The effect of the addition of soy protein isolate (SPI) (0, 15, 30, 45 and 60 g kg-1) on viscoelastic properties, large deformation measurements and microstructure of fresh (FM) and frozen/thawed (F/TM) mashed potatoes was investigated. Rheological data showed weak gel behaviour for both FM and F/TM potatoes without and with added SPI together with a significant decrease of system viscoelasticity (G' and G") with increasing SPI volume fraction, primarily attributed to the no interaction between the amylose/amylopectine matrix and the dispersed SPI particles or aggregates as revealed by scanning electron microscopy (SEM). Micrographs also showed that SPI formed white coarse aggregates. A freeze/thaw cycle produced a more significant decrease in viscoelastic functions, due to superior aggregation of denatured SPI and reduced water activity. In F/TM samples, high correlations between small and large deformation measurements were found. Results may be useful for technological applications in SPI-enriched mashed potatoes.
Surface coatings formed by immersion in the ionic liquids (ILs) 1,3-dimethylimidazolium methylphosphonate (LMP101), 1-ethyl-3-methylimidazolium methylphosphonate (LMP102) and 1-ethyl-3-methylimidazolium ethylphosphonate (LEP102) on magnesium alloy AZ31B at 50 °C have been studied. The purpose of increasing the temperature was to reduce the immersion time, from 14 days at room temperature, to 48 hours at 50 °C. The abrasion resistance of the coated alloy was studied by microscratching under progressively increasing load, and compared with that of the uncoated material. The order of abrasion resistance as a function of the IL is LEP102 > LMP101 > LMP102, which is in agreement with the order obtained for the coatings grown at room temperature. The maximum reduction in penetration depth with respect to the uncovered alloy, of a 44.5%, is obtained for the sample treated with the ethylphosphonate LEP102. However, this reduction is lower than that obtained when the coating is grown at room temperature. This is attributed to the increased thickness and lower adhesion of the coatings obtained at 50 °C, particularly those obtained from methylphosphonate ionic liquids. The results are discussed from SEM-EDX and profilometry.
KEYWORDSFlow behavior, long-chain inulin, microstructure, soy protein isolate, texture perception, trained and untrained panel 4 Corresponding
ABSTRACTThis study evaluated the effect of adding soy protein isolate (SPI) and long-chain inulin (INL) blends with 10 different SPI : INL ratios on the textural, rheological and microstructural properties of freshly made and frozen/thawed potato puree. All the potato puree samples were subjected to a sensory texture profile analysis and a trained panel rated the intensity of six descriptors, while an untrained panel did the same on six selected frozen/thawed products. The main SPI : INL ratio effect remained significant for all the descriptors evaluated, when the analysis of variance was applied considering the untrained assessors as random effects. However, only trained panel scores for creaminess corresponded well with untrained assessor ratings. Rheological flow index values were linked with variations in perceived consistency, and geometric and surface textural attributes were explained by structural features such as the presence of INL crystallites and SPI coarse strands.
PRACTICAL APPLICATIONSA potato puree (PP) serving of 200 g with added soy protein isolate (SPI) and/or inulin (INL) concentrations of 1.5-6% provides from 3 to12 g of SPI and/or INL, respectively. The presence of SPI strands is a dominant factor in texture perception of PP with regard to mouthfeel geometric attributes (visual graininess and fibrousness) and the after-feel attribute (mouth coating), while INL crystallites are the most important feature influencing creaminess. By adding small amounts of SPI (1.5%) together with INL at >3% increases the intensity of perceived creaminess, which was the most important descriptor in practical terms. In view of the foregoing, PP with ada'ed SPI and INL is a promising foodstuff for incorporating into a diet and in addition, even improves product structure.understanding texture perception would depend on a multidisciplinary approach considering sensory research, physiology and research into food structure.Basically, potato puree (PP) is formulated with native potato starch (Alvarez et al. 2009), and this starch-based food can be considered as a semisolid or soft-solid, viscoelastic material (Foegeding et al. 2011). Changing their composition by adding new ingredients would result in texture changes of the final product. Soy protein isolate (SPI) is an ingredient bs_bs_banner A journal to advance the fundamental understanding of food texture and sensory perception
Journal of Texture Studies
Summary
Developing products having a high nutritional value and good storage stability during freezing is a challenge. Inulin (I) and extra virgin olive oil (EVOO) have interesting functional properties. The effect of the addition of I and EVOO blends at different I:EVOO ratios (0:0, 0:60, 15:45, 30:30, 45:15, 60:0, 30:45 and 45:30) on the rheological, physical, sensory and structural properties of fresh and frozen/thawed mashed potatoes formulated without and with added cryoprotectants was analysed and compared. Addition of I and EVOO (either alone or blended) reduced apparent viscosity and pseudoplasticity producing softer systems, indicating that both ingredients behave as soft fillers. Samples with added I at the higher concentrations (≥45 g kg−1) showed lower flow index and consistency, which is related to formation of smaller I particles; microphotographs indicated that gelling properties of I depended mostly upon processing. Frozen/thawed samples were judged more acceptable and creamier than their fresh counterparts.
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