The effect of the addition of gelatin and starch on the rheological and sensory texture properties of sweetened plain stirred yogurt was studied. Six samples were prepared: two with gelatin (3 and 6 mg/g), three with starch (1, 5 and 10 mg/g) and a control sample without thickener. Rheological measurements were performed and flow curves were modelled according to the Herschel–Bulkley rheological model. Also, sensory evaluation was carried out using a trained panel. The addition of gelatin and starch significantly affected the instrumental texture parameters (Herschel–Bulkley's model parameters and syneresis) and the perceived sensory texture of yogurts. All sensory descriptors were well predicted by the partial least squares regression of the instrumental parameters. The addition of thickeners significantly reduced syneresis. Samples produced with 6 mg/g of gelatin did not show syneresis and showed the highest sensory viscosity, creaminess and mouth‐feel. Therefore, the use of 6 mg/g of gelatin could be a reasonable concentration to use in the production of low‐fat yogurts.

Although beef tallow (BT) has been considered a hard low-trans fat convenient to be used in several bakery applications, it has some undesirable characteristics like fatty acid composition, crystallization behavior, graininess formation and poor plastic range. This work studied the modification of BT by blending at different percentages with high oleic sunflower oil (HOSFO) followed by the enzyme-catalyzed interesterification of the blends. The reduction in the solid fat content achieved by the simple blending was enhanced by the interesterification process, as a result of the increase in the concentration of the diunsaturated monosaturated type triacylglycerols. Interesterification strongly impacted too on the crystallization behavior of the blends, since products showed more homogeneous and regular crystals than the starting mixture. Results show that lipase catalyzed interesterification of BT with HOSFO offers a useful tool for the design of fats with adjustable physicochemical properties, improved with respect to that of the starting fats.

The aim of this study was to analyze in detail the changes produced by the enzymatic interesterification of BT/RBO blends (beef tallow/rice bran oil) at different proportions, as an alternative for production of trans free fats. It was observed that the increase in the oil content produced a range of the content of saturated fatty acids from 20 to 38% in the blend and a range of polyunsaturated fatty acids from 35 to 18%. In TAG composition, the SUU and SSS type (S: saturated fatty acid; U: unsaturated fatty acid) increased in concentration as a result of interesterification process and this effect was more noticeable when the blend was richer in oil, arriving at 19 and 4% respectively in 50:50 BT/RBO blend. These variations in composition greatly improved the plastic range of BT. The process studied produced new trans free fatty materials with improving suitability as food ingredients. Therefore, promising new materials were developed.

Phase-equilibrium diagrams of biodiesel synthesis substrate (oil/alcohol/alkyl esters) and product (alkyl esters/glycerol/alcohol) mixtures containing methanol, ethanol and propanol, respectively, were used for the identification of those composition ratios leading to mixture homogeneity. Based on the diagrams, complete conversion of the substrate oil contained in a sunflower oil/ ethanol/ethyl ester mixture at a weight ratio of 7.6:11.4:81.0 resulted in the generation of an amount of glycerol capable of remaining in solution in the product mixture. In contrast, complete conversion using a mixture of a lower alcohol and ethyl ester content (19.0:6.0:75.0) leads to the separation of phases. A continuous reactor charged with Lypozyme TL-IM and fed with the former mixture showed constant conversion and productivity with time, whereas process efficiency was found to decrease drastically when the latter mixture was fed. When a sunflower oil/isopropanol/isopropyl ester mixture at a weight ratio of 35:35:30 was fed in the reactor charged with Novozym 435, the output glycerol concentration was equivalent to that theoretically expected. In contrast, feeding a sunflower oil/ethanol/ethyl ester mixture of equal proportions as above, the glycerol concentration was lower than expected, suggesting the occurrence of glycerol adsorption on the enzyme support.

In recent years vacuum frying was developed as an alternative methodology to traditional frying.In this study, sunflower oil thermoxidation was evaluated using conventional process conditions (180 °C and atmospheric pressure) and vacuum technology conditions (130 °C and 0,1 bar). Traditional thermoxidation lasted 20 h while vaccum thermoxidation was completed after 56 h.Total polar compounds reached 23 and 7,1 % at the end of atmospheric and vacuum thermoxidation respectively, while polymers content was 9,3 and 2,2 % for each oil.Tocopherols contents decreased 45 % for atmospheric thermoxidized oil and were reduced to 17 % for vacuum thermoxidized oil.These results clearly proved vacuum thermoxidation achieved a significantly lower deterioration rate than atmospheric thermoxidation of sunflower oil, conferring it much longer useful life and better nutritional qualities. Accordingly, a singnificantly slower vanishing rate of tocopherols was observed in vacuum thermoxidation.

No abstract

Extra virgin olive oil is recognized as a very stable oil because of its composition in fatty acids and its content in natural antioxidants (tocopherols and polyphenols). In the bibliography are works that address different aspects of this stability, from the duration of its useful life to its performance in the frying of foods. Some works also link their stability with the content of natural antioxidants. For example, Franco et al. (2014) studied the content of phenols and their antioxidant capacity in olive oils of seven different varieties. Baccouri et al. (2008) found a good correlation between the oxidative stability (measured in Rancimat) of the oils studied and the concentration of total phenols and tocopherols.

Due to the difficulty in determining polar compounds (PC) using the IUPAC method 2.507, simple and low cost devices for in situ determinations, such as Viscofrit, are commercialized for fried food processing establishments. This device is calibrated for oils but not for fats, such as beef tallow, since materials with a high melting point are rarely used worldwide. A large dispersion was observed in the measurements made with Viscofrit at 48 °C on thermoxidized beef tallow. The maximum emptying time was reached at about 6 hours of thermoxidation, at which point the fat still does not reach the maximum PC level allowed. In this test, a great dispersion in the data and a high percentage of “false values” were observed, which may be due to the presence of fatty solids at the measurement temperature, which affect the emptying time. In order to use Viscofrit for fats, such as beef tallow, it is suggested to perform a calibration at a temperature outside the range established by the manufacturer which ensures the absence of fatty solids, in this case 60 °C. Under these conditions, a maximum emptying time of 37 seconds was obtained.