Understanding changes in volatile compounds and fatty acids of Jincheng orange peel oil at different growth stages using GC-MS

Jincheng orange(Citrus sinensis Osbeck)is widely grown in Chongqing,China,and is commonly consumed because of its characteristic aroma contributed by the presence of diverse volatile compounds.The changes in aroma during the development and maturation of fruit are indicators for ripening and harvest time.However,the influence of growth stages on the volatile compounds in Jincheng orange remains unclear.In addition,volatiles originate from fatty acids,most of which are the precursors of volatile substances.On this basis,gas chromatography-mass spectrometry(GC-MS)was performed to elaborate the changes in volatile constituents and fatty acids as precursors.This study tested proximately 60 volatiles and 8 fatty acids at 9 growth and development stages(AF1-AF9).Of those compounds,more than 92.00%of total volatiles and 87.50%of fatty acids were terpenoid and saturated fatty acids,respectively.As shown in the PCA plot,the AF5,AF6,and AF9 stages were confirmed as completely segregated and appeared different.In addition,most of the volatiles and fatty acids first increased at the beginning of the development stage,then decreased from the AF6 development stage,and finally increased at the AF9 maturity stage.Moreover,the highest contents of terpenoid,alcohols,aldehydes,ketones,and saturated fatty acids in Jincheng orange peel oil were d-limonene,linalool,octanal,cyclohexanone,and stearic acid during development stages,respectively.Our results found that the growth stages significantly affected the volatile constituents and precursors in Jincheng orange peel oil.

A combined pig model to determine the net absorption of volatile fatty acids in the large intestine under different levels of crude fiber

Background:This study aimed to develop a combined model to quantify the net absorption of volatile fatty acids(VFA)in the large intestine(LI)of pigs.Methods:Fifteen female growing pigs(Duroc×Large White×Landrace)were ranked by body weight(30±2.1 kg)on day 0 and assigned to one of three treatments,namely the basal diet containing different crude fiber(CF)levels(LCF:3.0%CF,MCF:4.5%CF,and HCF:6.0%CF).The pigs were implanted with the terminal ileum fistula and the cannulation of the ileal mesenteric vein(IMV),portal vein(PV),and left femoral artery(LFA)from days 6 to 7.[13 C]-Labeled VFA and P-aminohippuric acid were constantly perfused into the terminal ileum fistula and the cannulation of the IMV(day 15),respectively.Blood samples were collected from the PV and the LFA during perfusion(5 h),and LI samples were collected.Results:The net flux of[12 C]-acetic acid in the PV was greater for LCF versus MCF(p=0.045),but no difference was observed in the net flux of[12 C]-propionic acid(p=0.505)and[12 C]-butyric acid(p=0.35)in the PV among treatments.The deposition of[12 C]-acetic acid in the LI was greater for LCF versus MCF(p=0.014),whereas the deposition of[12 C]-propionic acid(p=0.007)and[12 C]-butyric acid(p=0.037)in the LI was greater for LCF versus HCF.Conclusions:In conclusion,this pig model was found conducive to study the net absorption of VFAs in the LI,and LCF had more net absorption of VFAs in the LI than MCF and HCF.

Influence of Polyphosphate Hydrolysis on the Degradation of Volatile Fatty Acids (VFAs) in Anaerobic Digestion

The degradation rate of Volatile Fatty Acids (VFAs) produced predominantly in the acidogenesis stage is a key process parameter to be optimised to ensure a successful Anaerobic digestion (AD). Thermodynamically, the oxidation of the VFAs are energetically unfavourable, and as such external energy source apart from the energy derived from the hydrolysis of Adenosine Triphosphate (ATP) is needed for the initial activation of the VFAs, initial growth of the methanogens in AD process and improved degradation rate of the VFAs. Thus, this research investigated the influence of polyphosphate hydrolysis on the degradation rate of the VFAs at high concentration. Sodium-propionate, Sodium-butyrate and Sodium-acetate salts were added at the start of experiments in order to increase the concentration of the VFAs. The polyphosphate salts used were;Na-hexametaphosphate, Na-tripolyphosphate and potassium pyrophosphate. The control experiment was polyphosphate free and three process parameters (degradation rate, cumulative biogas production and specific methane content) of anaerobic digestion were investigated. The experiments were carried out at a mesophilic temperature of 37.5°C for 41 days. The results of the investigation showed that the treated reactors with the polyphosphate salt solution in low concentration performed better than the reactors with high concentration of the polyphosphate salts solution. All the treated reactors with poly-P salts performed better than reactor Nr-9 (control experiment), but reactor Nr-1 was outstanding with an improved degradation rate of 47%, cumulative biogas production of 21% and specific methane content of 23%.

Volatile fatty acids carbon source for biological denitrification

In the suspended sludge system, when pH and temperature were suitable and carbon source was not limited, the denitrification and C-uptake rate followed a zero-order reaction. Mixed VFA C-source had higher denitrification rate than single VFA C-source consisting of them. When VFA were used as carbon source, consumed carbon quantity for denitrification was closed to 1. 07 mg VFA-C/mg NO-N. About 20% of the applied C/N was used for assimilative purposes. As rising up influent C/N by increasing the C load ,the sludge yield YN increased. The part of carbon consumption increased and the effluent oxidized nitrogen decreased. At pH 7. 5, 25℃ and sludge yield 0.72 mg VSS/mg NO-N, the calculated influent VFA-C /NO critical value was 1. 43 for complete denitrification.

Impacts of the unsaturation degree of long-chain fatty acids on the volatile fatty acid profiles of rumen microbial fermentation in goats in vitro

This study investigated the impacts of the degree of unsaturation （unsaturity） of long-chain fatty acids on volatile fatty acid （VFA） profiles of rumen fermentation in vitro. Six types of long-chain fatty acids, including stearic acid （C18：0, control group）, oleic acid （C18：1, n-9）, linoleic acid （C18：2, n-6）, a-linolenic acid （C18：3, n-3）, arachidonic acid （C20：4, n-6） and eicosapentaenoic acid （C20：5, n-3）, were tested. Rumen fluid from three goats fitted with ruminal fistulae was used as inoculum and the inclusion rate of long-chain fatty acid was at 3% （w/w） of substrate. Samples were taken for VFA analysis at 0, 3, 6, 9, 12, 18 and 24 h of incubation, respectively. The analysis showed that there were significant differences in the total VFA among treatments, sampling time points, and treatment×time point interactions （P〈0.01）. a-Linolenic acid had the highest total VFA （P〈0.01） among different long-chain fatty acids tested. The molar proportion of acetate in total VFA significantly differed among treatments （P〈0.01） and sampling time points （P〈0.01）, but not treatment×time point interactions （P〉0.05）. In contrast, the molar proportion of propionate did not differ among treatments during the whole incubation （P〉0.05）. However, for butyrate molar proportions, significant differences were found not only among sampling time points but also among treatments and treatment×time point interactions （P〈0.01）, with eicosapentaenoic acid having the highest value （P〈0.01）. Additionally, no statistically significant differences were found in the acetate to propionate ratios among treatments groups （P〉0.05）, even the treatments stearic acid and a-linolenic acid were numerically higher than the others. The inclusion of 3% long-chain unsaturated fatty acids differing in the degree of unsaturation brought out a significant quadratic regression relation between the total VFA concentration and the double bond number of fatty acid. In conclusion, the a-linolenic acid with 3 double bonds appeared better for improving rumen microbial fermentation and the total VFA concentration.

Characteristics of physico-chemical properties, volatile compounds and free fatty acid profiles of commercial set-type Turkish yoghurts

Ten most popular brands of commercial Turkish set-type yoghurts were collected from local retail outlets in Hatay, Turkey for two separate periods, and analyzed for basic nutrients, physico-chemical properties, volatile aroma compounds and free fatty acid profiles to compare their differences among the yoghurt products. The results showed that there were significant differences (P<0.05, 0.01, or 0.001) and variations in physico-chemical indices, volatile aroma compounds and volatile free fatty acid profiles among the yoghurt brands, which ultimately influence the flavor quality of the product. Acetaldehyde was predominant volatile compound in yoghurts, which followed by acetone, acetoin, diacetyl and ethanol. The level of diacetly was inversely related to titratable acidity, acetaldehyde and ethanoic acid. From ketones with high carbones 2-undecanone and 2-pentadecanone were higher than 2-butanone, 2-nanonane and 2-tridecanone. These ketones are related to fat content of yoghurt. Among short chain free fatty acids, ethanoic (acetic) acid was the most abundant in yoghurts, followed by hexanoic, octanoic and butanoic acids. These differences in detected chemical compositions of volatile compounds and free fatty acids would be applicable to predict flavor, nutritional value, quality control or shelf-life of the commmercial set-type Turkish yoghurts.

Effects of Ultrasonic and Acid Pretreatment on Food Waste Disintegration and Volatile Fatty Acid Production

This study aims at investigating the effects of ultrasonic and acid pretreatment on food waste( FW)disintegration and volatile fatty acid( VFA) production. Single-factor experiments are carried out to obtain optimal conditions of individual ultrasonic and acid pretreatment,and response surface method( RSM) is applied to optimize the conditions of the combination of ultrasonic and acid( UA) pretreatment. Results show that the optimal acid,ultrasonic and UA pretreatments conditions are individual pH 2,individual ultrasonic energy density of 1. 0 W / mL and the combination of ultrasonic energy density1. 11 W / mL and pH 1. 43,respectively. Correspondingly,the maximum disintegration degrees( DD) of 46. 90%,57. 38% and68. 83%are obtained by acid,ultrasonic and UA pretreatments,respectively. After optimizing pretreatment conditions,batch experiments are operated to produce VFA from raw and pretreated FW under anaerobic fermentation process. Both the maximum VFA production( 976. 17 mg COD / gV S) and VFA / SCOD( 72. 89%) are obtained with ultrasonic pretreatment, followed by UA pretreatment, non-pretreatment and acid pretreatment,respectively. This observation demonstrates that a higher acidity on acid and UA pretreatments inhibits the generation of VFA. Results suggest that ultrasonic pretreatment is preferable to promote the disintegration degree of FW and VFA production.

Microbial Community Profiles Related to Volatile Fatty Acids Production in Mesophilic and Thermophilic Fermentation of Waste Activated Sludge Pretreated by Enzymolysis

Mesophilic and thermophilic anaerobic fermentation performance of waste activated sludge(WAS)pretreated by enzymes catalysis associated with microbial community shifts were investigated.WAS disintegration was boosted considerably by enzymolysis with 8750 mg/L of soluble COD release within 180 min.Mesophilic anaerobic fermentation(MAF)produced nearly equal VFA accumulation with over 3200 mg COD/L compared with that of thermophilic fermentation(TAF).Bacterial community consortia showed great shifting differences in dynamics of main T⁃RFs between MAF and TAF.Moreover,MAF was conducive to form intermediate bacterial community evenness compared to TAF,which preserved a robust function of VFA production.The enzymes catalysis prompted bio⁃energy(electricity)recovery potential of WAS organics via anaerobic fermentation(MAF/TAF)with evaluating electricity conversion efficiency of 0.75-0.82 kW·h/kg VSS(3.9 times higher than control test).Finally,this study proposed some novel thinking on future WAS treatment/management towards energy recovery coupled with energy⁃sufficient wastewater treatment by co⁃locating WAS anaerobic fermentation,MFC plant with wastewater treatment plant(s).

Processing Effect on the Physicochemical and Volatile Fatty Acid Profile of African Breadfruit (Treculia africana) Seed Oil

African breadfruit seeds were subjected to three processing methods—parboiling, cooking and toasting, and the raw was used as control. The purpose of this research was to extract the oil from the seed and to determine the effect of processing on the oil for physicochemical properties and volatile fatty acid profile. Physicochemical properties showed that the colour of the oil varied from golden yellow to brownish yellow with specific gravity varying between 0.802 g/cm3 and 0.813 g/cm3. Percentage yield of oil was 6.14% for raw extract, 6.62% for parboiled extract, 7.56% for toasted extract, and 5.01% for cooked extract. Acid, peroxide and saponification value for oil extracted from the raw seed varied with the processed samples value. The Volatile Fatty Acid (VFA), also known as Short Chain Fatty Acid (SCFA) found inherent in varying concentration, were formic, acetic, propionic, isobutyric, butyric, isovaleric, valeric, isocarproic, hexanoic and heptanoic acid. Overall results prove that heat results in increases in the VFA concentration of the processed oil.

Noria-PEI改性PVA载体固定化溶菌酶用于污泥发酵产VFAs研究

生物酶促进污泥厌氧消化具有反应温和、高效环保等优点,然而回收困难和催化稳定性差严重制约其应用,固定化酶是解决上述问题的关键。采用水轮酚(Noria)和聚乙烯亚胺(PEI)共沉积法改性聚乙烯醇(PVA)载体,并研究了Noria-PEI改性PVA载体固定溶菌酶对污泥厌氧发酵产挥发性脂肪酸(VFAs)效能的影响。结果表明,固定化溶菌酶可强化污泥发酵提高SCOD,在36 h内SCOD最高浓度达到2 892.4 mg/L,相比空白组提升3.4倍(第6天),VFAs质量浓度在第4天达到峰值2 130.8 mg/L,乙酸和丙酸占比达到61.8%~80.7%。固定酶系统中污泥的平均粒径为42.957μm,比表面积为0.413 m^(2)/g,固定化溶菌酶强化了颗粒态污泥水解。微生物群落结构分析显示,在固定酶系统中Firmicutes、Proteobacteria和Bacteroides等水解产酸菌门占比较高;在属水平上,以Macellibacteroides、Petrimonas、Lactobacillus和Clostridium_sensu_stricto_1菌属为主,从微观层面上解释了固定酶强化污泥发酵产酸机理。

春季果蔬类废弃物在厌氧条件下产生挥发性脂肪酸(VFAs)的效果

果蔬类废弃物是餐厨垃圾中重要的一类,其产生量不可小觑。对餐厨垃圾进行厌氧消化处理,产生的挥发性脂肪酸(VFAs)可以用于污水处理厂脱氮除磷的外加碳源。论文通过间歇模式研究了春季时令果蔬组合在厌氧水解过程中产生挥发性脂肪酸的效果,并考察了VFAs的浓度、组成以及VS(挥发性固体)转化率等指标随时间的变化。研究结果表明,在pH值为6、温度为35℃的间歇模式下,春季果蔬类废弃物的产酸效果良好,VFAs转化率为0.36 g·(gVfed)^(-1)。

Valorisation of industrial hemp (Cannabis sativa L.) residues and cheese whey into volatile fatty acids for single cell protein production

The production of single cell protein(SCP)using lignocellulosic materials stands out as a promising route in the circular bioeconomy transition.However,multiple steps are necessary for lignocellulosics-to-SCP processes,involving chemical pretreatments and specific aerobic cultures.Whereas there are no studies that investigated the SCP production from lignocellulosics by using only biological processes and microbial biomass able to work both anaerobically and aerobically.In this view,the valorisation of industrial hemp(Cannabis sativa L.)biomass residues(HBRs),specifically hurds and a mix of leaves and inflorescences,combined with cheese whey(CW)was investigated through a semi-continuous acidogenic co-fermentation process(co-AF).The aim of this study was to maximise HBRs conversion into VFAs to be further used as carbon-rich substrates for SCP production.Different process conditions were tested by either removing CW or increasing the amount of HBRs in terms of VS(i.e.,two and four times)to evaluate the performance of the co-AF process.Increasing HBRs resulted in a proportional increase in VFA production up to 3115 mg HAc L^(-1),with experimental production nearly 40%higher than theoretical predictions.The synergy between HBRs and CW was demonstrated,proving the latter as essential to improve the biodegradability of the former.The produced VFAs were subsequently tested as substrates for SCP synthesis in batch aerobic tests.A biomass concentration of 2.43 g TSS L^(-1) was achieved with a C/N ratio of 5.0 and a pH of 9.0 after two days of aerobic fermentation,reaching a protein content of 42%(g protein per g TSS).These results demonstrate the overall feasibility of the VFA-mediated HBR-to-SCP valorisation process.

VFAs组分调控对合成PHA影响研究进展

介绍了有机酸复配合成PHA的国内外研究现状,阐明了VFAs合成PHA的代谢途径,得出PHA的单体组成直接受VFAs中奇偶数酸的影响。围绕VFAs组分的调控策略,论述了有机废弃物厌氧发酵过程中VFAs组分的变化规律,归纳了不同组分VFAs合成PHA的性能和产率变化,指出提高奇数酸质量分数、增加HV单体占比是优化PHA性能的重要方式。通过归纳总结VFAs的各种调控策略,明确了合成优质PHA的研究方向。

Evaluation of in vitro digestibility of Aspergillus oryzae fungal biomass grown on organic residue derived‑VFAs as a promising ruminant feed supplement

Background As demand for high quality animal feed continues to raise,it becomes increasingly important to mini-mize the environmental impact of feed production.An appealing sustainable approach to provide feed fractions is to use organic residues from agro-food industry.In this regard,volatile fatty acids(VFAs)such as acetic,propionic and butyric acids,derived from bioconversion of organic residues can be used as precursors for production of micro-bial protein with ruminant feed inclusion potential.This study aims to investigate the in vitro digestibility of the Asper-gillus oryzae edible fungal biomass cultivated on VFAs-derived from anaerobic digestion of residues.The produced fungal protein biomass,along with hay clover silage and rapeseed meal were subjected to various in vitro assays using two-stage Tilley and Terry(TT),gas,and bag methods to evaluate and compare its digestibility for application in ruminant feed.Results The produced fungal biomass contained a higher crude protein(CP)(41%–49%)and rather similar neutral detergent fiber(NDF)(41%–56%)compared to rapeseed meal.The rumen in vitro dry matter digestibility(IVDMD)of the fungal biomass in the TT method ranged from 82%to 88%(statistically similar to that of the gas method(72%to 85%)).The IVDMD of fungal biomass were up to 26%and 40%greater than that of hay clover silage and rapeseed meal,respectively.The type of substrate and bag method had pronounced effect on the fermentation products(ammonium-N(NH4+-N),total gas and VFAs).Fungal biomass digestion resulted in the highest release of NH4+-N(340–540 mg/L)and the ratio of acetate to propionate ratio(3.5)among subjected substrates.Conclusion The results indicate that gas method can be used as a reliable predictor for IVDMD as well as fermenta-tion products.Furthermore,the high IVDMD and fermentation product observed for Aspergillus oryzae fungal biomass digestion,suggest that the supplementation of fungal biomass will contribute to improving the rumen digestion by providing necessary nitrogen and energy to the ruminant and microbiota.

不同谷物对断奶马驹肠道内容物酶活力、淀粉含量及VFA浓度的影响

【目的】探究不同谷物对断奶马驹肠道内容物中酶活力、淀粉含量及VFA浓度的影响,为断奶马驹肠道发育健康、养分消化、饲粮搭配等提供参考依据。【方法】选择出生日期、体重(112.39 kg±7.50 kg)相近,5月龄断奶的哈萨克公马驹18匹,随机分为3组,每组6匹,分别补喂玉米、燕麦和大麦。在相同的粗饲料条件下,以等淀粉原则确定各组精料的补喂量,进行为期60 d的补饲试验。马驹屠宰后,采集各肠段内容物,测定淀粉酶活力、淀粉含量及挥发性脂肪酸(VFA)浓度。【结果】①燕麦组马驹小肠淀粉酶活力极显著高于玉米组(P<0.01),显著高于大麦组(P<0.05);玉米组马驹小肠β-淀粉酶活力极显著高于燕麦组和大麦组(P<0.01)。②燕麦组马驹回肠支链淀粉含量极显著低于玉米组和大麦组(P<0.01),直链淀粉含量显著低于玉米组(P<0.05),粪便中支链淀粉含量显著高于大麦组(P<0.05);玉米组马驹盲肠直链淀粉含量显著低于燕麦组(P<0.05),极显著低于大麦组(P<0.01),结肠直链淀粉含量也显著低于燕麦组和大麦组(P<0.05)。③燕麦组与大麦组回肠总VFA含量极显著高于玉米组(P<0.01);玉米组马驹盲肠戊酸含量显著高于燕麦组和大麦组(P<0.05),异戊酸含量极显著高于燕麦组和大麦组(P<0.01),结肠中戊酸含量极显著高于大麦组(P<0.01)。【结论】玉米和燕麦淀粉对马驹小肠酶活力具有较好的改善作用;在马驹回肠中燕麦淀粉的消化利用效果较好;在马驹盲肠和结肠中玉米淀粉的消化利用效果较好。

Effect of TRH and TSH on Circulatory Glucose and Fatty Acids Responses in Hypoinsulenemic Male Dwarf Goats

Diabetes mellitus or hypoinsulinemia was induced successfully in the male dwarf goats aged be-tween 2 - 3 years with 2 consecutive administrations of streptozotocin. A comparable group of intact control goats was also maintained. In ruminants including goats unlike non-ruminants, insulin generally displays ineffectiveness or resistance in their biochemical setup to facilitate gluco-neogenesis, the only source of glucose in these animals. In present study almost in the absence of insulin through induced hypoinsulinemia the effects of thyrotropin releasing hormone (TRH) (30 μg/kg body weight) and thyroid stimulating hormone (TSH) (2.5 μg/kg body weight) on circulatory glucose and different fatty acid fractions were studied in insulin resistant ruminant model. Fatty acid fractions were estimated by gas chromatography. Both TRH and TSH administration lowered glycemia in insulin deficient goats compared to the controls but significantly with TSH dose only. In intact goats the detectable circulating long chain fatty acids (LCFAs) fractions of lauric, myristic, palmitic, stearic, oleic and linoleic acid were undetected except linoleic acid in the hypoinsulinemic state, however were found restored following TRH and TSH administrations and some of LCFAs;stearic (6417%), oleic (1676%) and linoleic acid (1225%) increased exceptionally with TSH dose. In Intact goats however the hormones variedly increased the fractions. The volatile fatty acid fractions (VFAs) of formic, acetic, propionic, iso-butyric, n-butyric, iso-valeric, n-valeric, iso-caproic, n-caproic and heptanoic acid were detected in the goats. The most VFAs fractions markedly increased in hypoinsulinemic goats compared to the control goats following TRH and TSH infusion. These results have indicated that endogenously stimulated thyroid hormones with TRH and TSH in insulin deficient state inhibit the mechanisms of utilizing the fatty acids in glucose production. Therefore the study reveals thyroid hormones inhibitory effects on gluconeogenesis in insulin resistance and hyperglycemia.

pH值调控方法对剩余污泥与柑橘废渣厌氧共发酵产酸影响

考察不同pH值调控方法对剩余污泥和柑橘废渣共发酵系统的产酸性能影响,结果表明:持续调节pH值为6可以提高共发酵系统的增溶过程,促进糖类物质水解,增强产酸和产甲烷过程,VFA产量和累积甲烷产量分别是空白组的1.36倍和1.25倍;提高共发酵系统中水解细菌和发酵产酸细菌的菌群丰度,促使甲烷生成途径从乙酰分解途径转向氢化营养途径.调节初始pH值为10可以有效促进共发酵系统中溶解性有机物的释放和达到快速水解的目的,促进产酸性能,但对产甲烷过程有抑制作用.

两种产地藏羊肉挥发性风味物质和脂肪酸组成比较研究

为评定不同地区藏羊肉的挥发性风味物质和脂肪酸组成,选取甘肃省甘南藏族自治州和青海省海北藏族自治州的藏羊各20只,分别取背最长肌进行肉品质、脂肪酸以及挥发性成分组成、感官评价等指标的测定。结果表明,两种产地的藏羊宰后pH45min和pH24h均在正常范围内,且二者之间无显著性差异;甘南藏羊的色泽和嫩度优于海北藏羊;共检测出18种脂肪酸,其中包括7种饱和脂肪酸和11种不饱和脂肪酸。两种产地藏羊肉的脂肪酸组成和含量均存在显著差异,甘南藏羊脂肪酸组成比例更佳,ω-6/ω-3接近1∶1,显著低于海北藏羊(P<0.05)。共检测出12类70种挥发性风味物质,气味活性值(OAV)分析结果表明,甘南藏羊肉比海北藏羊肉具有更丰富的肉脂香味和果香味。综上,甘南藏羊肉的脂肪酸和挥发性成分组成都更加优异,感官评分更高。

不同温度胁迫条件下太平洋牡蛎挥发性化合物的变化

为探究温度胁迫后太平洋牡蛎挥发性成分的变化,该研究采用感官评定、气相色谱-离子迁移谱(Gas Chromatography-Ion Mobility Spectroscopy,GC-IMS)、气相色谱-质谱联用(Gas Chromatography-Mass Spectrometer,GC-MS)结合多元统计分析的方法,对不同温度胁迫条件(12、22、32℃)的太平洋牡蛎挥发性成分进行了检测,同时测定了其存活率以及脂肪酸含量的变化。结果显示,胁迫6 d后,低温12℃组的存活率达到97.90%,n-3型多不饱和脂肪酸(Polyunsaturated Fatty Acid,PUFA)含量升高。感官评定、GC-IMS以及GC-MS结果显示辛醛等鱼腥味醛类成分含量下降,而呈紫罗兰气味的(E,Z)-2,6-壬二烯醛升至12.15%,提供了愉悦的气味。高温32℃胁迫后存活率降至26.00%,n-3 PUFA含量下降从46.07%下降至39.59%,同时饱和醛等腥味醛类含量显著上升,加重了太平洋牡蛎的腥味,导致牡蛎的品质严重下降。最后通过统计分析筛选6种关键成分:己醛、辛醛、(E,Z)-2,6-壬二烯醛、(E)-2-壬烯醛、(E,E)-2,4-庚二烯醛以及3-辛酮。温度对太平洋牡蛎的存活率、n-3 PUFA含量及挥发性成分有较大影响,该研究为提升太平洋牡蛎品质提供了有益参考。

6款市售狮子头的品质及风味分析

为明确现有市售狮子头产品的品质差异,本研究通过6款不同品牌(A1-口缘、A2-五亭桥、A3-琪津、A4-老扬城、A5-三珍斋、A6-黄珏)市售狮子头的感官、色泽、质构特性、失水率、脂肪氧化等理化指标综合分析市售狮子头的品质性状,结合游离脂肪酸和挥发性风味物质进行表征。结果表明,A1狮子头感官评分高达34分,6款市售狮子头中A4的红度值高达3.46±0.08,而A1的脂肪氧化值最低为0.44 mg MDA/kg,其中A5、A6的咀嚼性较低为0.21±0.02、0.32±0.11 mJ;6款市售狮子头以油酸为主,其次以棕榈酸、硬脂酸等饱和脂肪酸构成,狮子头中的多不饱和脂肪酸被大量氧化反应分解为醛类等物质,同时饱和脂肪酸含量明显提升。γ-松油烯、己醛、芳樟醇、壬醛等为其共有的挥发性风味物质,除此之外,A1主要关键挥发性风味物质为2-戊基呋喃,A2主要关键挥发性风味物质为巴伦西亚橘烯、甲基庚烯酮、异戊醛,而A4主要关键挥发性风味物质为辛酸乙酯,A5为4-萜烯醇、十一醇、甲硫醇、糠醇、糠醛、硬脂酸甲酯、茴香脑,A6则是十一醇、苯丙醛。因此烃类、醛类与醇类、酮类可能是影响不同市售狮子头产品风味品质的主要因素。该研究结果可为市售狮子头产品质量评价体系的构建以及风味统一与产品开发生产提供理论参考。