The Mozzarella cheese market is growing rapidly. Major concerns with cheese meltability and color have arisen in the fast food industry. Pre starter culture was used in this study to improve the physical properties of Mozzarella cheese. Three tests (stretch test, melt test, and browning test) were modified to evaluate the quality of cheese. A stretch test using the Brookfield helipath viscometer to stretch the cheese sample at 60°C was successful in distinguishing cheeses from different make procedures and from different proteolytic strains. A melt test using a glass tube to hold the cheese flow at 110°C for 60 min was used to determine meltability of cheese. A chroma meter was used to measure color change after the cheese sample was subjected to boiling water for 60 min. The b* value was used to indicate the color change. Cheese made with Pre strains of Lactobacillus bulgaricus stretched less but showed longer melting flow than that from Prt+ strains. Cheese made with Pre strains was lighter in color than cheese from Prt+ strains. An inverse relationship existed between stretchability and meltability. When mixed cultures of L. bulgaricus and Streptococcus thermophil us were used, the symbiotic interaction in acid production of Prt+ strains was more effective than mixed cultures of Prt- strains. Stretchability of...

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2017-12-20T17:22:53Z No. of bitstreams: 1 fernandapyramidesdocoutogomes.pdf: 1744041 bytes, checksum: 559614bb5909c675c36516c829997921 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-12-21T10:42:28Z (GMT) No. of bitstreams: 1 fernandapyramidesdocoutogomes.pdf: 1744041 bytes, checksum: 559614bb5909c675c36516c829997921 (MD5) / Made available in DSpace on 2017-12-21T10:42:28Z (GMT). No. of bitstreams: 1 fernandapyramidesdocoutogomes.pdf: 1744041 bytes, checksum: 559614bb5909c675c36516c829997921 (MD5) Previous issue date: 2017-08-31 / A presença de resíduos de antimicrobianos em leite pode representar grave problema de saúde pública. Por este motivo, algumas medidas legais foram tomadas pelos órgãos competentes, como a venda de medicamentos antimicrobianos sob prescrição médica ou médico veterinária, a observância de Boas Práticas Agropecuárias, e a definição de limites máximos de resíduos (LMR) em alimentos de origem animal. No entanto, os LMR estabelecidos não visam os efeitos sobre tecnologia e fabricação de produtos lácteos, mas sim a proteção da saúde pública. Sob o aspecto tecnológico, as bactérias lácticas são indispensáveis na produção de derivados lácteos fermentados, pois promovem a acidificação controlada e melhoram a textura e o sabor do produto. Assim, a hipótese norteadora deste estudo é que resíduos de antimicrobianos em leite, mesmo abaixo do LMR, são capazes de alterar negativamente a resposta fermentativa das bactérias lácticas. Para tal, foram empregados cinco antimicrobianos (amoxicilina, ceftiofur, gentamicina, sulfametazina e tetraciclina, representante dos cinco principais grupos de antimicrobianos constantes do Plano Nacional de Controle de Resíduos e Contaminantes do Ministério da Agricultura, Pecuária e Abastecimento - MAPA), em cinco diferentes concentrações (0; 0,50; 0,75; 1,0 e 1,25 do respectivo LMR), que foram testados frente a três fermentos comerciais, DELVO® FRESH FC-211 (Lactococcus lactis subsp. lactis e Lactococcus lactis subsp. cremoris), DELVO® CHEESE CP-101 (Streptococcus thermophilus) e DELVO® FRESH YS-131 (Lactobacillus bulgaricus e Streptococcus thermophilus), amplamente utilizados na fabricação de queijos e iogurtes. O leite foi proveniente de três animais diferentes, comprovadamente não-tratados com antimicrobianos. Os controles e tratamentos experimentais foram analisados com respeito à cinética fermentativa. O efeito inibitório das substâncias antimicrobianos foi determinado pela variação na curva de acidificação, bem como quanto ao tempo para se atingir o pH final de referência de cada fermentação. Ceftiofur e tetraciclina inibiram a atividade de cultura contendo Streptococcus thermophilus, mesmo quando empregados em concentrações abaixo de seus respectivos LMR. A cultura composta por Lactococcus lactis ssp. lactis e Lactococcus lactis ssp. cremoris foi inibida pelos antimicrobianos ceftiofur e gentamicina, mesmo quando empregados em concentrações abaixo dos respectivos LMR. Ceftiofur também inibiu a cultura mista de Streptococcus thermophilus e Lactobacillus delbrueckii ssp. bulgaricus, em concentrações abaixo de seu LMR. Assim, os resultados do presente estudo indicam que concentrações abaixo do LMR de antimicrobianos em leite podem interferir negativamente na atividade fermentativa de bactérias lácticas. / The presence of antimicrobial residues in milk represents a serious public health problem. For this reason, some legal measures have been taken by the governments, as a sale of antimicrobial drugs under medical or veterinary medical prescription, observation of Good Agricultural Practices, and the definition of maximum residue limits (MRLs) in foods of animal origin. However, the established MRL do not take into account effects on technology and manufacturing of dairy products, but only the protection of public health. Under the technological aspect, lactic bacteria are indispensable in the production of fermented dairy products, because promote controlled acidification and improve the texture and flavor of the product. Thus, the guiding hypothesis of this study is that antimicrobial residues in milk, even below the MRL, are capable of negatively altering the fermentative response of lactic bacteria. Five antimicrobials (amoxicillin, ceftiofur, gentamicin, sulfamethazine and tetracycline, representing the five main antimicrobial groups included in the National Plan for the Control of Residues and Contaminants of the Ministry of Agriculture, Livestock and Supply (MAPA), in five different concentrations (0, 0.50, 0.75, 1.0 and 1.25 of the respective MRL), which were tested against three commercial lactic cultures, DELVO® FRESH FC-211 (Lactococcus lactis subsp. lactis e Lactococcus lactis subsp. cremoris), DELVO® CHEESE CP-101 (Streptococcus thermophilus) and DELVO® FRESH YS-131 (Lactobacillus bulgaricus e Streptococcus thermophilus). Widely used in the manufacture of cheeses and yogurts. The milk came from three different animals, proven untreated with antimicrobials. Experimental controls and treatments were analyzed with respect to fermentative kinetics. The inhibitory effect of the antimicrobial substances was determined by the variation in the acidification curve as well as the time to reach the final reference pH of each fermentation. Ceftiofur and tetracycline inhibited the culture activity containing Streptococcus thermophilus, even when employed at concentrations below their respective MRL. The culture composed of Lactococcus lactis ssp. lactis and Lactococcus lactis ssp. cremoris was inhibited by ceftiofur and gentamicin antimicrobials, even when used at concentrations below their MRL. Ceftiofur also inhibited the mixed culture of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus, at concentrations below its MRL. Thus, the results of the present study indicate that concentrations below the antimicrobial MRL in milk may negatively interfere with the fermentative activity of lactic acid bacteria.