Starter plays an important role in flavors produced by lipolysis, proteolysis and carbohydrate hydrolysis of fermented sausage. As the precursor of various volatile flavor substances, the branched-chain amino acids are decomposed into 3-methylbutanal by microbial transaminase, which gives the fermented sausage unique malty/off-flavor or as nutty/chocolate-like aroma. This article summarized the contribution of 3-methylbutanal to the flavor of the fermented sausage. Two pathways of 3-methylbutanal production were reviewed, including leucine enzymatic biosynthesis of 3-methylbutanal pathway and temperature-dependent leucine Strecker degradation pathway. The differences and connections between direct and indirect pathways in biosynthesis were revealed. The production pathway and the influencing factors of 3-methylbutanal content in fermented sausage were described, to provide a theoretical basis for guiding 3-methylbutanal to play a role in the flavor contribution of fermented sausage.

In order to study the effects of different functional strains on alleviating protein oxidation and enhancing flavor in fermented sausage, Lactiplantibacillus plantarum NJAU-01 (LpN), with excellent antioxidant activity, L. plantarum CGMCC 18217 (Lp10), with the ability to improve the flavor of fermented sausage, and Staphylococcus saprophytic CGMCC 3475 (Ss), with high protease activity, were selected for use in a multi-strain starter culture for fermented sausage. The degree of protein degradation and oxidation in fermented sausage during fermentation and the final flavor of the product were evaluated. The results showed that the Lp10 + LpN + Ss starter culture could reduce the degree of protein oxidation in fermented sausage and increase the types and contents of volatile flavor substances, while endowing fermented sausage with better color and improving its texture characteristics, and the fermented product had high sensory scores. This study showed that the combination of Lp10, LpN and Ss could improve the quality and flavor of fermented sausage while delaying the oxidation of protein.

Methyl-branched aldehydes, especially 3-methylbutanal, have been reported to be perceived either as a malty or as a nutty/chocolate-like aroma and were considered an important flavor contributor in fermented meat products. Decomposition of leucine (Leu) by branched-chain amino acid transaminase (BACT) is a crucial step in the metabolism of Leu to 3-methylbutanal. This study was conducted to explore the effects of mixed-starter culture (Lactobacillus fermentum YZU-06 and Staphylococcus saprophyticus CGMCC 3475) and addition of Leu (0, 1, and 3 mM) on the flavor and quality of fermented sausages. The pH, water activity, texture profile analysis, color, counts of lactic acid bacteria (LAB) and staphylococci, peptide, and flavor compounds were detected during fermentation. The results showed that the starter culture group increased hardness, elasticity, the counts of LAB and staphylococci, peptide content, volatile flavor compounds, as well as the sensorial scores of sausage, while decreasing pH, aw, and L* and b* values compared with the non-inoculation group. The mixed starter of adding with 3 mM Leu enhanced the content of 3-methylbutanal and overall flavor of fermented sausages. It is applicable to directionally produce methyl-branched aldehydes and improve the overall quality of fermented sausage by the addition of Leu and using starter of L. fermentum YZU-06 and S. saprophyticus CGMCC 3475.

This study was to screen a strain with both branched-chain amino acid transaminase (BCAT) and protease activities for producing methyl-branched flavor compounds in a myofibrillar protein extract model. Lactic acid bacteria (LAB) was isolated from Jinhua ham and screened with BCAT activity by an electrochemical sensor and protease activity by the agar plate method. In the culture medium, strain L6 was selected with high utilization rate and characteristic metabolites content of branched-chain amino acids (BCAAs), and identified as Lactobacillus fermentum YZU-06 (L. fermentum). Compared with the previously reported L. plantarum, L. fermentum exhibited an excellent capacity of hydrolyzing myofibrillar protein with the higher contents of free amino acids, peptides and small molecular weight proteins. Moreover, L. fermentum group presented more BCAAs metabolites of 2-methylbutanal and 3-methylbutanal than that of L. plantarum group. In conclusion, L. fermentum YZU-06 is a promising starter culture to improve the flavor of fermented meat products.

通过响应面法对不同处理条件下的羊肉汤的感官得分以及5'-肌苷酸含量进行分析,研究羊肉汤经超声波辅助的工艺优化.结果 表明:最优条件为炖煮温度85.20℃、超声功率777.43 W、超声时间104.85 min,预测的感官得分为28.45,单核苷酸含量为5.57 mg/100 mL.通过观察羊肉汤中无机元素含量的变化,发现超声波的加入明显促进无机离子的溶出;通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳观察蛋白质的变化,发现超声波的加入能促进一部分蛋白聚合与降解,增强了风味的生成与吸附风味物质的能力.

为了探究煮制对鹅肉蛋白的影响,本文通过测定不同煮制时间(0、30、60、90、120 min)下鹅肉的蒸煮损失率、剪切力、蛋白电泳、肌原纤维小片化指数(myofibril fragmentation index,MFI)、游离氨基酸(free amino acid,FAA)构成及微观结构研究了煮制时间对鹅肉蛋白结构特性的影响.结果表明:蒸煮损失率随着煮制时间的延长而升高,由0 min处的27.5％升高到120 min处的39.0％;剪切力值则是随着煮制时间的延长而呈现先上升再下降的趋势,且在90 min时出现最低值;十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE)图谱显示,随着煮制时间的延长35～55 kDa处的条带逐渐变浅变细,10～15 kDa处条带随煮制时间延长颜色变深;MFI值随着煮制时间的延长显著增加(P＜0.05),煮制120 min时的MFI值约为处理0 min时的2倍;共检出三种呈味氨基酸,从总量看,苦味氨基酸的含量最多,甜味氨基酸含量次之,鲜味氨基酸含量最少.煮制过程中,这三类氨基酸总含量总体表现为随煮制时间的延长而增加的趋势(甜味氨基酸的总含量约增加了2.5倍,苦味氨基酸的总含量约增加了3.1倍,鲜味氨基酸的总含量约增加了3.4倍),而甲硫氨酸和半胱氨酸这两者的含量随煮制时间的延长而减少;扫描电镜(scanning electron microscope,SEM)图中发现肌纤维之间的空隙表现出先变大后减小到粘成一块.同时,肌纤维和肌束膜结构的完整程度随着煮制时间的延长逐步破坏,最终导致部分肌纤维束发生崩塌使它们相互黏成一块.因此,鹅肉在蒸煮过程中,其蛋白组成和含量、MFI值、游离氨基酸组成及微观结构会因时间变化而发生改变,从而影响了鹅肉蛋白结构的变化.研究表明,90 min为鹅肉的最佳煮制时间.

Summary This study aimed to evaluate the effect of branched‐chain amino acids (BCAAs, leucine, isoleucine and valine) combined with Lactobacillus plantarum CGMCC18217 ( L. plantarum ) on the flavours and quality of fermented sausages. The parameters included pH, water activity, colour, texture, BCAAs metabolites and flavour compounds of fermented sausages in eight different groups (sausages with L. plantarum and individual BCAAs, that is L + Leu, L + Ile and L + Val groups; sausages with individual BCAAs, that is the Leu, Ile and Val groups; sausages only with L. plantarum assigned as the L group; and sausages with no L. plantarum and BCAAs assigned as the CK group). The results showed that the addition of BCAAs and L. plantarum significantly increased the hardness, cohesiveness and springiness of sausages. A total of sixty‐nine flavour compounds were identified in fermented sausages. The content of methyl‐branched alcohols, aldehydes, acids in the L. plantarum and BCAAs group significantly increased compared with the other groups ( P < 0.05). Therefore, our data suggest the addition of L. plantarum and BCAAs potentially improved the texture of fermented sausages and formation of volatile flavours.

通过测定羊肉的蒸煮损失率、pH值、色泽、质构、蛋白降解状况、脂肪氧化情况及微观结构,研究不同蒸煮温度(中心温度分别为20、50、60、70、80、90?℃)对羊肉肌原纤维蛋白特性的影响.结果表明:蒸煮损失率随着蒸煮温度的升高而升高,由20?℃处理组的0.90%升至90?℃处理组的最高值41.47%;硬度、内聚力和咀嚼性均在80?℃时出现峰值;硫代巴比妥酸反应物值在中心温度升高至70?℃后呈下降趋势;亮度值(L*)和黄度值(b*)分别在70、60?℃时达到最大,红度值(a*)呈下降趋势;十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE)图谱中,分子质量36～130?kDa的蛋白质发生降解产生小分子肽;扫描电子显微镜观察结果表明,随着中心温度的升高,肌纤维之间的间隙逐渐增大,70?℃时最大,之后随中心温度的升高逐渐缩小,且造粒和崩解现象加剧.因此,羊肉蛋白结构及微观结构在蒸煮过程中会因蒸煮温度变化而发生改变,从而对羊肉品质造成影响.

The orthogonal test was designed to study different antioxidants and different edible package films on the lipid oxidation of dry-cured ham.The results showed that the anti-oxidation treat in the ferment metaphase was better than the end of fermentation and mid-maturing;natural antioxidants (grape seed extract,compound antioxidant of rosemary and VE)had the same anti-oxidation effect with synthetic antioxidant(BHT); carboxymethyl cellulose film inhibited the lipids oxidation best,whose Acid value,peroxide value and TBARs value in the semimembranosus muscles respectively reduced by 13%,27% and 10% compared with the treat without coating film(p>>0.05).The result of optimizing orthogonal test is as following:dry-cured ham was sprayied natural compound antioxidant of 0.05 % rosemary and 0.05% VE,then applied three layers carboxymethyl cellulose film on the surface of the dry-cured ham during the mid-fermention.It was well consistent with the sensory evaluation results.

Lipolysis-oxidation is major biochemical reaction process during dry-cured ham traditional process, which plays an important role in flavor formation. However, excessive oxidation has negative impact on the ham quality and safety.The research was aimed at studying the inhibition of lipid oxidative changes of dry-cured ham by natural antioxidant grape seed extract (GSE)during the ferment process. The results showed that the antioxidation treat effectively inhibited lipid oxidation of dry-cured ham during ferment aging processing.Compared to control, GSE treat retarded the formation of Semimembranosus peroxide value(POV) ,TBA value, carbonyl value and diene value by 57% ,48% ,29%, 18% separately at the end of aging time;surface fat reducing by 60% ,24%, 42% ,36% ;while the Semimembranosus lipids oxidation indicators of the joint treat of grape seed extract and lard (GSE + Lard ) separately reduced by 20%, 8%, 14%, 6% ; surface fat reducing by 27%, 5%, 25%, 24%. The antioxidation effect of GSE treat is better than the joint treat of GSE and lard.