Identifying adulteration of raw bovine milk with urea through electrochemical impedance spectroscopy coupled with chemometric techniques.

This study aimed to evaluate the applicability of electrochemical impedance spectroscopy to identify raw bovine milk adulteration with urea. Three batches of raw milk adulterated with urea were studied. Hierarchical clustering indicated that the samples could be split in three groups corresponding to low adulteration (less than 7 wt%), medium adulteration (between 8 and 16 wt%) and high adulteration (over than 16 wt%). A linear discriminant analysis was performed resulting in 90% of accuracy in classifying between groups. Besides, a partial least squares model containing three directions provided good accuracy in quantitatively predicting the urea mass fraction added to raw bovine milk. Finally, calculations using an approximated electric circuit model suggested the formation of urea aggregates that hinder charge transportation within the milk thus diminishing the solution conductivity. Results indicate that electrochemical impedance spectroscopy can be a useful, low cost and rapid tool to identify milk adulteration with urea.

Modeling Salmonella spp. inactivation in chicken meat subjected to isothermal and non-isothermal temperature profiles.

Salmonella genus has foodborne pathogen species commonly involved in many outbreaks related to the consumption of chicken meat. Many studies have aimed to model bacterial inactivation as a function of the temperature. Due to the large heterogeneity of the results, a unified description of Salmonella spp. inactivation behavior is hard to establish. In the current study, by evaluating the root mean square errors, mean absolute deviation, and Akaike and Bayesian information criteria, the double Weibull model was considered the most accurate primary model to fit 61 datasets of Salmonella inactivation in chicken meat. Results can be interpreted as if the bacterial population is divided into two subpopulations consisting of one more resistant (2.3% of the total population) and one more sensitive to thermal stress (97.7% of the total population). The thermal sensitivity of the bacteria depends on the fat content of the chicken meat. From an adapted version of the Bigelow secondary model including both temperature and fat content, 90% of the Salmonella population can be inactivated after heating at 60 °C of chicken breast, thigh muscles, wings, and skin during approximately 2.5, 5.0, 9.5, and 57.4 min, respectively. The resulting model was applied to four different non-isothermal temperature profiles regarding Salmonella growth in chicken meat. Model performance for the non-isothermal profiles was evaluated by the acceptable prediction zone concept. Results showed that >80% of the predictions fell in the acceptable prediction zone when the temperature changes smoothly at temperature rates lower than 20 °C/min. Results obtained can be used in risk assessment models regarding contamination with Salmonella spp. in chicken parts with different fat contents.

Effect of the addition of antimicrobial oregano (Origanum vulgare) and rosemary (Rosmarinus officinalis) essential oils on lactic acid bacteria growth in refrigerated vacuum-packed Tuscan sausage.

Lactic acid bacteria are the main bacterial group associated to meat spoilage. Herbal essential oils are promising alternatives that can be used to retard lactic acid bacterial growth and extend shelf life of meat products. In this study, the influence of oregano and rosemary essential oils on the growth of lactic acid bacteria and the physicochemical properties of refrigerated vacuum-packed Tuscan sausage was evaluated. In addition to the control (without the addition of oil), the sausage samples were separately treated with different concentrations of each essential oil (0.05 wt%, 0.1 wt%, 0.2 wt%, and 0.4 wt%). The shelf life was evaluated as the time to the lactic acid bacteria population to reach the levels of 106 and 107 CFU/g. After the addition of 0.05 wt% and 0.1 wt% of essential oil to the sausage, the rosemary essential oil provided a higher extension of the shelf life of the sausages (approximately 3 and 5 days, respectively) than the oregano essential oil (approximately 1 and 3 days, respectively). After adding 0.2 wt% and 0.4 wt% of essential oil, the oregano essential oil resulted in a larger increase of the shelf life of the samples (about 8 and 14 days, respectively) when compared with the rosemary essential oil (about 7 to 11 days, respectively). All the treatments slowed the growth of the lactic acid bacteria but they did not change the maximum bacterial population. New empirical models that relate the shelf life of the sausage and the maximum specific growth rate of the lactic acid bacteria with the oil concentration were obtained. These results can be applied to model the influence of essential oils on the shelf life of different meat products.

Use of modified Richards model to predict isothermal and non-isothermal microbial growth

Mathematical models are often used to predict microbial growth in food products. An important class of these models involves the adaptation of classical sigmoid functions, such as the Gompertz and logistic functions. This study aimed to validate the use of the modified Richards model in various situations, which have not previously been tested. The model was obtained through solving a system of two differential equations and could be applied to both isothermal and non-isothermal environments. To test and validate this model, we used published datasets containing data for the growth of Pseudomonas spp. in fish products. The results obtained after fitting the model showed that it could be effectively used to describe and predict the Pseudomonas growth curves under various temperature regimens. However, the influence of the shape parameter on the growth curve is an issue that needs further evaluation.(AU)

Use of modified Richards model to predict isothermal and non-isothermal microbial growth

Abstract Mathematical models are often used to predict microbial growth in food products. An important class of these models involves the adaptation of classical sigmoid functions, such as the Gompertz and logistic functions. This study aimed to validate the use of the modified Richards model in various situations, which have not previously been tested. The model was obtained through solving a system of two differential equations and could be applied to both isothermal and non-isothermal environments. To test and validate this model, we used published datasets containing data for the growth of Pseudomonas spp. in fish products. The results obtained after fitting the model showed that it could be effectively used to describe and predict the Pseudomonas growth curves under various temperature regimens. However, the influence of the shape parameter on the growth curve is an issue that needs further evaluation.

Use of modified Richards model to predict isothermal and non-isothermal microbial growth.

Mathematical models are often used to predict microbial growth in food products. An important class of these models involves the adaptation of classical sigmoid functions, such as the Gompertz and logistic functions. This study aimed to validate the use of the modified Richards model in various situations, which have not previously been tested. The model was obtained through solving a system of two differential equations and could be applied to both isothermal and non-isothermal environments. To test and validate this model, we used published datasets containing data for the growth of Pseudomonas spp. in fish products. The results obtained after fitting the model showed that it could be effectively used to describe and predict the Pseudomonas growth curves under various temperature regimens. However, the influence of the shape parameter on the growth curve is an issue that needs further evaluation.

Addition of palm oil in diet of dairy ewes reduces saturates fatty acid and increases unsaturated fatty acids in milk

Background: Sheep milk production is becoming an important alternative in the agricultural sector. It is used principally to produce fine cheeses, yogurts, and ice creams, and these produced from sheep’s milk are beneficial to human health. Previous study with palm oil shows increase in fat levels in sheep’s milk. Our hypothesis for increased fat in milk is that palm oil increases lipid metabolism as well as tissue reserves. Sheep consuming this palm oil will have a change in the fatty acid profile of milk, increasing levels of unsaturated fatty acids. Therefore, the aim of this study was to determine the levels of cholesterol and triglycerides, as well as fatty acid profile of milk these ewes fed of palm oil.Materials, Methods & Results: Thirty-six lactating sheep were divided in four groups (n = 9), with each group receiving various concentrations of palm oil in diet (0%, 2%, 4%, and 6% which corresponds to T 0, 2, 4 and 6, respectively). The diets in each treatment were isoproteic and isoenergetic. The experiment lasted 120 days, and blood and milk samples were collected on days 60 and 12 of the experiment. Blood was collected for seric analysis of lipid metabolism. Was collected milk samples and analyzed the content of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA). An increase (P 0.05) between groups, but numerically the animals in T4 and T6 had higher percentage of fat in milk. A decrease in milk SFA levels was observed on day 120 at T6. There was a significant reduction in caproic acid, caprylic acid, hendecanoic acid, lauric acid, and pentadecyl acid. The levels of palmitic acid (C16:0) increased when compared with the control group.[...]

Addition of palm oil in diet of dairy ewes reduces saturates fatty acid and increases unsaturated fatty acids in milk

Background: Sheep milk production is becoming an important alternative in the agricultural sector. It is used principally to produce fine cheeses, yogurts, and ice creams, and these produced from sheeps milk are beneficial to human health. Previous study with palm oil shows increase in fat levels in sheeps milk. Our hypothesis for increased fat in milk is that palm oil increases lipid metabolism as well as tissue reserves. Sheep consuming this palm oil will have a change in the fatty acid profile of milk, increasing levels of unsaturated fatty acids. Therefore, the aim of this study was to determine the levels of cholesterol and triglycerides, as well as fatty acid profile of milk these ewes fed of palm oil.Materials, Methods & Results: Thirty-six lactating sheep were divided in four groups (n = 9), with each group receiving various concentrations of palm oil in diet (0%, 2%, 4%, and 6% which corresponds to T 0, 2, 4 and 6, respectively). The diets in each treatment were isoproteic and isoenergetic. The experiment lasted 120 days, and blood and milk samples were collected on days 60 and 12 of the experiment. Blood was collected for seric analysis of lipid metabolism. Was collected milk samples and analyzed the content of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA). An increase (P < 0.05) in triglyceride and coleterol levels in the serum of the animals that received the highest concentrations of palm oil in the diet (T4 and T6). The centesimal composition of fat, lactose, and protein in milk was not different at days 60 and 120 (P > 0.05) between groups, but numerically the animals in T4 and T6 had higher percentage of fat in milk. A decrease in milk SFA levels was observed on day 120 at T6. There was a significant reduction in caproic acid, caprylic acid, hendecanoic acid, lauric acid, and pentadecyl acid. The levels of palmitic acid (C16:0) increased when compared with the control group.[...](AU)

Comparing non-linear mathematical models to describe growth of different animals / Avaliação comparativa de modelos matemáticos não lineares para descrever o crescimento animal

The main objective of this study was to compare the goodness of fit of five non-linear growth models, i.e. Brody, Gompertz, Logistic, Richards and von Bertalanffy in different animals. It also aimed to evaluate the influence of the shape parameter on the growth curve. To accomplish this task, published growth data of 14 different groups of animals were used and four goodness of fit statistics were adopted: coefficient of determination (R2 ), root mean square error (RMSE), Akaike information criterion (AIC) and Bayesian information criterion (BIC). In general, the Richards growth equation provided better fits to experimental data than the other models. However, for some animals, different models exhibited better performance. It was obtained a possible interpretation for the shape parameter, in such a way that can provide useful insights to predict animal growth behavior.

O principal objetivo deste estudo foi comparar a qualidade do ajuste de cinco modelos matemáticos recorrentemente utilizados na literatura para a descrição do ganho de peso animal. Ele também teve o objetivo de estudar a influência do parâmetro de forma sobre as curvas de crescimento. Os modelos de Brody, Gompertz, Logístico, von Bertalanffy e Richards, foram ajustados a dados experimentais de 14 grupos de animais diferentes. Como critério de qualidade de ajuste quatro índices estatísticos foram adotados: coeficiente de determinação (R2 ), raiz do quadrado médio do erro (RMSE) e os critérios de informação, Akaike (AIC) e Bayesian (BIC). Em geral, o modelo de Richards forneceu os melhores ajustes aos dados experimentais comparados aos demais modelos. No entanto, para alguns animais, diferentes modelos exibiram melhor desempenho. Foi possível obter uma possível interpretação para o significado do parâmetro de modo a fornecer ferramentas úteis para prever o comportamento do crescimento animal.

Comparing non-linear mathematical models to describe growth of different animals / Avaliação comparativa de modelos matemáticos não lineares para descrever o crescimento animal

The main objective of this study was to compare the goodness of fit of five non-linear growth models, i.e. Brody, Gompertz, Logistic, Richards and von Bertalanffy in different animals. It also aimed to evaluate the influence of the shape parameter on the growth curve. To accomplish this task, published growth data of 14 different groups of animals were used and four goodness of fit statistics were adopted: coefficient of determination (R2 ), root mean square error (RMSE), Akaike information criterion (AIC) and Bayesian information criterion (BIC). In general, the Richards growth equation provided better fits to experimental data than the other models. However, for some animals, different models exhibited better performance. It was obtained a possible interpretation for the shape parameter, in such a way that can provide useful insights to predict animal growth behavior.(AU)

O principal objetivo deste estudo foi comparar a qualidade do ajuste de cinco modelos matemáticos recorrentemente utilizados na literatura para a descrição do ganho de peso animal. Ele também teve o objetivo de estudar a influência do parâmetro de forma sobre as curvas de crescimento. Os modelos de Brody, Gompertz, Logístico, von Bertalanffy e Richards, foram ajustados a dados experimentais de 14 grupos de animais diferentes. Como critério de qualidade de ajuste quatro índices estatísticos foram adotados: coeficiente de determinação (R2 ), raiz do quadrado médio do erro (RMSE) e os critérios de informação, Akaike (AIC) e Bayesian (BIC). Em geral, o modelo de Richards forneceu os melhores ajustes aos dados experimentais comparados aos demais modelos. No entanto, para alguns animais, diferentes modelos exibiram melhor desempenho. Foi possível obter uma possível interpretação para o significado do parâmetro de modo a fornecer ferramentas úteis para prever o comportamento do crescimento animal.(AU)