DETERMINATION OF PRACTICALLY SIGNIFICANT DIFFERENCES IN THE SENSORILY PERCEIVED CONSISTENCY OF SEMILIQUID FOODS1

The consistency of commercial salad dressing, chocolate pudding and mustard samples before and after controlled disruption was assessed by squeezing flow viscometry and evaluated sensorily by an untrained panel. The instrumental parameters were the apparent stress at 1.5 and 1.0 mm height and the apparent residual stress after 60 and 120 s relaxation (at 1.0 mm height). The panelists were asked to identify the sample(s) with the stronger consistency in a triangular test. The percent correct identifications was plotted against the difference in the magnitude of the instrumental parameters and their ratios. The scatter of these plots suggests that the effective stimulus for consistency perception was primarily the overall resistance to deformation or flow and to a much lesser extent to more subtle rheological characteristics like the ‘degree of solidity'. In the range of consistencies examined, the detection thresholds were on the order of 0.5‐0.7 kPa and 0.4‐0.6 kPa at 1.0 and 1.5 mm height, respectively. They corresponded to stress ratios on the order of 0.75‐0.85. Results of this kind will enable setting objective standards for the consistency of commercial semi liquid foods and tolerance margins to deviations from them.     

Acidification kinetics,physicochemical properties and sensory attributes of yoghurts prepared from mixtures of goat and buffalo milks

Five formulations of set‐type yoghurt were produced using different caprine–bubaline milk ratios. They were investigated in regard to the acidification kinetics, yoghurt composition, rheology and sensory attributes. The acidification profile of all five experimental groups was similar, but the maximum acidification rate was higher for yoghurts of milk mixtures. The addition of buffalo milk increased total solids, fat and overall acceptance of yoghurt, besides decreasing synaeresis. Yoghurts made from caprine–bubaline milk mixtures reached good sensory scores and yoghurt prepared with 30% of goat milk and 70% of bubaline milk received the best sensory scores.     

DIFFERENTIAL SCANNING CALORIMETRY DETECTION OF HIGH OLEIC SUNFLOWER OIL AS AN ADULTERANT IN EXTRA-VIRGIN OLIVE OIL

Differential scanning calorimetry (DSC) was employed to detect high oleic sunflower oil (HOSo) as an adulterant in extra-virgin olive oil (EVOo) by means of cooling and heating thermograms. Addition of HOSo did not significantly alter cooling profiles of EVOo except for onset temperature of crystallization, which was significantly shifted toward lower temperature at 40% of adulterant addition. At the same percentage of adulteration, the heating profile of EVOo was significantly changed as the major endotherm broadened and the minor event became smaller and less evident. Cooling thermograms of pure oils and their admixtures were deconvoluted into three constituent exothermic peaks in an attempt to detect addition of HOSo at levels lower than 40%. Thermal properties of the two lower-temperature exotherms (area percentage, offset temperature and range of transition) were significantly changed at ≥ 20% of HOSo substitution, suggesting that DSC can be employed to detect this oil as an EVOo adulterant.

PRACTICAL APPLICATIONS

Adulteration of extra-virgin olive oil (EVOo) with cheaper oils from other vegetable sources or seeds, as well as with lower quality olive oils, is a serious concern for oil suppliers and consumers and requires the use of new analytical techniques for their detection. Differential scanning calorimetry (DSC) exhibits some advantages over the classical analytical methods as it does not require sample preparation and use of solvents, thus resulting in a reduced environmental impact. Results suggested that its application to the detection of EVOo adulteration with high oleic sunflower oil, a vegetable oil largely employed for this type of fraud, is promising with the support of the deconvolution analysis of cooling thermograms.     

Potentially probiotic açaí yogurt

The aim of this work was to evaluate the suitability of yogurt containing açaí pulp as a food carrier of probiotic cultures. Probiotic yogurts containing increasing amounts of açaí pulp (3, 5 and 7%) were processed and submitted to a physicochemical analysis and viable microbial count during refrigerated storage. In general, all the physicochemical parameters showed variations proportional to the amount of açaí pulp in the product formulation. Probiotic activity was verified throughout refrigerated storage for all the products, although there was a fall of one logarithmic cycle for both micro-organisms during this period (10⁷–10⁸ CFU/mL).     

Reconstruction of the absorption spectrum of an object spot from the colour values of the corresponding pixel(s) in its digital image: the challenge of algal colours

A novel procedure for deriving the absorption spectrum of an object spot from the colour values of the corresponding pixel(s) in its image is presented. Any digital image acquired by a microscope can be used; typical applications are the analysis of cellular/subcellular metabolic processes under physiological conditions and in response to environmental stressors (e.g. heavy metals), and the measurement of chromophore composition, distribution and concentration in cells. In this paper, we challenged the procedure with images of algae, acquired by means of a CCD camera mounted onto a microscope. The many colours algae display result from the combinations of chromophores whose spectroscopic information is limited to organic solvents extracts that suffers from displacements, amplifications, and contraction/dilatation respect to spectra recorded inside the cell. Hence, preliminary processing is necessary, which consists of in vivo measurement of the absorption spectra of photosynthetic compartments of algal cells and determination of spectra of the single chromophores inside the cell. The final step of the procedure consists in the reconstruction of the absorption spectrum of the cell spot from the colour values of the corresponding pixel(s) in its digital image by minimization of a system of transcendental equations based on the absorption spectra of the chromophores under physiological conditions.