Relationship between procyanidin and flavor contents of cocoa liquors from different origins

The flavor of eight cocoa liquors of different origins (Africa, America, and Asia) and different varieties (Fine grades: criollo, trinitario, and nacional. Bulk-basic grade: forastero.) was analyzed by headspace solid-phase microextraction mass spectrometry (HS-SPME-MS). Their procyanidin contents were quantified by HPLC-UV (280 nm). Fine varieties with short fermentation processes proved to contain more procyanidins, while criollo from New Guinea and forastero beans showed the highest aroma levels. The levels of cocoa aroma compounds formed during roasting are shown to vary directly with bean fermentation time and inversely with residual procyanidin content in cocoa liquor. Measurement of antioxidant activity in cocoa liquor proved to be a useful tool for assessing residual polyphenols.     

Obtention and characterization of phenolic extracts from different cocoa sources

The aim of this study was to evaluate several cocoa sources to obtain a rich phenol extract for use as an ingredient in the food industry. Two types of phenolic extracts, complete and purified, from different cocoa sources (beans, nibs, liquor, and cocoa powder) were investigated. UPLC-MS/MS was used to identify and quantify the phenolic composition of the extracts, and the Folin-Ciocalteu and vanillin assays were used to determine the total phenolic and flavan-3-ol contents, respectively. The DPPH and ORAC assays were used to measure their antioxidant activity. The results of the analysis of the composition of the extracts revealed that the major fraction was procyanidins, followed by flavones and phenolic acids. From the obtained results, the nib could be considered the most interesting source for obtaining a rich phenolic cocoa extract because of its rich phenolic profile content and high antioxidant activity in comparison with the other cocoa sources.     

Isolation and characterization of 2S cocoa seed albumin storage polypeptide and the corresponding cDNA

The amine pool of cocoa is known to be an essential component for the development of the typical cocoa flavor. To better understand and to produce an intense in vitro cocoa flavor, identification of the polypeptides that are the source of the amine flavor precursor pool is essential. Chromatographic analysis of the polypeptide profile of unfermented cocoa resulted in identification of a novel storage polypeptide of M(r) 8515. The N-terminal sequence of the first 34 residues of the purified polypeptide shows similarity to 2S storage albumins of cotton and Brazil nut and sweet protein, Mabinlin. To identify the corresponding cDNA of the putative cocoa 2S albumin, 18 randomly chosen clones from the cDNA library of immature Theobroma cacao seed mRNA were sequenced, and a full-length cDNA clone encoding a protein harboring the N-terminal sequence of the novel polypeptide was selected. The open reading frame of the clone encodes a polypeptide of M(r) 17125. Comparison of the translated amino acid sequence of the precursor protein or the mature polypeptide against the Swiss-Prot and TrEMBL databases shows high sequence similarity (>52%) and identity (>38%) to many plant 2S albumins. Tryptic peptide mass fingerprinting of the purified polypeptide by high-performance liquid chromatography-electrospray ionization mass spectrometry shows 10 masses that match the expected tryptic peptides of the deduced sequence. Together with the published work on plant 2S albumin processing, the results presented here suggest that post-translational processing yields a 73-residue polypeptide (residue positions 78-150) corresponding to the 9 kDa subunit of the mature cocoa 2S albumin protein.     

Identification of the key aroma compounds in cocoa powder based on molecular sensory correlations

Isolation of the volatile fraction from cocoa powder (50 g; 20% fat content) by a careful extraction/distillation process followed by application of an aroma extract dilution analysis revealed 35 odor-active constituents in the flavor dilution (FD) factor range of 8-4096. Among them, 4-hydroxy-2,5-dimethyl-3(2H)-furanone (caramel-like), 2- and 3-methylbutanoic acid (sweaty, rancid), dimethyl trisulfide (cooked cabbage), 2-ethyl-3,5-dimethylpyrazine (potato-chip-like), and phenylacetaldehyde (honey-like) showed the highest FD factors. Quantitation of 31 key odorants by means of stable isotope dilution assays, followed by a calculation of their odor activity values (OAVs) (ratio of concentration to odor threshold) revealed OAVs>100 for the five odorants acetic acid (sour), 3-methylbutanal (malty), 3-methylbutanoic acid, phenylacetaldehyde, and 2-methylbutanal (malty). In addition, another 19 aroma compounds showed OAVs>1. To establish their contribution to the overall aroma of the cocoa powder, these 24 compounds were added to a reconstructed cocoa matrix in exactly the same concentrations as they occurred in the cocoa powder. The matrix was prepared from deodorized cocoa powder, which was adjusted to 20% fat content using deodorized cocoa butter. The overall sensory evaluation of this aroma recombinate versus the cocoa powder clearly indicated that the 24 compounds represented the typical sweet, cocoa-like odor of the real sample.     

纯粮固态发酵白酒生产中的碳排放及低碳生产

锁定生产纯粮固态发酵白酒的关键碳排放点可以明确碳减排重点环节,引导企业低碳生产。该文基于生命周期理论,研究了纯粮固态发酵白酒生产碳排放,并根据各生产环节碳排放贡献率锁定了碳排放的关键点。结果表明,消耗煤炭的锅炉运转与蒸粮蒸酒的生产工艺联系紧密,成为纯粮固态发酵型白酒生产最关键的碳排放点,同时用电消耗和厂内运输也对碳排放具有一定的贡献。据此提出改善能源消耗结构,使用生物质能等清洁能源以促进纯粮固态发酵型白酒的低碳生产。该文研究结果为减少食品生产的碳排放提供了参考。     

Procyanidin and catechin contents and antioxidant capacity of cocoa and chocolate products

Cocoa and chocolate products from major brands were analyzed blind for total antioxidant capacity (AOC) (lipophilic and hydrophilic ORAC(FL)), catechins, and procyanidins (monomer through polymers). Accuracy of analyses was ascertained by comparing analyses on a NIST standard reference chocolate with NIST certified values. Procyanidin (PC) content was related to the nonfat cocoa solid (NFCS) content. The natural cocoa powders (average 87% of NFCS) contained the highest levels of AOC (826 +/- 103 micromol of TE/g) and PCs (40.8 +/- 8.3 mg/g). Alkalized cocoa (Dutched powders, average 80% NFCS) contained lower AOC (402 +/- 6 micromol of TE /g) and PCs (8.9 +/- 2.7 mg/g). Unsweetened chocolates or chocolate liquor (50% NFCS) contained 496 +/- 40 micromol of TE /g of AOC and 22.3 +/- 2.9 mg/g of PCs. Milk chocolates, which contain the least amount of NFCS (7.1%), had the lowest concentrations of AOC (80 +/- 10 micromol of TE /g) and PCs (2.7 +/- 0.5 mg/g). One serving of cocoa (5 g) or chocolate (15 or 40 g, depending upon the type of chocolate) provides 2000-9100 micromol of TE of AOC and 45-517 mg of PCs, amounts that exceed the amount in a serving of the majority of foods consumed in America. The monomers through trimers, which are thought to be directly bioavailable, contributed 30% of the total PCs in chocolates. Hydrophilic antioxidant capacity contributed >90% of AOC in all products. The correlation coefficient between AOC and PCs in chocolates was 0.92, suggesting that PCs are the dominant antioxidants in cocoa and chocolates. These results indicate that NFCS is correlated with AOC and PC in cocoa and chocolate products. Alkalizing dramatically decreased both the procyanidin content and antioxidant capacity, although not to the same extent.     

Sensory properties of virgin olive oil polyphenols: identification of deacetoxy-ligstroside aglycon as a key contributor to pungency

Polyphenols are an important functional minor component of virgin olive oils that are responsible for the key sensory characteristics of bitterness, pungency, and astringency. Polyphenols were isolated from virgin olive oils by using liquid/liquid extraction and then separated by using reverse phase HPLC followed by fraction collection. The sensory qualities of the isolated polyphenols were evaluated, and almost all fractions containing polyphenols were described as bitter and astringent. However, the fraction containing deacetoxy-ligstroside aglycon produced a strong burning pungent sensation at the back of the throat. In contrast, the fraction containing the analogous deacetoxy-oleuropein aglycon, at an equivalent concentration, produced only a slight burning/numbing sensation, which was perceived more on the tongue. No other polyphenol fractions from the analyzed oils produced the intense burning sensation; thus, deacetoxy-ligstroside aglycon is the polyphenol responsible for the majority of the burning pungent sensation found in pungent extra virgin olive oils.     

Factors affecting the formation of alkylpyrazines during roasting treatment in natural and alkalinized cocoa powder

The cocoa roasting process at different temperatures (at 125 and 135 degrees C for 3 min, plus 44 and 52 min, respectively, heating-up times) was evaluated by measuring the initial and final free amino acids distribution, flavor index, formol number, browning measurement, and alkylpyrazines content in 15 cocoa bean samples of different origins. These samples were also analyzed in manufactured cocoa powder. The effect of alkalinization of cocoa was studied. Results indicated that the final concentration and ratio of tetramethylpyrazine/trimethylpyrazine (TMP/TrMP) increased rapidly at higher roasting temperatures. The samples roasted with alkalies (pH between 7.20 and 7.92), such as sodium carbonate, or potassium plus air injected in the roaster during thermal treatment, exhibited a greater degree of brown color formation, but the amount of alkylpyrazines generated was adversely affected. The analysis of alpha-free amino acids at the end of the roasting process demonstrated the importance of the thermal treatment conditions and the pH values on nibs (cocoa bean cotyledons), liquor, or cocoa. Higher pH values led to a lower concentration of aroma and a higher presence of brown compounds.     

清酒乳杆菌固态发酵鳓鱼过程中的品质变化

为研究清酒乳杆菌固态发酵鳓鱼过程中品质的变化,以促进传统发酵水产品标准化生产中品质控制水平的提高,本研究综合测定了鳓鱼发酵过程中的理化、色度和质构等常规指标,采用电子舌技术对滋味特性进行分析,对感官品质进行了人工评价,并对各指标之间的相关性进行了分析。结果表明,在鳓鱼发酵过程中,pH值先下降后上升,最小值为4.88,水分含量减少,总酸度先升高后下降,最大值为13.4 g·kg-1,氨基酸态氮(ANN)、挥发性盐基氮(TVB-N)含量增加;内聚性、硬度和咀嚼性均先上升后下降,第9天达到最大值,分别为0.6、437.4 g和217.8 g,弹性和回复性持续下降;鳓鱼色泽变化显著(P0.01),L*值先升高后下降,a*值先下降后上升,b*值持续上升,逐渐呈现黄亮的发酵色泽。基于电子舌技术的滋味特性分析表明,发酵过程中主要形成酸味、苦味、甜味和复合滋味等,而鲜味和咸味的成分较少,且构建的主成分分析模型可明显区分不同发酵时间的样本。对感官品质的人工综合评价在第9天达到最大值(72.8)。综上所述,清酒乳杆菌固态发酵过程中,发酵鳓鱼的理化、质构、色度和滋味品质存在一定关联性,各指标在发酵中期达到最佳,发酵周期以9 d为宜,这为发酵水产品加工提供了一定的理论依据。     

利用响应面法优化石榴酒发酵工艺条件

攀枝花的石榴品种繁多,籽粒味甜汁多,为了充分利用这一优势资源,本文进行石榴酒发酵,并对其发酵工艺利用响应面分析法进行优化。以酒精度为指标,考虑发酵温度、二氧化硫添加量、酵母接种量对石榴酒发酵酒精度的影响,然后根据中心组合030x—Benhnken）原理采用三因素三水平的分析法,依据回归确定各工艺条件的影响因素,以石榴酒发酵酒精度为响应面和等高线,分析各个因素的显著性和交互作用,结果表明优化得到石榴酒发酵的最佳工艺条件为二氧化硫添加量51．3mg／kg,酵母菌接种量5．33％,发酵温度24．98℃,酒酒精度的理论值为9．58％。通过响应面分析优化发酵工艺,为今后石榴酒发酵的更进一步开发提供一定的理论依据。     

Factors Influencing Yeast Fermentation and the Effect of LMW Sugars and Yeast Fermentation on Hearth Bread Quality

The purpose of this study was to investigate how wheat cultivar, growth location, type of mill, LMW sugar composition of wheat flours, mixing time, and type of mixer affected yeast fermentation. Also studied was the effect of yeast fermentation and LMW sugar composition on hearth bread quality. To achieve this, 36 different flours were produced from two different mills using six different wheat cultivars grown at three locations. Yeast fermentation in doughs, measured as gas production, was determined using realtime pressure measurements and GasSmart software. A short mixograph mixing or spatula mixing was not efficient enough to rehydrate instant dry yeast. Compressed yeast and a short mixing time were enough to reach maximum fermentation rate. Maximum pressure after 210 min of fermentation was higher for instant dry yeast than for compressed yeast. Wheat cultivar and growth location had a significant effect on LMW sugar composition. Wheat cultivar, growth location, and type of mill used significantly affected pressure curve parameters. Oligosaccharides and damaged starch were positively correlated, and ash content and flour yield were negatively correlated with pressure curve parameters. Hearth bread characteristic crumb structure was positively correlated with all pressure curve characteristics except fast fermentation rate. Increased levels of mono‐ and disaccharides in wheat flour gave hearth breads with a more round shape.     

Bean Quality Traits and Sensory Evaluation of Wild Guianan Cocoa Populations (<Emphasis Type="Italic">Theobroma cacao</Emphasis> L.)

Naturalized cocoa populations originating from the Oyapok and Tanpok basins in French Guiana were studied for their technological characters (bean count, fat content, purine content) and sensory characters (overall aroma intensity, cocoa flavour, acidity, bitterness, astringency, fruity or floral tastes, aftertaste, etc.), along with three controls (Amelonado and Ecuadorian varieties). The bean count in Guianan cocoa was higher than that of the controls, but it generally remained acceptable (below 100). Caffeine content was much higher than that of the Amelonado control. The overall aroma intensity and cocoa flavour of the chocolates made with the dry cocoa beans from Guianan trees were statistically superior to those of the industrial reference, the West African Amelonado. The other criteria studied, particularly the fat content, did not reveal any significant differences from the controls. An erratum to this article is available at .     

Development of a gas-liquid chromatographic method for the analysis of fatty acid tryptamides in cocoa products

The determination of the occurrence and level of cocoa shells in cocoa products and chocolate is an important analytical issue. The recent European Union directive on cocoa and chocolate products (2000/36/EC) has not retained the former limit of a maximum amount of 5% of cocoa shells in cocoa nibs (based on fat-free dry matter), previously authorized for the elaboration of cocoa products such as cocoa mass. In the present study, we report a reliable gas-liquid chromatography procedure suitable for the determination of the occurrence of cocoa shells in cocoa products by detection of fatty acid tryptamides (FATs). The precision of the method was evaluated by analyzing nine different samples (cocoa liquors with different ranges of shells) six times (replicate repeatability). The variations of the robust coefficient of variation of the repeatability demonstrated that FAT(C22), FAT(C24), and total FATs are good markers for the detection of shells in cocoa products. The trueness of the method was evaluated by determining the FAT content in two spiked matrices (cocoa liquors and cocoa shells) at different levels (from 1 to 50 mg/100 g). A good relation was found between the results obtained and the spiking (recovery varied between 90 and 130%), and the linearity range was established between 1 and 50 mg/100 g in cocoa products. For total FAT contents of cocoa liquor containing 5% shells, the measurement uncertainty allows us to conclude that FAT is equal to 4.01 +/- 0.8 mg/100 g. This validated method is perfectly suitable to determine shell contents in cocoa products using FAT(C22), FAT(C24), and total FATs as markers. The results also confirmed that cocoa shells contain FAT(C24) and FAT(C22) in a constant ratio of nearly 2:1.     

Determination of polyphenolic profiles of Basque cider apple varieties using accelerated solvent extraction

Polyphenols in the peel and pulp of 15 Basque cider apple varieties were determined by accelerated solvent extraction followed by reversed phase high-performance liquid chromatography with diode array detection. It was observed that the polyphenolic composition in apple peel depended on varieties, whereas the main classes of phenolic compounds in apple pulp were flavan-3-ols and hydroxycinnamic acids in all cases, representing both together between 86 and 95% of total polyphenols assayed.     

Evolution of phenolic composition of red wine during vinification and storage and its contribution to wine sensory properties and antioxidant activity

The objective of this work was to study the evolution of the phenolic composition of red wine during vinification and storage and its relationship with some sensory properties (astringency and bitterness) and antioxidant activities. Thus, red wine was made by a classic vinification method with Castela?o and Tinta Miu?da grapes (Vitis vinifera L.) harvested at maturity (3:2; w/w). Samples were taken at 2 and 7 days of maceration, at second racking, at the time of bottling and at 6 and 14 months after bottling. The total polyphenols extract (TPx) in each sample was isolated by column chromatography. The phenolic composition (anthocyanins and proanthocyanidins), in vitro antioxidant activity, and sensory property (astringency, bitterness) of the isolated TPx from different winemaking stages were evaluated through high-performance liquid chromatography-diode array detection, 1,1-diphenyl-2-picrylhidrazyl radical test, ferric reducing antioxidant power assay, total phenolic index, MWI (polyphenol molecular weight index), TSA (tannin specific activity), and sensory panel tasting. The results showed that the phenolic composition of red wine varied significantly during winemaking. The intensity of astringency (IA) and the intensity bitterness (IB) of the isolated TPx from different winemaking stages increased from 2 days of maceration until second racking and then decreased. Furthermore, MWI and TSA are positively correlated with IA and IB. The in vitro antioxidant activity of the isolated TPx from different winemaking stages maintained unchanged after alcoholic fermentation, which was independent of the variation of phenolic composition and sensory properties.     

Impact of alkalization on the antioxidant and flavanol content of commercial cocoa powders

Cocoa is a food ingredient that is important for the contribution of flavor to foods but is also associated with potential health benefits. The chemistry thought to be responsible for its cardiovascular health benefits is the flavanol (flavan-3-ol) antioxidants. Evidence from the literature indicates that natural cocoas are high in flavanols, but when the cocoa is processed with alkali, also known as Dutch processing or Dutching, the flavanols are substantially reduced. This paper provides a survey of the physical and chemical composition of representative natural cocoas and lightly, medium, and heavily alkalized cocoas. As part of the survey, both brown/black and red/brown alkali-processed cocoas were measured. Natural cocoa powders have an extractable pH of 5.3-5.8. Alkalized cocoa powders were grouped into lightly treated (pH 6.50-7.20), medium-treated (pH 7.21-7.60), and heavily treated (pH 7.61 and higher). The natural, nonalkalized powders had the highest ORAC and total polyphenols and flavanols (including procyanidins). These chemical measurements showed a linear decrease as the extractable pH of the cocoa powder increased. Likewise, the flavanol monomers, oligomers, and polymers all showed a linear decrease with increasing pH of the final cocoa powder. When brown/black cocoa powders were compared to red cocoa powders, similar decreases in flavanols were observed with increased alkalization. The average total flavanol contents were 34.6 +/- 6.8 mg/g for the natural cocoas, 13.8 +/- 7.3 mg/g for the lightly processed cocoas, 7.8 +/- 4.0 mg/g for the medium processed cocoas, and 3.9 +/- 1.8 mg/g for the heavily processed cocoa powders. The observed linear and predictable impact of alkalization on flavanol content is discussed with respect to other reports in the literature as well as what implications it may have on diet and food manufacturing.     

普洱茶发酵阶段色泽的变化及其与品质的关系

为阐明普洱茶不同发酵阶段色泽变化及其与普洱茶品质的关系,研究了恒温恒湿与恒温非恒湿条件下,接种外源优势菌（酿酒酵母）与未接种外源优势菌的云南普洱茶在不同发酵阶段的感官品质、汤色的定量分析及茶色素含量的变化。结果表明：明度指数L及明度指数差ΔL与感官指标汤色的评分呈正相关;色品指数a、b及色差值Δa、Δb与汤色感官评分、滋味评分和品质总评分均呈正相关;不同发酵阶段样的ΔL、Δb的值逐渐减小,而Δa的值逐渐增大,这与其茶红素和茶黄素的值逐渐减小和茶褐素的值不断增大是一致的。普洱茶发酵阶段色泽的量化分析可作为普洱茶品质评价的重要指标,在自动化恒温恒湿条件下发酵普洱茶,有利于实现普洱茶清洁化加工和提高普洱茶品质的稳定性。     

土壤微生物—腐殖质—矿物间的胞外电子传递机制研究进展

微生物胞外电子传递是地球表层系统元素循环与能量交换的重要驱动力。近年来,以微生物—腐殖质—矿物之间电子转移为核心的生物地球化学过程得到重视,拓展了以带电的土壤胶体与离子之间的相互作用为重心的土壤界面过程的内涵,成为地球表层系统物质间相互作用新的关注点,启示我们从化学与生物两个角度重新认识地球表层系统过程。本文从微生物、腐殖质和矿物等要素入手,综述了其地球化学角色与功能,讨论了它们之间的相互关系以及胞外电子传递的途径与方式;从热力学的角度探讨了胞外电子传递过程的能量变化,从动力学的角度探讨了胞外电子传递的传质与速率;介绍了若干胞外电子传递的研究方法;并提出了今后需要重点关注的重要科学问题。     

生物转化玉米浆生产生物菌肥的共生发酵特性

玉米深加工是全球第二大宗农产品加工行业,玉米淀粉制备过程中产生大量的副产物,如玉米浆（Maize Steep Liquor, MSL）。玉米浆色深味重、毒素含量高、处理困难,已经成为众多玉米深加工企业发展的桎梏。该研究主要利用玉米浆中丰富的速效氮源和微生物的促生长因子进行微生物菌肥的开发。通过对前期筛选到的3株植物根际促生菌（PGPMs）的共生发酵研究,评估了3种菌在玉米浆中高密度发酵的可行性,并对发酵特性进行了研究。试验结果表明,三种菌通过共生发酵,并在模拟流加工业废料结晶糖母液作为补料时,发酵体系中的总生物量从6.6×109提升到了2.17×1010 CFU/mL,并在52 h氨基酸态氮含量达到最大。同时,采用葡萄糖模拟结晶葡萄糖母液流加补料显著提高了共生体系的总糖以及溶磷的利用率,可溶性磷利用率提高了近50%;此外,添加葡萄糖还能保持发酵体系的pH值稳定,奠定了生产稳定性。该研究为玉米浆的再利用提供了一种解决方法,对低成本生物肥料的开发与生产提供了一种新的思路。