Prevalence of Candida Species in ‘Thairu’ a Traditional Fermented Milk of Kerala, India

Aims: To determine the prevalence of Candida species in ‘thairu’, a traditional fermented milk prepared in the households of Kerala. Study Design: ‘Thairu’ samples collected randomly from the households in Wayanad, Kozhikode, Malappuram, Palakkad and Kannur districts of Kerala. This was followed by enumeration and identification of yeast using API 20CAUX Kit. Determination of pH and acidity of samples. Place and Duration of Study: Department of Dairy Microbiology, College of Dairy Science and Technology, Pookode, Wayanad, Kerala. September 2021- December 2021. Methodology: A total of 30 household ‘thairu’ samples were collected from households of Wayanad, Kozhikode, Malappuram, Palakkad and Kannur districts of Kerala in sterile bottles. The samples were serially diluted in normal saline and pour plated on to Yeast Extract Glucose Chloramphenicol Agar for isolation and enumeration. The pH was measured using pH meter by directly inserting the probe into the homogenized sample. Titratable acidity in per cent lactic acid was measured using N/10 NaOH. The isolates were identified based on the sugar fermentation pattern using API 20C AUX kit (Biomerieux, France). Results: The yeast count in the samples ranged from 5.0 to 6.7 log CFU/g with an average of 5.89±0.38 log CFU/g. Average acidity and pH of the samples were 1.92±0.34 % LA and 3.59±0.60 respectively. A total of 23 yeast isolates were identified based on morphology and carbohydrate fermentation pattern using API 20C AUX kit (Biomerieux, France). Exactly 86.95 per cent of isolates belong to Candida species. Conclusion: Observations of the study revealed the high prevalence of Candida species in traditional fermented milk ‘thairu’. Predominant Candida species were lactose fermenters, but the presence of a few species with spoilage and pathogenicity potential were also detected. The safety assessment of Candida species is essential before applying them as starter cultures for food fermentations.

Quantification of biogenic amines in fabrication steps of Gorgonzola-type cheese / Quantificação de aminas biogênicas nas etapas de fabricação do queijo tipo Gorgonzola

During the Gorgonzola-type cheese preparation there are proteolysis and lipolysis which may be influenced by the type of starter culture chosen. Six manufacturing steps were selected to identify which of them is most suitable for biogenic amines (BA) formation (1- milk, 2- lactic acid bacterial culture and fungus addition, 3- curd, 4- dry salting, 5- maturation at 30 days and maturation at 60 days); perform research on enterobacteria; accomplish the research of BA-producing bacteria (BAPB); detect and quantify the most abundant BA (putrescine, cadaverine, tyramine, histamine, spermidine and spermine) in the six steps of Gorgonzola cheese production and in bacterial isolates using high performance liquid chromatography and UV-Vis SPD/10AV detector and define if the presence of enterobacteria and BAPB would be correlated with BA production in this cheese. The bacterial culture used increased its log population by 7 log cycles and reached its highest level in batch 2 during cheese maturation. There was a decrease in the enterobacterial population in 2 log cycles after 60 days of maturation in batch 1. Tyramine was the BA with the highest concentration 306.32 mg.Kg-1 quantified in step 6 (60 days maturation) in batch 1. Criterion is requiered in bacterial starter culture selection because it is a quality determinant factor in relation to BA production and more rigor in raw material

Durante a elaboração do queijo tipo Gorgonzola ocorre proteólise a partir das bactérias e dos fungos adicionados ao leite que podem levar a formação de aminas biogênicas (AB) neste tipo de queijo. Portanto, no presente estudo foi feito o acompanhamento com coleta de amostras em seis etapas na fabricação deste queijo paraidentificar em qual delas haveria maior formação de aminas biogênicas (AB). As amostras coletadas em três diferentes lotes foram o leite cru (1), leite pasteurizado adicionado de cultura de bactérias ácido-láticas (2), massa coalhada (3), queijo após a etapa de salga seca (4), queijo após 30 dias de maturação (5) e queijo após 60 dias de maturação (6). Também foram realizadas a pesquisa de enterobactérias e bactérias ácido-láticas com característica capacidade de descarboxilação de aminoácidos e produção de aminas biogênicas (BPAB); detecção e quantificação da AB mais abundante (putrescina, cadaverina, tiramina, histamina, espermidina e espermina) nas seis etapas de fabricação do queijo tipo Gorgonzola e nos isolados bacterianos utilizando cromatografia líquida de alta eficiência e detector UV-Vis SPD/10AV e a verificação se a presença de enterobactérias e BPAB estariam correlacionadas com a produção de AB nesse queijo. A cultura bacteriana utilizada cresceu aumentando em sete ciclos logarítmicos sua população e alcançou seu maior nível no lote 2 na etapa de maturação do queijo. Houve diminuição da população enterobactérias em 2 ciclos logarítmicos após 60 dias de maturação no lote 1. A tiramina foi a AB com concentração mais elevada 306,32 mg.Kg-1 quantificada na etapa 6 (60 dias de maturação) no lote 1. É necessário dar mais atenção em duas etapas na elaboração dos queijos: mais critério na seleção da cultura bacteriana iniciadora por ser um fator determinante na qualidade em relação à produção de AB e mais rigor na seleção da matéria-prima.

Quantification of biogenic amines in fabrication steps of Gorgonzola-type cheese / Quantificação de aminas biogênicas nas etapas de fabricação do queijo tipo Gorgonzola

During the Gorgonzola-type cheese preparation there are proteolysis and lipolysis which may be influenced by the type of starter culture chosen. Six manufacturing steps were selected to identify which of them is most suitable for biogenic amines (BA) formation (1- milk, 2- lactic acid bacterial culture and fungus addition, 3- curd, 4- dry salting, 5- maturation at 30 days and maturation at 60 days); perform research on enterobacteria; accomplish the research of BA-producing bacteria (BAPB); detect and quantify the most abundant BA (putrescine, cadaverine, tyramine, histamine, spermidine and spermine) in the six steps of Gorgonzola cheese production and in bacterial isolates using high performance liquid chromatography and UV-Vis SPD/10AV detector and define if the presence of enterobacteria and BAPB would be correlated with BA production in this cheese. The bacterial culture used increased its log population by 7 log cycles and reached its highest level in batch 2 during cheese maturation. There was a decrease in the enterobacterial population in 2 log cycles after 60 days of maturation in batch 1. Tyramine was the BA with the highest concentration 306.32 mg.Kg-1 quantified in step 6 (60 days maturation) in batch 1. Criterion is requiered in bacterial starter culture selection because it is a quality determinant factor in relation to BA production and more rigor in raw material selection.

Durante a elaboração do queijo tipo Gorgonzola ocorre proteólise a partir das bactérias e dos fungos adicionados ao leite que podem levar a formação de aminas biogênicas (AB) neste tipo de queijo. Portanto, no presente estudo foi feito o acompanhamento com coleta de amostras em seis etapas na fabricação deste queijo paraidentificar em qual delas haveria maior formação de aminas biogênicas (AB). As amostras coletadas em três diferentes lotes foram o leite cru (1), leite pasteurizado adicionado de cultura de bactérias ácido-láticas (2), massa coalhada (3), queijo após a etapa de salga seca (4), queijo após 30 dias de maturação (5) e queijo após 60 dias de maturação (6). Também foram realizadas a pesquisa de enterobactérias e bactérias ácido-láticas com característica capacidade de descarboxilação de aminoácidos e produção de aminas biogênicas (BPAB); detecção e quantificação da AB mais abundante (putrescina, cadaverina, tiramina, histamina, espermidina e espermina) nas seis etapas de fabricação do queijo tipo Gorgonzola e nos isolados bacterianos utilizando cromatografia líquida de alta eficiência e detector UV-Vis SPD/10AV e a verificação se a presença de enterobactérias e BPAB estariam correlacionadas com a produção de AB nesse queijo. A cultura bacteriana utilizada cresceu aumentando em sete ciclos logarítmicos sua população e alcançou seu maior nível no lote 2 na etapa de maturação do queijo. Houve diminuição da população enterobactérias em 2 ciclos logarítmicos após 60 dias de maturação no lote 1. A tiramina foi a AB com concentração mais elevada 306,32 mg.Kg-1 quantificada na etapa 6 (60 dias de maturação) no lote 1. É necessário dar mais atenção em duas etapas na elaboração dos queijos: mais critério na seleção da cultura bacteriana iniciadora por ser um fator determinante na qualidade em relação à produção de AB e mais rigor na seleção da matéria-prima.Palavras chaves: cromatografia, cultura iniciadora, detector SPD/10AV UV­Vis, maturação, tiramina.

Review of Lactobacillus in the food industry and their culture media / Revisión de Lactobacilos en la industria alimentaria y sus medios de cultivo

ABSTRACT Lactic acid bacteria (LAB) are currently of great importance given their increasing use in the improvement of human and anima health and nutrition. They exhibit complex nutritional requirements, which is the reason why their production costs are high. Research efforts are being made aimed at evaluating different substrates for their production as well as the production of valuable metabolites from them. The purpose of this paper is to expose the main research and development trends for LAB production for industrial purposes with emphasis on the culture media required for their growth. The web of Science databases as well as the Google Patent Search tool were used in order to gather and analyze the scientific and technical information published in the last twelve years relating to LAB and their culture media. The use of milk, industrial cheese whey, cane molasses, hydrolyzed starches, lignocellulosic materials, organic food waste and bovine blood plasma, among others, have been proposed for Lactobacillus cultivation with the purpose of reducing costs and increasing performance in their production. Research groups and centers have the responsibility of intensifying their efforts to offer highly efficient technological alternatives to the industry that allow the production and application of LAB as a growth factor for the food sector. Also, research in prebiotic ingredients or additives derived from LAB that allow the enhancement of the benefits to the consumer must be continued. In this regard, it is necessary to increase the international visibility of Colombian scientific production in this area.

RESUMEN Las bacterias del ácido láctico (LAB) son actualmente de gran importancia dado su uso creciente en la mejora de la salud y nutrición humana y animal. Presentan requerimientos nutricionales complejos, por lo que sus costos de producción son altos. Se están realizando esfuerzos de investigación para evaluar diferentes sustratos para su producción, así como la producción de metabolitos valiosos a partir de ellos. El propósito de este documento es exponer las principales tendencias de investigación y desarrollo para la producción de LAB con fines industriales, con énfasis en los medios de cultivo necesarios para su crecimiento. Las bases de datos de Web of Science y la herramienta de búsqueda de patentes de Google se utilizaron para recopilar y analizar la información científica y técnica publicada en los últimos doce años relacionada con LAB y sus medios de cultivo. Se ha propuesto el uso de leche, suero de queso industrial, melaza de caña, almidones hidrolizados, materiales lignocelulósicos, desechos de alimentos orgánicos y plasma sanguíneo bovino, entre otros, para el cultivo de Lactobacillus con el fin de reducir costos y aumentar el rendimiento de su producción. Los grupos y centros de investigación tienen la responsabilidad de intensificar sus esfuerzos para ofrecer alternativas tecnológicas altamente eficientes a la industria que permitan la producción y aplicación de LAB como factor de crecimiento para el sector alimentario. Además, la investigación en ingredientes prebióticos o aditivos derivados de LAB que permite la mejora de los beneficios para el consumidor debe continuar. En este sentido, es necesario aumentar la visibilidad internacional de la producción científica colombiana en esta área.

Determination of changes during storage in chemical and microbial compositions of yoghurts made from buffalo milk and buffalo and cow milk mixtures

This study was aimed to determine and compare the chemical and microbiological properties of yoghurts made from different types of milk and their mixtures (35%, 65%, and 100%) during their storage at 4 °C for 28 days. For this purpose, chemical and microbiological properties of yoghurts during storage at 4 °C for 28 days were investigated. The total amount of dry matter, fat, pH and protein of yoghurt made from the buffalo and cow milk mixtures was significantly higher than that of pure buffalo milk (P<0.01). Also, storage time has led to significant differences in these components. Considering the results of microbiological analysis, a significant (P<0.01) difference was found between yoghurt samples in terms of total count of mesophilic aerobic bacteria, lactobacilli, lactococcus and yeast and mould. Hence, it is concluded that the addition of buffalo milk to that of cow improves the composition of yoghurt made from cow milk, which indicated the possibilities of processing and marketing of both types of milk especially because the health benefits of cow milk and the fermented products are well documented(AU)

El objetivo de este estudio fue determinar y comparar las propiedades químicas y microbiológicas de los yogures hechos con diferentes tipos de leche y sus mezclas (35%, 65% y 100%) durante su almacenamiento a 4° C por 28 días. La cantidad total de materia seca, grasa, pH y proteínas del yogur hecho con las mezclas de leche de búfala y vaca fue significativamente mayor que la de la leche de búfala pura (P <0.01). Además, el tiempo de almacenamiento generó diferencias significativas en estos componentes. De acuerdo con los resultados del análisis microbiológico, se encontró una diferencia significativa (P<0.01) entre las muestras de yogur en términos de bacterias mesófilas aerobias totales, lactobacilos, lactococcus y recuentos totales de levadura y mohos. Por lo tanto, se concluye que la adición de leche de búfala a la de vaca mejora la composición del yogur hecho de leche de vaca, lo que indica las posibilidades de procesamiento y comercialización de ambos tipos de leche, especialmente porque los beneficios para la salud de la leche de vaca y de los productos fermentados están bien documentados(AU)

Colour Profile, Pasting and Sensory Properties of Processed Sweet Potato Flour

In this study, sweet potato was purchased and processed using different methods to obtain 4 different sweet potato flour samples. Sample A was unfermented sweet potato flour, sample B was fermented spontaneously, while sample C and D were produced by fermentation using indigenous starter cultures of lactic acid bacteria and yeast for 48 h and 72 h respectively. Colour profile, Pasting and Sensory evaluation was conducted. The whiteness (L* value) obtained in this study is within the range of value (87.29-89.52), Also, the redness value (a*) and yellowness value (b*) of the sweet potato flour samples also showed a significant difference (p<0.05). Sample a had a higher value when compared with samples B,C and D. Pasting properties such as peak viscosity, trough viscosity, breakdown viscosity, setback, pasting temperature were determined. It was noticed that fermentation process and increase in fermentation time significantly (p<0.05) decrease the peak viscosity in this research work and all samples had a higher cooled paste viscosity than their corresponding hot paste viscosity. Nevertheless, sensory evaluation was carried out using thet 9-point hedonic scale, samples A,B,C,D are significantly different (P < 0.05).

Lactobacillus plantarum as a malolactic starter culture in winemaking: a new (old) player?

Malolactic fermentation (MLF) is a process in winemaking responsible for the conversion of L-malic acid to L-lactic acid and CO2, which reduces the total acidity, improves the biological stability, and modifies the aroma profile of wine. MLF takes place during or after alcoholic fermentation and is carried out by one or more species of lactic acid bacteria (LAB), which are either present in grapes and cellars or inoculated with malolactic starters during the winemaking process. Although the main bacterium among LAB used in commercial starter cultures for MLF has traditionally been Oenococcus oeni, in the last decade, Lactobacillus plantarum has also been reported as a malolactic starter, and many works have shown that this species can survive and even grow under harsh conditions of wine (i.e., high ethanol content and low pH values). Furthermore, it has been proved that some strains of L. plantarum are able to conduct MLF just as efficiently as O. oeni. In addition, L. plantarum exhibits a more diverse enzymatic profile than O. oeni, which could play an important role in the modification of the wine aroma profile. This enzymatic diversity allows obtaining several starter cultures composed of different L. plantarum biotypes, which could result in distinctive wines. In this context, this review focuses on showing the relevance of L. plantarum as a MLF starter culture in winemaking.

Multivariate optimization of Staphylococcus xylosus AD1biomass production using sugarcane molasses plus yeast extract and soybean meal

Staphylococcus xylosusis a microorganism that has important physiological and technological characteristics that make it suitable for use as a starter culture in fermented meat products. For the development of these products in the food industry, it is necessary to produce biomass by the multiplication of starter cultures using low-cost media. This study developed a culture medium based on sugarcane molasses (SCM) supplemented with yeast extract (YE) and soybean meal (SM) to produce S. xylosusAD1 biomass employing a Box Behnken multivariateoptimization design,usingthe best concentrations of the constituents of the culture medium for S. xylosusAD1 growth. By combining the mathematical models by the desirability function, it was possible to establish the optimal condition for the maximum production of viable cells and biomass. The optimal experimental condition was found when the fermentative process medium was composed of 10% SCM, 2% YE and 4% SM. In addition, the results of all experiments, except for the medium formulated with only SCM,presented a better performance than the commercial medium Brain Heart Infusion for the growth of S. xylosusAD1. The culture medium with agro-industrial byproduct (SCM) supplemented with YE and SM is an excellent alternative for producing S. xylosusAD1 biomass.

Potential biogenic amine-producing bacteria in ripened cheeses

This study aimed to determine which of the eight cheese varieties (Prato, Standard Minas, Gorgonzola-, Moleson-, Raclette-,Gruyère-, Sbrinz- and Reblochon-types) prepared at a dairy processing plant in the state of Rio de Janeiro had higher concentration of biogenic amines (BA) (putrescine, cadaverine, yramine, histamine, spermidine and spermine), to detect which BA were produced at higher oncentrations and to determine if the presence of Enterobacteriaceae, biogenic amine producing bacteria (BAPB) or physical-chemical parameters (pH, titratable acidity, fat, moisture, total solids, protein, ash and chloride) ould be correlated with BA production in the eight matured cheese varieties. Moleson-type cheese (72.50 mg.Kg-1) followed by Standard Minas (107.00mg.Kg-1) showed the lowest levels of biogenic amines. Prato (699.29 mg.Kg-1) and Gorgonzola-type (936.37 mg.Kg-1) cheeses contained larger amounts of BA. Concentrations of tyramine exceeded the maximum permissible limit in all varieties of cheese. Although the presence of potentially BA-producing bacteria was confirmed in all samples of cheese, there was no correlation with BA content produced in cheeses. Gorgonzola-type cheese showed a positive correlation with the amount of BA in the isolates. Gorgonzola-type, Sbrinz-type and Prato cheeses seem to require greater care in monitoring the presence of biogenic amines, particularly because tyramine reached the highest levels in these varieties. Regardless of the analysed cheese, physical and chemical parameters did not affect the amount of BA produced. An assessment of the capacity to produce biogenic amines should be included as a selection criterion for starter cultures for ripened cheeses.

Metagenome analysis of tempeh production: Where did the bacterial community in tempeh come from?

Aims: Tempeh is a soy-based traditional food fermented by Rhizopus oligosporus. Although this mold is the main microorganism responsible for tempeh fermentation, various unknown bacteria presence in tempeh could enhance tempeh’s nutritional value. This study is aimed to examine the identity of bacteria in tempeh bacterial community by combining metagenomics analysis and culturable technique. Methodology and results: Samples were obtained from a tempeh producer which consists of raw soybeans, fresh water used to soak the beans, soaking water after the beans were soaked for 18 h, dehulled-soybean before inoculation, starter culture, and fresh tempeh. All samples were plated onto Enterobacteriaceae and Lactic Acid Bacteria agar media, and the total DNA was extracted for metagenomics analysis based on 16S rRNA gene cloning and High-Throughput Sequencing (HTS). Metagenomic analysis indicated that Firmicutes and Proteobacteria were the predominant and subdominant bacteria, respectively, while the culturable technique showed Proteobacteria were the predominant bacteria. Firmicutes species detected in tempeh were similar to the ones in the soaking water, which were populated by Lactobacillus. However, another predominant bacteria from tempeh, Enterococcus, was similar to minor population of Enterococcus detected in dehulled-soybean before inoculation. Based on the cloned 16S rRNA genes, we observed L. agilis, L. fermentum, and E. cecorum as the predominant bacteria in tempeh. The starter culture, which was dominated by Clostridium, did not alter bacterial community in tempeh, since its proportion was only 2.7% in tempeh clean reads. Conclusion, significance and impact of study: The dominant bacteria in tempeh was Lactobacillus from Firmicutes. The bacterial community in tempeh was not affected by the starter culture used, but mainly because of the soybean soaking process.

Microbial Exopolysaccharides: Natural Modulators of Dairy Products.

Microbial exopolysaccharides (EPS) are considered as natural bio-thickeners abundantly used in dairy and fermented food industries for quality improvement. In fermentation based dairy industries, researchers are seeking their attention on substitution of artificial food stabilizers with naturals by exploring EPS, especially for improving the rheology of fermented food products. Lactic acid bacteria (LAB) being a starter player for fermented food products are believed to be as one of the best natural producers of EPS. These EPS are basically sugar residues, secreted by microbes in their surrounding environment but their in-vitro production is not economical due to the media and processing costs involved. The process of production is also complex due to the involvement of various enzymes and regulatory proteins. With modernization in dairy sector, our understanding towards EPS needs improvement. The review focuses on a brief explanation on the behavior and functionality of EPS from lactic acid bacteria.

Sourcing Starter Cultures for Parkia biglobosa Fermentation Part II: Potential of Bacillus subtilis Strains.

Aim: To select good strains of Bacillus subtilis for use as starter culture in the fermentation of Parkia biglobosa. Study Design: Fifteen (15) strains of Bacillus subtilis group obtained from commercial samples were used in starter-culture fermentation of Parkia biglobosa seeds to produce ‘iru’. Place and Duration of Study: Food Biotechnology Research Unit, National Center for Genetic Engineering and Biotechnology (BIOTEC), Pahumthani, Thailand, between March to May 2010. Methodology: The quality of the starter culture-fermented products were compared on the bases of sensory evaluation, degree of hydrolysis (DH), level of ammonia nitrogen (NH3-N), pH and enzymatic activities. The 15 strains were also screened for haemolytic activity. Results: On the basis of the sensory scores of 5 parameters (color, odor, consistency, texture and over-all liking), particularly the over-all liking, 5 strains were rated the best (in descending order): BC4333 > 8B > 2B > 7A > 5A, amongst the 15 tested. There were good correlations between pH and DH (r= 0.926), DH and NH3-N (r=0.962) and between pH and NH3-N (r=0.945). The strain BC4333 produced the very soft variant of ‘iru’ (‘iru-pete’), without the addition of ‘kuuru’ (local potash). The quantity of extracellular enzymes (protease, amylase, pectinase, phytase and lipase) produced during fermentation varied significantly. None of the 5 strains was haemolytic on sheep blood agar. Conclusion: The 5 strains of Bacillus subtilis (BC4333, 8B, 2B, 7A, 5A) that showed potentials of being used as starter cultures for industrial production of ‘iru’, were nonhemolytic on blood agar.

Inhibitory effect of essential oils against Lactobacillus rhamnosus and starter culture in fermented milk during its shelf-life period

The use of essential oils in foods has attracted great interest, due to their antagonistic action against pathogenic microorganisms. However, this action is undesirable for probiotic foods, as products containing Lactobacillus rhamnosus. The aim of the present study was to measure the sensitivity profile of L. rhamnosus and a yogurt starter culture in fermented milk, upon addition of increasing concentrations of cinnamon, clove and mint essential oils. Essential oils were prepared by steam distillation, and chemically characterised by gas chromatography-mass spectrometry (GC-MS) and determination of density. Survival curves were obtained from counts of L. rhamnosus and the starter culture (alone and in combination), upon addition of 0.04% essential oils. In parallel, titratable acidity was monitored over 28 experimental days. Minimum inhibitory concentration values, obtained using the microdilution method in Brain Heart Infusion medium, were 0.025, 0.2 and 0.4% for cinnamon, clove and mint essential oils, respectively. Cinnamon essential oil had the highest antimicrobial activity, especially against the starter culture, interfering with lactic acid production. Although viable cell counts of L. rhamnosus were lower following treatment with all 3 essential oils, relative to controls, these results were not statistically significant; in addition, cell counts remained greater than the minimum count of 10(8)CFU/mL required for a product to be considered a probiotic. Thus, although use of cinnamon essential oil in yogurt makes starter culture fermentation unfeasible, it does not prevent the application of L. rhamnosus to probiotic fermented milk. Furthermore, clove and mint essential oil caused sublethal stress to L. rhamnosus.

Viability of Staphylococcus xylosus during shelf-life of dulce de leche prepared by vacuum evaporation / Viabilidade de Staphylococcus xylosus na vida de prateleira de doce de leite elaborado em evaporador a vácuo

In this research an innovation in the manufacture of dulce de leche by vacuum evaporation is presented, based on the addition of Staphylococcus xylosus. The culture growth, lactic acid bacteria, pH, acidity, water activity, and lactose and sucrose contents were monitored. The cell counting of S. xylosus varied from log10 6.22cfu g-1 to log10 6.83cfu g-1. Lactic acid bacteria naturally occurring in the milk varied from log10 3.62cfu g-1 to log10 4.38cfu g-1 (90th day of storage). The pH was favourable to the growth of S. xylosus, showing the viability of using this culture in this kind of product.

Este trabalho apresenta uma proposta de inovação, que é a adição da cultura pura de Staphylococcus xylosus em doce de leite elaborado em evaporador a vácuo. Monitorou-se o desenvolvimento da cultura pura e das bactérias lácticas, o pH, a acidez, a atividade de água e os teores de lactose e sacarose. O número de colônias da cultura pura variou de log10 6,22ufc g-1 a log10 6,83ufc g-1, enquanto que as bactérias lácticas naturalmente presentes no doce variaram de log10 3,62ufc g-1 a log10 4,38ufc g-1 no 90° dia de armazenamento. O valor de pH foi favorável ao crescimento do S. xylosus, demonstrando a viabilidade do uso da cultura neste tipo de produto.

Influence of thermal enzymatic hydrolysis of cereal starch on the physico-chemical quality of kunun-zaki (A fermented non-alcoholic cereal beverage).

Millet grains were steeped in 1% sodium metabisulphite (1:2w/v) for 5min and subsequently washed and wet milled; the cereal paste was gelatinized with boiling water (1:1w/v, 76±2oC) and immediately hydrolyzed separately either with α+β-amylases, α+amyloglucosidase or rice malt. The hydrolyzed cereal starch was inoculated with a 12h starter culture (2%v/w) of Lactobacillus plantarum, L. fermentum, and Lactococcus lactis and fermented for 6h. Chemical (pH, titratable acidity), physical (viscosity, S.G., total soluble solids) and sensory quality of the hydrolyzed cereal slurry and the fermented product were determined. The results obtained in this study show that the pH of the products decreased with concomitant increases in titratable acidity (% lactic acid) during production; however, the decrease in pH was more prominent in the ‘kunun-zaki’ produced from the cereal starch treated with α+β-amylases and this, differed from the other products (p<0.05). There was an increase in viscosity with a corresponding decrease in the total soluble solids (TSS) in all the samples throughout production; the decrease in TSS is an indication of an increase in the activity of the fermenting LABs. Furthermore, the sensory quality attributes of the three products were generally acceptable by the taste panelist in all the parameters evaluated (appearance, aroma, taste), however, the ‘kunun-zaki’ produced using the cereal starch treated with rice malt was preferred in taste and this was significantly different (p<0.05) from the other products. This study has shown that ‘kunun-zaki’ of acceptable quality could be produced within 7h, the marked reduction in the processing time of ‘kunun-zaki’ from 12-7h could encourage large-scale production of this popular drink.

Effect of single bacterial starter culture on odour reduction during controlled fermentation of cassava tubers for foofoo production

Effects of single bacterial starter culture on odour reduction during controlled fermentation of cassava tubers for foofoo production were investigated. Pure cultures were used to ferment cassava tubers in water for 96 h. The cultures used include Bacillus subtilis, Klebsiela sp., Lactobacillus plantarum and Leuconostoc mesenteroides. L. plantarum exhibited the highest acid producing ability, decreasing the pH of the Cassava tubers from 6.2 to 3.68 with a corresponding increase in total titratable acidity (TTA) from 0.082% to 0.290% during the 96 h fermentation period. The effected changes in pH and TTA by other organisms ranged respectively from 4.88 and 0.135% for Klebsiella sp., 4.68 and 0.136% for L. mesenteroides to 4.90 and 0.139% for B. subtilis with in the period. All the cultures were found to contribute in varying degree to odour reduction in fermented cassava; B. subtilis effected the highest odour reduction followed by L. plantarum.

Indução da fermentação maloláctica em vinho Gewürztraminer / Induction of malolactic fermentation in Gewürztraminer wine

Fermentação maloláctica é o processo metabólico de degradação do ácido L-málico em ácido L-láctico e CO2. É responsável pela redução da acidez total, além de contribuir para a estabilidade biológica e modificação de flavor nos vinhos. Em operações normais de vinificação a fermentação maloláctica normalmente ocorre em vinhos tintos, mas recentemente seu uso vem aumentando em alguns vinhos brancos, tal como Chardonnay. O objetivo principal deste trabalho foi avaliar o comportamento de duas culturas comerciais de Leuconostoc oenos na indução da fermentação maloláctica. Uvas da cv. Gewürztraminer foram vinificadas e inoculadas com duas culturas lácticas, Viniflora Oenos e Vino, em diferentes níveis de açúcar residual: 55; 21,9; 1,1 e 0,9g/l. Os níveis de açúcares, em duas repetições, foram comparados com a ocorrência espontânea da fermentação maloláctica (controle). A degradação do ácido málico foi acompanhada através de cromatografia em papel. As determinações dos ácidos orgânicos foram realizadas através de cromatografia líquida de alta eficiência. Foram avaliados os açúcares redutores, °Brix, pH, acidez total e álcool. Foi observada uma baixa incidência (22,7 por cento) de fermentação maloláctica nos vinhos. Naqueles em que ocorreu, foi necessário longo tempo para o término, entre 56 e 92 dias. Nos estágios com 1,1 e 0,9g/l de açúcares redutores, os vinhos inoculados e os controles não realizaram a fermentação maloláctica. Os isolados de bactérias nativas foram identificados como pertencentes ao gênero Leuconostoc e devido algumas características fisiológicas encontradas nos isolados do vinho inoculado suspeitou-se da perda de viabilidade das culturas puras. O comportamento dos ácidos málico, acético, láctico, pirúvico e tartárico foi demonstrado pelos resultados.

Malolactic fermentation is the metabolic process of L-malic acid degradation in L-lactic acid and CO2. It is responsible by the reduction in total acidity and also contributes to the biological stability and a flavor modification of the wines. In normal winery operation it occurs commonly in red wines. However, recently malolactic fermentation had been also used in some white wines, such as Chardonnay. The main aim of this work was to evaluate the behavior of two commercial strains of Leuconostoc oenos in the induction of malolactic fermentation. Gewürztraminer grapes were fermented and inoculated with two lactic cultures, Viniflora Oenos and Vino, in several residual sugar levels: 55.0 - 21.9 - 1.1 e 0.9g/l. The sugar levels were compared with spontaneous malolactic fermentation (control), with two repetitions. Degradation of malic acid was followed by paper chromatography. Organic acids determinations were performed using eficiency high liquid chromatography. Reducing sugars, °Brix, pH, total acidity and alcohol values were evaluated. A low incidence (22.7 percent) of the malolactic fermentation in wines was observed. However, in those wines in which malolactic fermentation occurred it took a long time to reach the end, between 56 and 92 days. Using 1.1 and 0.9g/l of residual sugar the inoculated wines and the control did not undergo the malolactic fermentation. The wild lactic acid bacterias were identified as being as Leuconostoc genus and, due to some physiologic characteristics observed in the inoculated wine isolated, there was a raised suspicius that the cultures had lost the viability. The behaviour of the malic, acetic, lactic, piruvic and tartaric acids were demonstrates by the results.