[show abstract][hide abstract] ABSTRACT: The potential use of commercial fibres (pea fibre, inulin, and their blends), as fibre-enriching agents in frozen/thawed mashed potatoes was reported. Pea fibre and inulin supplementations conferred hardness and softness to the product, respectively. Differences were attributed to the relationship of the fibre with the potato starch matrix. The association of pea fibre at low concentration (<15 g/kg mashed potatoes) and inulin at high concentration (>45 g/kg) is strongly encouraged to fortify the diet without promoting negative effects on textural and rheological properties of frozen/thawed mashed potatoes or colour and overall acceptability of the resulting products.
International Journal of Food Properties 09/2012; 15(5):1022-1041. · 0.88 Impact Factor
[show abstract][hide abstract] ABSTRACT: The effect of the addition of soy protein isolate (SPI) (0, 15, 30, 45 and 60gkg−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.
[show abstract][hide abstract] ABSTRACT: The aim of this work was to study the effect of the addition of extra virgin olive oil (EVOO) on instrumental textural properties, sensory texture profile analysis, and microstructure of fresh and frozen/thawed mashed potatoes formulated without and with added cryoprotectants (kappa-carrageenan [κ-C] and xanthan gum [XG]). EVOO behaves as soft filler due to droplet aggregates, whereas addition of cryoprotectants led to more structured mashed potatoes (MP) thanks to the gelling properties of κ-C. Both the percentage of added EVOO and processing had a much less significant effect on the texture of the MP containing κ-C and XG, evidencing the ability of this biopolymer blend to impart freeze/thaw stability. All samples with added EVOO were perceived as significantly softer and creamier than the samples without EVOO, whereas all MP samples with added cryoprotectants were perceived as significantly thicker and creamier than those without hydrocolloids.PRACTICAL APPLICATIONSPrevious studies showed that the quality after freezing and thawing may be improved by the addition of 1.5 g/kg of kappa-carageenan and 1.5 g/kg of xanthan gum, and/or incorporation of dietary fiber, improvement of mashed potatoes texture by retarding starch retrogradation and increasing water-holding capacity. Growing awareness of the link between diet and health is fast changing consumer habits, so that there has been increasing demand for foods with health-enhancing properties. Extra virgin olive oil (EVOO) has important nutritional characteristics linked to its biophenol content and has very important antioxidant properties. The results have shown that although instrumental textural data were able to explain differences in consistency perceived, structural information is needed to understand differences in creaminess. Back extrusion test is recommended to industry as practical quality control tool in the commercial production of mashed potatoes with added EVOO.
[show abstract][hide abstract] ABSTRACT: The effect of the addition of inulin (0%, 1.5%, 3%, 4.5% and 6%) on viscoelastic properties and microstructure of fresh and frozen/thawed mashed potatoes (FMP and F/TMP, respectively) formulated without and with added cryoprotectants (kappa-carrageenan (κ-C) and xanthan gum (XG)) was investigated. Results showed that inulin concentration was the factor that set the minor difference among most of rheological properties, firmness and overall acceptability (OA) of the samples, whereas addition of κ-C and XG resulted in main differences between samples. Inulin effect on the thickening of the product was limited, which is mainly ascribed to a high heating temperature reached by the product during manufacture process inducing inulin hydrolysis. FMP samples presented more rigid structure than their F/TMP counterparts, although either inulin concentration or processing had much less significant effect on the viscoelasticity of the mashed potatoes containing cryoprotectants, evidencing the ability of this biopolymer blend to impart freeze/thaw stability.
Journal of Food Engineering. 01/2011; 102(1):66-76.
[show abstract][hide abstract] ABSTRACT: 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.
International Journal of Food Science & Technology 09/2010; 45(10):2108 - 2118. · 1.24 Impact Factor
[show abstract][hide abstract] ABSTRACT: Hydrocolloids and protein were added to fresh (F) and frozen/thawed (F/T) mashed potatoes in the form of mixtures of: (1) amidated low-methoxyl (ALM) pectin and xanthan gum (XG); (2) kappa-carrageenan (k-C) and XG; and (3) sodium caseinate (SC) and XG. F and F/T mashed potatoes without added biopolymers and with XG at 1.5 g/kg were also analyzed. Flow curves fit the power law and Casson models well – and preferentially the first of these. The Cox–Merz rule was not applicable to the steady and dynamic shear data on all of the mashed potatoes. In the F products, the departure of mashed potatoes–biopolymer mixtures from the Cox–Merz rule was XG concentration-dependent. It was concluded that most of the F mashed potatoes followed the linear modified Cox–Merz rule, with η*(ω) and ηa() well superimposed. However, after processing, the linearity – or otherwise of the relationship between viscosities – was more dependent on the type of biopolymer mixture. Also, in the case of the F/T mashed potatoes without added biopolymers and with added ALM/XG binary mixtures, the relationships may be considered linear. Conversely, in the case of F/T mashed potatoes with added XG alone and mixed with k-C and SC, small amplitude dynamic properties cannot be used directly to predict changes in texture perceived in the mouth given that the relationship between these properties and steady shear measurements is nonlinear. The effects of addition of either XG alone or binary mixtures to F and F/T mashed potatoes were very dependent on the magnitude of the strain deformation applied to the system (i.e., low strain in oscillatory shear and high strain in steady shear).PRACTICAL APPLICATIONSMashed potato can be a suitable food for freezing as a ready-meal component or as a single product in the form of potato gratin. Freezing and thawing processes reduce most of the quality parameters measured in the product. One way of minimizing damage from freezing and thawing is to incorporate cryoprotectants to alter crystal shapes. Previous studies have shown that xanthan gum (XG) is preferred for sensory purposes because of its creamy mouthfeel. The result of this study could serve as a guide for thickening of mashed potatoes by addition of a kappa-carrageenan (k-C)/XG blend, and also for softening of the product by addition of a sodium caseinate (SC)/XG mix together. These data have served as a resource in order to further explore the utilization of XG mixed with either k-C or SC in developing commercially prepared frozen/thawed mashed potatoes.
Journal of Food Process Engineering 12/2009; 34(2):224 - 250. · 0.56 Impact Factor
[show abstract][hide abstract] ABSTRACT: Blends of amidated low methoxyl (ALM) pectin and xanthan gum (XG) were added to fresh (F) and frozen/thawed (F/T) mashed potatoes. Product was tested by instrumental texture profile (TPA), color, expressible water (Ew) and sensory analyses. A central composite rotatable experimental design was used to study the effects of variation on ALM pectin (1.5–4.5 g/kg) and XG (0.5–2.5 g/kg) concentrations. The effects were highly dependent on the levels of ALM and XG added, although XG influenced the mechanical behavior, color and water-holding capacity of the mashed potatoes more than ALM pectin. F and F/T mashed potatoes with 3 g/kg added ALM pectin and 2.91 g/kg added XG exhibited the greatest consistency, adhesiveness and gumminess, which could be associated with an increase in the amount of XG–water interactions. Instrumental and sensory tests showed that, when 3 g/kg of ALM pectin and 1.5 g/kg of XG were included in the formulation, the mechanical and functional properties of F/T product were very acceptable, with almost no detectable changes in color attributes, and very good overall acceptability (OA) associated with a pronounced creamy sensation conferred by the XG.PRACTICAL APPLICATIONSMost frozen products exhibit some loss of quality due to freezing, frozen storage and thawing. In the case of mashed potatoes, freezing and thawing has a detrimental effect on physical properties and water-holding capacity (WHC). The results show that the quality after freezing and thawing may be improved by the addition of 3 g/kg of amidated low methoxyl pectin and 1.5 g/kg of xanthan gum, incorporation of dietary fiber, improvement of mashed potatoes texture by retarding starch retrogradation and increasing WHC, and enhancing the principal characteristics determining consumer acceptance. These results have important implications for the production of frozen/thawed mashed potatoes with improved sensory quality and freeze-thaw stability over time.
Journal of Food Process Engineering 08/2009; 34(3):746 - 776. · 0.56 Impact Factor
[show abstract][hide abstract] ABSTRACT: Cryoprotectant mixtures were added to frozen/thawed (F/T) mashed potatoes in the form of amidated low-methoxyl (ALM) pectin and xanthan gum (XG), kappa-carrageenan (κ-C) and XG and sodium caseinate (SC) and XG, and the effect of frozen storage was examined. F/T mashed potatoes without added biopolymers had higher storage modulus G′ after freezing and frozen storage, associated with sponge formation due to amylose retrogradation. Oscillatory measurements indicated weakening of the structure of mashed potatoes without biopolymers and with added κ-C/XG and SC/XG mixtures at the end of storage due to ice recrystallisation, whereas the structure of samples with added ALM/XG mixtures was reinforced by increasing time in storage. Mashed potatoes with added mixtures exhibited water-holding capacity for 1 year. Samples with added κ-C/XG mixtures were more structured, although when both κ-C/XG and SC/XG mixtures were included in mashed potato, very acceptable sensory quality was maintained in usual frozen storage conditions.
International Journal of Food Science & Technology 05/2009; 44(7):1373 - 1387. · 1.24 Impact Factor
[show abstract][hide abstract] ABSTRACT: Oscillatory data obtained for mashed potatoes made from fresh tubers from measuring geometries of different designs and sizes were analyzed and compared at the sample temperatures of 25 and 55C. The measuring geometries used were smooth parallel plates (PP40 and PP20, 40- and 20-mm-diameter plates, respectively); truncated cone and plate (CP 4/40, 40-mm-diameter cone having an angle of 4°); FL25 four-bladed vane tool (diameter: 25 mm, height: 55 mm); and serrated parallel plate (SPP40, 40-mm-diameter plate). Three different gaps between plates were used (2, 1.5 and 1 mm) to simulate the range of aggregate spacing in fresh mashed potatoes. The measured oscillatory rheological properties were significantly affected not only by the sample temperature but also by the test geometry used and the friction of and gap between its shearing surfaces. Dynamic parameter values were higher at 55 than at 25C, possibly indicating the onset and propagation of gelatinization of the potato starch grains. Unexpectedly, test geometries with higher friction capabilities, such as the serrated plate and vane tool, presented lower viscoelastic properties compared with results of other test geometries with lower friction capabilities. This result provides evidence of the influence of other factors on the measured oscillatory rheological properties of the mashed potato, such as measurement accuracy of the rheometer at different very small strains, homogeneity of the temperature for the different samples, existence of a complex dependency on the possibly complex stress condition that is imposed on the material upon loading, or even samples being prone to drying. The effect of the variation of the gap between parallel plates on oscillatory parameters depended on the shearing wall friction. The study highlights the difficulty in reconciling rheological results from different sources and the need for standardized rheological test methods so that rheological interlaboratory results can be critically analyzed and compared.
Journal of Food Process Engineering 06/2007; 30(3):267 - 292. · 0.56 Impact Factor
[show abstract][hide abstract] ABSTRACT: The effect of low-temperature blanching (LTB) prior to cooking on colour, textural, firmness and oscillatory parameters, sensory attributes and overall acceptability of either fresh or frozen/thawed mashed potatoes was studied using response surface methodology (RSM) to establish the optimum temperature and time for blanching in both types of mashed potatoes. A central composite rotatable design was used to study the effects of variation in levels of blanching temperature (57.93–72.07 °C) and time (15.86–44.14 min) on the quality parameters. Stationary points showing maximum thickening had critical temperatures (approximately 67–69 °C) and times (approximately 26–30 min) in the ranges of temperature and time used for each independent variable for both fresh and frozen/thawed mashed potato. Results showed a high correlation between structural reinforcement and overall acceptability under optimum experimental blanching conditions. This demonstrates the potential of this experimental approach in terms of tailoring physical properties to predetermined levels in order to meet consumer preferences in mashed potatoes, and of altering the changes that occur after freezing and thawing.
International Journal of Food Science & Technology 12/2005; 41(5):577 - 595. · 1.24 Impact Factor
[show abstract][hide abstract] ABSTRACT: The effect of sample temperature on texture, firmness and the sensory attributes of fresh and frozen/thawed natural and commercial mashed potatoes was studied. Scanning electron microscopy was used to obtain information on the structure of potato cells and how this is affected by processing. Various parameters were measured and were found to increase at 55 °C, these changes could be related to gelatinisation of the starch remaining in the products. In natural mashed potato, texture profile analysis (TPA) and firmness parameters were lower in the processed than in the fresh samples, indicating a weakening of the structure; this was confirmed by photomicrographs. In commercial mashed potato, TPA parameters measured at 55 and 65 °C and firmness parameters measured at 25 °C were higher in the processed samples, indicating enhanced structural strength; this was confirmed by photomicrographs. Firmness per gram of product was the best instrumental parameter for measuring texture in these products. The results of the different analyses indicated that 55 °C was the preferred temperature for consumption of mashed potatoes.
International Journal of Food Science & Technology 04/2005; 40(5):481 - 493. · 1.24 Impact Factor
[show abstract][hide abstract] ABSTRACT: Green beans (cv. Moncayo) were blanched at 65, 70, 75, 80, 85, 90 and 97C for 2.5, 5, 10, 20 and 40min. Pectinesterase (PE) activity was highest in cell-wall-bound extracts of beans blanched at 70C/10min. The lowest water-soluble pectin fraction, the highest EDTA-soluble pectin fraction and the lowest degree of esterification of the EDTA-soluble fraction were all recorded for the same temperature/time combination; these effects can therefore be attributed to PE activity. Chemical changes did not affect initial firmness of the beans, which was practically constant after blanching at 65, 70, 75 and 80C. Simple first-order models were adequate to establish softening kinetics for beans blanched at 85, 90 and 97C. In this temperature range, Kramer maximum force was the mechanical parameter that best characterised bean softening by blanching. For all temperatures, short-time blanching increased the coloration and total chlorophyll content of the samples with respect to fresh control, thus precluding the use of simple models. In the treated beans, the ascorbic acid content was consistently lower than in the control and decreased continuously with increasing time. Microphotographs showed no appreciable differences in morphology between fresh and blanched beans at 65, 70 and 75C, which would explain the similarity of mechanical behaviour in these samples. Blanching at 85, 90 and 97C caused loosening and swelling of the cell walls owing to breakdown of the pectic material, which again helps to explain the observed loss of firmness.
European Food Research and Technology 02/2005; 220(3):421-430. · 1.44 Impact Factor
[show abstract][hide abstract] ABSTRACT: Low-temperature blanching (LTB) of potatoes (cv. Kennebec), both without further processing and prior to cooking or freezing + cooking, significantly increased firmness retention as measured from compression parameters. The increase in firmness with respect to that of unblanched potatoes diminished in the order: blanched at 60C for 60min and cooked > blanched at 60C for 60min frozen and cooked > blanched at 60C for 60min. Potato tubers were kept in refrigerated storage, and firmness, PME activity and dry matter (DM) content were periodically sampled over a period of 80 days. In the early stages of storage, PME activity lost 40% of its original value after 60min at 60C, indicating that the contribution of starch breakdown products to the firmness of cooked and frozen cooked potatoes predominated over the effect of enzyme activity. With increasing time in storage, PME activity measured in the fresh tissue increased by 95% of its original value after 35 days; this resulted in changes in the pectic polymers which made for a firmer texture and different PME behaviour versus LTB temperature and time. A central composite rotatable design was used to study the effects of variation in levels of temperature (52.93–67.07C) and time (31.72–88.28min) on compression parameters and PME activity. Stationary points showing maximum mechanical resistance had critical temperatures and times in the ranges of temperature (58–60C) and time (66–75min) used for each independent variable. Results show a high correlation between PME activity and tissue firmness, suggesting that the contribution of the changes in the composition of the cell wall to the firmness of frozen cooked potatoes increased with increasing time in storage and reached a maximum in the intermediate stages of storage (35 days). Engineering stress (u) proved to be the most appropriate compression parameter for detecting the firming effect that the PME activity produced on the frozen-cooked potato tissues as a consequence of LTB under these conditions.
European Food Research and Technology 01/2005; 221(3):423-433. · 1.44 Impact Factor
[show abstract][hide abstract] ABSTRACT: This was a study of the effect on quality parameters of reprocessing (blanching at 97C for increasing times+freezing) prior to domestic cooking (boiling or stir-frying) of frozen green peas (cv. Mastim) and beans (cvs. Paloma and Moncayo). The results were compared with those of frozen control samples directly boiled or stir-fried. Kramer shear was the most suitable mechanical test for evaluating the effect of reprocessing on mechanical behaviour in both boiled and stir-fried frozen vegetables. Reprocessing significantly affected the mechanical behaviour of both green bean varieties with both cooking methods. Reprocessed products were softer than those supplied by the industry, and softening was significantly greater the longer the blanching time. The colour was more uniform and homogeneous in boiled than in stir-fried reprocessed vegetables; colour parameters showed that reprocessing affected the colour of stir-fried samples more significantly than that of boiled samples. In all the studied vegetables, less chlorophyll and more ascorbic acid were retained when samples were stir-fried than when they were boiled, although chlorophyll and ascorbic acid decreased with increasing reprocessing time in both cooking methods. In the two frozen green bean varieties in particular, SEM microphotographs confirmed the results of mechanical tests, indicating that with both cooking methods, the mechanical parameters were lower in the reprocessed samples than in the controls. The shortest reprocessing procedure (blanching at 97C for 2, 3min+freezing), as a compromise among quality parameters, could shorten the time required for domestic stir-frying of frozen green peas and boiling or stir-frying of frozen green beans.
European Food Research and Technology 07/2004; 219(3):240-250. · 1.44 Impact Factor
[show abstract][hide abstract] ABSTRACT: Rheological behaviour of natural and commercial potato purees was studied in steady and dynamic shear conditions at sample temperatures ranging from 25–65C. Both types of puree were frozen-then-thawed to determine how changes occurring in their structure affected their rheological behaviour. All of the purees presented shear-thinning behaviour with yield stress. Dynamic shear data revealed weak gel-like behaviour in the purees: magnitudes of G were higher than those of G, and both increased with frequency. For fresh natural puree and fresh and frozen/thawed commercial puree, the frequency dependence of G increased, and the frequency dependence of G decreased with sample temperature. Processing weakened the structure of natural puree but resulted in a coarsely aggregated structure in commercial puree. The effect of sample temperature on dynamic parameters was more significant in processed than in fresh purees. The Cox-Merz rule was not applicable to the steady and dynamic shear data on all of the purees. For fresh natural puree, the two types of data conformed to the use of shift factor on frequency, and therefore for this product it would be possible to estimate steady shear data from dynamic shear data, and vice versa. For fresh commercial puree, the relationship between steady and dynamic shear data was non-linear. In both processed purees, the linearity or otherwise of the relationship between viscosities was dependent on sample temperature.
European Food Research and Technology 04/2004; 218(6):544-553. · 1.44 Impact Factor
[show abstract][hide abstract] ABSTRACT: Five different hydrocolloids (amidated low-methoxyl [ALM] and high-methoxyl [HM] pectins, kappa- and iota-carrageenans [κ-C and ι-C], and xanthan gum [XG]) and two dairy proteins (whey protein [WP] and sodium caseinate [SC]) were added at five different
concentrations to fresh (F) and frozen/thawed (F/T) mashed potatoes to investigate ways of improving the effects of freezing
and thawing. It was found that each hydrocolloid and protein, depending on the concentration, affected the viscoelastic properties
of F and F/T mashed potatoes in a different way. Color, drip loss (DL), total soluble solid (TSS) content, and overall acceptability
(OA) were also determined. All systems showed weak gel behavior, although the F samples exhibited higher values of G′ and G″ as compared to F/T counterparts. However, the effects were highly dependent on the type and level of biopolymer added. F
and F/T mashed potatoes with added WP presented higher values of G′ and G″, and values were lowest in both when XG was added. After freezing and thawing, the addition of ingredients (3 to 5g kg−1 ALM and HM, 3 to 8g kg−1
κ-C, and 1.5g kg−1 WP) had the effect of thickening the mash and thus improving freeze/thaw stability. Processed samples were darker than F
samples, although this darkening was not detected by the panelists. Color was affected less by κ-C or ι-C than by the other ingredients added. ALM pectin, κ-C and ι-C, XG, and SC all exhibited water-holding capability, whereas HM and WP did not. The product yielded by XG was softer than
controls without added cryoprotectants in both F and F/T samples, but samples containing 0.5 and 1.5g kg−1 added XG were judged more acceptable than the F control because of the creamy mouth-feel it produced.
Food and Bioprocess Technology 3(1):55-70. · 4.12 Impact Factor