Retention of lipid-soluble components can be increased in a curd matrix by using emulsions rather than the direct addition of fortified oil. The retention of vitamin D_3 was increased in a model system with fortified emulsions (emulsifier: dairy proteins) 96-97% compared to 62-72% control. Retention of fortified emulsions (78%) remained greater than the control (58%) in small-batch Cheddar cheese. Bilayer emulsions were evaluated to increase retention of lipid-soluble components even further. Physicochemical characteristics of the bilayer emulsions were evaluated prior to curd inclusion. Nonfat dry milk (NDM) was used as the primary emulsifier at 1wt% dairy proteins. Polysaccharides (iota-carrageenan, low-methoxyl [LMp] and high-methoxyl pectin) and gelatin were secondary layers. Secondary emulsions formulation was 2.5 wt% oil, 0.5 wt% protein, and 0.2 wt% secondary biopolymer. Emulsions were adjusted to pH 3, 5, and 7 after homogenization. Factors that influence stability are biopolymer concentration, droplet size/distribution/charge (zeta-potential), and viscosity. iota-Carrageenan was the most stable, independent of pH, of all the emulsions. This increased stability was a consequence of the affinity of the protein layer and iota-carrageenan through the additional homogenization step. LMp was also stable at pH 7 due to calcium bridging, which correlates with the increased viscosity. The microstructure of the emulsions was examined using scanning electron microscopy. A strong correlation was found between emulsion instability and the presence of thick webbing, due to excess biopolymer, as seen in the micrographs. Stable emulsions were likely to have distinct droplets without a thick web. The exception was gelatin (pH 3), which still had individual droplets but was unstable due to depletion flocculation. The retention of lipid-soluble substances using secondary emulsion was evaluated in a model curd matrix between primary (50:50 fortified: non-fortified oil) and secondary (100% fortified oil) emulsions. There was no significant difference (α=0.05) in retention of “fortified” oil between primary and secondary emulsions; however, the same fortification level was obtained using secondary emulsions using half the oil. Curd made with 0.01M CaCl_2 had overall lower retention than curd with no additional calcium. Secondary emulsions could be used to fortify various gel matrices (e.g., curd, yogurt, and tofu). Marketing possibilities are endless after preliminary evaluation.

This study determined the impact of starches on the properties of low fat rennet curd as measured by microstructural and instrumental analysis. In experiment 1, 17 starches were initially screened for swelling power, impact of curd yield at 5 g/L and 10 g/L in milk, and settling in rennet-induced partially acidified low fat curd. Starches examined were narrowed down to five in experiment 2; they included: modified waxy corn starch, waxy rice starch, instant tapioca starch, dextrin, and a modified tapioca starch. These starches were added to skim milk to make rennet-induced partially acidified milk gels. Gels were made by adding starch to skim milk, heating to gelatinize starch, followed by addition of rennet and glucono-delta-lactone (GDL) to induce gelation. Once gels were set they were cut and centrifuged to sediment the curd. The amount of starch lost in whey was quantified to estimate starch retention in the curd. Confocal laser scanning microscopy was used to determine starch impact on curd microstructure. Curds yields were 13.1%, 18.4%, 20.7%, 21.5%, 23.5%, and 13.2% for control gel, and gels containing waxy corn, waxy rice, instant tapioca, modified tapioca and dextrin starches, respectively. Estimated starch retentions in the curds were 71%, 90%, 90%, 21%, and 1% for these curds. Waxy corn, waxy rice, and instant tapioca starches have the potential to improve the texture of low fat cheese because they are retained well in the protein network during coagulation and concentration of the milk proteins, and they generate interruptions in curd network that may help limit extensive protein-protein interactions. Modified tapioca starch causes the protein structure of the curd to be very loose, but it was not retained optimally in the curd. Also, because there were few distinct starch particles in the modified tapioca curd network, it is likely that when it is subjected to all the cheesemaking steps the same loose protein structure would not be observed. Dextrin was not retained well in the curd, nor did it disrupt the protein network, making it unsuitable for use in low fat cheese. In experiment 3, low fat cheddar cheeses were made with waxy corn starch, waxy rice starch, modified tapioca starch, and instant tapioca starch. Modified tapioca starch did not increase the moisture content of the cheese. Waxy corn starch, waxy rice starch, and instant tapioca starch all increased the moisture content of the cheeses significantly. However, when moisture contents of cheeses were over 61%, the body of the cheese visibly softened during storage, making the cheese very pasty. When starch-containing cheeses had moisture levels lower than that, the curd did not knit together well.

No description available.

Test procedures were developed for measuring the residual milk clotting activity of a protease produced by Endothia parasitica in curd and viii whey separated from freshly coagulated milk. A substrate was prepared by reconstituting 6 g low heat nonfat dry milk in 500 ml buffer containing 50 ml 0.5M cacodylic acid, 50 ml 0.2M CaCl2 , 30 ml 0.2M triethanolamine and 370 ml double distilled water. The substrate was stored at 2 to 4 C for 20 hours before use. Two milliliters of whey or supernatant from centrifuged curd-water slurries were inoculated into 25 ml of substrate at 30 C and the coagulation time noted, and compared with that produced by a known dilution of a standard enzyme solution. Endothia parasitica curd formed at pH 6.7 contained 45 per cent of the enzyme activity added to 454 g milk hut when formed at pH 5.2 the curd contained only 25 per cent. ix The recovery of Endothia parasitica protease in curd was made by preparing a 1:5 curd-water slurry, adjusting to pH 5.4, filtering and testing the filterate.

O presente estudo teve por finalidade avaliar os efeitos da contagem de células somáticas (CCS) no leite cru (nos níveis de 100-200.000, 400-500.000 e >800.000 céls./mL) sobre as características físicas, químicas, microbiológicas, sensoriais e funcionais dos queijos Minas Frescal e tipo Mussarela. Utilizou-se um delineamento experimental em parcelas subdivididas em blocos, considerando-se a contagem de células somáticas como efeito principal, os dias de análise como subparcelas e os processamentos como blocos. Cada tipo de leite foi obtido da ordenha de animais previamente selecionados de acordo com o nível de células somáticas. As etapas de elaboração dos queijos incluíram a pasteurização do leite (65º C, 30 minutos), adição de cloreto de cálcio, fermento (para a Mussarela) e coalho, coagulação e obtenção do coágulo, dessoragem, salga na massa, filagem, moldagem, salga na salmoura (para a Mussarela), e embalagem dos produtos. Os queijos foram mantidos em B.O.D. a 4 ºC e avaliados nos dias 2, 9, 16, 23 e 30 após a fabricação. A seqüência de elaboração dos queijos Minas e tipo Mussarela foi repetida 5 e 3 vezes, respectivamente, para cada tratamento. As análises realizadas nos queijos foram: pH, acidez, percentuais de gordura, matéria seca (MS), cinzas, nitrogênio total (NT), nitrogênio não protéico (NNP), nitrogênio não caseinoso (NNC), índice de proteólise, ácidos graxos livres (AGL), textura, avaliação sensorial, propriedades funcionais (capacidade de derretimento a 107 ºC e percentual de óleo livre - somente no queijo tipo Mussarela), contagem de mesófilos, psicrotróficos e número mais provável a 35 e 45 ºC. No queijo Minas Frescal, não houve interação entre CCS e dias de armazenamentos nas avaliações físico-químicas, microbiológicas, funcionais e índice de lipólise, porém houve efeito significativo (P<0,05) para índices de proteólise e profundidade da proteólise. Já para mesófilos, psicrotróficos, acidez, matéria seca, firmeza e ácidos graxos livres houve efeito significativo (P<0,05) ao avaliar dias de armazenamento. A avaliação sensorial, no primeiro dia de análise, não apresentou diferença significativa nos atributos, porém o queijo de alta CCS (> 800.000 céls./mL) diferiu dos demais no dia 30, em que recebeu menor nota em todas as características. No queijo tipo Mussarela, houve interação entre CCS e dias de armazenamento apenas para a capacidade de derretimento, resultando em aumento do derretimento no decorrer do tempo. Para as características de pH, ácidos graxos livres, índices de proteólise, extensão e profundidade da proteólise, mastigabilidade e elasticidade houve efeito significativo (P<0,05) para dias de armazenamento. Entre os atributos avaliados na sensorial, apenas a aparência apresentou diferença entre tratamentos. O rendimento dos queijos, Minas frescal e tipo Mussarela, não foram influenciados pela quantidade de células somáticas dos leites. Os resultados do trabalho indicaram que o leite destinado à fabricação dos queijos Minas e tipo Mussarela deve apresentar CCS até 400-500.000 céls./mL, de maneira a evitar alterações na qualidade dos produtos ao longo do período de armazenagem. / The aim of the present study was to evaluate the effect of somatic cells counts (SCC) in raw milk (at levels of 100-200,000, 400-500,000 and 800,000 cells./mL) on physical, chemical, microbiological, sensorial and functional characteristics of Minas frescal and Mozzarella type cheeses. A completely randomized block design was used, considering SCC as the main effect, the days of analysis as sub parcels and the processing batches as the blocks. Each type of milk was obtained from cows previously selected according to its individual SCC. The manufacture of cheeses included: pasteurization of milk (65ºC, 30 minutes), addition of calcium chloride, starter culture (for Mozzarella) and rennet, coagulation and separation of the curd, whey drainage, salting (for Minas cheese), stretching of the curd, kneading and salting in brine (for Mozzarella), and packing the products. The cheeses were stored in a B.O.D. oven at 4ºC and evaluated on days 2, 9, 16 23 and 30 after the manufacture. The sequence of elaboration of the Minas frescal and Mozzarella cheeses was repeated 5 and 3 times, respectively, for each treatment. The analyses carried out in the cheeses were: pH, acidity, percentages of fat, dry matter (DM), ashes, total nitrogen (NT), non-protein-nitrogen (NPN), non-casein nitrogen (NCN), proteolysis, free fatty acids (FFA), texture, sensorial evaluation, functional properties (melting capacity the 107 ºC and percentage of free oil - only in the cheese Mozzarella), mesophile and psychrotrophic counts and the most probable number at 30 and 45ºC. For Minas frescal cheese, no interaction was found between SCC and days of storage when considering the data on chemical, physical, microbiological, functional and lipolysis index. However, a significant effect (P<0.05) was observed for proteolysis and depth of proteolysis. For mesophiles, psychrotrophics, acidity, dry matter, firmness and free fatty acids, there was a significant effect (P<0.05) for days of storage. The sensorial evaluation made on the first day of analysis did not present significant differences for all attributes. However, the Minas cheese made with high SCC (800,000 cells/mL) differed on day 30, when it received worse grades for all the attributes. For the Mozzarella cheese, an interaction between SCC and days of storage was observed only for the melting capacity, which resulted in an increment of the melting along the time of storage. The parameters of pH, free fatty acid, proteolysis, extension and depth of proteolysis, springiness and elasticity had significant effect (P<0.05) for days of storage. Amongst the attributes evaluated in the sensorial, only the appearance presented difference between treatments. The yield of Minas frescal and Mozzarella cheese was not influenced by the amount of somatic cells in the original milk. Results indicated that milk used for the manufacture of Minas frescal and Mozzarella cheeses should present SCC up to 400-500,000 cells/mL, in order to avoid quality changes in those products during storage.

A processing procedure for the manufacture of directly acidified cottage cheese curd from 16% total solids ultrafiltered retentate was developed. The effects of preacidification of skim milk before ultrafiltration and heat treatment of retentate were investigated to improve the functional and sensory qualities of retentate curd. Retentate directly acidified with phosphoric acid and glucono-delta-lactone to pH 4.7 formed a dense, rubbery curd that could not be handled well in a vat. A heat treatment of 71.1°C for 30 min applied to the retentate resulted in a curd with acceptable handling properties. However, this heat treatment caused the curd to shift in pH, become translucent in appearance, and have a pasty texture. Preacidification of the skim milk to pH 5.8 12 h prior to ultrafiltration, and a less severe heat treatment of 71.1°C for 6 min made a stable curd with good sensory quality. A 3 x 4 x 3 randomized split block design experiment was done to test the effects of preacidification and heat treatment on the properties of retentate curd. Skim milk was pasteurized at 62.8°C for 30 min and split into three lots which were unacidified, phosphoric acid added to pH 6.2, and phosphoric acid added to pH 5.85. The three lots of skim milk were ultrafiltered at 54.4°C to 16% total solids. Each lot was divided into four treatments which were unheated, heated to 71.1°C for 7 s, 76.7°C for 7 s, and 82.2°C for 7 s. Each vat was replicated three times. Cottage cheese pH, total solids, and six sensory attributes were measured. Finished cottage cheeses were evaluated by an expert panel of five judges. Total solids, protein content, and fines content of the whey were also measured. Preacidification treatment at pH 6.2 enhanced curd structure, which increased solids recovery, reduced fines, and improved curd appearance, firmness, and texture. Heat treatments caused softening of the curd and increased moisture content in the curd. Excessive heat treatment caused shattering, fines, and mealiness. The best curd from the experiment was produced from pH 6.2 retentate heat treated at 71.1°C for 7 s. Whey proteins decreased in wheys from retentates heat treated at 76.7°C for 7 sand 82.2°C for 7 s. The effects of heat treatment were more pronounced with increasing acidification.

The effects of whey-based and milk -based starter media, and low concentrations (0.02% each) of citrate, phosphate and calcium upon various milk coagulation properties were measured. Samples inoculated with milk-based starter medium had shorter coagulation times, faster rate of curd formation, and greater final curd firmness than those inoculated with externally neutralized whey-based starter. Starter medium treatment was statistically interacted with calcium for coagulation time and rate of curd formation. Citrate addition caused longer coagulation times, slower rates of curd formation, and weaker final coagula. Citrate interacted with calcium and phosphate for several of the parameters measured. Addition of phosphate did not affect any of the measured parameters but was involved in several significant two-factor interactions as was calcium addition.

A procedure was developed for measuring residual rennin activity in curd extracts and whey. A sensitive substrate at pH 5.8 was prepared by mixing 6 grams of low-heat nonfat dry milk in 500 milliliters buffer containing 0.05 molar cacodylic acid, 0.02 molar calcium chloride, and 0.012 molar triethanolamine, and storing it at 2 degrees centigrade for 18 hours. Two milliliters of whey or curd extract were inoculated into 25 milliliters of substrate at 30 degrees centigrade. The coagulation time was measured and compared to that induced by 2 milliliters of a known rennin concentration added at the same time to identical substrate. Recovery of activity was determined by adjusting milk samples to pH 5.20 and coagulating them with a known concentration of rennin. The clot was broken by agitation and the curd separated from the whey by centrifugation. Activities accounted for in the curd and whey amounted to 91±1.6 per cent the activity added to the milk. Maximum release of activity from curd was achieved by diluting the curd 1:15 with water and adjusting the pH to 6.80. Inclusion of curd particles with the inoculum decreased the sensitivity of the substrate.

Curd syneresis, a critical step in cheesemaking, directly influences the quality of cheese. The syneresis process is empirically controlled in cheese manufacturing plants. A sensor technology for this step would improve process control and enhance cheese quality. A light backscatter sensor with a Large Field of View (LFV) was tested using a central composite design over a broad range of cheese process conditions including milk pH, calcium chloride addition level, milk fat to protein ratio, temperature, and a cutting time factor (β). The research objectives were to determine if the LFV sensor could monitor coagulation and syneresis steps and provide information for predicting pressed curd moisture. Another objective was to optimize cheese yield and quality. The LFV sensor was found to monitor coagulation and syneresis and provide light backscatter information for predicting curd moisture content. A model for relating final curd moisture content with light backscatter response was developed and tested. Models for predicting whey fat losses, pressed curd moisture, and cheese yield were successfully developed (R2>0.75) using the test factors as independent variables. This was the first attempt to develop a technology for controlling pressed curd moisture using a sensor to monitor the syneresis step.

Submitted by (edna.saturno@ufrpe.br) on 2016-07-26T13:34:20Z No. of bitstreams: 1 Hayanna Adlley Santos de Arruda.pdf: 941142 bytes, checksum: 4082df66e0edafbe7aa83a99d239011b (MD5) / Made available in DSpace on 2016-07-26T13:34:20Z (GMT). No. of bitstreams: 1 Hayanna Adlley Santos de Arruda.pdf: 941142 bytes, checksum: 4082df66e0edafbe7aa83a99d239011b (MD5) Previous issue date: 2013-02-27 / Numerous functional products are commercially available and variety of products continues to expand. Much research in terms of probiotics and prebiotics are fermented products, as well as those products having great acceptance by the general public have excellent nutritional value and are potential vehicles for the use of these substances. According to Brazilian legislation, the following definitions apply curd product derived from the fermentation of milk by specific bacteria, mesophilic, producing lactic acid. Given the above this study aimed to develop different formulations curd, added probiotic cultures and fructooligosaccharides, passion fruit flavor, as well as select which present better performance in sensory evaluation, assessing their stability during storage from physical-chemical and microbiological. From an experimental design were developed five tests: with skim milk curd with 8g of FOS, with whole milk curds with 8g of FOS, curd with skim milk with 16g of FOS, curd milk with 16g of FOS with milk and curds semi-skimmed 12g FOS. The formulations prepared were well accepted by consumers for all attributes evaluated in the sensory test, index acceptability and purchase intent. Two formulations (with 8 and 16g FOS / 1000 mL of whole milk, tests 2 and 4, respectively) were selected because they have better performance in sensory evaluation and evaluated for stability from physical-chemical and microbiological properties in periods 1 7, 14, 21 and 28 days of storage. During the storage time the formulations show variations of pH and acidity, yet not lead to undesirable changes in the final product. Also showed satisfactory results for counts of Lactobacillus Acidophilus, Streptococcus Thermophilus, Bifidobacterium bifidum, being above the minimum recommended by the current legislation, in addition to satisfactory sanitary conditions, lack of contamination by microorganisms such as total coliforms, Escherichia coli, Staphylococcus aureus, coagulase positive, standard counting aerobic bacteria, molds and yeasts. Therefore, it is concluded that the use of probiotic microorganisms and fructooligosaccharides in formulating curds provided the preparation of a product sensory quality, nutritional and technological. / Inúmeros lacticínios funcionais são disponíveis comercialmente e a variedade desses produtos continua em expansão. Muitas pesquisas em termos de probióticos e prebióticos encontram-se voltadas para produtos fermentados, pois além destes produtos possuírem grande aceitação pelo público em geral apresentam excelente valor nutritivo e são veículos em potencial para o consumo dessas substâncias. Segundo a Legislação Brasileira, entende-se por Coalhada o produto oriundo da fermentação do leite, por bactérias específicas, individuais ou mistas, mesófilas, produtoras de ácido lático. Diante do exposto esta pesquisa teve como objetivo desenvolver diferentes formulações de coalhada, adicionadas de culturas probióticas e frutooligossacarídeos, sabor maracujá, bem como selecionar as que apresentarem melhor índice de aceitabilidade, avaliando sua estabilidade durante o armazenamento a partir de análises físico-químicas e microbiológicas. A partir de um planejamento experimental foram desenvolvidos 5 ensaios: coalhada com leite desnatado com 8g de FOS, coalhada com leite integral com 8g de FOS, coalhada com leite desnatado com 16g de FOS, coalhada com leite integral com 16g de FOS e coalhada com leite semi-desnatado com 12g de FOS. As formulações elaboradas foram bem aceitas pelos provadores para todos os atributos avaliados no teste sensorial, teste de aceitação e intenção de compra. Duas formulações (com 8 e 16g de FOS/ 1000 mL de leite integral, ensaios 2 e 4, respectivamente) foram selecionadas por apresentarem melhor índice de aceitabilidade e submetidas à avaliação da estabilidade a partir de análises físico-químicas e microbiológicas nos períodos 1, 7, 14, 21 e 28 dias de estocagem. A partir dos resultados obtidos constatou-se que os valores encontrados nas duas formulações quanto à composição centesimal estão dentro dos padrões estabelecidos para este tipo de produto. Durante o tempo de estocagem, as formulações apresentaram variações de pH e acidez, contudo não levou a alterações indesejáveis no produto final. Também apresentaram resultados satisfatórios para contagens de Lactobacillus Acidophilus, Streptococus Thermophilus, Bifidobacterium Bifidum, sendo superiores ao mínimo preconizado pela legislação vigente, além de qualidade higiênico-sanitária satisfatória, pela ausência de contaminação por microrganismos como: Coliformes totais, Escherichia coli, Staphylococcus aureus, Estafilococos coagulase positiva, contagem padrão de bactérias aeróbias e bolores e leveduras. Portanto, conclui-se que a utilização de microrganismos probióticos e frutooligossacarídeos na formulação de coalhadas proporcionou a elaboração de um produto com qualidade sensorial, nutricional e tecnológica.