1.3% salt that also contained 0.9% sugar (T2). SA indicated that the sensory quality of the control, T1, and T2 was unacceptable after 8, 12, and 12 days of storage, respectively. Moreover, the cadaverine concentration of treated samples was significantly lower (P < 0.05) than the control after storing for 8 days. T1 and T2 were significantly higher (P < 0.05) than the control in inosine 5-monophosphate (IMP) content from the 2th to 10th day. Cadaverine, putrescine, hypoxanthine, and TAC were correlated significantly (P < 0.01) with SA, and these seemed to be reliable indicators of fish quality. The results indicated that curing treatments extended the shelf life of rainbow trout fillets, which could be exploited by processors.     

Potential protein degradation balance and total metabolizable protein supply to dairy cows from heat‐treated faba beans

The effects of pressure toasting (100, 118 and 136 °C for 3, 7, 15 and 30 min) on potential protein nutritional value of faba beans were evaluated with the NRC 2001 dairy model, by determining undegraded (RUP) and degraded rumen protein (RDP), undegraded (RUST) and degraded rumen starch (RDST), truly absorbed undegraded protein (ARUP), microbial protein (MCP_RDP) synthesized in the rumen from rumen‐available protein, truly absorbed rumen synthesized microbial protein (AMCP), truly absorbed rumen endogenous protein (AECP), total metabolizable protein (MP) in the small intestine, and the protein degradation balance (PDB). The treatments increased RUP, RUST, ARUP and MP (p < 0.001), and decreased RDP, RDST, MCP_RDP and PDB (p < 0.001), the effects increasing with increasing temperature and time. The treatments increased (p < 0.001) ARUP without affecting AECP and AMCP, so that the net absorbable total MP in the small intestine was increased. The PDB was reduced (p < 0.001) but never became negative. These results indicated that potential microbial protein synthesis would not be impaired due to sufficient nitrogen in the rumen, but the high positive PDB values with most treatments, except 136 °C for 15 min (PDB 2.0 g kg^?1 DM) indicated that there were large potential losses of nitrogen in the rumen, particularly for the control with a value of 88.9 g kg^?1 dry matter. It is concluded that predicted potential protein degradation balance and total metabolizable protein supply from faba beans were improved by the treatments. Copyright © 2005 Society of Chemical Industry     

Amino acid and soluble nitrogen evolution throughout ripening of Serra da Estrela cheese

Four batches of Serra da Estrela cheese originating from as many dairy farms were sampled throughout the ripening period, and assayed for the evolution of free amino acid (FAA) content, total nitrogen content (TN), water-soluble nitrogen content (WSN), trichloroacetic acid-soluble nitrogen content (TCASN) and phosphotungstic acid-soluble nitrogen content (PTASN). The WSN content increased from 1% (on the day of manufacture) up to 43% of TN by 180 d of ripening, thus reflecting the intense proteolytic activity of the enzymes contributed by the plant coagulant utilized. The TCASN was also found to be high in this cheese by the end of ripening (16–20%), which suggests a high extent of FAA release throughout maturation. The major FAA by 180 d of ripening were Glu, Val, Leu and Lys, representing 56–70% of the total in all four dairies sampled. Cheeses produced from refrigerated milk possessed higher amounts of γ-amino-n-butyric acid (Gaba) and lower amounts of Glu when compared with those manufactured with non-refrigerated milk.     

食盐用量对四川腊肉加工及贮藏过程中肌肉蛋白质降解的影响

以不同食盐用量（食盐用量分别为原料肉质量的3%、4%、5%、6%、7%,用A、B、C、D、E来表示）腌制的四川腊肉为研究对象,分析了肌肉中非蛋白氮（non-protein nitrogen,NPN）、游离氨基酸（free amino acids,FAA）含量以及肌浆蛋白和肌原纤维蛋白在加工贮藏过程中随时间变化的规律。结果显示：A、B、C组NPN含量较高;C组FAA含量最高,含量最高时达到11.75 mg/g;肌浆蛋白、肌原纤维蛋白在腊肉的腌制期和烟熏期大量降解,而肌原纤维蛋白的降解主要集中在分子质量大于99 kD的区域,A、B、C组的两种蛋白变化趋势一致,D、E组一致。结果表明：食盐用量会抑制蛋白质的降解,当食盐用量为肉质量的5%时,最有利于游离氨基酸的生成,并且腊肉中较低的食盐用量会缩短贮藏阶段肌浆蛋白含量达到最大值的时间,却延缓了肌原纤维蛋白含量达到最大值的时间。     

Genetic and Environmental Variation for Seed Yield,Protein, Lipid and Amino Acid Composition in Cowpea (Vigna unguiculata (L) Walp)

The genetic and environmental variability for seed yield (kg ha^-1), protein content (g kg^-1 DM), lipid content (mg g^-1 DM) and essential amino acid composition (g per 16 gN) of cowpea seeds using 15 cultivars grown in three locations (Kano (12°00′ N 8°31′ E), Mokwa (9°17′ N 5°04′ E) and Ago-Iwoye (6°58′ N 4°00′ E)) that differ markedly in climate was studied. The environmental effect accounted largely for the variability observed in yield (93%), protein (71%), lipid (100%), threonine (96%), cystine (80%) and arginine (81%) while the genotypic effect accounted largely for the variability observed in methionine (56%) and lysine (51%) contents. Correlation coefficients (pooled data) from the three locations indicated that yield was negatively correlated to protein content (r=-0·87, P<0·001) and positively correlated to lipid content (r=0·73, P<0·001). Protein content was negatively correlated to lipid content (r=-0·67, P<0·001) and positively correlated to threonine (r=0·66, P<0·01), cystine (r=0·69, P<0·001) and methionine (r=0·88, P<0·001) contents. Similarly, yield was positively correlated to threonine (r=0·22, 0·01<P<0·05), cystine (r=0·38, 0·001<P<0·01) and methionine (r=0·67, 0·001<P<0·01). Yield showed a strong negative correlation with protein content (r=-0·81) and a strong positive correlation with lipid content (r=0·97) at the environmental level. Cystine, methionine and to some extent, threonine were the limiting amino acids in the three environments. This research established the degree of variability for these characters in cowpea and indicated that concurrent selection for yield, lipid content, threonine and sulphur amino acids compositions is feasible. © 1997 SCI.