Bruno Ricardo de Castro Leite Júnior

Minimally processed yellow melon enriched with probiotic bacteria

The demand for healthy diets with fresh foods, especially minimally processed fruits and vegetables, resulted in a variety of products available to consumers...

Fruit salad as a new vehicle for probiotic bacteria

This work aimed to study the use of fruit salads as carriers for Lactobacillus rhamnosus HN001. We evaluated the viability of this probiotic in fruit salads and the phsyico-chemical, microbiological and sensory properties of this food. Scanning electron microscopy (SEM) was used to verify microorganism adhesion on the fruit tissues. The viability of L. rhamnosus in fruit salads was 8.49 log CFU.g-1 after 120 hours. SEM images showed that fruit tissue provided protection for probiotic. Adhesion sites were observed in higher quantity in banana, apple and guava. The addition of L. rhamnosus did not alter texture of fruits (p > 0.05). Fruit salads containing probiotic had different values of pH and acidity compared to the control (p 0.05). Fruit salads containing L. rhamnosus showed counts of psychotrophic microorganisms of at least 2.0 log CFU.g-1 lower than control salad after 120 h of refrigerated storage. The fruit salad was well accepted by consumers. Therefore, this product can be used as a carrier for probiotic and an alternative to consuming functional foods.

High Pressure Homogenization of Porcine Pepsin Protease: Effects on Enzyme Activity, Stability, Milk Coagulation Profile and Gel Development.

This study investigated the effect of high pressure homogenization (HPH) (up to 190 MPa) on porcine pepsin (proteolytic and milk-clotting activities), and the consequences of using the processed enzyme in milk coagulation and gel formation (rheological profile, proteolysis, syneresis, and microstructure). Although the proteolytic activity (PA) was not altered immediately after the HPH process, it reduced during enzyme storage, with a 5% decrease after 60 days of storage for samples obtained with the enzyme processed at 50, 100 and 150 MPa. HPH increased the milk-clotting activity (MCA) of the enzyme processed at 150 MPa, being 15% higher than the MCA of non-processed samples after 60 days of storage. The enzyme processed at 150 MPa produced faster aggregation and a more consistent milk gel (G’ value 92% higher after 90 minutes) when compared with the non-processed enzyme. In addition, the gels produced with the enzyme processed at 150 MPa showed greater syneresis after 40 minutes of coagulation (forming a more compact protein network) and lower porosity (evidenced by confocal microscopy). These effects on the milk gel can be associated with the increment in MCA and reduction in PA caused by the effects of HPH on pepsin during storage. According to the results, HPH stands out as a process capable of changing the proteolytic characteristics of porcine pepsin, with improvements on the milk coagulation step and gel characteristics. Therefore, the porcine pepsin submitted to HPH process can be a suitable alternative for the production of cheese.

Effect of dynamic high pressure on functional and structural properties of bovine serum albumin

Dynamic high pressure (DHP) has been investigated as an innovative suitable method to induce protein modifications. This work evaluated the effect of DHP (up to three passes at 100, 150 and 200MPa, with an inlet temperature of 20°C) on functional and structural properties of bovine serum albumin (BSA). Results indicated that DHP process applied up to an energy limit of 100MPa increased the protein foaming capacity (FC) (p<0.05 - increase up to 63% after 1 pass at 100MPa) and the utilization of multiple passes at high pressure promoted a reduction in this property (p<0.05 - reduction up to 31.6% after 3 passes at 200MPa). Similar results were observed for sulfhydryl group, indicating an influence of free thiol groups on FC. Complementarily, DHP process promoted an increase of proteins particles size, suggesting a new rearrangement of their conformational structure. DHP did not affect tryptophan microenvironment in BSA; however, this process induced the rearrangement of secondary structure elements. In the first cycle, the pressure increase resulted in a loss of secondary structure, while in the second and third cycles the DHP process resulted in the gain of secondary structure elements. These results indicated that the second and third passes triggered a molecular rearrangement of the protein structure, giving rise to a novel and more stable conformational state. This conclusion was also supported by thermal unfolding studies (melting temperature reduction from 67.5 to 54.6°C after 1 pass at 200MPa), in which the additional cycles of DHP caused the occurrence of an initial denaturation at high temperatures, compared to the first cycle.

Effect of High-Pressure Technologies on Enzymes Applied in Food Processing

High isostatic pressure (HIP) and high-pressure homogenization (HPH) are considered important physical technologies that able to induce changes on enzymes. HIP and HPH are emerging food processing technologies that involve the use of ultra high pressures (up to 1200 MPa for HIP and up to 400 MPa for HPH), where the first process is based on the principle that the maintenance of a product inside vessels at high pressures induces changes in the molecules conformation and, consequently, in the functionality of polysaccharides, proteins and enzymes. To the contrary, for HPH process, the high shear and sudden pressure drop are the responsible phenomena for the changes on the processed product. This chapter aims to evaluate comparatively the effects of HIP and HPH on the activity of enzymes currently applied in food industry and to identify the main structural changes induced by each process. The overall evaluation of the results shows that mild conditions of both processes were recently highlighted as able to improve the activity and the stability of several enzymes, whereas extreme process conditions (pressure, time and temperature) induce enzyme denaturation with consequent reduction of biological activity. Considering the complexity and diversity involved in the enzyme structure and its ability to react, it is not possible to determine specific conditions that each process is able to promote increase or reduction of enzyme activity, being necessary to evaluate HIP and HPH for each enzyme. Finally, in terms of molecular structure, the effect of HIP and HPH on enzymes can be explained by the alterations in the quaternary, tertiary and secondary structures of enzymes, which directly affects its active site configuration.

Biophysical evaluation of milk-clotting enzymes processed by high pressure

High pressure processing (HPP) is able to promote changes in enzymes structure. This study evaluated the effect of HP on the structural changes in milk-clotting enzymes processed under activation conditions for recombinant camel chymosin (212MPa/5min/10°C), calf rennet (280MPa/20min/25°C), bovine rennet (222MPa/5min/23°C), and porcine pepsin (50MPa/5min/20°C) and under inactivation conditions for all enzymes (600MPa/10min/25°C) including the protease from Rhizomucor miehei. In general, it was found that the HPP at activation conditions was able to increase the intrinsic fluorescence of samples with high pepsin concentration (porcine pepsin and bovine rennet), increase significantly the surface hydrophobicity and induce changes in secondary structure of all enzymes. Under inactivation conditions, increases in surface hydrophobicity and a reduction of intrinsic fluorescence were observed, suggesting a higher exposure of hydrophobic sites followed by water quenching of Trp residues. Moreover, changes in secondary structure were observed (with minor changes seen in Rhizomucor miehei protease). In conclusion, HPP was able to unfold milk-clotting enzymes even under activation conditions, and the porcine pepsin and bovine rennet were more sensitive to HPP.

Uso da água ozonizada na sanitização dos tetos de bovinos e sua influência na qualidade do leite

This study evaluated the efficiency of ozonated water compared with chlorhexidine to disinfect teats of cattle and their influence on milk quality. 48 cows were separated in 2 groups of sanitation: (I) using ozonated water at 2 mg.L -1 for 30s and (II) using 2%(v/v) chlorhexidine for 30s (standard methodology of disinfection). Before and after sanitation, swabs of teat were collected for carry out microbiological analysis. Additionally, after teats sanitation, the milking was performed and the obtained milk were evaluated by microbiological and physico-chemical parameters. The number of decimal reductions (NDR) reached after ozone sanitation was 2.52, 2.09 and 1.50 for aerobic mesophilic, Staphylococcus sp. and Enterobacteriaceae, respectively. The use of chlorhexidine promoted NRD of 2.38 (aerobic mesophilic), 2.04 ( Staphylococcus sp.) and 1.16 (Enterobacteriaceae). Therefore, no significant differences were found between NRD caused by chlorhexidine and ozonated water. Moreover, no significant differences were observed in the psychrotrophic and aerobic mesophilic counts of the milk obtained after teats sanitation with ozonated water and chlorhexidine. Furthermore, it was observed that only samples obtained from cows treated with chlorhexidine showed the presence of Enterobacteriaceae. There were no changes in the physico-chemical parameters of milk obtained after both treatments. Thus, the ozonated water is a potential substitute of chlorhexidine for cows teats sanitation, resulting in similar microbiological reductions without risks of bacterial resistance development and waste generation.

In vitro and in vivo resistance of Lactobacillus rhamnosus GG carried by a mixed pineapple (Ananas comosus L. Merril) and jussara (Euterpe edulis Martius) juice to the gastrointestinal tract

This study evaluated the viability of Lactobacillus rhamnosus GG (LGG) and its in vitro and in vivo resistance to the gastrointestinal tract (GIT) when carried by a mixed fermented pineapple and jussara juice. The effects of product ingestion on the biochemical characteristics of the blood and on the development of aberrant crypt foci (ACF) in Wistar rats were also determined. The LGG viability in probiotic juice was higher than 7.2 log CFU/mL throughout 28 days at 8 °C. The mean count of the probiotic microorganism in the fecal samples of the rats was 5.6 log CFU/g, identical to the count at the end of the in vitro trial (enteric phase II), indicating that the mixed pineapple and jussara juice was an excellent vehicle for LGG. No difference (p > .05) was verified to ACF among the groups. However, the results for the probiotic culture viability and its in vitro and in vivo resistance to the gastrointestinal tract suggest that this juice is an excellent carrier matrix for LGG and contributed to a reduction in the levels of the LDL (low density lipoprotein) fraction of the blood cholesterol, thus being an aid in the control of coronary diseases.

Microbiological quality of food of animal origin commercialized in Minas Gerais

* Bacharel em Ciência e Tecnologia de Alimentos. Mestrando em Tecnologia de Alimentos da Faculdade de Engenharia de Alimentos, da Universidade Estadual de Campinas, na área de Tecnologias Emergentes no Processamento de Alimentos DTA-FEA-UNICAMP – Campinas/SP Brasil ** Bacharela em Ciência e Tecnologia de Alimentos. Mestranda em Ciência e Tecnologia de Alimentos Universidade Federal de Viçosa – Viçosa/MG Brasil *** Professor no Departamento de Ciência e Tecnologia de Alimentos (DCTA) do IF Sudeste MG, Campus Rio Pomba Minas Gerais Brasil **** Bacharel em Ciêcnia e Tecnologia de Laticinios –UFV. Doutor e Mestre em Microbiologia Agrícola – UFV – Viçosa/MG Brasil Objetivou-se, neste estudo, avaliar a qualidade microbiológica de leite pasteurizado, queijo Minas Frescal (QMF) e carne moída bovina. Um total de 74 amostras, coletadas nos estabelecimentos comerciais dos municípios de Barbacena, Juiz de Fora, Muriaé, Rio Pomba e Ubá, foram submetidas às análises de coliformes totais, coliformes termotolerantes, Escherichia coli e Salmonella sp. Além disso, as amostras de QMF foram submetidas às análises de estafilococos coagulase positiva (ECP) e Listeria monocytogenes. Todas as amostras apresentaram contaminação por coliformes totais, e 81,6 % das amostras apresentaram valores acima do preconizado pela RDC n°12 da ANVISA para coliformes termotolerantes, além de alta incidência de E. coli. Dentre as amostras de QMF, 75% estavam em desacordo com a legislação para ECP. Todas as amostras apresentaram ausência de Salmonella sp. e L. monocytogenes. Os resultados mostraram que esses alimentos de origem animal comercializados na região de Minas Gerais não estão aptos para o consumo humano devido à baixa qualidade microbiológica. Existe, portanto, a necessidade de adoção de boas práticas de fabricação, além de sanitização eficiente para minimizar os riscos de transmissão de patógenos de origem alimentar por meio destes alimentos.