Abstract Jaboticaba peels are an important source of health-benefit and antimicrobial compounds. The present work aims to evaluate concentration of polyphenolics and the mode of action of aqueous extract from jaboticaba peels against Staphylococcus aureus and Escherichia coli. Jaboticaba peel extract showed minimum inhibitory concentration and minimum bactericidal concentration against S. aureus of 5.1 g L-1 and 10.1 g L-1, respectively; meanwhile, against E. coli the parameters were 2.0 g L-1 and 3.4 g L-1. Kinetics of viable cell counts indicated a bacteriolytic action against both bacteria and Scanning Electron Microscopy (SEM) showed that jaboticaba peel extract causes subtle morphological changes in bacterial cells. Concentration of total polyphenols in the extract was 1535.04±36.05 mg of gallic acid equivalent (GAE) mL-1, monomeric anthocyanins was 14.52 ± 0.98 mg of cyanidin 3-glucoside mL-1, condensed tannins was 0.49 ± 0.05 mg of epicatechin equivalent mL-1 and phenolic acids was 80.04 ± 4.11 mg of caffeic acid equivalent (CAE) mL-1, which have demonstrated well-documented antibacterial activity. In conclusion, jaboticaba peel aqueous extract may be an interesting natural preservative to control Gram-positive and Gram-negative bacteria growth when interacting with the bacteria cell wall.

Resumo As cascas de jabuticaba são uma importante fonte de benefícios à saúde e compostos com atividade antimicrobiana. O presente trabalho tem como objetivo avaliar a concentração de polifenóis e o modo de ação do extrato aquoso da casca da jabuticaba contra Staphylococcus aureus e Escherichia coli. O extrato da casca da jabuticaba apresentou concentração inibitória mínima e concentração bactericida mínima contra S. aureus de 5,1 g L-1 e 10,1 g L-1, respectivamente; já contra E. coli, esses parâmetros foram 2,0 g L-1 e 3,4 g L-1. A cinética da contagem de células viáveis indica uma ação bacteriolítica contra ambas as bactérias e a microscopia eletrônica de varredura mostrou que o extrato da casca da jabuticaba causa sutis alterações morfológicas nas células bacterianas. A concentração de polifenóis totais no extrato foi 1.535,04±36,05 mg ácido gálico equivalente mL-1; antocianinas monoméricas, 14,52±0,98 mg cianidina 3-glicosídeo mL-1; taninos condensados, 0,49 ± 0,05 mg equivalente epicatequina mL-1, e ácidos fenólicos, 80,04±4,11 mg ácido cafeico equivalente mL-1, compostos que já demonstraram atividade antibacteriana bem documentada. Em conclusão, o extrato aquoso da casca de jabuticaba mostra-se um bioconservante interessante para o controle de bactérias Gram-positivas e Gram-negativas, e interage com a parede celular bacteriana.

Abstract The objective of this work was to evaluate the use of cellulase and pectinase as pretreatments for the drying of beetroot (Beta vulgaris). The experiment consisted of slices of beetroots subjected to four different treatments before the drying procedure, as follows: no wet pretreatment; wet pretreatment without enzymes; pectinase solution pretreatment; and cellulase solution pretreatment. Treatments were compared for drying rates, color change, content of betalains, and plant tissue structure. A modified Page model was used to describe the drying process. The enzymatic pretreatments did not improve the drying kinetics, although they changed the plant tissue structure. A negative influence on the drying was observed when pectinase was used; however, no effect was observed when cellulase was used. Slices treated with cellulase remained unchanged for color. Slices treated with pectinase showed significant changes of color, in comparison with the control treatments. The enzymatic pretreatments studied did not change the betalain concentrations and showed similar drying performance in the comparison with control treatments. Cellulase pretreatment is promising because it does not change the beetroot color or the betalain concentration.

Resumo O objetivo deste trabalho foi avaliar o uso de celulase e pectinase como pré-tratamentos para a secagem de beterraba (Beta vulgaris). O experimento consistiu de fatias de beterraba submetidas a quatro diferentes tratamentos, antes do procedimento de secagem, conforme a seguir: pré-tratamento sem água; pré-tratamento com água, sem enzimas; pré-tratamento com solução de pectinase; e pré-tratamento com solução de celulase. Os tratamentos foram comparados quanto às taxas de secagem, mudança de cor, teor de betalaínas e estrutura do tecido vegetal. Um modelo Page modificado foi usado para descrever o processo de secagem. Os pré-tratamentos enzimáticos não melhoraram a cinética de secagem, embora tenham alterado a estrutura do tecido vegetal. Observou-se influência negativa sobre a secagem, quando a pectinase foi usada; no entanto, nenhum efeito foi observado quando a celulose foi usada. As fatias tratadas com celulase permaneceram inalteradas em relação à cor. As fatias tratadas com pectinase apresentaram alterações significativas de cor, em comparação aos tratamentos-controle. Os pré-tratamentos enzimáticos estudados não alteraram as concentrações de betalaínas e apresentaram desempenho de secagem similar aos dos tratamentos-controle. O pré-tratamento com celulase é promissor, pois não altera a cor da beterraba nem a concentração de betalaína.

Abstract The objective of this work was to develop a drying process using the foam-layer method to obtain the powder from butiá (Butia spp.) pulp, as well as to characterize this powder according to its yield and physicochemical and technological characteristics. The foam was optimized for density and stability by varying whipping times and albumin and xanthan gum concentrations. Foam drying was optimized for vitamin C retention and yield using different foam thicknesses and drying temperatures. The optimized foam showed a density of 0.25 g cm-3 and a high stability, being suitable for subsequent drying. The lowest foam thickness (0.50 cm) and the highest drying temperature (80°C) resulted in the highest retention of vitamin C, whereas the increase in drying temperature improved yield. The butiá pulp powder obtained under the optimized condition presented an acid pH of 3.25, a low humidity of 7.97%, a water activity of 0.206, a water retention capacity of 4.90 g H2O per gram of powder, a solubility of 74.40%, a soluble solids content of 61°Brix, and a predominantly yellow color. The foam-layer drying method can be used to obtain butiá pulp powder.

Resumo O objetivo deste trabalho foi desenvolver um processo de secagem, com o método de camada de espuma, para obter o pó da polpa de butiá (Butia spp.), bem como caracterizar esse pó de acordo sua produtividade e características físico-químicas e tecnológicas. A espuma foi otimizada quanto à sua densidade e estabilidade, tendo-se variado os tempos de batimento e as concentrações de albumina e goma xantana. Já a secagem da espuma foi otimizada em relação à retenção de vitamina C e à produtividade, com uso de diferentes espessuras da camada de espuma e temperaturas de secagem. A espuma otimizada apresentou densidade de 0,25 g cm-3 e alta estabilidade, sendo adequada para posterior secagem. A menor espessura de espuma (0,50 cm) e a maior temperatura de secagem (80°C) resultaram na maior retenção de vitamina C, enquanto o aumento da temperatura de secagem melhorou a produtividade. O pó de polpa de butiá obtido na condição otimizada apresentou pH ácido de 3,25, baixa umidade de 7,97%, atividade de água de 0,206, capacidade de retenção de água de 4,90 g de H2O por grama de pó, solubilidade de 74,40%, teor de sólidos solúveis de 61°Brix e cor predominantemente com tonalidade amarela. O método de secagem por camada de espuma pode ser utilizado para obter o pó de polpa de butiá.

Abstract The aim of this study was to investigate the combined effect of carvacrol, thymol and nisin against Staphylococcus aureus and the combined effect of carvacrol and thymol against Salmonella Enteritidis. Minimum inhibitory concentrations (MIC) of carvacrol, thymol, and nisin for S. aureus were 200, 150 and 30 µg/mL, respectively. MIC of carvacrol and thymol for Salmonella Enteritidis was 200 µg/mL. A factorial method of independent variables was then used to study the combined effect of antimicrobials. Results showed that combinations of carvacrol-thymol-nisin (reduction of 1.2 log CFU/mL for MIC and 4.98 log CFU/mL for 2MIC), carvacrol-thymol (reduction of 1.33 log CFU/mL for 2MIC), nisin-thymol (reduction of 3.52 log CFU/mL for 2MIC) and nisin-carvacrol (reduction of 3.41 log CFU/mL for 2MIC) attained a significant inhibition of S. aureus. Similarly, there was significant reduction of Salmonella Enteritidis due to combined effect of thymol-carvacrol (reduction of 4.5 log CFU/mL for MIC and inhibition below detection limit for 2MIC). Therefore, the combinations of natural antimicrobials described in this work showed potential to be used as an additional barrier for food safety.

Resumo O queijo artesanal serrano é um queijo tradicional de leite cru no sul do Brasil. Para o consumo seguro de produtos lácteos não pasteurizados, a maturação é um período crítico para reduzir populações de microrganismos patogênicos e deteriorantes, sendo, portanto, necessário o conhecimento da cinética de inativação de microrganismos para garantir a segurança e a qualidade dos alimentos. No presente trabalho, a cinética de inativação de patógenos de origem alimentar exigida pela regulamentação brasileira em queijos artesanais serrano foi avaliada estatisticamente durante a maturação. Salmonella spp., Listeria monocytogenes, Staphylococcus aureus coagulase positivo e coliformes fecais foram analisados por até 60 dias. Os dados experimentais foram ajustados aos modelos de primeira ordem de inativação, Weibull e log-linear + ombro. Os resultados mostraram que os queijos são seguros para a presença de Salmonella spp. e L. monogyatogenes ao longo do período estudado. Os modelos de primeira ordem e Weibull apresentaram bom desempenho para representar S. aureus coagulase positiva e coliformes fecais durante a maturação, embora a distribuição de Weibull tenha se mostrado melhor para descrever os dados experimentais. A equação log-linear + ombro foi descartada para descrever a redução na contagem de microrganismos por critérios físicos. A cinética mostrou resistência inicial dos coliformes fecais a serem inativados, diferentemente da população de S. aureus coagulase positiva. A análise de modelagem permitiu estimar o período de maturação do queijo serrano em mais de 33 dias para a obtenção de um produto seguro, de acordo com as normas brasileiras.

Abstract Serrano artisanal cheese is a traditional raw milk dairy product from southern Brazil. For safe consumption of raw milk products, ripening is a critical period for reducing populations of pathogenic and spoilage microorganism and, then, the knowledge on inactivation kinetics of microorganisms is necessary to guarantee food safety and quality. In the present work, inactivation kinetics of foodborne bacterial pathogens required by Brazilian regulations in serrano artisanal cheeses were statistically evaluated during ripening. The Salmonella spp., Listeria monocytogenes, coagulase-positive strain of Staphylococcus aureus and fecal coliforms were analyzed for up to 60 days. Experimental data were fitted using first-order model, Weibull and log-linear + shoulder models. Results showed no presence of Salmonella spp. and L. monogyatogenes in the cheeses through the studied period. The first-order and Weibull models presented good performance to represent coagulase-positive strain of S. aureus and fecal coliforms during ripening, although Weibull distribution showed better outcomes to experimental data. Log-linear+shoulder equation was discarded to describe the reduction of microorganism counts for physical criteria. Kinetics showed an initial resistance of fecal coliforms to be inactivated, unlike to coagulase-positive strain of S. aureus population. Modeling analysis allowed estimating serrano artisanal cheese ripening period to be longer than 33 days for achieving a safe product according to the Brazilian Regulatory Standards.

Resumo O objetivo deste trabalho foi desenvolver formulações de misturas para preparo de bolos de caneca, sem ovos e sem leite, com farinhas de cascas e sementes de uvas, além de avaliar características físico-químicas, tecnológicas e sensoriais, com enfoque nos efeitos dos ácidos ascórbico e cítrico sobre os bolos, com substituição parcial da farinha de trigo por farinha de bagaço de uva. Aos produtos, foram incorporados 5% de farinhas de cascas e sementes em relação à farinha de trigo. Foram realizadas análises de polifenóis, atividade antioxidante, cor, pH, volume específico, perda de massa e sensorial. Entre as formulações com farinha de uva, a amostra com adição de ácido ascórbico apresentou maior (p < 0,05) atividade antioxidante, medida pelo método ABTS, do que as amostras sem adição de ácidos. Entretanto, a formulação não apresentou diferença significativa (p > 0,05) quando comparada com a formulação com a adição de ácido cítrico ou a combinação de ácidos. De acordo com o coeficiente de correlação de Pearson, quanto mais ácido (menor pH) se mostrou o bolo, maior foi a tendência de aumento na concentração de polifenóis totais, antocianinas e compostos com atividade antioxidante. Com relação ao volume específico, a maioria das formulações controles apresentou os maiores volumes em relação às suas respectivas amostras com farinha de uva. Assim, a incorporação dos ácidos ascórbico e cítrico nos bolos com farinha de bagaço de uva possivelmente acarretou estabilização da coloração vermelha e o bolo com farinha de bagaço de uva e ácido ascórbico apresentou as maiores quantidades de compostos fenólicos totais, quando comparado aos outros bolos com o subproduto, além de ter sido um dos bolos mais bem aceitos pelos provadores, demonstrando o potencial de mercado para esses produtos alimentícios inovadores.

Abstract This study aimed to develop formulations of mixtures to prepare mug cakes, without eggs and milk, with grape skin and seed flours, and to evaluate their physicochemical, technological and sensory characteristics focusing on the effects of ascorbic and citric acids on cakes with partial replacement of wheat flour with grape marc flour. The products were incorporated with 5% grape marc flour in relation to wheat flour. The following analyses were performed: polyphenols, antioxidant activity, color, pH, specific volume, loss of mass, and sensory. Among the formulations with grape marc flour, the sample with addition of ascorbic acid showed higher (p < 0.05) antioxidant activity measured by the ABTS method than the samples without addition of acids. However, this formulation showed no statistically significant difference (p > 0.05) compared with those with addition of citric acid or a combination of acids. According to the Pearson’s correlation coefficient, the more acidic (lower pH) the cake was, the greater the tendency for increased concentration of total polyphenols, anthocyanins, and compounds with antioxidant activity. Regarding specific volume, most of the control formulations presented higher values compared with those of their respective samples with grape marc flour. Thus, incorporation of ascorbic and citric acids into cakes with grape marc flour possibly resulted in red color stabilization, and the cake with grape marc flour and ascorbic acid presented the highest amounts of total phenolic compounds compared with those of other cakes with this by-product, in addition to being one of the cakes most accepted by the tasters, demonstrating the market potential of these innovative food products.

Abstract Pecan nutshell is a residue from food industry that has potential to be used as biopreservative in foods. The objective of this study was to evaluate the antimicrobial activity of pecan nutshell aqueous extract in vitro and its effectiveness to inhibit spoilage microorganisms on lettuce leaves. The results indicate that the aqueous extract presents inhibitory activity against important foodborne pathogenic bacteria such as Listeria monocytogenes, Salmonella Enteritidis, Staphylococcus aureus, Bacillus cereus, Aeromonas hydrophila and Pseudomonas aeruginosa. Antimicrobial activity was not observed against Corynebacterium fimi, Clostridium perfringens, Escherichia coli, and the phytopathogenic fungi tested. When applied onto lettuce leaves, pecan nutshell extract reduced the counts of mesophilic and psychrotrophic bacteria in 2 and 4 log CFU/g, respectively, during storage of leafy for 5 days at refrigeration temperature (5 °C). The extract was not effective to inhibit yeast on lettuce leaves. Thus, the aqueous extract of pecan shell showed great potential to be used as a natural preservative in foods, acting mainly in the inhibition of spoilage and pathogenic bacteria.

Lactobacillus sakei subsp. sakei 2a is a bacteriocinogenic lactic acid bacterium isolated from Brazilian pork sausage, capable of inhibiting the growth of microbial pathogens, mainly Listeria monocytogenes. In order to optimize bacteriocin production for industrial applications, this study evaluated the effect of supplementation of MRS broth with glucose, Tween 20, Tween 80, sodium citrate, potassium chloride and cysteine, and effect of the initial pH and temperature of incubation of the medium on production of bacteriocins by L. sakei 2a. Adding glucose and Tween 20 to the medium, an initial pH of 5.0 or 5.5, and incubation temperatures of 25 °C or 30 °C resulted to the highest bacteriocin yields. Thus, a 24 factorial design with the four variables was performed, and statistical analysis showed that it was an adequate model (R2 = 0.8296). In the studied range, the four parameters significantly influenced bacteriocin production, with the maximum yield produced at an initial pH between 5.5 and 7.0, a temperature between 25 and 30 °C and supplementation of the MRS broth with glucose from 3.25 to 6.0 g L−1 and Tween 20 from 0.575 to 1.15% (v/v). Response Surface Methodology analysis indicated that the highest bacteriocin production (12800 AU mL−1) occurred in the MRS broth supplemented with 5.5 g L−1 glucose and 1.05% Tween 20 at an initial pH of 6.28 and an incubation temperature of 25 °C. The amount of bacteriocin produced in commercial MRS broths under the same conditions was only 5600AU mL−1.