骏枣果醋发酵过程中营养品质变化及风味成分分析

以骏枣果酒为原料发酵果醋,对发酵过程中营养品质指标变化及发酵前后挥发性成分进行比较研究。结果表明,36～72 h期间为发酵产酸的主要时期,发酵过程中共检测到醋酸、草酸、柠檬酸、乳酸、琥珀酸、苹果酸6种有机酸,发酵后果醋中醋酸和琥珀酸含量分别为发酵前的15倍和3.7倍,乳酸和草酸含量则显著性降低,总酸味强度是果酒的6.17倍。发酵过程中总酚含量不断下降,维生素C含量先下降后趋于稳定,DPPH自由基清除率和总抗氧化能力显著升高。醋酸发酵前后共检测到挥发性成分65种,其中果醋检测到39种,相比果酒减少8种,果醋中酯类物质相对含量最高为37.42%,其中乙酸乙酯和乙酸异戊酯为主要的酯类物质,其次是酸类物质相对含量为30.69%。     

Determination of volatile fatty acids C1–C6, and lactic acid in silage juice

A method for the determination of volatile fatty acids, C₁–C₆, and lactic acid in silage juice is described. The procedure is simple and capable of application to large numbers of samples. It involves separation of the free acids by ion exchange, formation of their benzyl esters by the addition of benzyl bromide to a solution of the tetrabutylammonium salts in acetone and ultimate determination by gas liquid chromatography.     

Effect of lactic acid bacterial fermentation on amino acids and volatile compounds of pork trimming hydrolysate

The objective of this research was to improve the volatile flavour profile of a pork trimming hydrolysate by lactic acid bacteria (LAB) fermentation. Five probiotic strains and one dairy strain were used. The dominant aliphatic aldehydes (80.90%) in the unfermented hydrolysate were greatly reduced to <15% by converting into respective carboxylic acids and alcohols after fermentation. Strain GG was the only LAB that produced a significant level of succinic acid (1.62 mg mL⁻¹) and ketones (14.92%) (mainly diacetyl and acetoin) in the hydrolysate. Strains 299V and GG showed moderate proteolytic activities as their amino acid content reduced to 126.05 and 219.14 mg per 10 mL compared to the control (316.45 mg per 10 mL) after fermentation, respectively. However, little amino acid-derived volatiles were found in all fermented samples. These findings indicate that LAB fermentation modulates the flavour compounds of pork hydrolysates, which has the potential to be developed to novel flavouring materials.     

Aerobic deterioration of lucerne (Medicago sativa) and maize (Zea mais) silages—effects of fermentation products

Eleven laboratory lucerne silages, ten farm-scale lucerne silages and one maize silage were analysed for fermentation products to determine if chemical composition could explain differences in aerobic stability. Three of the farm-scale lucerne silages and the maize silage heated within 4 days of exposure to air whereas the other lucerne silages were stable for longer than 7 days even after inoculation with a destabilising yeast inoculum. The silages were analysed for lactic acid, volatile fatty acids (C₁ to C₆), succinic acid, ethanol, and 2,3-butanediol. The concentrations of these compounds in the unstable silages were not different from levels found in stable silages on either a dry matter basis or an undissociated water basis. However, unstable silages tended to be lower in 2,3-butanediol than other silages. The time until heating in these silages was simulated using a model of aerobic fungal growth in silage. This model considered the effects of yeast and mould numbers, pH, moisture content, and lactic and acetic acid concentrations on stability. Aerobic stability in three of the four unstable silages, with and without inoculation of destabilising yeasts, was reasonably predicted by the model. Stability in the other silages was consistently underpredicted by the model. These results indicate that the stability factor found in many lucerne silages is unlikely to be one of the principal products of silage fermentation.     

有机酸对赤霞珠干红葡萄酒的提酯增香效应研究

目的 探究有机酸对葡萄酒发酵香气物质的组成与含量及感官品质的影响。方法 以赤霞珠酿酒葡萄为原料进行酿造试验,在酒精发酵前分别进行酒石酸、苹果酸、柠檬酸、乳酸4种不同有机酸添加处理,酒精发酵结束后采用顶空固相微萃取结合气相色谱-质谱法(headspace solid-phase microextraction gas chromatography-mass spectrometry,HS-SPME-GC-MS)对发酵香气物质进行定性、定量分析,香气特征通过专业品评小组进行量化评价。结果 酒样共检测出18种酯类物质,其中有6种成分的气味活性值(odor activity value, OAV)大于1.0;有机酸处理可以增加赤霞珠干红葡萄酒的酯类物质整体含量;苹果酸处理显著提高了酒样中乙酸酯的含量,乳酸、苹果酸处理显著增加了短链脂肪酸乙酯的含量。进一步对各酯类物质的OAV分析发现,乳酸、苹果酸处理显著增加了多种酯类的OAV。结论 在酒精发酵前添加一定浓度的乳酸、苹果酸等有机酸可以有效保留葡萄酒中的酯类香气物质,尤其是乙酸酯和短-中链脂肪酸乙酯等果香酯类物质的含量,有效增强葡萄酒的花香、果香和...     

The effects of free amino acids,nucleic compounds,and volatile constituents of funazushi (fermented sushi of crucian carp (Cyprinus auratus)) on preference

BACKGROUND: Funazushi is a fermented sushi containing n3 polyunsaturated fatty acids. Moreover, the functionality of lactic acid fermentation foods has come to be expected. Funazushi is therefore worthy of study. Funazushi has a specific flavor which is either strongly liked or strongly disliked. We examined the components of funazushi and investigated their relation to preference. RESULTS: Many free amino acids with sweetness and/or umami were present in funazushi, but nucleic compounds were scarce as taste elements. Twelve kinds of volatile elements were detected in all samples, which were thought to form the basis of the flavor of funazushi, although a total of 30 or more kinds of volatile elements were detected from each sample. The smell greatly influenced the overall evaluation. Panelists who had not eaten funazushi before, or only rarely, showed a tendency to prefer the same sample, from which ketones, aldehydes, or acids did not volatilize so much. On the other hand, individual variation was large among panels who commonly ate funazushi. CONCLUSION: The smell and sourness of funazushi greatly influenced preference, especially in persons who had little experience of eating funazushi. Funazushi containing low ketone, aldehyde, or acid levels is suitable for the first eating experience. Copyright © 2008 Society of Chemical Industry     

The use of fatty acids as grass silage additives

The effects of a range of fatty acids (C₁-C₁₈) on silage fermentation in laboratory silos have been examined. When acids were applied to ryegrass in equimolar concentrations (50 mM) in the C₁-C₆ range, only the C₆ acid (hexanoic) had a marked effect in inhibiting lactate production. When hexanoic acid was examined in a second experiment over the concentration range 9 mM to 50 mM, concentrations below 50 mM did not prevent acid production, and at the lower levels production of lactate was stimulated. When higher fatty acids hexadecanoic (16:0), octadecanoic (18:0) and octadecenoic (18:1) were added at similar concentrations (8 to 9 mM) and octadecadienoic (18:2) added at concentrations ranging from 8 mM to 29 mM to ryegrass samples, lactic acid fermentation was not inhibited.     

Determination of short chain volatile fatty acids in silages from artichoke and orange by‐products by capillary gas chromatography

A simple, rapid and sensitive capillary gas chromatographic method was investigated to determine volatile fatty acids (VFA) in juice from silage made from artichoke and orange byproducts. The procedure uses a capillary column fused‐silica, 30 m×0.25 mm×0.25 mm ID and coated with FFAP‐TR. Centrifuged samples can be injected directly after lowering the pH to 1 and using a simple deproteinisation method. No adsorption, tailing or ghost phenomena occured. Separate analyses of VFA are quick and reliable. The average duration of an analyses is 7 min. The concentration, not only of the major acids, such as acetic acid, but also of the minor fermentation products such as butyric acid can be determined. The retention times of the products of fermentation and the extraction reagents were sufficiently different to avoid interference problems. © 1999 Society of Chemical Industry     

Characterization of volatile compounds and organic acids in ultra-high-temperature milk packaged in tetra brik cartons

A study was conducted to evaluate the basic chemical composition, organic acids and volatile compound profiles of ultra-high-temperature milk samples sold in Turkey. The organic acids were determined by reverse-phase high-performance liquid chromatography method, and volatile compounds were analyzed by headspace solid phase micro-extraction/gas chromatography/mass spectrometry technique. A total of 43 volatile compounds including 4 aldehydes, 5 alcohols, 10 ketones, 9 acids, 9 aromatic hydrocarbons, 3 nitrogenous, 2 sulfur containing compounds, and 1 alkane hydrocarbon, were identified in the ultra-high-temperature milk samples. The main compounds were found to be oxime methoxy phenyl, 2-heptanone, 2-mercapto-4-phenylthiazole, 2-amino-5-ethoxycarbonyl benzophenone, acetic acid, 2,6,10,14-tetramethyl pentadecane, and 2-nonanone. The main organic acid in the ultra-high-temperature milk was citric acid a mean value of 133 mg/100 mL, followed by formic, lactic, succinic, oxalic, acetic, orotic, propionic, pyruvic, hippuric, and uric acids.     

Influence of ensiling temperature, simulated rainfall, and delayed sealing on fermentation characteristics and aerobic stability of corn silage

The aim of this study was to determine how delayed silo sealing, high ensiling temperatures, and rainfall at harvest affect the fermentation and aerobic stability of corn silage. One-half of each of 4 replicated, 6 × 1.5 m plots of a corn hybrid was harvested at 35% dry matter (Dry), and each of the other halves was harvested after they were sprinkled with sufficient water to simulate 4 mm of rainfall (Wet). Six representative (2 kg) subsamples were taken from the Wet and Dry forage piles and ensiled immediately (Prompt). Three hours later, 6 additional representative (2 kg) samples were taken from each pile and ensiled (Delay). Half of the bags from each moisture × sealing time treatment combination were stored for 82 d in a 40°C incubator (Hot) and the other half were stored in a 20°C air-conditioned room (Cool). A 2 (moisture treatments) × 2 (sealing times) × 2 (ensiling temperatures) factorial design with 3 replicates per treatment was used for the study. Wetting the corn silage increased concentrations of NH₃-N, ethanol, and acetic acid. Ensiling at 40 instead of 20°C increased pH, in vitro digestibility, and concentrations of NH₃-N, residual water-soluble carbohydrates and acid detergent insoluble crude protein. The higher ensiling temperature also reduced concentrations of neutral and acid detergent fiber and lactic and acetic acid. Delayed sealing reduced concentrations of NH₃-N and total volatile fatty acids. Wetting, high temperature ensiling, and delayed sealing each reduced yeast counts slightly, and marginally (8 h) increased aerobic stability. Hot-Wet-Delay silages were more stable than other silages but had the lowest lactic to acetic acid ratio, and total volatile fatty acid concentration. This study indicates that the fermentation of corn silage is adversely affected by wet conditions at harvest and high ensiling temperatures, whereas delayed silo sealing for 3 h caused no adverse effects.     

Lecithin Associated Off-Aromas in Fermented Milk

ABSTRACT Soy, rice and hydrogenated soy lecithins were added to milk with lactic acid fermentation to characterize and elucidate formation of volatile off‐aromas. Sensory panelists detected off‐aromas in fermented milk containing unmodified soy or rice lecithin. Instrumental aroma analysis revealed that off‐flavor compounds included (E,E)‐2,4–nonadienal and (E,Z)‐ and (E,E)‐2,4–decadienal. Formation of 2,4–decadienals occurred within the first 4 h of lactic acid fermentation and reached maximum levels within 14 h of incubation. Enzymatic assays confirmed that washed cells of Lactococcus produced H₂O₂. Hydrogenated soy lecithin was suitable to use in cultured dairy products, but use of other soy or rice lecithin resulted in off‐flavor formation due to oxidation of polyunsaturated fatty acids.     

Variation in short chain fatty acid and ethanol concentration resulting from the natural fermentation of wheat and barley for inclusion in liquid diets for pigs

Fifty‐six samples of wheat and 44 samples of barley were taken, at harvest, from locations across the UK. Lactic acid bacteria (LAB) and yeasts were enumerated before the samples were ground. Following grinding, triplicate 30‐g samples of each cereal were mixed with sterile distilled water and incubated at 30, 35 or 40 °C. Samples were taken immediately after mixing and at 24‐h intervals for analysis of short‐chain fatty acids (SCFA) and ethanol by isocratic ion‐exclusion liquid chromatography. The number of LAB and yeasts present in samples ranged from 0 to 5.0 (mean 2.25 ± 1.31) and 3.30 to 6.25 (mean 4.96 ± 0.74) log₁₀ colony‐forming units (cfu) ml^?1 respectively. At 30 °C the mean concentrations (mmol l^?1) of SCFAs and ethanol were, lactic acid 59.6 ± 40.0 (range 0.14–134.9), acetic acid 23.2 ± 11.1 (range 2.9–51.4), butyric acid 17.2 ± 16.8 (range 0.0–62.2) and ethanol 15.0 ± 9.0 (range 4.6–53.7) respectively. After fermentation for 24 h only 9 of 300 fermentations produced more than 75 mmol l^?1 lactic acid, which has previously been demonstrated to prevent the growth of Salmonella in liquid pig feed. Fermenting at 35 or 40 °C had no effect on lactic acid concentration but significantly (p < 0.001) increased the concentrations of acetic and butyric acids and ethanol. These results indicate that natural fermentation cannot be relied upon to produce levels of SCFAs that will prevent the proliferation of enteropathogens. Copyright © 2004 Society of Chemical Industry     

桑椹酒发酵过程中有机酸含量变化

利用高效液相色谱法测定桑椹酒发酵过程中七种有机酸的变化,结果显示:桑椹原果汁中琥珀酸含量最高,柠檬酸次之;发酵过程中酒石酸、苹果酸、柠檬酸、琥珀酸、草酸、抗坏血酸含量变化均先呈上升趋势,达到最大值后呈下降趋势,而乳酸含量则一直上升;发酵结束后检测到酒石酸、苹果酸、柠檬酸、琥珀酸、草酸、抗坏血酸、乳酸含量分别为1.822、2.54、2.44、0.76、0.772、0.0756、0.0846g/L。     

葡萄酒酿造过程中有机酸变化规律研究

采用离子色谱法分析了葡萄酒中9种有机酸含量。通过对赤霞珠葡萄酒发酵过程中主要有机酸变化分析,研究其从葡萄汁到原酒的酿造过程中有机酸含量变化规律和量变的幅度。结果表明,葡萄酒中有机酸主要有酒石酸、苹果酸、乳酸、柠檬酸和琥珀酸,葡萄汁经发酵产生了乳酸、乙酸和琥珀酸。酿造过程中酒石酸、苹果酸、抗坏血酸和柠檬酸含量一直呈下降趋势;草酸和琥珀酸含量先增高后减少,乳酸含量一直呈上升趋势。乙酸是葡萄酒酒精发酵的主要副产物,含量为0.2～0.3 g/L。     

Physical,chemical and microbiological changes during green plant juice fermentation

Protein was precipitated from alfalfa juice by fermentation at 30°C, 35°C and 40°C.During fermentation there was a decrease in the pH, the total non-structural carbohydrate and the solid content while there was an increase in the lactic acid concentration and the population of the lactic acid bacteria in the juice. The lactic acid bacteria, which were initially only about 0·1% to 1·0% of the total bacteria count in the juice, predominated after a period of fermentation, producing mostly lactic acid and considerable amounts of acetic acid but only trace amounts of other volatile fatty acids.The addition of some lactic acid bacteria cultures—Lactobacillus plantarum and Pediococcus cereviseae—to the juice at the beginning of fermentation substantially reduced the lag phase and the final pH of the juice.     

Exclusion of dietary sodium bicarbonate from a wheat-based diet: effects on milk production and ruminal fermentation

Milk production, rumen fermentation, and whole-tract apparent nutrient digestibility in response to feeding 20% steam-rolled wheat with or without sodium bicarbonate were evaluated in 12 Holstein cows averaging 165 ± 16 DIM. Cows were fed 1 of 2 isoenergetic and isonitrogenous diets containing either 0 or 0.75% sodium bicarbonate on a DM basis for 21 d in a crossover design. Rumen fluid samples were obtained 18 times during the last 2 d of each period, and fecal samples were collected on 12 occasions from d 18 to 21 of each period. Removal of sodium bicarbonate from the diet did not affect DMI (21.0 kg/d), yields of milk (30.8 kg/d), or milk components (1.16, 1.01, and 1.40 kg/d for fat, protein, and lactose, respectively). Whole-tract apparent digestibility of DM, CP, ADF, and NDF did not differ between the 2 treatments (75.3, 76.6, 67.2, and 63.6%, respectively). The mean rumen pH was 6.24 and was not affected by excluding sodium bicarbonate from the diet. Rumen NH₃-N (12.31 mg/dL) and lactic acid (3.63 mM) concentrations were not different, whereas total volatile fatty acids concentration tended to increase when sodium bicarbonate was present in the diet (110 vs. 116 mM). However, average concentrations of the individual volatile fatty acids, as a proportion of total volatile fatty acids, were not affected by treatment. In conclusion, dairy cow diets can include up to 20% steam-rolled wheat without the need for added sodium bicarbonate as long as the diets are formulated to meet the fiber requirements of the cow.     

有机酸含量对葡萄酒发酵的影响

为了考察有机酸含量对葡萄酒发酵的影响,在初始有机酸含量分别为4 g/L、7 g/L和10 g/L的模拟葡萄汁中接种酵母,于25 ℃发酵,比较不同初始有机酸含量对葡萄酒发酵过程中酵母生长、降糖、有机酸及挥发性化合物含量的影响。结果表明,初始有机酸含量7 g/L时酵母生长和耗糖最慢,乙醇和乙醛产生量最低;随初始有机酸含量升高,pH值、酒石酸、苹果酸、乳酸、乙酸、总酸、乙酸乙酯和总酯含量呈下降趋势;琥珀酸、正丙醇、异丁醇、异戊醇及总高级醇含量呈上升趋势;但对β-苯乙醇、正丁醇及丁酸乙酯含量影响较小。初始有机酸含量10 g/L的葡萄酒发酵过程酵母生长快、降糖最快,产酸含量适中,同时香气较好。因此,葡萄酒发酵的适宜初始有机酸含量为10 g/L。     

Studies of the effects on the fermentation pattern in the rumen of the addition of various sources and levels of the lower volatile fatty acids

The short term effects on rumen fermentation of the direct addition to the rumen of 1·5 M and 3 M of acetate, propionate and butyrate, given as the Ca²⁺, Na⁺, and NH⁺₄ salts and as the free acid were measured in a mature cow. Longer term effects of the oral addition of I·5 M of calcium and ammonium acetates were also measured in growing heifers. For all volatile fatty acids (VFA) each rate of addition consistently increased the level of VFA in rumen liquor, but these fell gradually over about 4 h. Total volatile fatty acids (TVFA) were lower when free acids were given than when their salts were used. There was little effect on rumen pH. Calcium acetate was unpalatable when offered orally, and it tended to depress TVFA levels. Mean effects of acetate salts given orally on molar percentage of acetate in rumen liquor were smaller than those found by direct addition.     

Development and origin of the volatile fatty acids in budu

The origin and mechanism of formation of the volatile fatty acids (VFA) present in budu were investigated. The acids did not appear to derive from the breakdown of the fish lipid. When the fish was allowed to spoil, a single bacterial species predominated, and as the fermentation progressed, the appropriate VFA were formed. Using (U^?14C)-protein hydrolysate it was shown that amino acids are the precursors of the n-butanoic and n-pentanoic acid and also contributed to the formation of other acids. The bacterium did not use glucose as a carbon source nor did any particular combination of unlabelled amino acids produce the fatty acids. The metabolic route by which the fatty acids are produced from the amino acids is not known. An experiment that allowed spoilage to occur, prior to salting, in the normal environment involved in the preparation of budu, showed that the VFA were produced.     

Effect of different Bacillus strains on the profile of organic acids in a liquid culture of Daqu

A reversed‐phase high‐performance liquid chromatography method for the analysis of malic, lactic, acetic, citric, succinic, propionic and butyric acids, during the incubation of Bacillus spp., was developed. All samples taken from cultivation were centrifuged (20 min, 11,500g at 5°C) and filtered through a 0.45 µm membrane filter before injection. A programme pumping phosphate buffer at pH 2.50 and acetonitrile was used to separate the compounds on a C₁₈ column. Various parameters affecting analysis were optimized to take less than 30 min with a good linearity (R > 0.999). Bacillus licheniformis or B. subtilis, isolated from Daqu, was inoculated to ferment a liquid culture of Daqu. Growth of bacteria and organic acid production during the fermentation were investigated. Although there were no significant differences in the production of organic acids between B. licheniformis and B. subtilis during the first 8 h, significant differences in the production rates of organic acids, except for citric acid, were observed between B. licheniformis and B. subtilis from 8 to 48 h, with the final concentration of each organic acid varying. Copyright © 2013 The Institute of Brewing & Distilling