Pulsed electric field treatment of red wine: Inactivation of Brettanomyces and potential hazard caused by metal ion dissolution

Pulsed electric field (PEF) technology is an attractive alternative method of wine preservation by inactivating Brettanomyces bruxellensis, a major spoilage concern affecting wines worldwide. Currently, wine preservation using SO₂ can have negative effects on consumers including headaches and allergic reactions. Therefore, the objectives of this study were to investigate the effect of PEF processing conditions, B. bruxellensis yeast strain and alcohol concentration on B. bruxellensis inactivation in red wine, as well as whether PEF treatment could have a harmful effect on wine through the release of metal ions. Electric field intensity was found to have a greater impact on inactivation than specific energy, with 31, 40 and 50 kV/cm treatments resulting in B. bruxellensis D values of 181.8, 36.1 and 13.0 μs, respectively. At 50 kV/cm, a temperature rise of almost 10 °C, doubled inactivation to 3.0 log reductions (cfu/mL). Yeast strain and alcohol concentration were also shown to influence inactivation, even though cell size comparisons of the three yeasts tested proved inconclusive. Overall, PEF treatment of wine was shown to be a possible preservation alternative for the wine industry. After PEF treatment, the wine produced remained safe for human consumption, with Fe, Cr and Ni ions contents well below dangerous levels.     

Effect of storage conditions on the volatile composition of wines obtained from must stabilized by PEF during ageing without SO2

The aim of this work was to study the effect of the storage conditions on the evolution of volatile composition of white wines aged in bottles without the addition of SO₂. Therefore Parellada must was stabilized by pulsed electric fields (PEF) and fermented without the employment of SO₂ and later on the wine was aged in bottles, without addition of this preservative, at low and controlled temperature and at room temperature. The obtained results showed that the concentration of some important compounds for wine aroma such as isoamyl acetate, and ethyl esters of fatty acids was higher in the wines stored at low and controlled temperature than in those aged at room temperature. However, the temperature favoured the formation of total alcohols during the aging of wines in the bottles. Consequently, from the point of view of the aromatic quality, the conservation of white wines obtained from fermentation of must processed by PEF and aged in bottles without the addition of SO₂ was improved under controlled storage conditions than at room temperature.

Industrial relevance

SO₂ is used as a preservative agent in wine due to its multi-action in the wine conservation. Although neither carcinogenicity nor mutagenic effects have been found in SO₂, this compound has an influence on human health. For that reason, several competent international organizations (WHO, FAO, OIV) have set down maximum limits for wines as well as promote a reduction of its concentration in wines. Therefore, potential industrial applications of this work include the possibility to produce and store wines without SO₂. This has been achieved by stabilizing the musts with PEF. The wines produced under these conditions can be conserved without this additive when used under controlled conditions of storage.     

Some new findings on the potential use of biocompatible silver nanoparticles in winemaking

There is currently an increasing commercial demand for silver nanoparticles (Ag NPs) due to their wide applicability in various markets. Because of their powerful antimicrobial properties, these nanoparticles are frequently used for food-associated consumer products. In this paper, the effect of two Ag NPs coated with biocompatible materials – PEG-Ag NPs 20 (polyethylene glycol) and GSH-Ag NPs (reduced glutathione) – to control microbial growth in wines was assessed. Both Ag NPs were subjected to an in vitro three-step digestion, and changes in their morphology and an assessment of their cytotoxicity against Caco-2 cells were determined. Both Ag NPs were effective against the different microbial population present in tested wines. Regarding their in vitro digestion, the size and shape of the nanoparticles were almost unaltered in the case of GSH-Ag NPs, while in PEG-Ag NPs 20 some particle agglomeration was observed. Overall, these results suggest that Ag NPs may reach the intestine in a nano-scaled form. Finally, Caco-2 cell experiments seemed to exclude toxicity of Ag NPs at the intestinal epithelium.Industrial relevanceTraditionally, sulphur dioxide (SO₂) has been used by oenologists to control the microbial population in wine. As a result of increasing evidence of possible health risks associated with this additive in wine, there has been growing interest in finding new alternatives to replace it. Silver nanoparticles display a broad spectrum of antimicrobial activity, so they could constitute a very promising approach to reducing SO₂ in winemaking.     

Effectiveness of dimethyldicarbonate to stop alcoholic fermentation in wine

The alcoholic fermentation of Botrytis-affected wines is stopped by the addition of high concentrations of sulfur dioxide (SO₂). The natural microbial unstability of these wines and the binding phenomena forces winemakers to periodically add sulfur dioxide during maturation, leading to a high concentration of a maximum of 400 mg/l in the bottled wine. Dimethyldicarbonate (DMDC) is now considered as a reliable fungicide which could be partially used instead of SO₂, especially just before bottling. This study investigated the use of DMDC to stop alcoholic fermentation. The experiment was carried out on pure cultures of three yeast species present in this type of wine (Saccharomyces cerevisiae, Candida stellata and Zygosaccharomyces bailii). The results were very promising and suggested that DMDC was more effective than SO₂. The yeast cells died after the addition of DMDC whereas they partially entered into a viable but non-culturable (VBNC) state with SO₂. However, the same experiment carried out on botrytized must, whose fermentation was carried out using indigenous microflora, was less conclusive. It pointed out that DMDC, used in a concentration of 200 mg/l, was more effective than SO₂ but leading to the same results: the entering of a part of the cells into a VBNC state. DMDC could be used to stop alcoholic fermentation, but could not replace SO₂. Nevertheless, the concentrations of SO₂ added in this type of wine could be reduced in this way.     

Use of Sulfur Dioxide in Winemaking

Ten juices of common wine cultivars were studied to determine if pretreatment of the juice with air, blanketing the juice with nitrogen or pretreatment with sulfur dioxide (SO₂) was the most satisfactory method to make the better wine. Further treatment with SO₂ was made later at intervals. The pretreatment with aeration lowered the final color in the wine compared to nitrogen blanketing. SO₂ pretreatment gave the lowest colored juice for the white wines. All juices treated with SO₂ later had much lower color. Wines without SO₂ were generally less liked. Pretreatment of juice with SO₂ helped preserve good color and sensory attributes of the wines but later treatments with SO₂ were more essential in improving and maintaining quality. Oxidation was probably the most important control exercised by SO₂ additions.     

Limit SO2 content of wines by applying High Hydrostatic Pressure

Sulphur dioxide (SO₂) has an important role in wine industry as an antioxidant, antioxidasic and antiseptic additive. However, since SO₂ is also responsible for allergic reactions, it is of great interest its replacement with alternative additives or technologies. The potential use of High Pressure (HHP) as an alternative antimicrobial technique to preserve wine with reduced amounts of SO₂ was explored in this study. Red wine samples containing 0, 30, 60 and 100 mg/L total sulphur dioxide (SO₂) were subjected to pressure treatment at 350 MPa for 10 min at 8 °C. Another group of non-treated samples containing similar amounts of SO₂ was used as control. Color parameters, total flavanols and antioxidant activity were determined by spectrophotometry while for individual anthocyanin content and tannin structural characteristics HPLC and HPLC/MS were employed respectively. Analyses were initially performed every two months (up to 6 months of storage) and thereafter at 12 months. Sensory analysis was also performed at the end of storage period by a trained panel. Pressurised wines with <60 mg/L SO₂ showed reduced total flavanols, anthocyanins and antioxidant activity values and higher hue after six months of storage when compared to the non-treated samples. These results were in line with the sensory evaluation of the treated samples, perceived as less aromatic, more oxidized and with higher intensity of dried fruit odor. However, after twelve months of storage these differences between the non-pressurised and pressurised wines, which contained over 60 mg/L SO_2, were not significant indicating that HHP could potentially preserve wine when combined with addition of reduced contents of SO_2.Industrial relevanceSince SO₂ is a cheap and effective wine preservative; its complete replacement seems not feasible at the moment. However, a more realistic approach is the reduction of the quantities required for wine protection and preservation by combining the antimicrobial action of the HHP process and the antioxidant effect of Sulphur Dioxide. This work shows that HHP can potentially be employed in winemaking to complement the action of SO₂ making thus possible to reduce the required doses in wine.     

Effect of sulphur dioxide and must extraction on colour,phenolic composition and sensory quality of red table wine

Red wines were made during 1992 from Vitis vinifera var Roriz grapes using a high and a low level of extraction and three levels of total sulphur dioxide (0, 75 and 150 mg SO₂ kg⁻¹). From this single experiment, the effects of total SO₂ and extraction on anthocyanin composition and colour were observed by HPLC, spectrophotometry and tristimulus colorimetry. High extraction produced a wine with more total pigments and total phenols than low extraction and increased the amount of organic acids extracted during fermentation. More anthocyanins were extracted with increasing SO₂ levels. On maturation, all wines lost colour and increased in brownness. Wines made without SO₂ browned more than the wines made with SO₂. The anthocyanins normally present in wines were all rapidly lost to trace levels at 24 months. Vitisin A, a more stable and highly coloured anthocyanin than malvidin 3-glucoside, showed a slower decrease in concentration than malvidin 3-glucoside and contributed significantly to the wine colour during aging. At the first analysis, the wines made without SO₂ had a higher percentage colour due to polymers than the wines made with SO₂. Polymerisation progressed during maturation, although the initial differences were maintained. Sensory analysis after 6 and 18 months storage by expert tasters revealed differences mainly related to the colour attributes, indicating that when wines are made using modern hygienic techniques, total SO₂ has a negligible effect on aroma and flavour attributes. © 1998 Society of Chemical Industry.     

Optimising the inactivation of grape juice spoilage organisms by pulse electric fields

The effect of some pulsed electric field (PEF) processing parameters (electric field strength, pulse frequency and treatment time), on a mixture of microorganisms (Kloeckera apiculata, Saccharomyces cerevisiae, Lactobacillus plantarum, Lactobacillus hilgardii and Gluconobacter oxydans) typically present in grape juice and wine were evaluated. An experimental design based on response surface methodology (RSM) was used and results were also compared with those of a factorially designed experiment. The relationship between the levels of inactivation of microorganisms and the energy applied to the grape juice was analysed. Yeast and bacteria were inactivated by the PEF treatments, with reductions that ranged from 2.24 to 3.94 log units. All PEF parameters affected microbial inactivation. Optimal inactivation of the mixture of spoilage microorganisms was predicted by the RSM models at 35.0 kV cm^− 1 with 303 Hz pulse width for 1 ms. Inactivation was greater for yeasts than for bacteria, as was predicted by the RSM. The maximum efficacy of the PEF treatment for inactivation of microorganisms in grape juice was observed around 1500 MJ L^− 1 for all the microorganisms investigated. The RSM could be used in the fruit juice industry to optimise the inactivation of spoilage microorganisms by PEF.     

Influence of some technological practices on the quantity of resveratrol in wine

A study of the effects of some prefermentative and fining practices on the resveratrol concentration in wine was carried out. The trans- and cis-resveratrol contents in a red wine obtained using must hyperoxidation were reduced to about 50% compared with those of control wines; this decrease was greater than that observed for total phenols and catechins. In contrast, sparging the red grapes with SO₂ and ascorbic acid before crushing them resulted in the trans-resveratrol concentration being greater than that of the control wines. Moreover the amounts of trans- and cis-resveratrol in commercial and synthetic wines were determined before and after addition of charcol, polyvinylpolypyrrolidone (PVPP), bentonite, casein, gelatine, and two inert materials, cellulose and diatomaceous earth (kieselgur), used as a filter aid. The results showed that PVPP, charcoal and casein were more effective at removing trans- and cis-resveratrol both in synthetic wine and in commercial wines. In all the wines tested the other fining agents gave a limited decrease (2?–?5%) of trans- and cis-resveratrol. After charcoal and PVPP treatments, significant correlations were observed between the percentage of residual resveratrol and the total phenols in the wines.     

Modeling inactivation kinetics and occurrence of sublethal injury of a pulsed electric field-resistant strain of Escherichia coli and Salmonella Typhimurium in media of different pH

A study of the effect of pulsed electric fields (PEF) on the kinetics of inactivation and the occurrence of cell damage in Escherichia coli O157:H7 and Salmonella Typhimurium 878 treated in McIlvaine buffer covering a range from pH 3.5 to 7.0 was conducted. Mathematical equations based on the Weibull distribution were developed to describe the influence of the electric field strength, treatment time and pH of the treatment medium on the lethality and generation of cell damage of both Gram negative pathogenic bacteria after the application of PEF treatments. E. coli O157:H7 was more PEF resistant than Salmonella Typhimurium at all pH investigated. PEF resistance of E. coli was influenced by the pH but the pH hardly affected the PEF resistance of Salmonella Typhimurium 878. After 150 μs at 35 kV/cm, 1 and 5 log₁₀ cycles of inactivation of E. coli O157:H7 were observed in the range of pH 3.5–4.5 and 5.5–6.5, respectively. Cell damage increased with the field strength and treatment time. A maximum cell damage level of 4.2 and 2.7 log₁₀ cycles for E. coli O157:H7 and Salmonella Typhimurium was observed respectively after a treatment of 30 kV/cm at pH 3.5. PEF induced cell damage was not detected at pH higher than 5.0 for both microorganisms. The developed equations can be applied to design combining processes which can increase the lethality of PEF or to reduce the intensity of PEF treatments to achieve a determine level of microbial inactivation.Industrial relevanceThis study demonstrates that when the influence of several factors on the microbial behavior is investigated, the development of mathematical models is a very useful tool to evaluate the influence of each parameter and their interactions. In this study, it has been mathematically described for first time the influence of the pH of the treatment medium and the occurrence of sublethal injury in a wide range of electric field strengths and treatment times in two Gram negative pathogenic bacteria, Escherichia coli O157:H7 and Salmonella Typhimurium 878. These models would also be of interest for engineering design, evaluation and optimization of PEF process as a new technique for food preservation.     

Efficacy of ultraviolet radiation as an alternative technology to inactivate microorganisms in grape juices and wines

Since sulphur dioxide (SO₂) is associated with health risks, the wine industry endeavours to reduce SO₂ levels in wines with new innovative techniques. The aim of this study was, therefore, to investigate the efficacy of ultraviolet radiation (UV)-C (254 nm) as an alternative technology to inactivate microorganisms in grape juices and wines.A pilot-scale UV-C technology (SurePure, South Africa) consisting of an UV-C germicidal lamp (100 W output; 30 W UV-C output) was used to apply UV-C dosages ranging from 0 to 3672 J l⁻¹, at a constant flow rate of 4000 l h⁻¹ (Re > 7500). Yeasts, lactic and acetic acid bacteria were singly and co-inoculated into 20 l batches of Chenin blanc juice, Shiraz juice, Chardonnay wine and Pinotage wine, respectively. A dosage of 3672 J l⁻¹, resulted in an average log₁₀ microbial reduction of 4.97 and 4.89 in Chardonnay and Pinotage, respectively. In Chenin blanc and Shiraz juice, an average log₁₀ reduction of 4.48 and 4.25 was obtained, respectively.UV-C efficacy may be influenced by liquid properties such as colour and turbidity. These results had clearly indicated significant (p < 0.05) germicidal effect against wine-specific microorganisms; hence, UV-C radiation may stabilize grape juice and wine microbiologically in conjunction with reduced SO₂ levels.     

Effect of the Closure Type on the Evolution of the Physical‐Chemical and Sensory Characteristics of a Montepulciano d'Abruzzo Rosé Wine

The present work studied the effect of the kind of closure (a screw cap, a natural cork, and 2 synthetic closures) on the evolution of the oxygen content and on the physical‐chemical and sensory characteristics of a Montepulciano d'Abruzzo rosé wine during the 1st 12 mo of bottle aging. The chemical analyses concerned the parameters more involved in the oxidative reactions (SO₂, acetaldehyde, phenols, wine color), as well as the main fermentative volatile compounds. The kind of closure influenced the oxygen content in wines, free and total SO₂ concentration, and wine color (color intensity and hue). During bottle aging, free and total SO₂ concentration was significantly and negatively correlated with absorbance at 420 nm (A420), whereas the correlations with A520 were weak. Probably, the limited extent of the variations in red color (A520), when varying SO₂ concentration, were due to the low pH of this rosé wine. No effect of the kind of closure on phenols and the main fermentative volatile compounds was observed. The wines bottled with cork closures (N trials), after 12 mo of storage, had higher color intensity and hue, measured by spectrophotometry, and were visually distinguished from the other trials for the more intense pink reflections. On the whole, under the conditions of this work, all the used closures guaranteed a good preservability to the rosè wines during the 1st year of bottle aging, and the changes in composition did not significantly affect wine sensory characteristics. Therefore, these synthetic closures can represent an alternative to the cork closures for a medium to long term bottle aging of these wines.     

Influence of some technological practices on the quantity of resveratrol in wine

 A study of the effects of some prefermentative and fining practices on the resveratrol concentration in wine was carried out. The trans- and cis-resveratrol contents in a red wine obtained using must hyperoxidation were reduced to about 50% compared with those of control wines; this decrease was greater than that observed for total phenols and catechins. In contrast, sparging the red grapes with SO₂ and ascorbic acid before crushing them resulted in the trans-resveratrol concentration being greater than that of the control wines. Moreover the amounts of trans- and cis-resveratrol in commercial and synthetic wines were determined before and after addition of charcol, polyvinylpolypyrrolidone (PVPP), bentonite, casein, gelatine, and two inert materials, cellulose and diatomaceous earth (kieselgur), used as a filter aid. The results showed that PVPP, charcoal and casein were more effective at removing trans- and cis-resveratrol both in synthetic wine and in commercial wines. In all the wines tested the other fining agents gave a limited decrease (2 – 5%) of trans- and cis-resveratrol. After charcoal and PVPP treatments, significant correlations were observed between the percentage of residual resveratrol and the total phenols in the wines. Received: 16 June 1997     

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.     

Spectral evaluation of young red wines: Anthocyanin equilibria,total phenolics,free and molecular SO2, “chemical age”

Red wine colour is an integration of contributions from monomeric anthocyanins and polymeric pigment forms. Because of gross differences between the two fractions in their responses to pH change and to SO₂ addition, approximate measures of the states of anthocyanin equilibria in young red wines can be routinely made. Recent correlations of such measures with independent assessments of relative wine quality have prompted further examination and development of the original analytical concepts. The equilibria may be described in terms of two percentage parameters α and α ', the values of which are related to wine pH and to SO₂ added after fermentation. Measures of free SO₂ and also molecular SO₂, anthocyanin content and total phenolics are obtained from the same set of spectral data. The interpretations are based upon a number of analytical premises for which certain approximations have been necessary. These appear to be well justified in comparative evaluations because of the wide range of parameter values observed in surveys of current vintage wines. Observations of ageing changes in the composition of wine colour, with proposed spectral indices of “chemical age”, are also presented.     

Comparison of the effect of pulsed electric field or high voltage electrical discharge for the control of sweet white must fermentation process with the conventional addition of sulfur dioxide

The present work discusses the efficiency of pulsed electrical treatments for the inactivation of yeasts. The application of pulsed electric fields (PEFs) and high voltage electrical discharges (HVEDs) as alternatives to sulfites, which are used as anti-microbial to stop the fermentation of sweet white wine, was investigated. The influence of sulfite concentration (from 0 mg·L^− 1 to 500 mg·L^− 1), PEF (from 4 kV·cm^− 1 to 20 kV·cm^− 1; from 0.25 ms to 6 ms) and HVED (40 kV/cm; 1 ms or 4 ms) treatments on the inactivation of total yeasts and non-Saccharomyces yeasts was determined. The addition of SO₂ (250 mg·L^− 1) resulted in 8 log total yeast reduction. The maximum yeast inactivation obtained with PEF and HVED was respectively 3 and 4 logs. The use of SO₂, HVED and PEF allows decreasing the non-Saccharomyces yeast level by 7, 5 and 4 logs respectively. However, the wine browning was less pronounced for the samples treated by PEF in comparison with HVED and SO₂ treatments. PEF seems to be the most suitable alternative technique to sulfite addition.     

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.     

Sulphite-binding power of wines and ciders. II. Theoretical consideration and calculation of sulphite-binding equilibria

The Law of Mass Action is used to explain the SO₂-binding behaviour of carbonyl compounds in wines and ciders and to calculate the contribution of each carbonyl compound to the SO₂-binding power of the system. On a model wine the calculated graph of bound SO₂ with increasing concentration of free SO₂ agreed closely with experimental determinations. Fractionation of the model wine on a column of Dowex 1 (bisulphite) gave good recoveries (95 to 103.5%) of the individual components.     

Bactericidal effect of cold plasma on microbiota of commercial fish balls

This study evaluated the bactericidal effect of cold plasma on three spoilage bacteria isolated from commercial fish balls: Psychrobacter glacincola 38–1, Brochothrix thermosphacta 38–2, and Pseudomonas fragi 38–8. Bacterial suspensions were treated by pulsed discharge plasma (PDP, 50 Hz, 3.0 L/min) and gas phase surface discharge plasma (GPSDP, 75 Hz, 6.5 L/min). The inactivation behavior was closely related to the peak discharge voltage, initial bacterial concentration, and exposure time. After treatment with GPSDP for 300 s (12.8 kV), a reduction of 6.87, 4.81 and 3.32 log₁₀ CFU/mL was observed for 38–1, 38–2 and 38–8, respectively. However, when the voltage of PDP reached 20 kV, inactivation was initiated. P. glacincola 38–1 was the most sensitive to plasma treatment. After 4-min treatment with PDP or 30-s treatment with GPSDP, the 38–1 (approximately 10⁵ CFU/mL) were completely inactivated. A Weibull model and a modified Whiting-Buchanan model provided a good fit for the survival curves, with R² ≥ 96%. After plasma treatment, deformation and rupture of bacterial cells were observed by SEM and TEM; the leakage of cellular contents was also observed by TEM. The oxidation by active particles (H₂O₂ and O₃) was the primary mechanism of bacterial inactivation exerted by GPSDP. PDP acted synergistically through physical penetration and chemical oxidation, which combined to lead to cell death.Industrial relevanceCommercial fish balls are popular in China, and they are usually transported and stored in the cold chain (mainly frozen environment). Although efficient cold chain can reduce the rate of microbial changes in fish balls, there are still limits of cold chain. The inevitable fluctuations in temperature during cold chain provide conditions for the attachment and growth of cold-tolerant bacteria that may lead to spoilage of commercial fish ball. The proposed research gives insight into how to control microbial contamination of commercial fish balls. Cold plasma treatment proved to be effective at killing the three bacteria tested, and the inactivation achieved by GPSDP was far superior to that achieved by PDP treatment. Dynamic fitting of a mathematical model was performed to describe the inactivation behaviors. This also provides a basis for predicting the inactivation of microorganisms. The study offers firm theoretical foundation and practical guidance for the application of cold plasma in the quality control of commercial fish balls, and further contributes to the safety of foods in cold chain.     

游离SO2、溶解氧浓度对葡萄酒颜色及花色苷含量的影响

目的：探索不同浓度溶解氧与游离SO₂对赤霞珠干红葡萄酒在陈酿中的颜色及相关参数的影响。方法：以新疆吐鲁番鄯善县新葡王酒庄赤霞珠干红葡萄酒为酿制试材,在葡萄酒陈酿过程中通过添加不同浓度的游离SO₂与溶解氧,观察其对葡萄酒色度、色调和花色苷含量等指标的影响。结果：溶解氧与游离SO₂浓度较低时葡萄酒呈鲜艳的酒红色,充氧量为2 mg/(L·30 d)时可促进葡萄酒中花色素苷、单宁适度聚合,改善葡萄酒品质;游离SO₂质量浓度为15~30 mg/L时对葡萄酒的色调值影响不大,但对色度影响较为明显,超过30 mg/L时会使葡萄的酒颜色逐渐显橙色。结论：赤霞珠干红葡萄酒陈酿的适宜游离SO₂质量浓度为25 mg/L,充氧量为2 mg/(L·30 d)。