Luiz Ronaldo de Abreu

Formation of biofilms by Staphylococcus aureus on stainless steel and glass surfaces and its resistance to some selected chemical sanitizers

The objectives of this work were to verify the capability of Staphylococcus aureus of forming bio-film on stainless steel and glass surfaces; to evaluate the efficiency of sodium dichloroisocyanurate, hydrogen peroxide and peracetic acid in inactivating Staphylococcus aureus cells adhered onto these surfaces; and to visualize biofilm development by scanning electron microscopy before and after sanitizer treatment. The surfaces studied consisted of 10x20mm chips immersed in Petri dishes containing BHI broth inoculated with S. aureus ATCC 25923. Biofilm formation was observed after 15-day incubation, when the cells were removed using the swab technique, followed by Baird Parker agar plating. Also, the efficiency of the chemical sanitizers on the chip surfaces was tested and the non-removed cells were counted on the Baird-Parker agar. After biofilm formation and use of sanitizers, the chips were respectively observed by scanning electronic microscopy following a pre-existing protocol. The obtained results showed biofilm formation on both surfaces, with bacterial count in the order of 107 CFU/cm2 on and 108 CFU/cm2 on stainless steel and glass surfaces, respectively. Peracetic acid was the most efficient in removing adhered cells, presenting 5.26 and 4.5 decimal reduction for adhered cells on stainless steel and glass surfaces, respectively.

Caracterização química e efeito inibitório de óleos essenciais sobre o crescimento de Staphylococcus aureus e Escherichia coli

Objetivou-se avaliar o efeito inibitorio dos oleos essenciais de Cymbopogon citratus (capim-limao), Origanum vulgare (oregano) e Syzygium aromaticum (cravo-da-india); os experimentos foram realizados com as bacterias Staphylococcus aureus e Escherichia coli, importantes patogenos causadores de contaminacoes em queijos e outros alimentos. Para quantificacao e identificacao dos constituintes quimicos dos oleos, utilizou-se um cromatografo gasoso acoplado a um espectrometro de massa. Os resultados dos testes in vitro, os oleos essenciais de C. citratus, O. vulgare e S. aromaticum promoveram efeito inibitorio sobre as bacterias S. aureus e E. coli, porem o S. aromaticum apresentou melhor formacao de halo de inibicao nas menores concentracoes. Para o efeito sinergistico dos oleos sobre as bacterias nao foram observadas diferencas quando comparados com o efeito individual dos mesmos. Foi possivel verificar que os oleos possuem efeito inibitorio sobre os microrganismos estudados, sendo, portanto uma alternativa no controle microbiologico de alimentos.

Efeito da Suplementação de Lipídios na Ração sobre a Produção de Ácido Linoléico Conjugado (CLA) e a Composição da Gordura do Leite de Vacas

The objective of this work was to verify the effects of lipid sources (ground soybean and soybean oil) added to the diet on the fatty acids profile of milk fat, specially in the increasing of CLA. Six multiparus 7/8 Holstein-Zebu cows, 30 days after calving, with average body weight of 500 kg and average milk production of 20 kg/day, were used. The animals were divided in three groups in order to receive isoprotein and isocaloric diets (treatments), in which control diet had 3% ether extract in total dry matter and the others 7%. Comparing to the control one, the treatments containing supplementar lipids, decreased the percentage of short chain fatty acids and decreased the content of butyric, caproic, caprilic, capric, lauric, miristic and the percentage of saturated fatty acids. There was still a trend for reduction in the content of palmitic and palmitoleic acids and a trend for increasing the percentage of unsaturated fatty acids and long chain fatty acids. Supplementar lipids increased stearic acid and tended to increase oleic acid and CLA. Soybean oil, compared to ground soybean, decreased the content of linoleic and linolenic acids and increased CLA, tended to increase the content of undentified fatty acids and tended to decrease the saturated fatty acids. In conclusion, adding soybean oil and not crushed soybean in the diet increased the content of CLA in milk fat.

Effect of calcium chloride addition on ice cream structure and quality.

The influence of calcium fortification by the addition of calcium chloride on quality parameters of ice cream based on physical properties was investigated, as was the effect of kappa-carrageenan at modifying the effects of this calcium fortification. Four ice cream mixes of conventional composition, with added kappa-carrageenan (0 or 0.025%) and added calcium chloride (0 or 4.4 g L(-1) = 40 mM of added Ca(2+)), were prepared. Modulated temperature-differential scanning calorimetry was used to investigate the effect of calcium chloride on the nucleation temperature, enthalpy of melting, and freezing point depression. The protein composition of 15.4% (wt/wt) reconstituted skim milk powder solutions with or without 4.4 g L(-1) added CaCl(2) and in the supernatant after ultracentrifugation was determined. Fat particle size distributions in ice cream were characterized by light scattering. Ice crystal sizes before and after temperature cycling were determined by cold-stage light microscopy. The results demonstrated that the addition of calcium chloride led to a substantial increase in ice crystal sizes and in fat partial coalescence, which were exacerbated by the addition of kappa-carrageenan. These results can be explained by the interaction between Ca(2+) ions and casein micelles, rather than any effects on freezing point depression. The calcium ions led to a more compact micelle, less serum beta-casein, and high fat destabilization, all of which would be expected to reduce macromolecular structure and volume occupancy in the unfrozen phase, which led to increased rates of ice recrystallization.

Controle microbiológico da vida de prateleira de ricota cremosa

The occurrence of spoiler microrganisms in creamy ricotta during its shelf-life was assessed. The results showed the following contamination levels: < 0.3 MPN/g of coliforms, < 1.0 x 102 CFU/g of coagulase producing Staphylococcus and total aerobic mesofilic counts of between 2.0 x 102 and 2.45 x 104 CFU/g. The aerobic mesofilic counts decreased with storage time, with the samples being kept during twenty days under refrigerating condition (7 oC). The results of creamy ricotta microbiological assessment showed satisfactory hygienical-sanitary conditions.

Utilização de APPCC na indústria de alimentos

A busca e o aperfeicoamento pela qualidade dos alimentos, por exigencia de consumidores e mercado, aumentam a procura por sistemas que possam proporciona-la e, que tambem, sejam efetivos nao so no quesito sanitario, mas na reducao de perdas e no aumento da competitividade. O sistema APPCC vem ao encontro da satisfacao dessas exigencias, por ser um programa que tem como filosofia a prevencao e, por trabalhar junto a outros ja utilizados, nao desperdicando pre-investimentos, ou seja, aproveitando os investimentos feitos em outros programas. A implantacao do APPCC satisfaz a legislacao nacional e internacional, dando seguranca e abrindo as portas para a exportacao, porem, no Brasil, ainda existem algumas dificuldades para que este programa seja totalmente difundido e fiscalizado.

Rendimento e composição físico-química do queijo prato elaborado com leite pasteurizado pelo sistema HTST e injeção direta de vapor

Avaliaram-se o rendimento, a transicao de gordura e extrato seco do leite para a coalhada e as caracteristicas fisico-quimicas do queijo prato produzido com leite pasteurizado pelo sistema de placas (ou HTST) e injecao direta de vapor (IDV). Utilizou-se o delineamento inteiramente casualizado, constituido por dois tratamentos (HTST e IDV) e seis repeticoes (fabricacoes). O sistema IDV incorporou cerca de 8,5% de agua ao leite, havendo como consequencia reducao (P<0,05) no teor de solidos totais, na gordura e na acidez do leite pasteurizado. Observou-se maior transicao de gordura do leite para a coalhada, quando esse foi submetido ao sistema de pasteurizacao por IDV, o que resultou em maior rendimento dos queijos fabricados com leite pasteurizado por esse sistema (8,48 litros de leite/kg de queijo), quando comparado ao sistema HTST (9,54 litros de leite/kg de queijo). Os queijos fabricados com o sistema IDV apresentaram teores mais elevados de gordura e gordura no extrato seco (GES) (29,06 e 55,25%), quando comparados aos do sistema HTST (27,02 e 49,88%), respectivamente. Conclui-se que o sistema IDV proporciona aumentos expressivos no rendimento de queijos e que, entre os constituintes do leite, a gordura foi a principal responsavel por este aumento.

Avaliação microbiológica de bebidas lácteas fermentadas adquiridas no comércio varejista do sul de Minas Gerais

The objective of this work was to evaluate the microbiological characteristics of fermented dairy beverages commercialized in southern Minas Gerais. The enumeration of total and heat-tolerant coliforms, filamentous fungi and lactic bacteria and yeasts was carried out. Samples were collected from different manufacturing lots of five brands of dairy beverages commercialized in Lavras-MG, with four repetitions and submitted to microbiological analyses. The fermented dairy beverages met the standards required by ANVISA for presence of microbial contamination, since no contamination was detected in the samples analyzed. Lactic bacteria count was lower than 106 UFC/mL in all the analyses and did not meet out legal parameters established by the Brazilian legislation for fermented dairy beverages.

Temporal dominance of sensations sensory profile and drivers of liking of artisanal Minas cheese produced in the region of Serra da Canastra, Brazil

The Serra da Canastra region, located in southwestern Minas Gerais, Brazil, is recognized worldwide for its tradition of producing artisanal cheeses. However, as production is done by hand, great variability exists in the characteristics of artisanal Minas cheese. Thus, it is important to characterize the sensory profile of these products and verify the quality attributes that lead to their acceptance. Therefore, this study aimed to characterize the dynamic sensorial profile of artisanal Minas cheese produced in the Serra da Canastra region through temporal dominance of sensations and sensory acceptance tests and verify the attributes that lead to product quality. We observed that the texture and flavor profile varied among the evaluated artisanal Minas cheeses from Serra da Canastra, some cheeses being more characterized by creamy and soft or hard and firm sensations, whereas others had high dominance rates for crumbly texture. In relation to flavor, salty and bitter tastes were dominant in most cheeses, some also being characterized by a sour taste, and others by buttery and rancid attributes, which indicates a lack of product standardization. However, all samples obtained scores between 6 (liked slightly) and 7 (liked moderately), indicating good acceptability in relation to the texture and flavor of the evaluated cheeses. Moreover, it is possible to infer that creamy and soft or hard and firm are positive attributes for cheese texture, and bitter, buttery, salty, and acid taste drive cheese acceptance. This study provides important information for product standardization, quality improvement, and process origin indications, besides providing quality attributes that meet consumer desires.

Addition of water-soluble soy extract and probiotic culture, viscosity, water retention capacity and syneresis characteristics of goat milk yogurt

Yogurts from goat milk were elaborated and water-soluble soybean extract (WSSE) and Bifidobacterium lactis probiotic culture added during processing. The characteristics of apparent viscosity, water retention capacity and syneresis were analyzed during 29 days of storage and it was verified the influence of WSSE and the probiotic on these rheological properties. The suplementation of WSSE provoked an increase in the viscosity and water retention capacity of the yogurts while reducing the syneresis. The inoculation of the probiotic culture during elaboration of the yogurts did not significantly alter the rheological characteristics of the products. Therefore, the water-soluble soybean extract and the probiotic culture can contribute to the rheological characteristics of yogurts, besides the nutritional and functional improvement advantages already known with the use of these products.