Caracterização de propriedades físicas do leite de diferentes espécies: ferramenta para aplicação de ultrassom
Carregando...
Data
2022-10-05
Autores
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
O leite é um produto importante na alimentação humana devido a seu elevado valor nutricional, e utilizado como ingrediente em diversos tipos de alimentos. Diferentes processos industriais são aplicados ao leite para consumo como leite fluido, assim como para a fabricação de diversos derivados, tais como queijos, leites fermentados, manteiga, leites concentrados e desidratados, entre outros. Esses processos são essenciais para garantir segurança e qualidade ao produto final. O conhecimento das propriedades termofísicas dos alimentos, tal como o calor específico e viscosidade, são necessários para o dimensionamento de projetos térmicos, bem como a determinação do campo acústico em processos que envolvam o uso do ultrassom (US). Este trabalho objetivou determinar o calor específico e a viscosidade de leite de quatro diferentes espécies (vaca, búfala, cabra e ovelha) em uma ampla faixa de temperatura (1 – 90°C), propor um modelo matemático para descrever os dados experimentais, comparar os modelos obtidos com as equações tradicionais, determinar o campo acústico, assim como testar o efeito da aplicação de US ao leite cru recém ordenhado, para as espécies de vaca e cabra, a fim de analisar a conservação. A composição química do leite foi determinada para verificar sua influência no calor específico e na viscosidade. O calor específico aumentou com a temperatura e é maior para leite com baixos teores de sólidos e de lipídeos. Os modelos polinomiais de primeira e segunda ordem melhor se ajustaram aos dados experimentais do calor específico em função da temperatura. A viscosidade do leite das diferentes espécies foi descrita pela Lei de Newton e a influência da temperatura na viscosidade foi descrita pela equação de Arrhenius. O campo acústico foi determinado para potências nominais de 300, 500 e 700W, com eficiência decrescente à medida que se aumentou a potência nominal, de 18,8 a 12,9%. O leite de cabra apresentou valores mais altos de eficiência comparado ao leite de vaca, provavelmente em função da estrutura dos glóbulos de gordura. Os teores de lipídeos e de proteínas e a acidez titulável foram determinados para verificar a ação do US, imediatamente após tratamento e após 7 dias sob refrigeração. Nas condições estudadas, US alterou as características do leite, evidenciado pelo aumento da acidez, que aumentou em potências mais elevadas. Estudos adicionais, incluindo uma maior diversidade de análises se fazem necessários para melhor entendimento do aumento da acidez com a aplicação de US.
Milk is an important product in human nutrition due to its high nutritional value, and it has been used as an ingredient in several types of food. Different industrial processes are applied to milk for consumption as fluid milk, as well as to the manufacture of various dairy products, such as cheese, fermented milk, butter, concentrated and dehydrated milk, among others. These processes are essential to guarantee the safety and quality of the final product. The knowledge of thermophysical properties of foods, such as specific heat and viscosity, are necessary for the design of thermal projects, as well as the determination of the acoustic field in processes involving the use of ultrasound (US). This study aimed to determine the specific heat and viscosity of milk from four different species (cow, buffalo, goat and sheep) over a wide temperature range (1 - 90°C), to propose a mathematical model to describe the experimental data, to compare the obtained models with the traditional equations, as well as determining the acoustic field and testing the effect of US applying to freshly milked raw milk, for cow and goat species, in order to evalute its preservation. The chemical composition of milk was determined to verify its influence on specific heat and viscosity. The specific heat increased with temperature and it is higher for milk with low solids and lipids. The first and second order polynomial models best fit the experimental data of specific heat as a function of temperature. The milk viscosity from diferent species was described by Newton model and the influence of the temperature in the viscosity was described by Arrhenius equation. The acoustic field was determined for nominal input power of 300, 500 and 700W, with efficiency from 18.8 to 12.9%, decreasing as the nominal input power increased. The goat milk showed higher values of efficiency than in cow's milk, probably due to its structure of fat globules. Analysis of lipids and protein content, and acidity were determined to verify the action of US, immediately after US treatment and after 7 days under refrigeration. Under the studied conditions, US altered the milk’ characteristics, as evidenced by the increase in acidity, which increased in higher power. Further studies, including a greater diversity of analyzes are necessary for a better understand the increase in acidity with US.
Milk is an important product in human nutrition due to its high nutritional value, and it has been used as an ingredient in several types of food. Different industrial processes are applied to milk for consumption as fluid milk, as well as to the manufacture of various dairy products, such as cheese, fermented milk, butter, concentrated and dehydrated milk, among others. These processes are essential to guarantee the safety and quality of the final product. The knowledge of thermophysical properties of foods, such as specific heat and viscosity, are necessary for the design of thermal projects, as well as the determination of the acoustic field in processes involving the use of ultrasound (US). This study aimed to determine the specific heat and viscosity of milk from four different species (cow, buffalo, goat and sheep) over a wide temperature range (1 - 90°C), to propose a mathematical model to describe the experimental data, to compare the obtained models with the traditional equations, as well as determining the acoustic field and testing the effect of US applying to freshly milked raw milk, for cow and goat species, in order to evalute its preservation. The chemical composition of milk was determined to verify its influence on specific heat and viscosity. The specific heat increased with temperature and it is higher for milk with low solids and lipids. The first and second order polynomial models best fit the experimental data of specific heat as a function of temperature. The milk viscosity from diferent species was described by Newton model and the influence of the temperature in the viscosity was described by Arrhenius equation. The acoustic field was determined for nominal input power of 300, 500 and 700W, with efficiency from 18.8 to 12.9%, decreasing as the nominal input power increased. The goat milk showed higher values of efficiency than in cow's milk, probably due to its structure of fat globules. Analysis of lipids and protein content, and acidity were determined to verify the action of US, immediately after US treatment and after 7 days under refrigeration. Under the studied conditions, US altered the milk’ characteristics, as evidenced by the increase in acidity, which increased in higher power. Further studies, including a greater diversity of analyzes are necessary for a better understand the increase in acidity with US.
Descrição
Palavras-chave
Leite, Modelagem matemática, Processos térmicos, Viscosidade, Calor específico, Campo acústico, Acidez, Milk, Mathematical modeling, Thermal processes, Viscosity, Specific heat, Acoustic field, Acidity