复合酶水解牡蛎蛋白的动力学研究

对太平洋牡蛎蛋白进行复合酶(风味蛋白酶、胰蛋白酶的酶活力比为2.3:1)水解特性研究,探讨了底物浓度和酶浓度对水解度(DH)的影响。建立了复合酶水解牡蛎蛋白的动力学模型,确定了模型常数,并分析了多肽的平均链长、相对分子质量与酶解时间的关系。验证实验证实模型预测结果与实际测得的结果一致,表明该动力学模型具有一定的实用价值。     

Influence of packaging strategy on microbiological and biochemical changes in high‐pressure‐treated oysters (Crassostrea gigas)

BACKGROUND: High‐pressure (HP) treatment is being increasingly employed for commercial processing of oysters, but there is relatively limited information on the microbiological quality and enzymatic activity of HP‐treated in‐shell oysters. The objective of this research was to study the influence of packaging strategy on microbiological and biochemical changes in oysters HP treated at 260 MPa for 3 min or 400 MPa for 5 min at 20 °C and stored at 0 °C either aerobically on ice, in vacuum packaging (VP) or under modified atmosphere packaging (MAP; 40% CO₂, 60% N₂), compared with changes in untreated oysters. RESULTS: Both HP treatments reduced the microbiological load to below the detection limit (<100 colony‐forming units g^?1). MAP and VP also delayed subsequent microbial growth compared with aerobically stored samples. After 21 days of storage, total volatile base levels remained lower than the proposed acceptability limits for all samples; however, after 28 days, only oysters HP treated at 400 MPa, irrespective of the packaging system used, did not exceed this limit. HP increased the thiobarbituric acid‐reactive substance (TBARS) values of oysters, indicating increased lipid oxidation. During storage, TBARS values of all MAP and VP oysters remained lower than those of aerobically stored oysters. CONCLUSION: HP treatment, in combination with adequate chilled storage and MAP, can extend the shelf‐life and safety of oysters. Copyright © 2008 Society of Chemical Industry     

Identification of aroma‐active compounds in fresh and stored ‘Mor’ mandarins

In this study, gas chromatography–olfactometry (GC‐O) (sniffing) combined with gas chromatography–mass spectrometry (GC‐MS) analysis was applied to identify volatile aroma‐active compounds in homogenised segments of fresh and stored ‘Mor’ mandarins. The GC‐O nasal impact frequency method was used to identify Twenty‐three aroma‐active compounds, of which seventeen odorants were identified by GC‐MS. The aroma of fresh ‘Mor’ mandarins derived from a mixture of eleven odorants that contribute ‘green’ [(E)‐3‐hexenol and hexanal], ‘fresh’ [(E)‐carveol], ‘fruity’ (ethyl 2‐methylbutanoate), ‘citrus’ (limonene), ‘floral’ (linalool), ‘musty’ (β‐myrecene and γ‐terpinene), ‘potato’ (α‐terpinene), ‘mushroom’ (unknown 2) and ‘cabbage’ (α‐cubebene) odours. During postharvest, storage losses were observed in ‘green’ [(E)‐3‐hexenol] and ‘fresh’ [(E)‐carveol] odours, accompanied by increases in ‘fruity’ (ethyl propanoate) and several unpleasant aromas, such as ‘alcohol’ (ethanol), ‘musty’ [α‐pinene, (E)‐2‐nonenal and 1‐terpinen‐4‐ol] and ‘fatty’ (octyl acetate and δ‐cadinene) odours, all of which possibly account for the observed decrease in sensory acceptability after harvest.     

Effects of different distillation patterns on main compounds of Chinese Luzhou‐flavour raw liquors

This study aimed to investigate the effects of different distillation patterns on main compounds of Chinese Luzhou‐flavour liquor. Results showed that more volatiles of raw liquor might originate from fresh grains for a newly constructed pit. A modest (p  = 0.05) increase in the total amount of volatiles was found in the heart liquor from fermented grains added to fresh grains and rice hulls to distillate (AG pattern), reaching a maximum value of 1012.22 mg/L. The percentage of esters in the AG pattern ranged from 81.22 to >95.03% compared with samples from fermented grains only added to rice hulls to distillate (NG pattern). Acids in the heart liquor obtained by the AG pattern were higher than those for NG, but the corresponding proportion was opposite. Alcohols were detected at ~1.62% in NG pattern but were 1.42% in AG. Cyanide and ethyl carbamate content in the head liquor were far higher than those in the heart and tail liquor. In particular, cyanide content dramatically increased after adding fresh grains during the distillation process. Copyright © 2017 The Institute of Brewing & Distilling     

Heat treatments of peptides from oyster (Crassostrea gigas) and the impact on their digestibility and angiotensin I converting enzyme inhibitory activity

Food Science and Biotechnology - The changes of protein digestibility, the peptides in the digestive juice and angiotensin I converting enzyme (ACE) inhibitory activity after heating of oysters...     

Identification of odour‐active compounds in muscle of brown trout (Salmo trutta) as affected by dietary lipid sources

The effect of fatty acid composition on odour‐active compounds in brown trout (Salmo trutta) muscle was evaluated. The fillets were obtained from three groups of fish fed experimental diets containing either fish oil (FO), soybean oil (SO) or linseed oil (LO). Muscle fatty acid composition was shown to be influenced by diet. Thirty‐one odorous compounds were detected by gas chromatography/olfactometry (frequency‐of‐detection method). Most of these compounds were formed by the oxidation of unsaturated fatty acids. Independently of diet, (E)‐2‐pentenal, (E)‐2‐pentenol and (E)‐2‐hexenol contribute strongly to the odour of brown trout. (E,Z)‐2,4‐Heptadienal was detected with high frequency in fish fed diets containing high levels of n‐3 PUFAs (FO and LO groups). Hexanal, (E)‐2‐hexenal and 2‐nonanol seem to contribute most to the odour of fish fed diets containing vegetable oils. Many odorous compounds were derived from the oxidation of mono‐ and di‐unsaturated fatty acids, which could be promoted by high levels of PUFAs. © 2002 Society of Chemical Industry     

盐析辅助水蒸气蒸馏法提取甘松精油及其挥发性香气成分分析

为提高甘松精油提取效率,该试验以精油得率为评价指标,通过单因素试验及正交试验优化了盐析辅助水蒸气蒸馏法提取条件,并采用气相色谱-质谱联用法（GC-MS）分析甘松精油的香气成分。结果表明,盐析辅助水蒸气蒸馏法提取甘松精油最佳条件为NaCl含量3%、料液比1∶5(g∶mL)、浸泡时间5 h、蒸馏时间4 h。此优化条件下甘松精油得率为3.72%。GC-MS结果表明,共检测出56种挥发性香气物质,其主要成分多为萜类化合物,且以倍半萜数种类最多。该研究优化了盐析辅助水蒸气蒸馏提取甘松精油的工艺,可为甘松精油的进一步开发利用提供理论依据。     

Identification of key odor volatile compounds in the essential oil of nine peach accessions

BACKGROUND: Volatile compounds, together with sugars and acids, are the main chemical species determining the characteristic aroma and flavor of food. In peach, more than 100 volatiles have been identified. RESULTS: The essential oil of six peach and three nectarine accessions used in Italian breeding programs was obtained by steam distillation, and the volatiles were investigated. A total of 47 known volatiles, two unidentified compounds and nine hydrocarbons were identified, including 12 aldehydes, six alcohols, three acids, three esters, six terpenes, two phenylalanine derivates, two C₁₃ norisoprenoids, one ketone (C₉) and 10 lactones. A wide variation in the number of volatiles and in their concentration was observed among the nine accessions. Twenty‐one compounds presented odor activity values (OAVs) higher than 1 in at least one of the accessions and were therefore putatively considered as key odorants in the peach volatile composition. CONCLUSION: This study reports the identification, quantification and potency, based on the OAVs, of the most important volatile compounds, along with fruit quality characteristics, of nine different peach/nectarine accessions and will help future peach volatile breeding programs for the selection of odor‐rich accessions to be used in the development of new improved cultivars. Copyright © 2010 Society of Chemical Industry     

Growth,nutritional quality and safety of oysters (Crassostrea gigas) cultured in the lagoon of Venice (Italy)

Quality aspects of oysters (Crassostrea gigas) from a suspended culture in the lagoon of Venice (Valle Dogà) were examined in different seasons over a 1‐year period. Ecophysiological and commercial quality indicators (condition index, content of meat, shell and intervalvar fluid), nutritional quality parameters (proximate and mineral composition, glycogen content, fatty acid profile, cholesterol, plant sterols, fat‐soluble vitamins content) and levels of organic pollutants (polychlorinated biphenyls and organochlorine pesticides) were determined at different times of the year. Seasonal variations were observed in the nutrient content, with particular regard to moisture (ranging from 866.8 g kg^?1 in June to 938.8 g kg^?1 in September), protein (23.9 g kg^?1 in September to 76.6 g kg^?1 in June), ash (22.5 g kg^?1 in February to 29.5 g kg^?1 in July), lipid (3.0 g kg^?1 in September to 8.8 g kg^?1 in June) and glycogen (0.7 g kg^?1 in September to 11.5 g kg^?1 in February). In spite of this variability, the nutritional quality of the oysters was generally good, especially just before gamete release when the concentration of nutrients was at its maximum. Low levels of organochlorine chemicals were detected in the edible meat of oysters but, because only a limited number of samples were analysed, no general conclusion can be drawn on the safety of seafood from this area. Copyright © 2004 Society of Chemical Industry     

Characterisation of odour‐active compounds in lupin flour

BACKGROUND: Lupin ingredients are promising alternatives to soybean products owing to their similarly high protein content. Lupin flour exhibits a green and bean‐like off‐flavour in higher amounts. The aim of this study was to characterise and identify the main odour‐active compounds in lupin flour. RESULTS: The orthonasal aroma of lupin flour was evaluated by means of aroma profile analysis and was found to be characterised by grassy‐green, metallic, fatty, fruity, hay‐like, cheese‐like, and meat‐like odour qualities. Volatile compounds of lupin flour of Lupinus angustifolius cv. Boregine were extracted with dichloromethane and isolated by solvent‐assisted flavour evaporation. Aroma extract dilution analysis (AEDA) was carried out with the obtained extract. In total, 50 odorants were detected by high‐resolution gas chromatography–olfactometry. AEDA revealed 26 odour‐active compounds with flavour dilution factors higher or equal to 32. The substances were unequivocally identified by their odour characteristics, their retention indices and their mass spectra using one‐dimensional or two‐dimensional gas chromatography–mass spectrometry, respectively. CONCLUSION: A series of unsaturated and saturated aldehydes, ketones, carboxylic acids, alkyl‐methoxypyrazines and terpenes were identified for the first time as odour‐active contributors to the aroma of lupin flour. Copyright © 2009 Society of Chemical Industry     

Analysis and characterization of aroma‐active compounds of Schizandra chinensis (omija) leaves

Volatile components from leaves of Schizandra chinensis (omija), a native plant of Korea, were extracted by simultaneous distillation–extraction (SDE) and analyzed by gas chromatography–mass spectrometry (GC‐MS) using two types of capillary column with different polarities (DB‐5MS and DB‐Wax). The GC‐MS analysis of volatile compounds obtained by SDE revealed that germacrene D is the most abundant compound (22.6%) in omija leaves, followed by β‐elemene (17.4%), (E)‐2‐hexenal (8.7%), and (E)‐β‐ocimene (7.2%). Aroma‐active compounds were determined by gas chromatography–olfactometry (GC‐O) using the aroma‐extract‐dilution analysis method. (E,Z)‐2,6‐Nonadienal (cucumber) was the most intense aroma‐active compound due to its higher flavor‐dilution factor (243–729) than any other compound. (Z)‐3‐Hexenal (green/apple), (E)‐2‐hexenal (green/fruity), and (E)‐β‐ocimene (wither green/grass) were also identified as important aroma‐active compounds by GC‐O. In addition, the volatile compounds were extracted by solid‐phase microextraction (SPME), and the quantitative analysis of the SPME samples gave slightly different results, depending on the type of SPME fiber, compared with those from SDE, However, the aroma‐active compounds identified in SPME were similar to those in SDE. Copyright © 2004 Society of Chemical Industry     

Influence of composition and structure of oil‐in‐water emulsions on retention of aroma compounds

The influence of the composition and structure of oil‐in‐water emulsions on aroma retention was examined for 20 volatile compounds. Compositional and structural parameters included the fraction of emulsifier phase, the fraction of lipid phase and the particle size distribution of the dispersed lipid phase in the emulsion. Air/liquid partition coefficients of dimethyl sulphide, 1‐propanol, diacetyl, 2‐butanone, ethyl acetate, 1‐butanol, 2‐pentanol, propyl acetate, 3‐methyl‐1‐butanol, ethyl butyrate, hexanal, butyl acetate, 1‐hexanol, 2‐heptanone, heptanal, α‐pinene, 2‐octanone, octanal, 2‐nonanol and 2‐decanone were determined by static headspace gas chromatography. The hydrophobicity of the compounds determined the influence of the compositional and structural parameters of the emulsions on air/liquid partitioning. Increase of the emulsifier fraction increased the retention of mainly hydrophilic aroma compounds and decreased the retention of hydrophobic compounds. Higher lipid levels led to increased retention of hydrophobic compounds and release of hydrophilic compounds. Emulsions with larger particles showed increased aroma retention, which was independent of the lipid fraction and the polarity of the aroma compounds. The data demonstrated a profound effect of both composition and structure of oil‐in‐water emulsions on the air/liquid partitioning of the 20 aroma compounds under equilibrium conditions. © 2002 Society of Chemical Industry     

The effect of distillation conditions and alcohol content in ‘heart’ fractions on the concentration of aroma volatiles and undesirable compounds in plum brandies

This study investigates the effect of double‐ or single‐stage distillation and different alcohol content in ‘hearts’ (middle fractions) on the distribution of aroma volatiles and undesirable compounds (methanol, hydrocyanic acid, ethyl carbamate) during distillation of plum brandies. Irrespective of the distillation method used, the first fractions (‘heads’) included mainly aliphatic aldehydes, acetals and esters as well as higher alcohols (1‐propanol, 2‐methyl‐1‐propanol, 1‐butanol, 2‐methyl‐1‐butanol and 3‐methyl‐1‐butanol). Furfural, 1‐hexanol, benzyl alcohol, 2‐phenylethanol and ethyl carbamate occurred in relatively high concentrations in the ‘tail’ fractions. Increasing the concentration of alcohol in the heart fractions from 70 to 90% v /v resulted in a gradual decrease in the concentration of all detected volatile compounds. Compared with single‐stage distillation, double distillation produced heart fractions with lower concentration of acetaldehyde and benzaldehyde and with higher contents of furfural and esters, such as isobutyl acetate and isoamyl acetate. There was a statistically significant increase in the amounts of methanol and ethyl carbamate obtained from double distillation compared with similar fractions derived from the single‐stage process. However, in all fractions these compounds occurred in concentrations much lower than the limits specified by EU regulations. The heart fraction from the double‐stage process with 83% v /v alcohol content received the best scores for aroma and flavour. Copyright © 2017 The Institute of Brewing & Distilling     

Batch distillation of spirits: experimental study and simulation of the behaviour of volatile aroma compounds

This paper focuses on the behaviour of volatile compounds during batch distillation of wine or low wine, in traditional Charentais copper stills, heated with a direct open flame at laboratory (600 L) and industrial (2500 L) scale. Sixty‐nine volatile compounds plus ethanol were analysed during the low wine distillation in the 600 L alembic still. Forty‐four were quantified and classified according to their concentration profile in the distillate over time and compared with previous studies. Based on the online recording of volume flow, density and temperature of the distillate with a Coriolis flowmeter, distillation was simulated with ProSim® BatchColumn software. Twenty‐six volatile compounds were taken into account, using the coefficients of the ‘Non‐Random Two Liquids’ model. The concentration profiles of 18 compounds were accurately represented, with slight differences in the maximum concentration for seven species together with a single compound that was poorly represented. The distribution of the volatile compounds in the four distillate fractions (heads, heart, seconds and tails) was well estimated by simulation. Finally, data from wine and low wine distillations in the large‐scale alembic still (2500 L) were correctly simulated, suggesting that it was possible to adjust the simulation parameters with the Coriolis flowmeter recording and represent the concentration profiles of most of the quantifiable volatile compounds. © 2019 The Institute of Brewing & Distilling     

Discrimination of Luzhou‐flavoured fresh raw liquor distilled from Zaopei fermented in new,trend to‐be aged and aged pit mud based on their aroma and flavour compounds

Fresh raw liquors distilled from Zaopei fermented in new, trend to‐be aged and aged pit mud, labelled as N1 and N2, T1 and T2, and A1 and A2, respectively, were analysed by sensory evaluation, two‐dimensional gas chromatography/time‐of‐flight mass spectrometry with combined principal component analysis, gas chromatography–flame ionization detection, liquid chromatography–mass spectrometry with combined hierarchical cluster analysis, and partial least square–discrimination analysis. Results showed that samples had the same grouping situations by each method: the N‐group containing N1 and N2; the T‐group containing T1 and T2; and the A‐group containing A1 and A2. The specific markers for the N‐group liquors were 2‐butanol and butanoic acid, and those for the A‐group were 1‐hexanol, ethyl pentanoate and 2‐pentanone. The threshold contents of 1‐hexanol, ethyl pentanoate, and 2‐pentanone for the A‐group liquors were 1207.95 ± 252.59, 469.89 ± 73.08 and 1105.12 ± 141.91 mg L⁻¹, while those of 2‐butanol and butanoic acid for the N‐group liquors were 215.66 ± 179.50 and 430.65 ± 60.47 mg L⁻¹, respectively. The results from modern chromatographic techniques and chemometric analyses verify the correctness of the traditional sensory evaluation used in controlling the quality of Chinese liquor, contribute to further studies related to the aroma and flavour of Chinese Luzhou‐ flavour of fresh raw liquors and may provide significantly helpful thresholds in distinguishing Chinese Luzhou‐ flavour fresh raw liquors distilled from Zaopei fermented in new, trend to‐be aged and aged pit muds. Copyright © 2017 The Institute of Brewing & Distilling     

A novel approach for the production of a non‐alcohol beer (≤0.5% abv) by a combination of limited fermentation and vacuum distillation

Despite the increasing demand, the production of non‐alcohol beers is still limited by unsatisfactory or artificial flavour and taste. In this study, a novel approach to producing non‐alcohol beer is presented, in which the alcohol‐reducing techniques, limited fermentation and vacuum distillation were combined. Starting from barley and wheat malts, wort with a low level of fermentable sugars was prepared by infusion mashing and lautering. Limited fermentation was carried out by Saccharomycodes ludwigii at 18°C. When the level of fermentable sugar was reduced by 25%, the fermented wort was quickly cooled from 18 to 0°C and held at that temperature for two days. The young beer was obtained after degassing and removal of yeast and was then subjected to vacuum distillation at 0.06 MPa to remove the alcohol. The concentrated extract is suitable for storage and transportation. The final product of non‐alcohol beer was obtained by dilution with deoxygenated water and carbonation with 6.0 g/L CO₂, followed by addition of 8–12% of regular beer and equilibration for 2–3 days to develop normal beer aroma. The results showed that the non‐alcohol beer had several favourable properties, including the alcohol level of <0.5% (v /v), colour 7.0 (EBC), thiobarbituric acid value of 1.05 and ratio of alcohols to esters of 1.08. Compared with other methods for the production of non‐alcohol beer, this novel approach produced a favourable alternative to regular beers with similar flavour characteristics and satisfactory stability. Copyright © 2017 The Institute of Brewing & Distilling