G. Clemente

Ultrasonic determination of the composition of a meat-based product

Abstract The use of ultrasonics as an analytical technique to estimate the composition of a fermented meat-based product (sobrassada) was assessed. Moisture, fat and protein contents and ultrasonic velocity at 4, 8, 12 and 25 °C were measured in samples using different formulae. In this study, it was considered that a meat-based product is formed of three different constituents: fat, water and protein+others. Ultrasonic velocity was related, by a semiempirical equation, to the composition and the ultrasonic velocity of the above three components. The ultrasonic velocity temperature dependence allowed the determination of fat, moisture and protein+others contents. The explained variance was 98.0% for protein+others, 97.6% for fat and 95.6% for moisture. The results obtained show the feasibility of using ultrasonic velocity measurement to assess, in a rapid and non-destructively way, the composition of a meat-based product.

Bioaccessibility of tocopherols, carotenoids, and ascorbic acid from milk- and soy-based fruit beverages: influence of food matrix and processing.

A study was made of the effect of high-pressure processing (HPP) and thermal treatment (TT) on plant bioactive compounds (tocopherols, carotenoids, and ascorbic acid) in 12 fruit juice-milk beverages and of how the food matrix [whole milk (JW), skimmed milk (JS), and soy milk (JSy)] modulates their bioaccessibility (%). HPP (400 MPa/40 °C/5 min) produced a significant decrease in carotenoid and ascorbic acid bioaccessibility in all three beverages and maintained the bioaccessibility of tocopherols in JW and JS while decreasing it in JSy. TT (90 °C/30 s) produced a significant decrease in tocopherol and carotenoid bioaccessibility in all three beverages and increased the bioaccessibility of ascorbic acid. With regard to the food matrix, α-tocopherol and ascorbic acid bioaccessibility was greatest in JW beverages and lowest in JSy beverages, whereas no significant differences were found among the three beverages in terms of carotenoid bioaccessibility. HPP-treated samples showed higher tocopherol and carotenoid bioaccessibility than TT-treated samples, thus indicating that HPP combined with a milk matrix positively modulates the bioaccessibility of certain types of bioactive components of food, mainly those of a lipophilic nature.

Copper, iron, and zinc contents in human milk during the first three months of lactation: a longitudinal study.

The aim of the study has been to analyze the evolution of copper, iron, and zinc contents in human milk, from colostrum to the third postpartum month, following a longitudinal design, under specific conditions of sample collection and to apply an analytical procedure previously optimized to reduce any variation outside physiological lactation.The copper, iron, and zinc concentrations in 144 milk samples from 39 healthy puerpera women, were analyzed in five stages by flame atomic absorption spectrometry, following a standardized protocol.Copper presented a gradual decrease from 0.38 mg/L to 0.19 mg/L by the 90th day; the particular analysis from colostrum to transitional milk manifested the following two tendencies. Whereas an increase from 0.19 to 0.42 mg/L was observed in some women, a decrease from 0.53 to 0.45 mg/L was detected in others; therefore, copper presented two significant behaviors in the evolution from colostrum to transitional milk. In both cases, the evaluated changes were significant. The iron content varied from 0.56 to 0.40 mg/L by the 30th day, remaining constant until the first trimester concluded. The average zinc concentration decreased sharply from 7.99 to 3.3 mg/L on d 15; the rate of decrease slowed down gradually until 1.05 mg/L.

Drying modelling of defrosted pork meat under forced convection conditions

Drying is the lengthiest and the most energy consuming step during the production of dry-cured ham, affecting also the curing process and consequently product quality. In order to manage the drying process, it is quite interesting to establish the complexity of model needed. For that purpose, pork meat cylinders (Biceps femoris and Semimembranosus muscles) were dehydrated under forced convection conditions (25°C and air velocity 0.6±0.1, 2.0±0.1 and 2.8±0.1 m/s). Experimental drying kinetics were modelled by means of 4 diffusion models: model 1 (not considering shrinkage and no external resistance), model 2 (considering shrinkage and no external resistance), model 3 (not considering shrinkage and considering external resistance) and model 4 (considering both shrinkage and external resistance). From the effective diffusivity values identified, it was concluded that when external resistance was negligible (air velocity 2.0±0.1 and 2.8±0.1 m/s), the results obtained for D(e) with the four models were the same. Nevertheless, when external resistance was not negligible (0.6±0.1 m/s) the D(e) identified was influenced by the model due to the fact that models 1 and 2 neglect that resistance and for that reason they do not describe experimental conditions properly. The effect of shrinkage did not influence the identified D(e) values for the drying conditions considered. In order to model water losses in meat curing chambers, external resistance must be considered.

A study of factors that may influence the determination of copper, iron, and zinc in human milk during sampling and in sample individuals.

The aim of this study was to establish the possible effects of the sampling protocol (between-breast, within-feed, and diurnal differences) and the mother’s personal factors (age, parity, iron supple-mentation, smoking habits, and lactation period) on the copper, iron, and zinc contents in human milk.One hundred thirty-six human milk samples identified by their origin and sampling conditions were analyzed. The samples were obtained from the 2nd to 15th d postpartum from 62 women. The data on the individuals required for the study were available. Mineral determinations were analyzed by flame atomic absorption spectrometry following a standarized protocol.The results showed that iron contents were higher in hind-milk samples and at the nighttime feeding and depended on the breast from which the sample was taken. The copper and zinc concentrations showed no significant variations. There was no significant relationship among the mothers’ age, parity, smoking habits, iron supplementation, and copper content. Milk from older women had lower zinc contents than that of younger women. Increased amounts of iron were found in multiparous women. Between colostrum and transitional milk, a sharp decrease in zinc content was observed, whereas copper and iron contents remained constant.All of these results make it clear that standardized sampling protocols are needed in order to obtain comparable values.

Modelling drying kinetics of thyme (Thymus vulgaris L.): Theoretical and empirical models, and neural networks

The drying kinetics of thyme was analyzed by considering different conditions: air temperature of between 40 ℃ and 70 ℃, and air velocity of 1 m/s. A theoretical diffusion model and eight different empirical models were fitted to the experimental data. From the theoretical model application, the effective diffusivity per unit area of the thyme was estimated (between 3.68 × 10−5 and 2.12 × 10 −4 s−1). The temperature dependence of the effective diffusivity was described by the Arrhenius relationship with activation energy of 49.42 kJ/mol. Eight different empirical models were fitted to the experimental data. Additionally, the dependence of the parameters of each model on the drying temperature was determined, obtaining equations that allow estimating the evolution of the moisture content at any temperature in the established range. Furthermore, artificial neural networks were developed and compared with the theoretical and empirical models using the percentage of the relative errors and the explained variance. The artificial neural networks were found to be more accurate predictors of moisture evolution with VAR ≥ 99.3% and ER ≤ 8.7%.

Impact of Fruit Beverage Consumption on the Antioxidant Status in Healthy Women

Background: Epidemiologic studies suggest that antioxidant-rich foods might reduce the risk of cancer and cardiovascular diseases. Aim: To test the health-protective potential of three fruit beverages, Fb (grape-orange-apricot), FbM (Fb with skimmed milk) and FbMFe [FbM + Fe(II)], in healthy women. Methods: The influence of fruit beverage consumption (500 ml/day) upon serum antioxidant capacity determined by ORAC and TEAC methods and erythrocyte superoxide dismutase (SOD) activity was assessed in 32 healthy female volunteers. In the intervention study, each subject received the fruit beverages during three periods (3 weeks for Fb and FbM, and 12 weeks in the case of FbMFe), with a 2-week washout period between treatments. Results: Intake of fruit beverages does not improve total antioxidant capacity. However, the induction of SOD found after fruit beverage consumption may be more effective than the effects of antioxidants present in these beverages, which can only stoichiometrically scavenge reactive species derived from oxidative stress. Conclusion: Iron added to FbM (FbMFe) showed induction of SOD activity, with no prooxidant effect, and could constitute a complementary source of iron, because the regular consumption of FbMFe may be beneficial for women of fertile age.

Detection of Internal Cracks in Manchego Cheese Using the Acoustic Impulse-Response Technique and Ultrasounds

Nowadays, due to the more global nature of markets, the commercialization of cheese relies on the high quality of the product. Internal defects such as cracks or flaws may affect quality. Two different nondestructive inspection techniques (ultrasonic and acoustic experiments) were used to detect cracks in Manchego cheese. The existence of small eyes in this type of cheese limited the use of ultrasonic pulse-echo experiments due to high scattering, and only cracks close to the surface of the cheese could be detected. The acoustic impulse-response technique, however, allowed us to study wheel pieces with cracks located elsewhere in the cheese. Two different impact probes (A and B) were assayed. The energy content of the acoustic spectrum was higher for cracked wheel pieces (7,116 and 17,520 V Hz(1/2) for probes A and B, respectively) than for normal ones (6,841 and 16,821 V Hz(1/2)). The differences were mainly found for frequencies higher than 150 Hz, which made the centroid for cracked pieces higher (162 and 170 Hz for probes A and B, respectively) than that for normal cheeses (132 and 148 Hz for probes A and B, respectively). Discriminant functions were developed to classify wheel pieces, and the input variables used were the acoustic parameters from the spectrum and the principal components extracted from the whole spectrum. The best classification procedure used the principal components from the principal components analysis of the spectrum for probe B. In this case, the 50 wheel pieces used in this study were correctly classified. These results showed that a simple and low-cost acoustic impulse-response technique could be used to detect cheese cracks, formed at different moments of Manchego cheese maturation.

Desorption isotherms and isosteric heat of desorption of previously frozen raw pork meat.

Some meat products involve drying previously frozen pork meat, which makes the knowledge of sorption characteristics very important for the design and management of meat dehydration processes. The sorption isotherms of raw pork meat from the Biceps femoris and Semimembranosus muscles were determined at four temperatures: 25, 30, 35 and 40°C. The experimental results were modelled using the GAB (Guggenheim, Anderson and De Boer) model. The effect of temperature was also taken into account to model the experimental sorption isotherms using four models (GAB, Oswin, Halsey and Henderson). The best results were provided by the GAB model. From the experimental sorption isotherms the isosteric heats of sorption were determined. For a moisture content higher than 0.15kgwater/kgdm, the isosteric heat of meat was similar to the latent heat of vaporization for pure water. For a lower moisture content, an increase in the isosteric heat was observed when the moisture content decreased.

Determination of Shrinkage Function for Pork Meat Drying

The shrinkage of pork meat cylinders was measured and correlated with moisture content. Samples of different sizes were dehydrated under different drying conditions: forced convection (25°C and 0.6, 2.0, and 2.8 m/s) and natural convection (5, 10, 15, and 20°C). A linear relationship was found between the quotients R/R0 and V/V0 and the moisture content. This linear relationship was not found to be dependent on the size of the samples, their salt content, or drying conditions. For the experimental conditions in this study, water losses are responsible for shrinkage.