Influence of SO2 on the consumption of nitrogen compounds through alcoholic fermentation of must sterilized by pulsed electric fields

The aim of this work was to study the influence of SO₂ on the use of nitrogenous compounds by yeast during wine alcoholic fermentation. Thus Parellada must was sterilized by a pulsed electric field treatment and inoculated with Saccharomyces cerevisiae Na33 strain. The fermentations were carried out with SO₂ (20 mg/l) and without SO₂. Results showed that yeast better consumed the amino acids in the first half of fermentation in the presence of SO₂. The final concentration of amino acids in the obtained wine was greater when the must was fermented without SO₂ than when the latter compound was present. Therefore, the presence of SO₂ facilitated the consumption of amino acids and, hence, such wine should have more complex flavour and better microbiological stability than that obtained from fermentation without SO₂.     

Pre-fermentative replacement of sulphur dioxide by lysozyme and oenological tannins: Effect on the formation and evolution of volatile compounds during the bottle storage of white wines

In this work, the effects on the volatile profile of the pre-fermentative substitution of SO₂ with lysozyme and oenological tannins were studied in white wines. At the same time, in order to understand the changes of volatile compounds in SO₂-free wines, the evolution of volatiles was evaluated over 1 year of storage in bottles. For this purpose, a number of laboratory scale fermentations of SauvignonBlanc musts were carried out and the effects of three variables (SO₂, lysozyme and oenological tannins) were investigated by means of GC–MS analysis. Results showed that the replacement of SO₂ with lysozyme and oenological tannins influenced the volatile composition of wines at the end of the alcoholic fermentation. Wines fermented with SO₂ showed higher total alcohol amounts, while the presence of oenological tannins augmented the level of esters. The presence of SO₂ influenced also the alcohols and esters profiles of wines during bottle storage. Moreover, the presence of oenological tannins displayed a positive role in maintaining the amounts of esters over certain levels in wine stored for 1 year, likely due to their oxygen scavenging ability. By contrast, acids were less affected by the investigated adjuvants both at the end of the alcoholic fermentation and during the storage time.     

Influence of SO<Subscript>2</Subscript> on the evolution of volatile compounds through alcoholic fermentation of must stabilized by pulsed electric fields

The aim of this work was to study the influence of sulphur dioxide (SO₂) on the formation of volatile compounds by yeast through wine alcoholic fermentation. Thus Parellada must was microbiologically stabilized using a pulsed electric field (PEF) treatment and inoculated with Saccharomyces cerevisiae Na33 strain. Fermentation was carried out with or without SO₂ and the results showed that the evolution of the volatile compounds profile throughout the process was similar. The content of volatile acids in wine obtained by using sulphur dioxide was not significantly different from that fermented without adding the compound. However, the final content of total alcohols and esters was significantly different even thought the differences were small. Consequently, when grape must is treated by PEF the sulphur dioxide concentration usually used in winemaking could be reduced to safer levels or even eliminated without an important effect on the volatile compounds content of the final product. Therefore, the absence of sulphur dioxide should not have a negative impact on the sensory characteristics of wine.     

Effect of a pulsed electric field treatment on the anthocyanins composition and other quality parameters of Cabernet Sauvignon freshly fermented model wines obtained after different maceration times

The influence of the application of a pulsed electric field (PEF) treatment (5 kV/cm, 2.1 kJ/kg) to the grape pomace on different quality parameters and anthocyanins content of Cabernet Sauvignon wines obtained after different maceration times (48, 72, 96 and 248 h) has been investigated.Regardless of the maceration time, the application of a PEF treatment led to freshly fermented model wines that were richer in colour intensity, total polyphenols index (TPI), tannins and showed better visual characteristics. It was observed that the concentration of anthocyanins compounds in the freshly fermented model wines obtained from PEF-treated pomace was higher, as compared to the control wine. The HPLC anthocyanic profiles of freshly fermented model wines obtained from PEF-treated pomace were similar to those of control wine indicating that the permeabilization of the cell membranes of pomace did not produce a selective effect on any anthocyanin. Malvidin-3-glucoside and Malvidin-3-glucoside acetate were the predominant anthocyanins in both control and PEF wine.According to the results obtained in this investigation the application of a PEF treatment permitted to reduce the maceration time during vinification of Cabernet Sauvignon grapes from 268 to 72 h.     

Enhancement of the solid-liquid extraction of sucrose from sugar beet (Beta vulgaris) by pulsed electric fields

A systematic study of the impact of pulsed electric fields (PEF) parameters (1–7 kV/cm, 5–40 pulses, specific energy of 0.006–0.19 kJ/kg per pulse, pulse frequency of 1–10 Hz, pulse width of 2–5 μs, square and exponential decay pulses) on the kinetics of the sucrose extraction from sugar beet at different temperatures (20–70 °C) has been carried out in this investigation. The efficiency of the solid-liquid extraction was independent of the frequency, as well as of the pulse width, and the pulse shape at 7 kV/cm, and it was influenced by the electric field strength applied and by the temperature of the extracting medium. Sucrose yield increased with both field strength, time of extraction, and temperature. The effect of the field strength was higher the lower the temperature. The application of 20 pulses at 7 kV/cm (3.9 kJ/kg) increased the maximum yield by 7 and 1.6 times, compared to non-PEF-treated samples, at 20 and 40 °C, respectively. A mathematical expression was generated, which enabled to evaluate the influence of the electric field strength (from 0 to 7 kV/cm) and temperature (from 20 to 70 °C) on the sucrose extraction efficiency and the extracting time in a solid-liquid PEF-assisted sucrose extraction process. Based on this equation, for 80%-sucrose extraction in 60 min, the temperature could be reduced from 70 °C to 40 °C, when 20 pulses of 7 kV/cm were applied.     

Effect of storage on the phenolic content,volatile composition and colour of white wines from the varieties Zalema and Colombard

Different quality attributes and chemical components of wines change during storage as a function of a series of factors. Thus, in young white wines, changes in phenolics, that lead to modifications of their colour as a result of oxidation processes, are well-known. These reactions can also alter their volatile profile giving rise to the appearance of new aromas, which in some cases are undesirable. In this study we have carried out a thorough evaluation of the changes in the colour, volatiles and phenolics of Zalema and Colombard wines during 1 year of storage under different conditions of temperature and position. The phenolics and colour were more affected than was the volatiles profile and wines kept in the cold could be clearly distinguished from the others, whilst the position of the bottles onlt slightly affected the wines during storage. Results showed that the blending of Zalema wines with Colombard wines may be an appropriate means of enhancing the acidity of the former without dramatically affecting its character.     

陆英挥发油超临界CO2萃取工艺优化及其成分分析

以陆英为原料,采用单因素和响应面试验优化其挥发油的超临界CO_2萃取工艺,重点探讨CO_2流量、萃取压力、萃取时间、萃取温度对陆英挥发油得率的影响,并通过气相色谱-质谱(GC-MS)对陆英挥发油成分进行定性定量分析。结果表明,优化的陆英挥发油提取工艺条件为:CO_2流量25L/h、萃取压力30.5 MPa、萃取温度45.0℃、萃取时间2.8h,该条件下陆英挥发油得率为0.86%。从陆英挥发油中鉴定出了16个成分,占挥发油含量约93.87%,其中含量较多的有3-甲基戊酸(29.37%)、3-甲基丁酸(13.83%)、E-4-己烯-1-醇(8.27%)等,另外3-乙硫基丁醛(6.46%)含量也较多。     

Effects of processing conditions on the chemical distribution of mate tea leaves extracts obtained from CO2 extraction at high pressures

This work reports the effects of industrial manufacturing steps on the distribution of chemical components of the extracts obtained from supercritical carbon dioxide (SCCO₂) of processed mate tea leaves. For this purpose, samples of mate tea leaves were collected from the actual industrial processing after the fast pre-heating, drying and storage (5 and 21 days) steps. To provide a consistent basis for comparisons, extractions were also conducted for the unprocessed leaves fed in the industrial environment. In order to select the appropriate extraction parameters at high pressure, it was evaluated the effects of temperature from 15 to 55 °C and pressure from 10 to 20 MPa on the liquid yield of unprocessed mate tea leaves. The SCCO₂ extraction experiments regarding the effects of industrial processing conditions were then performed at 35 °C and 20 MPa and the extract chemical analyses were carried out in a GC/MSD. Results show that the extraction yield and chemical composition of the extracts are strongly affected by the industrial processing steps. Chromatographic analyses permitted the identification of caffeine, theobromine, hexadecanoic acid, phytol, squalene, octacosanol, 2-heptacosanone, steroids and triterpenes as the main constituents in the extracts.     

含水量对新疆鲜食核桃贮藏期黄曲霉生长及黄曲霉毒素M1积累的影响

目的:提高新疆鲜食核桃的贮藏安全性。方法:以新疆“新2”薄皮核桃为材料，无菌水接种为对照组，黄曲霉菌接种为试验组，将从自然霉变核桃上分离纯化出的黄曲霉菌人工接种至不同含水量(10%,15%,20%,25%,30%)的新疆薄皮鲜食核桃上，探究黄曲霉菌生长量及产毒变化情况。结果:最适宜黄曲霉菌生长繁殖并分泌黄曲霉毒素M₁的核桃含水量为15%;随着核桃含水量的升高，黄曲霉菌生长量呈先上升后下降趋势，但各含水量之间的生长量各不相同，且黄曲霉菌生长量与产生黄曲霉毒素M₁的量成正比。结论:原料的含水量与黄曲霉菌生长量及产生黄曲霉毒素M₁的量有着密切的关系。     

Effect of refermentation conditions and micro-oxygenation on the reduction of volatile acidity by commercial S. cerevisiae strains and their impact on the aromatic profile of wines

Herein, we evaluate the applicability of previously characterized commercial and indigenous Saccharomyces cerevisiae strains and non-S. cerevisiae species for the deacidification of white and red wines at a pilot scale. The effect of the refermentation process (mixture of acidic wine with musts from freshly crushed grapes or with residual marc) as well as micro-oxygenation (MO) on acetic acid removal efficiency and wine aromatic composition was also assessed in a red wine. The commercial strains S26 and S29 efficiently reduced both acetic acid (43 and 47%, respectively) and sugar (100%) after 264 h of refermentation of an acidic white wine that was supplemented with grape must. Similar results (60-66% of acetic acid removal) were observed for red wine deacidification using grape must, independently of MO. When residual marc was used for deacidification, strain S26 removed 40% of acetic acid, whereas strain S29 did not initiate refermentation with or without MO. Wines obtained by refermentation with the must had significantly lower acetic acid and a higher total SO₂ concentration in comparison to the wines deacidified by the grape marcs. The volatile aroma compound's composition of deacidified red wines was dependent on the refermentation process used, rather than on MO. The marc-deacidified wine obtained by the use of strain S26 and without MO achieved the best sensory classification. When data from all analytical and sensory evaluation were combined, Principal Component Analysis (PCA) separated the wines into three distinct groups according to the strain and the refermentation process independently of MO. We successfully established an efficient and cheap enological solution for the rectification of volatile acidity of wines.