A study was conducted to investigate the use of bacterial numbers and metabolites for their Value in predicting potential shelf-life of pasteurized fluid milk. The study consisted of two phases. In the first phase, chemical inhibitors were evaluated for their ability to allow growth of gram-negative psychrotrophic bacteria while inhibiting growth of gram-positive organisms. Crystal violet, benzalkonium chloride, a mixture of crystal violet and benzalkonium chloride, and alkylaryl sulfonate were tested. These were incubated with milk samples separately inoculated with gram-negative and gram-positive bacteria, at 2l°C for 18 hours. Alkylaryl sulfonate allowed growth of gram-positive organisms. Crystal violet inhibited gram-positive organisms but was not as effective as the mixture of crystal violet and benzalkonium chloride, The inhibitor of choice was benzalkonium chloride as it inhibited growth of all gram-positive organisms tested and allowed growth of the gram-negative psychrotrophic organisms. / Master of Science

O objetivo desse estudo foi validar a aplicação da metodologia isotópica de identificação da origem dos gliceróis em gorduras presentes em requeijões e especialidades lácteas com o intuito de oferecer uma ferramenta de controle de qualidade, de fiscalização de mercado e detecção de fraudes. Para atingir esse objetivo, isolou-se o glicerol de compostos lácteos como requeijões, especialidades lácteas, leite e óleos vegetais (empregados como padrões de origem animal e vegetal, respectivamente) e aplicou-se a metodologia isotópica. O glicerol foi isolado através da centrifugação. Foram analisadas todas as marcas de requeijões e similares (28 marcas) disponíveis nos supermercados da cidade de Piracicaba, e depois, agrupadas conforme sua identificação: requeijão cremoso, especialidade láctea com requeijão cremoso, alimento à base de requeijão e creme vegetal, requeijão cremoso com amido e não identificado. Do total, cinco marcas apresentaram resultados com diferença significativa (p<0,05) quando comparados ao controle (padrão animal - leite). A metodologia isotópica permitiu identificar a origem do material analisado e detectar alterações nos padrões. Comprovou-se a eficácia da metodologia isotópica na identificação da origem da matéria graxa de requeijões e a aplicabilidade da técnica no controle de qualidade de lácteos, auxiliando tanto no recebimento de matéria-prima como de produto final. / The objective of this study was to validate the application of the isotopic methodology of identification of glycerol origin in the fat fraction of "requeijões" (Brazilian soft cheeses) and similar products aiming at the identification of a quality control instrument for market fiscalization and fraud detection. In order to pursue the specific objectives of this study, the glycerol was isolated from spreadable dairy products such as "requeijões" and others. Cow's milk and vegetable oils of known origins were adopted as standards. The isotopic methodology was applied to identify the origin of the carbon present in the glycerol molecule of the fats present in those foods. Glycerol was isolated according to a conventional based on centrifugation. Twenty-eight commercial brands of "requeijões" available in the supermarkets of Piracicaba city were classified according to the information provided in the lables and analyzed. Out of the total, 5 brands were significantly different (p<0,05) when compared to the control (animal pattern - milk), indicating absence of the milk fat in the formulation. The isotopic methodology allowed to identify the origin of the analyzed material and to detect alterations in the patterns. The effectiveness of the isotopic methodology in the identification of origin of the lipid constituents of "requeijão" was proven as well as the applicability of the technique in dairy industry quality control, both in the final product as well as in process supplies.

There is growing public concern about the high proportion of saturated fatty acids in milk fat; however, feed intake, energy partitioning toward milk synthesis, and milk fat concentrations can decrease when cows are fed high concentrations of unsaturated lipids. The objective of this study was to identify the optimal rate for feeding OmegaBoostTM (a flaxseed supplement that was processed using a proprietary technique by Double Pass LLC, Tualatin, OR) to dairy cows. The central hypothesis was that supplementation with OmegaBoost will decrease the proportion of saturated fatty acids in milk fat in a dose dependent manner. Using a latin-square design, 10 Holstein cows in mid to late lactation were fed for two-week periods 0, 2, 4, or 6 lbs/d of OmegaBoost or 4lbs/d ground flax as top dressing to their total mixed ration. Feed intake, body weight, activity and resting time, milk production and milk composition were measured daily. At the end of each two-week period, milk and serum samples were taken and analyzed for fatty acid composition using gas chromatography. In addition, fresh Mozzarella cheese and butter was manufactured and tested to determine the fatty acid composition and the effects of flaxseed supplementation on texture. Feeding OmegaBoost at 2, 4, and 6 lbs/d linearly decreased the proportion of saturated fatty acids in milk by 6, 15, and 18%, respectively, and linearly increased the proportion of mono-unsaturated fatty acids (14, 32, and 35%), poly-unsaturated fatty acids (16, 49, and 82%), and α-linolenic acid (26, 52, and 70%). Similar changes in fatty acid composition were observed in butter and cheese samples, resulting in butter that was less hard and adhesive at refrigeration temperature in response to feeding cows increasing concentrations of OmegaBoost. Feed intake, body weight, serum metabolite concentrations, milk production and composition, and butter and cheese yield were not significantly affected by feeding processed flaxseed. Therefore, feeding 4 or 6 lbs/d of OmegaBoost to dairy cows is effective in improving the nutritional and textural profile of dairy products without negatively affecting feed intake, milk production, or weight gain. / Graduation date: 2012

O objetivo desse estudo foi validar a aplicação da metodologia isotópica de identificação da origem dos gliceróis em gorduras presentes em requeijões e especialidades lácteas com o intuito de oferecer uma ferramenta de controle de qualidade, de fiscalização de mercado e detecção de fraudes. Para atingir esse objetivo, isolou-se o glicerol de compostos lácteos como requeijões, especialidades lácteas, leite e óleos vegetais (empregados como padrões de origem animal e vegetal, respectivamente) e aplicou-se a metodologia isotópica. O glicerol foi isolado através da centrifugação. Foram analisadas todas as marcas de requeijões e similares (28 marcas) disponíveis nos supermercados da cidade de Piracicaba, e depois, agrupadas conforme sua identificação: requeijão cremoso, especialidade láctea com requeijão cremoso, alimento à base de requeijão e creme vegetal, requeijão cremoso com amido e não identificado. Do total, cinco marcas apresentaram resultados com diferença significativa (p<0,05) quando comparados ao controle (padrão animal – leite). A metodologia isotópica permitiu identificar a origem do material analisado e detectar alterações nos padrões. Comprovou-se a eficácia da metodologia isotópica na identificação da origem da matéria graxa de requeijões e a aplicabilidade da técnica no controle de qualidade de lácteos, auxiliando tanto no recebimento de matéria-prima como de produto final. / The objective of this study was to validate the application of the isotopic methodology of identification of glycerol origin in the fat fraction of "requeijões" (Brazilian soft cheeses) and similar products aiming at the identification of a quality control instrument for market fiscalization and fraud detection. In order to pursue the specific objectives of this study, the glycerol was isolated from spreadable dairy products such as "requeijões" and others. Cow's milk and vegetable oils of known origins were adopted as standards. The isotopic methodology was applied to identify the origin of the carbon present in the glycerol molecule of the fats present in those foods. Glycerol was isolated according to a conventional based on centrifugation. Twenty-eight commercial brands of "requeijões" available in the supermarkets of Piracicaba city were classified according to the information provided in the lables and analyzed. Out of the total, 5 brands were significantly different (p<0,05) when compared to the control (animal pattern - milk), indicating absence of the milk fat in the formulation. The isotopic methodology allowed to identify the origin of the analyzed material and to detect alterations in the patterns. The effectiveness of the isotopic methodology in the identification of origin of the lipid constituents of "requeijão" was proven as well as the applicability of the technique in dairy industry quality control, both in the final product as well as in process supplies.