Volatile Acid Levels Research Articles

Influence of Native Saccharomyces cerevisiae Strains on Malvasia aromatica Wines.

In the search of tools to deal with climate change-related effects along with the aim of avoiding the loss of aromatic typicity in wine, two native yeasts strains of Saccharomyces cerevisiae (CLI 271 and CLI 889) were evaluated to determine their influence on white Malvasia aromatica wines aroma composition and sensory characteristics. The strains were tested versus a commercial yeast strain (LSA). The fermentations were performed on grape must of the Malvasia aromatica variety previously macerated. Wine quality was studied by analysis of oenological parameters together with volatile aroma components using gas chromatography coupled to flame ionization detector (GC-FID) to quantify major volatiles compounds and headspace-solid phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME/GC-MS) to determine terpenoids and C13-norisoprenoids. Sensorial analysis was also realized by an experienced taster panel. Wines from locally-selected yeasts strains used had lower volatile acidity levels and higher concentration of aromatic compounds compared to the commercial strain ones. The yeast strain S. cerevisiae CLI 271 provided wines with a higher concentration of esters related to fruity attributes, especially isoamyl acetate. The tasting panel highlighted the strong floral character of wines from S. cerevisiae CLI 889 fermentation. The use of microorganisms well adapted to climatic conditions can be used to produce quality wines of the Malvasia aromatica variety.

Yeast diversity in pit mud and related volatile compounds in fermented grains of chinese strong-flavour liquor

Chinese strong-flavour liquor is produced via a traditional solid-state fermentation strategy facilitated by live microorganisms in pit mud-based cellars. For the present analysis, pit mud samples from different spatial locations within fermentation cellars were collected, and the yeast communities therein were assessed via culture-based and denaturing gradient gel electrophoresis (DGGE) approaches. These analyses revealed significant differences in the composition of yeast communities present in different layers of pit mud. In total, 29 different yeast species were detected, and principal component analyses revealed clear differences in microbial diversity in pit mud samples taken from different cellar locations. Culture-dependent strategies similarly detected 20 different yeast species in these samples. However, while Geotrichum silvicola, Torulaspora delbrueckii, Hanseniaspora uvarum, Saturnispora silvae, Issatchenkia orientalis, Candida mucifera, Kazachstania barnettii, Cyberlindnera jadinii, Hanseniaspora spp., Alternaria tenuissima, Cryptococcus laurentii, Metschnikowia spp., and Rhodotorula dairenensis were detected via a PCR-DGGE approach, they were not detectable in culture-dependent analyses. In contrast, culture-based approaches led to the identification of Schizosaccharomyces pombe and Debaryomyces hansenii in these pit mud samples, whereas they were not detected using DGGE fingerprints profiles. An additional HS-SPME-GC-MS-based analysis of the volatile compounds present in fermented grains samples led to the identification of 66 such compounds, with the highest levels of volatile acids, esters, and alcohols being detected in fermented grains from lower layer samples. A canonical correspondence analysis (CCA) suggested they were significant correlations between pit mud yeast communities and associated volatile compounds in fermented grains.

Torulaspora delbrueckii May Help Manage Total and Volatile Acidity of Santorini-Assyrtiko Wine in View of Global Warming.

Non-Saccharomyces (NS) yeasts are gaining popularity in modern winemaking for improving wine quality. Climate change is one of the biggest challenges winegrowing now faces in warm regions. Here, Lachancea thermotolerans LtS1 and Torulaspora delbrueckii TdS6 combined with Saccharomyces cerevisiae ScS13 isolated from Assyrtiko grapes from Santorini island were evaluated in grape must fermentation with the aim to mitigate major consequences of temperature rise. Different inoculation protocols were evaluated, including simultaneous and sequential mixed-strain inoculations, displaying significant variation in the chemical and kinetic characteristics. Both LtS1 and TdS6 could raise the titratable acidity (TA). TdS6 also reduced the volatile acidity (VA) and was thus chosen for further evaluation in microvinifications and pilot-scale fermentations. Consistent with lab-scale trials, sequential inoculation exhibited the longest persistence of TdS6 resulting in minimum VA levels. Diethyl succinate, ethyl propanoate, and ethyl isobutyrate were significantly increased in sequential inoculations, although a decline in the net total ester content was observed. On the other hand, significantly higher levels of TA, succinic acid, and 2-methylpropanoic were associated with sequential inoculation. The overall performance of TdS6 coupled with a high compatibility with S. cerevisiae suggests its use in the fermentation of Santorini-Assyrtiko or other high sugar musts for the production of structured dry or sweet wines.

Single and combined effects of Drosophila suzukii and Drosophila melanogaster on sour rot development in viticulture

AbstractSour rot is a disease complex that causes serious damage in viticulture. The common vinegar fly Drosophila melanogaster (Diptera: Drosophilidae) is associated with sour rot in overripe or otherwise damaged grapes. Drosophila suzukii (Diptera: Drosophilidae) is an invasive species, which is suspected to induce sour rot in previously undamaged grapes due to the flies' ability to infest healthy, undamaged soft fruits with its serrated ovipositor. As a consequence, infection of healthy grapes by D. suzukii may facilitate the colonization by D. melanogaster. We investigated the single and combined effects of D. suzukii and D. melanogaster on sour rot development by measuring volatile acidity under near‐natural conditions in the vineyard, along with laboratory experiments under controlled climate. In 2017, the combined field and laboratory experiments suggested that the presence of D. suzukii and D. melanogaster increased the volatile acidity levels at a similar rate. In 2018, the field experiments showed an only marginal increase in sour rot development in treatments with both Drosophila species. Under more favourable laboratory conditions, the presence of D. suzukii, but not D. melanogaster triggered sour rot emergence. A facilitating effect of D. suzukii infestation for D. melanogaster was not detectable. These findings suggest that D. suzukii does in fact have the potential to trigger sour rot, but will probably rarely do so under field conditions in the vineyard, at least in the studied region. Instead, our study showed that D. melanogaster can have a similar impact on sour rot development as D. suzukii, emphasizing the need of comparative studies.

English

Wine yeasts (Saccharomyces cerevisiae) vary in their ability to develop the full aroma potential of Sauvignon blanc wine due to an inability to release volatile thiols. Subsequently, the use of ‘thiol-releasing’ wine yeasts (TRWY) has increased in popularity. However, anecdotal evidence suggests that some commercially available TRWY intermittently exhibit undesirable characteristics for example, volatile acidity (VA) formation. Therefore, a trial was undertaken to select and evaluate S. cerevisiae hybrids for the production of Sauvignon blanc wine with enhanced fruity and tropical aromas, but low VA. Hybrids were characterised by clamped homogeneous electrical field (CHEF) DNA karyotyping and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) biotyping, and subsequently trialled against top commercial TRWY that is, Zymaflore VL3 and Zymaflore X5 (Laffort Oenologie), and Fermicru 4F9 (DSM Oenology) in laboratory-scale Sauvignon blanc vinifications during 2013. Most hybrids produced wines with VA levels significantly lower than those produced with Zymaflore VL3, Zymaflore X5 and Fermicru 4F9. Low VA forming hybrids also produced wines with tropical wine aroma notes. Wines produced by Fermicru 4F9 had the lowest acetic acid (the main volatile acid) of the commercial TRWY in this study. However, some hybrid yeasts produced wines with less acetic acid on average than wines produced by Fermicru 4F9. Overall, hybrids NH 6, NH 48, NH 56, NH 88 and NH 145 produced wines with enhanced tropical fruity aroma, but lower VA compared to wines produced by commercial TRWY. Key words: Hybrid yeasts, CHEF, MALDI-TOF/TOF MS biotyping, Sauvignon blanc, tropical fruit aroma, volatile acidity.

Simultaneous Alcoholic and Malolactic Fermentations by Saccharomyces cerevisiae and Oenococcus oeni Cells Co-immobilized in Alginate Beads.

Malolactic fermentation (MLF) usually takes place after the end of alcoholic fermentation (AF). However, the inoculation of lactic acid bacteria together with yeast starter cultures is a promising system to enhance the quality and safety of wine. In recent years, the use of immobilized cell systems has been investigated, with interesting results, for the production of different fermented foods and beverages. In this study we have carried out the simultaneous immobilization of Saccharomyces cerevisiae and Oenococcus oeni in alginate beads and used them in microvinifications tests to produce Negroamaro wine. The process was monitored by chemical and sensorial analyses and dominance of starters and cell leaking from beads were also checked. Co-immobilization of S. cerevisiae and O. oeni allowed to perform an efficient fermentation process, producing low volatile acidity levels and ethanol and glycerol concentrations comparable with those obtained by cell sequential inoculum and co-inoculum of yeast and bacteria cells in free form. More importantly, co-immobilization strategy produced a significant decrease of the time requested to complete AF and MLF. The immobilized cells could be efficiently reused for the wine fermentation at least three times without any apparent loss of cell metabolic activities. This integrated biocatalytic system is able to perform simultaneously AF and MLF, producing wines similar in organoleptic traits in comparison with wines fermented following traditional sequential AF and MLF with free cell starters. The immobilized-cell system, that we here describe for the first time in our knowledge, offers many advantages over conventional free cell fermentations, including: (i) elimination of non-productive cell growth phases; (ii) feasibility of continuous processing; (iii) re-use of the biocatalyst.

Influence of Lachancea thermotolerans on cv. Emir wine fermentation.

The present paper describes the behaviour of Lachancea thermotolerans and Saccharomyces cerevisiae in pure, co-cultured and sequential fermentations in cv. Emir grape must. Faster fermentation rates were observed in wine made with a pure culture of S. cerevisiae and wine produced with simultaneously inoculated cultures of L. thermotolerans and S. cerevisiae. Both L. thermotolerans and S. cerevisiae gave high population numbers. The use of L. thermotolerans in mixed and sequential cultures led to an increase in final total acidity content in the wines, varying in the range 5.40-6.28 g/l (as tartaric acid), compared to pure culture S. cerevisiae, which gave the lowest level of total acidity (5 g/l). The increase was in the order of 1.18-2.06 g/l total acidity. Increase in final acidity by the use of L. thermotolerans might be useful to improve wines with low acidity due to global climate change. Volatile acidity levels (as acetic acid) were in the range 0.53-0.73 g/l, while the concentration of ethyl alcohol varied in the range 10.76-11.62% v/v. Sequential fermentations of wines and pure culture fermentation of L. thermotolerans resulted in reduction in the concentrations of acetaldehyde and higher alcohols, with exception of N-propanol and esters. According to the sensory analysis, wine obtained with sequential inoculation of L. thermotolerans followed by inoculation of S. cerevisiae after 24 h, and simultaneous inoculation of these yeasts, was the most preferred. Copyright © 2016 John Wiley & Sons, Ltd.

A balanced microbiota efficiently produces methane in a novel high-rate horizontal anaerobic reactor for the treatment of swine wastewater

A novel combination of structurally simple, high-rate horizontal anaerobic reactors installed in series was used to treat swine wastewater. The reactors maintained stable pH, alkalinity, and volatile acid levels. Removed chemical oxygen demand (COD) represented 68% of the total, and the average specific methane production was 0.30L CH4 (g removed CODtot)−1. In addition, next-generation sequencing and quantitative real-time PCR analyses were used to explore the methane-producing Archaea and microbial diversity. At least 94% of the sludge diversity belong to the Bacteria and Archaea, indicating a good balance of microorganisms. Among the Bacteria the Proteobacteria, Bacteroidetes and Firmicutes were the most prevalent phyla. Interestingly, up to 12% of the sludge diversity belongs to methane-producing orders, such as Methanosarcinales, Methanobacteriales and Methanomicrobiales. In summary, this system can efficiently produce methane and this is the first time that horizontal anaerobic reactors have been evaluated for the treatment of swine wastewater.

Designing and creating Saccharomyces interspecific hybrids for improved, industry relevant, phenotypes.

To remain competitive in increasingly overcrowded markets, yeast strain development programmes are crucial for fermentation-based food and beverage industries. In a winemaking context, there are many yeast phenotypes that stand to be improved. For example, winemakers endeavouring to produce sweet dessert wines wrestle with fermentation challenges particular to fermenting high-sugar juices, which can lead to elevated volatile acidity levels and extended fermentation times. In the current study, we used natural yeast breeding techniques to generate Saccharomyces spp. interspecific hybrids as a non-genetically modified (GM) strategy to introduce targeted improvements in important, wine-relevant traits. The hybrids were generated by mating a robust wine strain of Saccharomyces cerevisiae with a wine isolate of Saccharomyces bayanus, a species previously reported to produce wines with low concentrations of acetic acid. Two hybrids generated from the cross showed robust fermentation properties in high-sugar grape juice and produced botrytised Riesling wines with much lower concentrations of acetic acid relative to the industrial wine yeast parent. The hybrids also displayed suitability for icewine production when bench-marked against an industry standard icewine yeast, by delivering icewines with lower levels of acetic acid. Additionally, the hybrid yeast produced wines with novel aroma and flavour profiles and established that choice of yeast strain impacts on wine colour. These new hybrid yeasts display the desired targeted fermentation phenotypes from both parents, robust fermentation in high-sugar juice and the production of wines with low volatile acidity, thus establishing their suitability for wine styles that are traditionally troubled by excessive volatile acidity levels.

The impact of oxygen on the final alcohol content of wine fermented by a mixed starter culture.

We have developed a wine fermentation procedure that takes advantage of the metabolic features of a previously characterized Metschnikowia pulcherrima strain in order to reduce ethanol production. It involves the use of M. pulcherrima/Saccharomyces cerevisiae mixed cultures, controlled oxygenation conditions during the first 48 h of fermentation, and anaerobic conditions thereafter. The influence of different oxygenation regimes and initial inoculum composition on yeast physiology and final ethanol content was studied. The impact of oxygenation on yeast physiology goes beyond the first aerated step and influences yields and survival rates during the anaerobic stage. The activity of M. pulcherrima in mixed oxygenated cultures resulted in a clear reduction in ethanol yield, as compared to S. cerevisiae. Despite relatively low initial cell numbers, S. cerevisiae always predominated in mixed cultures by the end of the fermentation process. Strain replacement was faster under low oxygenation levels. M. pulcherrima confers an additional advantage in terms of dissolved oxygen, which drops to zero after a few hours of culture, even under highly aerated conditions, and this holds true for mixed cultures. Alcohol reduction values about 3.7 % (v/v) were obtained for mixed cultures under high aeration, but they were associated to unacceptable volatile acidity levels. In contrast, under optimized conditions, only 0.35 g/L acetic acid was produced, for an alcohol reduction of 2.2 % (v/v), and almost null dissolved oxygen during the process.Electronic supplementary materialThe online version of this article (doi:10.1007/s00253-014-6321-3) contains supplementary material, which is available to authorized users.

Thermal and Nonthermal Factors Affecting Survival of Salmonella and Listeria monocytogenes in Animal Manure–Based Compost Mixtures

Reduction of enteric pathogens in animal manures before field application is essential for mitigating the risk of foodborne illness associated with produce. Aerobic composting of manures has been advocated as an effective treatment for reducing pathogen populations, and heat is a major factor contributing to pathogen inactivation. This study was initiated to determine the potential contribution of both thermal and nonthermal (pH, volatile acids, and ammonia) factors to pathogen inactivation during aerobic composting in bioreactors for mixtures containing manure from various sources (dairy, chicken, and swine). The test mixtures were formulated with an initial moisture content of 60% and a C:N ratio of 20:1, using straw and cottonseed meal as amendments. Mixtures were then inoculated with Salmonella and Listeria monocytogenes labeled with green fluorescent protein at initial populations of ca. 10(7) CFU/g. Three replicate trials of each treatment were conducted. Temperatures within the bioreactors were recorded at 30-min intervals, and duplicate samples were withdrawn daily from two sampling locations within the bioreactor. Significant regression models were derived relating decreases in pathogen populations to the degree of heat generated in the mixture (cumulative heat) and the pH of the mixture on the day before the pathogen losses were calculated (P < 0.0002). Although pathogens in swine manure compost mixtures were inactivated by the third day of composting, very little heat was generated in these mixtures, which were characterized by significantly higher levels of volatile acids compared with the other two compost mixtures. Therefore, volatile acids could help achieve pathogen inactivation when temperatures are too low such as when heat is lost too quickly at the surface of static compost piles or during winter composting.

Ocorrência de carbamato de etila em cachaças de alambique e em aguardentes industriais

Este trabalho teve como objetivo verificar a ocorrência de carbamato de etila, o grau alcoólico e a acidez volátil em cachaças e aguardentes de cana. As amostras foram obtidas de fabricantes de São Paulo, Minas Gerais, Rio de Janeiro, Espírito Santo e Ceará, de sistema de produção em destilador de cobre ou coluna de aço inoxidável, e de estabelecimentos registrados ou não. As análises de acidez volátil e de grau alcoólico foram realizadas conforme metodologia descrita pelo Ministério da Agricultura, Pecuária e Abastecimento. Os teores de carbamato de etila foram determinados pelo método de padronização externa, em sistema de cromatografia gasosa acoplada a espectrometria de massa (CG/EM), utilizando-se o modo MSI (Monitoramento Seletivo de Íons) para a quantificação. Os valores obtidos para o grau alcoólico variaram de 32,4 a 49,2 ºGL, sendo o teor médio de 40, 4 ºGL. Observou-se que 17 (22,7%) das bebidas apresentaram o grau alcoólico abaixo de 38 ºGL, que representa o valor mínimo imposto pela legislação vigente. Somente uma cachaça apresentou o grau alcoólico acima de 48 ºGL, limite máximo para esta bebida. Dentre as bebidas analisadas, 24 (32%) apresentaram acidez volátil acima do limite máximo. Os valores obtidos das 75 bebidas para o carbamato de etila variaram de 20 a 948 µg/L, apresentando um teor médio de 378, 25 µg/L. Somente 10 das 75 bebidas apresentaram teores de carbamato de etila abaixo de 150 µg/L, que é o limite máximo permitido pela Instrução Normativa nº 13 de 21 de junho de 2005.

Identification of lactic acid bacteria associated with traditional cachaça fermentations.

During the production of traditional cachaça (alembic´s cachaça), contamination of the fermented must is one of the factors leading to economic losses in the beverage manufacturing industry. The diversity of bacterial populations and the role of these microorganisms during the cachaça production process are still poorly understood in Brazil. In our work, the fermentation process was followed in two distilleries located in the state of Minas Gerais. The objective of this work was to identify the populations of lactic acid bacteria present during cachaça fermentation using physiological and molecular methods. Lactic acid bacteria were isolated in high frequencies during all of the fermentative processes, and Lactobacillus plantarum and L. casei were the most prevalent species. Other lactic acid bacteria were found in minor frequencies, such as L. ferintoshensis, L. fermentum, L. jensenii, L. murinus, Lactococcus lactis, Enterococcus sp. and Weissella confusa. These bacteria could contribute to the increase of volatile acidity levels or to the production of compounds that could influence the taste and aroma of the beverage.

Enhanced ethanol production, volatile compound biosynthesis and fungicide removal during growth of a newly isolated Saccharomyces cerevisiae strain on enriched pasteurized grape musts

AbstractThe kinetic behavior of a newly isolated Saccharomyces cerevisiae strain, grown on pasteurized grape musts enriched with industrial sugars, was studied after the addition of various concentrations [0.0 (reference), 0.4 and 2.4 mg/L] of the fungicide quinoxyfen to the medium. Batch‐flask cultures were carried out. Significant quantities of biomass (10.0±0.8 g/L) were produced regardless of quinoxyfen addition to the medium; therefore, the addition of the fungicide did not seriously inhibit biomass production. Ethanol was synthesized in very high quantities in all trials (highest concentrations 106.4–119.2 g/L). A slight decrease of ethanol production in terms of both absolute value and conversion yield of ethanol produced per sugar consumed was, however, observed when the quinoxyfen concentration was increased. The addition of quinoxyfen led to significantly lower ethylic ester levels, which also pertains to the acetates analyzed in this study. Fusel alcohol synthesis seemed to be activated when 0.4 mg/L quinoxyfen was added, but at 2.4 mg/L of added fungicide, no statistically significant differences were observed compared with the control trial. Volatile acid levels did not present a uniform trend in relation with the added fungicide. Finally, the fermentation was accompanied by a significant reduction of the fungicide concentration (79–82 wt% fungicide removal).

Caracterização físico-química do mosto e do vinho Moscato Giallo em videiras cultivadas sob cobertura de plástico

O objetivo deste trabalho foi avaliar a influência da cobertura de plástico sobre as características físico-químicas do mosto e do vinho da cultivar Moscato Giallo. Na safra 2006, um experimento em delineamento completamente casualizado foi realizado em vinhedo com cobertura de plástico impermeável, e sem cobertura como controle. De cada vinhedo, três microvinificações (20 L) foram elaboradas. Foram realizadas avaliações físico-químicas quanto ao: mosto - ºBrix, açúcares redutores, densidade, acidez total, ácido tartárico, ácido málico e pH; e vinho - densidade, graduação alcoólica, acidez total, acidez volátil, pH, extrato seco, açúcares redutores, cinzas, I 420, compostos voláteis e minerais. O mosto das videiras cobertas apresentou maior rendimento, porém, menor concentração de açúcares pelo fato de a maturação das uvas ter-se atrasado. Como conseqüência, os vinhos do cultivo protegido tiveram menor graduação alcoólica, embora tenham sido beneficiados pela sanidade das uvas, com a redução de acetato de etila e acidez volátil. O microclima da cobertura também restringiu a concentração de alguns minerais no vinho, principalmente P e K. A cobertura beneficiou a qualidade enológica, porém requer atraso na data de colheita, para as uvas atingirem adequada maturação fisiológica e tecnológica.

Impact of Yeast Strain on the Production of Acetic Acid, Glycerol, and the Sensory Attributes of Icewine

High concentrations of volatile acids, consisting mainly of acetic acid, are often found in icewine. Wine yeasts produce acetic acid as a by-product of the hyperosmotic stress response caused by high sugar concentrations (&gt;35 Brix) in grape must. Volatile acid levels in icewine often exceed legal limits. We compared seven commercially available wine yeast strains (ST, N96, Vin13, Vin7, EC1118, 71B, V1116) for icewine production. Yeast strains were evaluated for acetic acid and glycerol formation, fermentation rates, and sensory characteristics. Fermentations were conducted using both synthetic grape must and Riesling icewine grape must obtained from a commercial winery. Fermentations were conducted until approximately 11% (v/v) ethanol was produced. The yeast strains fermented Riesling icewine must at different rates and fermentations were completed in 17 to 49 days. Acetic acid and glycerol formation were significantly different (<i>p</i> &lt; 0.05) and linked to the yeast strain. Sensory analysis of the icewines produced with the different yeast strains showed significant differences for overall quality, perceived sulfur-like aroma, and color (<i>p</i> &lt; 0.05). ST, N96, and EC1118 were identified as the most suitable yeast strains for the production of icewine.

Influence of Enzymatic Clarification with a Pectin Methylesterase on Cider Fermentation

In this study, the effect of two apple juice treatments (clarification with a pectin methylesterase in the presence and absence of sulphiting) on the cidermaking process was investigated. Pre-fermentative clarification with the pectin methylesterase (Rapidase CPE) slowed the alcoholic fermentation in respect to traditional fermentation, the greatest effect being found for the combination of the enzymatic treatment with sulphur dioxide addition. With this treatment the start of the fermentation was delayed seven days. Enzymatic clarification delayed malolactic fermentation (MLF) and the interaction of both treatments produced a cider in which malolactic fermentation had not occurred. Both treatments ensured that the volatile acid levels during the maturation phase were significantly lower than in the traditional fermentation. Enzymatic clarification led to lower levels of yeasts during the active phase of alcoholic fermentation with respect to the control. When this treatment was combined with sulphiting, a decrease in apiculate yeast numbers during alcoholic fermentation was observed and a better survival of these species was noted after 59 days of fermentation.

The effect of wilting grass and grass-clover mixtures on silage effluent flow, chemical oxygen demand of silage effluent and silage quality

Increasing importance of home grown proteins has resulted in a renewed interest in grass-clover mixed swards. The objective of this experiment was to asses the effect of wilting on effluent production levels, polluting potential of the silage effluent, and silage quality in grass and grass-clover mixed swards.Perennial rye grass (G) and a grass clover mixed sward (0.75 perennial ryegrass, 0.25 white clover, GC) was cut in mid may. The G and GC was then precision chopped and ensiled in experimental silos at 0, 24 and 48 hours following cutting, with 5 replicate silos of each silage being made at each time period. The silage effluent was collected, the quantity produced was recorded and the biochemical oxygen demand and the chemical oxygen demand was measured. The silage was allowed to ferment followed by which the silage was sub-samples and composite samples 3 of each silage were analyzed for dry matter content, crude protein levels, neutral detergent fibre, water soluble carbohydrate, pH, lactic acid, acetic acid, proprionc acid, butyric acid, total volatile acid levels. The data were analyzed using the general linear model ANOVA in Minitab.

The effect of wilting grass and grass-clover mixtures on silage effluent flow, chemical oxygen demand of silage effluent and silage quality

Increasing importance of home grown proteins has resulted in a renewed interest in grass-clover mixed swards. The objective of this experiment was to asses the effect of wilting on effluent production levels, polluting potential of the silage effluent, and silage quality in grass and grass-clover mixed swards.Perennial rye grass (G) and a grass clover mixed sward (0.75 perennial ryegrass, 0.25 white clover, GC) was cut in mid may. The G and GC was then precision chopped and ensiled in experimental silos at 0, 24 and 48 hours following cutting, with 5 replicate silos of each silage being made at each time period. The silage effluent was collected, the quantity produced was recorded and the biochemical oxygen demand and the chemical oxygen demand was measured. The silage was allowed to ferment followed by which the silage was sub-samples and composite samples 3 of each silage were analyzed for dry matter content, crude protein levels, neutral detergent fibre, water soluble carbohydrate, pH, lactic acid, acetic acid, proprionc acid, butyric acid, total volatile acid levels. The data were analyzed using the general linear model ANOVA in Minitab.

Use of Lysozyme to Inhibit Malolactic Fermentation and to Stabilize Wine After Malolactic Fermentation

Lysozyme was evaluated for its ability to reduce the lactic bacteria flora in musts and in wines after completion of the malolactic conversion. An addition of 500 mg lysozyme per liter of grape must inhibited malolactic fermentation, while the addition of 250 mg/L to red wines, after malolactic fermentation, promoted microbiological stabilization. Control lots (without lysozyme) had higher bacterial populations. In the wines to which lysozyme was added, there was no increase in the content of acetic acid and biogenic amines during a period of six months at 18°C. Control lots after fermentation and processing had volatile acidity levels 20% higher and a cumulative value for histamine, tyramine, and putrescine four times higher.