Using proteinase negative variants of Streptococcus cremoris UC310 or UC320 to manufacture cottage cheese, theoretical yields were increased 1 .97% and 1 .56% respectively when compared to the theoretical yields of the proteinase positive parents. Yield differences were strain dependant and differences between positive and negative variants were not manifest with strains of UC73 and UC97. It was necessary to produce bulk culture using pH control and to add sufficient nitrogenous stimulant to provide carry-over stimulant into the cheese milk. All cultures examined developed normally even when the bulk medium contained a blend of 5% yeast extract and casein hydrolysate. It was possible to use the culture to complete the required acidification after direct acidification to pH 5.2 with phosphoric acid. Careful selection of lactic

Protein quality in freeze-dried skimmilk (SM), regular cottage cheese (RCC), retentate (Ret) and cottage cheese made from ultrafiltrated skimmilk (UFCC) were evaluated by chemical (amino acid score) and biological methods. Biological evaluation was at 5, 8 and 11% protein level in growing rats by measuring biological value (BV), net protein utilization (NPU) and nitrogen efficiency for growth (NEG) over a 14-day period. A 28-day protein efficiency ratio (PER) was determined on the same products at 10% protein level. Effects of added lactose on PER of retentate, regular and UFCC were also evaluated. The most limiting amino acids were cystine + methionine. Amino acid score for Animal Nutrition Research Council (ANRC) reference casein, SM, RCC, Ret and UFCC was 0.72, 0.91, 0.87, 0.91 and 0.98 respectively according to Food and Agricultural Organization/World Health Organization (FAO/WHO) pattern and 0.45, 0.56, 0.54, 0.57 and 0.61 respectively according to whole egg pattern. PER was 2.7, 3.0, 2.7, 3.1 and 2.8 for ANRC reference casein, SM, RCC, Ret and UFCC respectively. PER for retentate and skimmilk were significantly different from the cottage cheese. No significant difference in protein quality was obtained when the products were fed at 5, 8 and 11% levels. Average BV was 93, 91, 91, 95 and 94 for ANRC reference casein, SM, RCC, Ret and UFCC respectively. Average NPU was 87, 84, 83, 85 and 85 for ANRC reference casein, SM. RCC, Ret and UFCC respectively. Average NEG values were 66, 73, 70 77 and 73 for ANRC reference casein, SM, RCC, Ret and UFCC respectively. PER values were 2.7, 3.0, 2.7, 3.1 and 2.8 for ANRC reference casein, SM, RCC, Ret and UFCC respectively. Addition of lactose to a level equal to that in skimmilk reduced the PER value of RCC, Ret and UFCC by about 4%, 6% and 4% respectively. Though no significant difference in protein quality of the products were obtained, there was a tendency of ultrafiltration to increase protein quality.

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.

Three different methods of acidifying skim milk(milk starter, whey base starter and direct acid set) for making cottage cheese were evaluated for their effect on yield, quality and acidification cost. Cultured cottage cheese was produced with milk starter and pH controlled whey-base starter by the short set method. Five percent milk starter and 2.4% whey base starter were approximately equivalent in activity and gave average setting times of 234 to 255 minutes. Direct acid set cottage cheese was made by the Vitex/American method. The setting time required for direct acid set cottage cheese was 158 minutes. Yields of cottage cheese made by direct acid set were significantly higher than with the two cultured methods. Mean yield for direct acid set was 16.1%, the milk starter yield was 14.5% and the whey base method gave a yield of 14.8%. Protein in the milk starter was less efficiently recovered in the cottage cheese curd than the protein in pasteurized milk. The direct acid set method produced cottage cheese curd that was more mealy than the curd produced by cultured methods, but was still equal in over-all quality to curd made by milk starter methods. The cottage cheese produced by the different acidification methods were judged superior to commercially made direct acid and commercial cultured cottage cheese by an panel of trained judges. Cottage cheese made by whey base starter was preferred over all of the other cottage cheese. Acidification costs per kilogram of cottage cheese curd were $0.54 for milk starter, $0.019 for whey base starter and $0.114 for direct acid set curd. Overall ingredient cost per 1,000 Kg of skim milk set were $160.04, $154,43 and $170.17 respectively. Saving in time with direct acid set methods probably offset the additional cost of ingredients.

Pasteurized skimmilk at 4°C was acidified to pH 5.8 with 85.5% phosphoric acid (136g H3Po4;100 kg skimmilk), then warmed to 54°C and ultrafiltered to a protein concentration 9.1 ± 0.2%. The retentate was heated to 76.5°C for 16 s then cooled to 2°C. Phosphoric acid (85.5%) was added at a rate of 3.41g per kg retentate. The acidified retentate was slowly warmed to 29.5 °C (3°C/5 min) when the pH was checked. The pH at this point was no lower than 5.4. Heating was continued until a temperature of 32.2°C was reached. Glucono delta lactone was added to the retentate (17.6 g/kg retentate) and left undisturbed for approximately 80 min. The curd was cut at pH 4.7 with 0.64 cm curd knives and allowed 10 min for syneresis. Permeate obtained from the same lot of milk was acidified to pH 4.8 (66 g H3Po4;100 kg permeate), then added to the curd at 32.2°C (three parts permeate to four parts retentate) and used as a cooking vehicle. The curd was cooked to 59°C in 90 min. The curd was held at 59°C for 10 min, drained and washed once with ice water. Cream dressing containing 12.5% fat and 3% salt was used at the rate of two parts curd to one part dressing. Control cottage cheese was produced by a direct acid method from the same skimmilk used to produce ultrafiltered curd. Use of ultrafiltered skimmilk retentate for cottage cheese making resulted in 2.24% more curd (corrected to 20% solids) and 2.24% more curd per kg original milk protein than the control. However, satisfactory firmness in UF curd required slightly more than 20% solids in the final product. Sensory evaluations indicated that creamed cottage cheese was not significantly different (p

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The growing popularity of functional foods, has promoted advances in the research of new products, specially in the dairy industry. The objective of this study was to evaluate the influence of different levels of fat and inulin on the physicochemical and sensorial characteristics, instrumental color and texture, and viability of probiotic cultures of cottage cheese with the addition of Streptococcus termophilus, Lactobacillus acidophilus La - 5 and Bifidobacterium Bb 12, during storage for 21 days at 4 ± 1 °C. Twelve treatments of cottage cheese were elaborated with different fat and inulin concentrations according to a central composite design with 4 repetitions on the central point. Significant changes were observed on the physicochemical characteristics (tritable acidity, protein, fat, salt, moisture and ash) due to the different levels of fat and inulin in the cheeses. The assessment of the sensory attributes (global appearance, aroma, texture, acidity and taste) was carried out using a test with hedonic scale of 7 levels and an ordering test. The surface response showed different areas with tendency to better acceptance, varying according to the sensory attribute, in spite of no significant difference having been found by Tukey s test (p> 0.05). Only the linear and interaction of multiple linear regression terms were significant (p< 0.05) for the aroma sensory attribute; only the intercept of the equation of each attribute was significant (p< 0.05). The differences in the lipid profile were related to different fat levels in each formulation. The surface response was done to verify the influence of different levels of fat and inulin on pH and tritable acidity during storage; only linear terms of fat and inulin levels were significant (p< 0.05). The pH and tritable acidity affect the viability of the cultures during all the storage period. Streptococcus termophilus, Lactobacillus acidophilus e Bifidobacterium animalis had counts above 7 UFC g-1 during all the period, assuring the probiotic potential in all the cottage cheese formulations. The extent proteolysis increased significantly during storage, but this change has no reduce the firmness of the cheeses. The parameters of instrumental color and texture vary significantly (p< 0.05) between 1 and 21 days of storage for most formulations, but these results did not affect the acceptability of the tasters. / A crescente popularidade dos alimentos funcionais tem promovido avanços nas pesquisas com novos produtos, principalmente no setor de laticínios. O objetivo deste estudo foi avaliar a influência de diferentes concentrações de gordura e de prebiótico (inulina) sobre as características físico-químicas, sensoriais, cor e textura instrumental, bem como a viabilidade das culturas probióticas em queijo cottage adicionado de Streptococcus termophilus, Lactobacillus acidophilus La - 5 e Bifidobacterium Bb 12, durante o armazenamento por 21 dias a 4 ± 1 °C. Doze ensaios de queijo cottage foram elaborados com diferentes concentrações de gordura e inulina planejados através do Delineamento Central Composto Rotacional com quatro repetições no ponto central. Foi observada mudança significativa (p< 0,05) nas características físico-químicas (acidez, proteína, gordura, cloretos, umidade e cinzas) conforme as variações dos teores de gordura e inulina dos queijos. A avaliação dos atributos sensoriais (aparência geral, aroma, textura, acidez e sabor) foi realizada através de teste com escala hedônica de 7 níveis e teste de ordenação. As superfícies de resposta geradas mostraram diferentes regiões com tendência à melhor aceitação, variando cada região conforme o atributo analisado, apesar de não ter sido encontrada diferença estatística pelo Teste de Tukey (p> 0,05) nestas avaliações. Apenas o termo linear e de interação da regressão linear múltipla foram significativos (p< 0,05) para o atributo aroma; somente o intercepto da equação de cada atributo apresentou significância estatística (p< 0,05). Para o perfil lipídico, as diferenças significativas observadas foram atribuídas aos diferentes teores de gordura de cada formulação. A superfície de resposta foi elaborada para verificar a influência das diferentes concentrações de gordura e inulina sobre a acidez (expressa em ácido láctico) e o pH das formulações durante o armazenamento, tendo somente o termo linear da concentração de gordura e inulina apresentado significância (p< 0,05). O pH e acidez titulável das formulações influenciaram a viabilidade das culturas durante todo o armazenamento. Os Streptococcus termophilus, Lactobacillus acidophilus e Bifidobacterium animalis apresentaram contagens acima de 7 UFC g-1 durante todo o período, garantindo a potencialidade probiótica de todas as formulações. A extensão da proteólise aumentou significativamente durante o armazenamento, mas esta mudança não reduziu a firmeza dos queijos. Os parâmetros de cor e textura instrumental variaram significativamente (p< 0,05) entre o 1º e 21º dia de armazenamento para a maioria das formulações, mas estes resultados não interferiram na aceitabilidade dos provadores.