Thesis (Ph. D.)--University of Wisconsin--Madison, 1938. / Typescript. Includes abstract and vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 73-75).

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A sensory method was developed to determine cheese texture by hand evaluation. Cheese sensory evaluation was conducted by panelists (n=8) on four commercial samples in duplicates. Standards, descriptors, methods of each attribute evaluation, sample size, and ballot were developed based on panelists' consensus. Fifteen total attributes, divided into five groups, were tested. Crumbliness was defined as the ease of the sample to break apart during manipulation using the thumb and two fingers for five times. Using Principal Component Analysis (PCA), four components were extracted with the first two explaining most of the variability (60.4%). PCA showed that moistness, crumbliness, color, cohesiveness, irregularity, and oiliness were the main attributes describing the samples. Irregularity and cohesiveness had 83.6% and -88.1% correlations with crumbliness, respectively. Panelists' performances were not significantly different (p≤0.05) and each subject used the method consistently for crumbliness. This method was then applied to evaluate and compare the sensory attributes of Queso Fresco. Three types of Queso Fresco cheese were made: raw cheese (RC), High Hydrostatic Pressure (HHP) treated raw cheese (HP), and cheese made from HHP treated milk (HPM). Sensory attributes, compositions, microstructures and protein profile were compared. Sensory attributes were examined by ten trained panelists using hand evaluation method developed and instrumental methods (Texture Profile Analysis (TPA) and 80% compression test). Protein, fat, and moisture contents were valuated by Micro Kjeldahl, Babcock, and Forced air draft oven respectively. Microstructure was examined by light microscopy using Acid Fuschin protein staining, while native and SDS PAGE were carried out to show the protein profile. One and eight days storage times were studied. HHP treatment of cheese or cheese milk (400 MPa, 20 min, ambient temperature) were shown to reduce microbial loads. HP and RC had similar microstructure, compositional (p-value≤0.05), and sensory attributes, except color (p-value≤0.05). HP and RC had distinct protein network, while HPM had a very diffuse network. HPM was different from both RC and HP. HPM was the least firm, least crumbly, most sticky and oily. HPM day one was firmer, less oily, less springy than day eight. HPM had higher moisture and yield, due to incorporation of denatured whey proteins, than RC and HP cheese. The hand evaluation method developed was proven to be able to differentiate cheese textural attributes. Overall, HHP treatment of Queso Fresco produced cheese with similar characteristics as traditionally made Queso Fresco, while HHP treatment of cheese milk created cheese with weak texture characteristics. HHP treatment of cheese might be an alternative way to produce Queso Fresco with acceptable attributes and reduced microbial load. / Graduation date: 2003

Thesis (Ph. D.)--University of Wisconsin--Madison, 1955. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 296-309).

Please read the abstract in the front section of this document / Dissertation (MSc (Food Science))--University of Pretoria, 2005. / Food Science / unrestricted

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Cheese ripening is a costly and lengthy process. Increasing the enzyme pool in the cheese curd has been shown to accelerate the cheese ageing process, enhance flavour and texture. The characteristics of two lactic acid bacteria attenuated by pulsed electric fields were studied in a milk system and in cheese slurry. The potential of accelerating cheese ripening via the addition of starter cultures attenuated by pulsed electric fields (PEF) was studied. / Pulsed electric field treatment was performed in a static treatment chamber using bi-polar waveform with a field intensity of 20 kV and 2 mus pulse width. The number of pulses ranged from 10 to 500. Evaluation of the starter cultures was assessed through the analysis of acidifying abilities, survival fractions, enzymatic activities and proteolysis (RP-HPLC and Cd-ninhydrin) in water soluble nitrogen extracts following the different attenuation treatments. / Pulsed electric fields significantly affected the general viability of the cells through a delayed acidification and an inhibition of enzymatic activity. A study in cheese slurry systems showed that the cultures under investigation were not able to provide an increased proteolysis levels following PEF treatment. The results of this study also suggest that optimal PEF treatment varies for each LAB strain and that the Lactococcus strains do not possess high enough proteinase and peptidase activities to be beneficial for the acceleration of cheese ripening.

CAPES / A Mesorregião do Sudoeste Paranaense se destaca pela atividade leiteira, com produção, industrialização e comercialização de derivados. O uso de bactérias láticas endógenas vem ganhando o mercado mundial com pesquisas e elaboração de produtos, e despertando o interesse de Instituições de Ensino do Brasil. Este trabalho teve como objetivo isolar, caracterizar e identificar a microbiota lática do leite cru, para desenvolver um fermento endógeno e, a partir deste, elaborar o Queijo Típico. Foram desenvolvidos dois fermentos, compostos pelas bactérias Streptococcos thermophillus e Lactobacillus delbrueckii sp. bulgaricus. Os fermentos foram testados em dois laticínios da região, utilizando leite pasteurizado e os conservantes nitrato de sódio e a enzima lisozima. Os queijos elaborados foram submetidos a análises para o acompanhamento das modificações durante a maturação (30, 60 e 180 dias) e todas as amostras avaliadas exibiram características físico-químicas e microbiológicas de acordo com a legislação brasileira, podendo ser classificados, de um modo geral, como queijos de média umidade, variando de 40,71 a 42,44 g/100 g (30 dias), 35,37 a 40,28 g/100 g (60 dias) e 33,63 a 38,63 g/100 g (180 dias), de acordo com o teor de matéria gordurosa no extrato seco classificam-se em gordos, 40,37 a 48,80 (g/100 g) (30 dias), 44,42 a 48,25 (g/100 g) (60 dias) e 45,30 a 49,80 (g/100 g) (180 dias). As proteínas (g/100 g) variaram de 20,57 a 23,95 g/100 g (30 dias), 21,88 a 24,71 (60 dias), 23,52 a 30,57 (180 dias), os lipídeos entre 20,57 a 23,95 (30 dias), 24,71 a 21,88 (60 dias), e 30,57 a 23,52 (180 dias). Os teores de cinzas ficaram entre 2,99 a 4,88 (g/100 g) (30 dias), 4,10 a 5,00 (g/100 g) (60 dias) e 4,58 a 5,19 (g/100 g) (180 dias), atividade de água (Aw) entre 0,9531 a 0,9635 (30 dias), 0,9366 a 0,9547 (60 dias) e 0,9284 a 0,9380 (180 dias). As análises de textura apontaram que o queijo desenvolvido, no decorrer dos períodos de maturação, apresentou aumento da dureza, onde o menor valor aos 30 dias estava em 18377,19 g passando aos 180 dias para um valor máximo de 27401 g. A elasticidade, que aos 30 dias apresentava-se em 0,82, passou a 0,88 aos 180 dias. A mastigabilidade de 11412,92 (30 dias) passou para 5116,76 (180 dias). A coesividade de 0,67 (30 dias) ficou em 0,20 (180 dias). A adesividade que era de -205,45 (30 dias) passou para -25,04 (180 dias) e a resistibilidade que inicialmente era de 0,21 (30 dias) ficou com 0,04 (180 dias). Em relação à análise de cor, as amostras apresentaram alta luminosidade (L*) chegando a ter aos 180 dias (73,51 ± 3,62 a 79,75 ± 0,56), com predominância da componente amarela (b*) (34,10 ± 0,55 a 36,81 ± 0,29), e amostras dentro do espectro verde (a*) (-7,40 ± 0,06 a -7,82 ± 0,21), com pequenas variações entre si. As análises sensoriais do queijo apontaram para aceitação diante dos provadores. Este trabalho representa uma das etapas acerca da utilização do fermento endógeno na fabricação de um Queijo Típico Regional, que recebeu a denominação de “Santo Giorno” e contribuiu para a compreensão das variações e interações dos componentes fisíco-químicos e microbiológicos no desenvolvimento de um produto de elevada qualidade. / The Greater Region Southwest of Paraná stands out for dairy farming, with production, processing and trading of derivatives. The use of endogenous lactic acid bacteria is gaining global market research and product development is attracting the interest of Educational Institutions in Brazil. This work aimed to isolate, identify and characterize the lactic microflora of raw milk, to develop endogenous starter culture, and using it, prepare the Cheese Typical. Two starters cultures, Streptococcus thermophillus compounds by bacteria and Lactobacillus delbrueckii sp bulgaricus were developed. The starter culture were tested in two dairy region, using pasteurized milk, preservatives sodium nitrate and lysozyme enzyme. The elaborate cheeses were subjected to analysis for the monitoring of changes during maturation (30, 60 and 180 days) and all samples exhibited physicochemical and microbiological characteristics according to Brazilian legislation. They can be classified broadly as cheese medium humidity ranging from 40.71 to 42.44 g/100 g (30 days), from 35.37 to 40.28 g/100 g (60 days), and from 33.63 to 38.63 g/100 g (180 days), according to the content of fatty matter in dry matter, cheeses can be classified as fat, from 40.37 to 48.80 (30 days), from 44.42 to 48.25 (60 days) and 45.30 to 49.80 (180 days). Proteins ranged from 20.57 to 23.95 g/100 g (30 days), from 21.88 to 24.71 g/100 g (60 days), from 23.52 to 30.57 g/100 g (180 days), lipids between 20.57 to 23.95 g/100 g (30 days), from 24.71 to 21.88 g/100 g (60 days), and from 30.57 to 23.52 g/100 g (180 days). The ash content ranged from 2.99 to 4.88 (30 days), from 4.10 to 5.00 (60 days) and from 4.58 to 5.19 (180 days) the water activity from 0.9531 to 0.9635 (30 days), 0.9366 to 0.9547 (60 days) and 0.9284 to 0.9380 (180 days). Textural analyzes indicated that the cheese developed during periods of maturation, showed an increase in hardness, where the lowest value at 30 days was at 18377.19 g passing the 180 days to a maximum value of 27401 g. The elasticity at 30 days showed that in 0.82, went 0.88 at 180 days. The chewiness of 11412.92 (30 days) increased to 5116.76 (180 days). The cohesiveness of 0.67 (30 days) stood at 0.20 (180 days). The adhesiveness which was -205.45 (30 days) increased to -25.04 (180 days) and the resistivity which was initially 0.21 (30 days) was 0.04 (180 days). Regarding the analysis of the samples showed high color brightness (L*), coming to have 180 days (73.51 ± 3.62 to 79.75 ± 0.56), with a predominance of yellow component (b*) (34.10 ± 0.55 to 36.81 ± 0.29), and samples within the green spectrum (a*) (-7.40 ± 0.06 and -7.82 ± 0.21), showed minor variations. The sensory analysis of Cheese Typical pointed to acceptance by the panelists. This work represents one of the steps of using endogenous starter culture in a cheese, which was called as "Santo Giorno", and contributed to understanding the variations and interactions of physico-chemical and microbiological development of a regional product, with high quality components.

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