Elucidation of potential relationship between endogenous proteases and key flavor substances in dry-cured pork coppa

Dry-cured meat products are considerably popular around the world due to unique flavor.Proteolysis is one of the enzymatic reactions from which flavor substances are derived,which is affected by endogenous proteases.The purpose aimed to reveal the potential relationship between endogenous proteases and key flavor substances in dry-cured pork coppa in this paper.The dynamic changes of endogenous proteases activity,free amino acids,and volatiles during dry-cured pork coppa processing were characterized.The results showed that 5 kinds of free amino acids,Glu,Lys,Val,Ala,and Leu,were identified as significant contributors to taste.Meanwhile,key volatiles,such as hexanal,nonanal,octanal,benzaldehyde,3-methyl butanoic acid,2-methyl propanoic acid,and ethyl octanoate,greatly contributed to the flavor characteristics of dry-cured pork coppa.Further partial correlation analysis was performed to better elucidate the relationship among parameters.The results revealed that close relationship between endogenous proteases and key substances.RAP not only significantly affected the accumulation of key active-amino acids,but also affected the accumulation of ethyl octanoate,2,3-pentanedione,and 2,3-octanedione by regulating the accumulation of octanoic acid and Leu.In addition,cathepsin B and D,DPP II,DPP IV and RAP notably affected accumulation of hexanal.

Evaluation and selection of yeasts as potential aroma enhancers for the production of dry-cured ham

Yeasts play a critical role in the flavor formation of dry-cured ham.In this study,41 yeast isolates from the dry-cured ham at different processing stages were evaluated for their technological properties.Debaryomyces hansenii was the most dominant yeast and has been detected at each phase of dry-cured ham,followed by Candida zeylanoides which was mainly detected in salting phase.Yarrowia bubula and Yarrowia alimentaria were found at the first two-phase of dry-cured ham.All isolates of yeast showed enzymatic activities against milk protein and tributyrin,while only 4 strains displayed proteolytic activity on meat protein.Yeast strains were grown in a meat model medium and volatile compounds were identified.The result showed that inoculated yeast strains could promote the production of volatiles and there were significant differences among strains.D.hansenii S25 showed the highest production of volatile compounds,followed by the strain C.zeylanoides C4.D.hansenii S25 was the highest producer of alcohols showing the highest production of benzeneethanol and 3-(methylthio)-1-propanol.Based on OAV and PLS analysis,D.hansenii S25 was strongly correlated with overall flavor and key volatile compounds of dry-cured ham,which could be selected as potential starter cultures.

Flavor release from traditional dry-cured pork during oral processing

The rate of flavor release in the mouth from traditional dry-cured pork was evaluated in this study.It was hypothesized that a slow steady release of flavor would occur on chewing and hydration.To test this,high salt dry-cured pork was chewed and held in oral cavity without swallowing for 4 different chewing stages(B,NC_(30),C_(30),EC).Saliva and food bolus from 16 healthy subjects were collected during oral processing,and analyzed for saliva flow rate,total saliva protein content,saliva pH,conductivity,saliva and sodium,and taste components.Results show that oral processing behavior and salivary release have important effects on flavor release of dry-cured pork.Sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE)analysis showed that oral processing has a certain effect on the protein composition and concentration in saliva.This study suggests that the interaction between food and saliva that accompanies chewing can lead to significant changes in sensory perception during oral processing.

Effect of the Inclusion of Chestnut in the Finishing Diet on Volatile Compounds of Dry-Cured Ham from Celta Pig Breed

The effect of the inclusion of chestnut in pigs ifnishing diet on volatile compounds of dry-cured Celta ham was studied. Twelve hams of each type （from three different pigs ifnishing diets：concentrate （CO）, mixed （MI） and chestnut （CH）） were used. Volatiles were extracted using a purge-and-trap method and analyzed by gas chromatography/mass spectrometry （GC/MS）. Thirty-nine volatile compounds were identified in dry-cured Celta ham samples. Most abundant volatiles in ham samples were aldehydes, which represented respectively, 53% （CO）, 51% （MI） and 46% （CH） of the total volatile composition. With the exception of 2-butenal, 2-methyl, all aldehydes were affected by feeding system. On the other hand, hydrocarbons n-alkanes were the second major group in the volatile proifle of dry-cured Celta hams and represented 28.9, 35.7 and 32.4%of the total volatile composition for CO, MI and CH groups, respectively. Ham samples from chestnut group showed a higher content of alcohols and this result could be related with the inclusion of chestnut in the ifnishing diet of pigs. Principal component analysis showed a good separation among groups. The discriminant analysis selected eight variables （butanoic acid, hexanal, octanal, nonenal （E）, decenal （E）, tetradecane, decane trimethyl and pyridine 2-methyl） and calculated two discriminating functions to predict if chestnut has been included in the ifnishing diet. Thus, it was possible to discriminate between groups fed with ifnishing diets containing chestnuts in their composition （mixed and chestnut group）.

Study Progress on Pests in Dry-cured Ham

Dry-cured ham can become infested with pests during the curing and ag-ing process, which not only damages the ham quality, but also causes economic loss. The advance of study on the effects of ham pests on the ham quality, the main species and distributions of ham pests in process of dry-cured ham were intro-duced in this article.

Reducing the Levels of Sodium, Saturated Animal Fat, and Nitrite in Dry-Cured Pork Meat Products: A Major Challenge

The curing of meat is a conservation technique widely used since ancient times to prolong shelf-life. It consists in exposing meat to a mixture of sodium chloride and nitrate/nitrite. Sodium chloride affects the flavor, texture and shelf-life of meat products. Animal fat mainly affects the flavor and texture, and nitrate and nitrite affect the color and flavor, and give cured meat products their typical aroma. Excessive intake of sodium has been linked to arterial hypertension and increased risk of cardiovascular diseases. Excessive intakes of saturated fatty acids in pork fat, and also of nitrite, have been identified as factors promoting some cancers. There is consequently an increasing consumer demand to reduce these ingredients in processed meat and so develop healthier cured meat products. This paper reviews how and to what extent sodium, animal fat rich in saturated fatty acids, and nitrite contents can be reduced in the production of dry-cured hams and dry-fermented sausages.

Formation mechanisms of reactive carbonyl species from fatty acids in dry-cured fi sh during storage in the presence of free radicals

This study aimed to better understand the changes of fatty acids in dry-cured fish during storage,and to analyze the reactive carbonyl species(RCS)formation mechanism primarily from the standpoint of oxygen-derived free radical reactions interactions.Oleic acid and linoleic acid were the predominant unsaturated fatty acids in dry-cured fish.The content of unsaturated fatty acids in dry-cured fish increased over time at 4℃,while decreased at 25℃.Singlet oxygen,superoxide anion and hydroxyl-alkyl radical levels increased with time,and more free radicals were yielded in the samples held at 25℃.Redundancy analysis revealed that hydroxyl-alkyl radicals had the greatest influence on the oxidation of lipids.Hydroxyl-alkyl radicals and singlet oxygen levels were positively correlated with 4-hydroxy-2-nonenal(HNE),malondialdehyde(MDA),peroxide value and acid value levels,but adversely to 4-hydroxy-2-hexenal(HHE)and fatty acids levels.Moreover,HNE and MDA were both inversely linked with fatty acids contents.It is possible that the intermediates of lipid oxidation undergo oxidation,cleavage and other reactions due to free radical activity,resulting in the generation of aldehyde precursors.These findings help us further characterize the lipid oxidation and RCS formation mechanism in dry-cured fish during storage.

Inhibition of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase enzyme by dipeptides identified in dry-cured ham

High cholesterolemia is a key risk factor for the development of cardiovascular diseases,which are the main cause of mortality in developed countries.Most therapies are focused on the modulation of its biosynthesis through 3-hydroxy-3-methylglutaryl-coenzyme A reductase(HMG-CoAR)inhibitors.In this sense,food-derived bioactive peptides might act as promising health alternatives through their ability to interact with crucial enzymes involved in metabolic pathways,avoiding the adverse effects of synthetic drugs.Dry-cured ham has been widely described as an important source of naturally-generated bioactive peptides exerting ACEI-inhibitory activity,antioxidant activity,and anti-inflammatory activity between others.Based on these findings,the aim of this work was to assess,for the first time,the in vitro inhibitory activity of HMG-CoAR exerted by dipeptides generated during the manufacturing of dry-cured ham,previously described with relevant roles on other bioactivities.The in vitro inhibitory activity of the dipeptides was assessed by measuring the substrate consumption rate of the 3-hydroxy-3-methylglutaryl CoA reductase in their presence,with the following pertinent calculations.Further research was carried out to estimate the possible interactions of the most bioactive dipeptides with the enzyme by performing in silico analysis consisting of molecular docking approaches.Main findings showed DA,DD,EE,ES,and LL dipeptides as main HMG-CoAR inhibitors.Additionally,computational analysis indicated statin-like interactions of the dipeptides with HMG-CoAR.This study reveals,for the first time,the hypocholesterolemic potential of dry-cured ham-derived dipeptides and,at the same time,converges in the same vein as many reports that experimentally argue the cardiovascular benefits of dry-cured ham consumption due to its bioactive peptide content.

干腌牛肉活性肽的分离与抗氧化性能研究

该研究对不同时期干腌牛肉进行了抗氧化和抑菌活性的评价,并发现了5个具有良好抗氧化活性的短肽。盐酸提取法发现腌制后粗肽含量相比未腌制增加了17.8%。3种不同处理方式(未处理、胃蛋白酶和胰蛋白酶)后粗肽液氨基酸含量分别为29.81、64.199、258.111 mg/mL。圆二色谱发现粗肽在195、215 nm附近有吸收带,在205 nm附近有较弱吸收带。茚三酮法测试肽链平均分子质量为19.26~27.02 kDa。通过检测DPPH自由基、超氧阴离子自由基、ABTS阳离子自由基和羟自由基清除率确定其抗氧化能力。结果表明,干腌牛肉具有较好的抗氧化活性,粗肽(1 mg/mL)对4种自由基的清除率分别为78.33%、81.05%、26.89%和36.92%。通过稳定性测试,发现0%NaCl、60℃和pH 7.0时抗氧化能力最强。粗肽也对O517型大肠杆菌、金黄色葡萄球菌和白色念珠菌有抑菌能力,5 mg/mL时分别可以达到75.45%、48.53%和44%。经过SephadexG-25和SephadexG-15分别进行2次分离纯化后发现5个肽具有良好的抗氧化活性,分别为DALKKK、FDGDF、HLPSDF、FLSDH、TPTDWK。所以,干腌牛肉制品可能在抗氧化以及抑菌方面促进人体健康。

皖浙花猪干腌火腿源血糖调节肽的分离纯化、鉴定及量子化学表征

为探究小肽抑制糖类消化的机理,制备皖浙花猪干腌火腿肌肉的水提物和胃胰酶消化产物,分离纯化出α-淀粉酶和α-葡萄糖苷酶抑制活性较高的组分,鉴定、筛选其中的肽序列,采用量子化学方法计算分子前线轨道分布和能量、静电荷分布、键长等结构和电荷参数,推测活性位点。结果表明:1)酶解后火腿肌肉的粒径减小、降糖活性提高;2)水提物和胃胰酶消化产物经过葡聚糖凝胶分离后分别获得两个组分(S-Ⅰ、S-Ⅱ)和3个组分(WY-Ⅰ、WY-Ⅱ和WY-Ⅲ);3)利用质谱技术从高活性组分WY-Ⅱ中鉴定出104条长度8~24的肽序列,筛选出Peptide Ranker程序评分大于0.7的5条序列;4)前述序列的最高占据轨道多分布在精氨酸的胍基及氨基端附近基团,而最低未占轨道多分布在羧基端及附近基团;5)能级差ΔEL-H较低的序列GPMGPSGPR、LGFGGPSGPNAGR、APAPAPAPAPAPPK可能具有较高活性。根据库伦定律,其活性位点分别定位于精氨酸的C106H108、亮氨酸的C10H12和赖氨酸的C176H177,都位于C—H键。研究为探究肽的血糖调节机制,证明地方品种猪的营养价值提供了理论支撑。

微波预处理对加热卷烟用烤烟烟叶常规化学成分及挥发性香气成分的影响

以河南产区的下部烤烟样品为原料,采用微波干燥和微波水热两种方法预处理原料,利用连续流动分析、高效液相色谱、气相色谱-离子迁移谱(GC-IMS)等技术对不同微波预处理烤烟烟叶中的常规化学成分及挥发性香气成分进行分析。结果表明:微波水热处理可降低烤烟烟叶中水溶性糖、还原糖、植物碱及酚类物质含量,提高总氮、石油醚提取物含量,并显著增加烤烟原叶的氮碱比(P≤0.05),其中微波水热700 W-6 min处理组氮碱比高达1.65;而经微波干燥处理后,烤烟烟叶中常规化学成分整体仍处于优质烟叶指标范畴,且挥发碱含量显著增加(P≤0.05),部分预处理组中绿原酸和芸香苷含量增加;此外,GC-IMS共鉴定出56种挥发性香气成分,微波水热处理可增加烤烟的新鲜清香,微波干燥处理则可增加其甜香味。

霉菌发酵剂的制备及其对干腌肉块品质的影响

以干腌肉块作为宣威火腿的模拟体系,探讨6组霉菌发酵辅助剂对其物理化学特性和风味品质的影响。在6组发酵辅助剂中,鲁本斯青霉W10-1+褐藻青霉V8展现出了最高的中性、酸性蛋白酶和脂肪酶酶活性。将发酵辅助剂接种至干腌肉块中,发现相较于自然发酵组,接种霉菌均能提高干腌肉块的水分活度、pH、蛋白降解指数,且能使其维持在干腌肉制品的最佳范围内;此外,能增加挥发性风味化合物的种类并降低醛类物质的含量,改善亮度和红度,降低剪切力和硫代巴比妥酸值。其中,W10-1+V8组表现最为优异。电子鼻分析表明,W10-1+V8组与自然发酵组的风味特性最为接近,还能缓解脂质过度氧化。电子舌分析表明,W10-1+V8组在鲜味、丰富度上显著高于自然发酵组,酸味显著低于自然发酵组。因此,鲁本斯青霉W10-1+褐藻青霉V8最适宜作为干腌肉制品的发酵剂,为提升宣威火腿的品质提供技术支撑。

干硬性碱激发钢渣混凝土的力学性能优化试验研究

为了优化干硬性碱激发钢渣混凝土的力学性能,试验通过调整粉煤灰的掺量结合碱激发的掺量优化混凝土凝结时间和流动度,并采用正交试验法分析粉煤灰掺量、水玻璃模数、水玻璃掺量和养护方式4种因素对干硬性碱激发钢渣混凝土抗压强度的影响。结果表明,掺入粉煤灰可延长干硬性碱激发混凝土的凝结时间,减小维勃稠度,优化工作性能;干硬性碱激发钢渣混凝土的抗压强度受多因素综合影响,影响大小的顺序为:水玻璃掺量>水玻璃模数>养护方式>粉煤灰掺量;当采用2.0模数和20%掺量的水玻璃、替换率为25%粉煤灰优化配合比后,再结合浸水养护2 d,接着自然养护,干硬性碱激发钢渣混凝土的抗压强度最高。

传统干腌猪肉制品加工过程中理化性质及挥发性风味变化

采用干腌法对猪肉制品进行腌制,以水分含量、水分活度、pH值、色度和钠、钾含量为考察指标,借助气相色谱-质谱联用的方法分析干腌肉的主要风味物质。结果表明:腌制50 d后干腌猪肉制品的水分质量分数、水分活度和pH值分别为44.5%、0.89和5.8,色差中的亮度值、红度值和黄度值分别下降至32.75、10.66和5.15,钠、钾离子质量分数分别为2.33%和1.36%;在整个加工过程中,脂肪水解酶活力整体呈下降趋势,脂肪氧合酶活力呈先上升后下降的趋势,13 d时活力达到峰值9.16 U/mg;利用气相色谱-质谱联用的方法鉴别出干腌肉加工过程中9种酮类、8种醇类、9种醛类、9种酯类、10种烃类和6种杂环类挥发性化合物;通过挥发物的感官阈值分析,鉴定出7种脂肪水解产生的成熟关键风味物质及8种修饰性风味化合物。

西式干腌火腿中蛋白降解与粗肽抑菌能力相关性分析初步研究

该研究以不同成熟时期的西式干腌火腿作为研究对象,分别对水分含量、水分活度、蛋白降解指数进行分析,优化得到干腌火腿提取粗肽工艺中乙醇沉淀的条件:乙醇使用量2倍,沉淀时间10 h。通过对比不同时期和不同提取手段下火腿粗肽的抑菌能力,发现采用磷酸法提取24月成熟期火腿的粗肽抑菌能力最强。进一步结合多元回归分析和偏最小二乘判别分析对粗肽的氨基酸组分、蛋白降解指数和抑菌能力进行分析,发现组氨酸、脯氨酸和蛋白降解程度对抑菌呈显著正相关,这可能跟抗菌肽中N端大多数为碱性氨基酸,其中含有大量疏水性氨基酸有关。该结果为深入分析西式干腌火腿中抗菌肽性能与蛋白降解之间的关系提供了理论基础。

干腌火腿活性肽的抗氧化性能研究与鉴定

以金华火腿为研究对象,借助凝胶层析色谱对火腿粗肽进行初步分离,测定各组分的抗氧化性,将样品经由配备在线钠喷离子源的液相色谱串联质谱分析,采用串联EASY-nanoLC 1200的Orbitrap Q-Exactive Plus质谱仪鉴定金华火腿中所含活性肽的序列,发现了31条丰度高且未被鉴定的短肽。并利用PeptideRanker进行预测分析,得到丰度和活性都比较高的3个肽段,氨基酸序列分别为:DHDGPDHW、FPPDVGD、PFGDTH。用DPPH自由基清除能力、ABTS阳离子自由基清除能力和羟自由基清除能力检测抗氧化能力,证明金华火腿粗肽液具有良好的抗氧化性。红外光谱发现粗肽在1600~1700 cm-1有吸收带。通过合成短肽,验证肽段的抗氧化能力,分子对接实验表明超氧化物歧化酶与DHDGPDHW、FPPDVGD、PFGDTH均有结合能力,FPPDVGD的结合能力最强为-6.6 kcal/mol。综上,FPPDVGD具有较好的抗氧化能力,可作为天然抗氧化剂应用于食品、药品或化妆品,应用前景非常广泛,为干腌制品的进一步开发利用提供理论支持。

干腌火腿抗氧化肽的研究进展

自由基过量累积会导致人体许多慢性疾病的产生,如衰老、慢性炎症、心血管疾病等,目前常规的解决方法是使用抗氧化剂。然而人工合成的抗氧化剂对人体有潜在危害,因此无毒副作用的抗氧化肽成为了当今研究的热点。作为发酵肉制品之一的干腌火腿,因其蛋白质含量丰富,且在发酵过程中受到内源酶和微生物的影响,会对蛋白质进行分解,从而产生具有抗氧化活性的小肽。大量的研究表明,来源于干腌火腿的肽具有极强的抗氧化活性。因此,干腌火腿作为天然抗氧化肽的潜在来源,备受研究人员的关注。本文综述了干腌火腿中抗氧化肽研究的最新进展,主要包括抗氧化肽的形成、制备、纯化鉴定及抗氧化机制4个方面,其中特别指出外源微生物对抗氧化肽形成的影响,以期为干腌火腿抗氧化肽的进一步研究提供理论基础。

喷雾干燥结合紫外交联制备甲基丙烯酸缩水甘油酯改性丝胶中空微球及其性能

为了制备高耐水性光固化丝胶蛋白(SS)微球,采用喷雾干燥与紫外交联相结合的方法,以丝胶为原料制备了甲基丙烯酸缩水甘油酯(GMA)交联SS中空微球(GMA-g-SS),该法赋予了其良好的耐水稳定性和紫外光固化性能。优化的喷雾干燥工艺参数包括:SS浓度、进风温度及进液速度;研究了GMA浓度、二苯甲酮(BP)用量及紫外辐照时间对接枝率的影响。借助扫描电镜、红外光谱及热分析对微球表面形貌结构及稳定性进行了表征与分析。结果表明,喷雾干燥SS微球呈单分散空心结构,直径约5~20μm;GMA-g-SS微球红外光谱在1152 cm^(-1)和764 cm^(-1)处出现环氧基的吸收峰,表明GMA与SS交联成功。交联后微球呈黏连聚集状态,具有较高的紫外光固化性能且耐水稳定性大幅提升,溶失率仅为17.1%。所制备的GMA-g-SS微球具有可调的耐水稳定性和紫外光固化性,是一种有潜力的光固化3D打印生物材料。

蒸养条件下机制砂混凝土的力学性能及干缩性能

为推动机制砂在预制混凝土构件中的应用,实现机制砂在建筑行业的更广阔应用,进而有效减缓天然砂资源短缺的问题,通过混凝土抗压强度、动弹性模量和干燥收缩试验等宏观性能测试和扫描电镜测试、压汞测试及显微硬度测试等微观测试方法,探讨养护条件和砂型对混凝土力学性能及干缩性能的影响规律及相应机理。试验结果表明:无论采用河砂还是机制砂,蒸养混凝土相较标养混凝土具有更高的早期力学性能和更低的干燥收缩,但高温导致水化产物分布不均,阻碍了后续的水化反应,使其后期力学性能出现不同程度的劣化。结合微观测试结果可知,孔径粗化、界面过渡区间隙增大和水化产物结构疏松是造成蒸养混凝土后期性能劣化的主要原因,但采用机制砂替代河砂能有效减弱蒸养热伤损效应产生的劣化影响。此外,蒸养机制砂混凝土相较蒸养河砂混凝土具有更高的力学性能和更优的微观结构,具体表现为:蒸养机制砂混凝土孔结构更加细化,界面过渡区间隙更小,同时基体显微硬度均值更高,整体密实度更高。但小于50 nm毛细孔增加将导致蒸养机制砂混凝土干缩变形增大。基于GL 2000收缩模型,通过引入考虑机制砂的影响因子,建立了蒸养机制砂混凝土干燥收缩预测模型,可较准确且有效地进行蒸养机制砂混凝土的干燥收缩预测。

基于HS-SPME-GC×GC-TOFMS技术分析传统干腌腊肉加工过程中的挥发性有机物

为全面了解干腌腊肉加工过程中风味品质的变化规律,以原料期、腌制期、发酵前期、发酵后期及成熟期的传统干腌腊肉为研究对象测定理化指标,并利用顶空固相微萃取结合全二维气相色谱-飞行时间质谱技术对加工过程中挥发性有机物(volatile organic compounds,VOCs)进行鉴定。结果表明:干腌腊肉加工过程中水分含量持续下降,以不易流动水蒸发为主,并伴随自由水和结合水含量下降;pH值先减小后缓慢增大;整个加工过程中肉样颜色持续变深;干腌腊肉中VOCs主要为醇类、醛类、酯类、烃类及酮类等;3-丁二酮、2-甲基丁醛、庚醛和2-辛烯醛在整个加工过程中风味贡献较大;感官风味特征分析发现,干腌腊肉以甜味及水果风味为主;蛋白质降解、脂肪氧化和美拉德反应多途径共同作用,形成干腌腊肉特有的复杂风味特征。