Ultrasonication and thermo-sonication belong to alternative, non-thermal food processing methods. The aim of this study was to investigate the influence of different ultrasound power inputs (240 W, ...320 W, 400 W) without and in combination with heat pre-treatment on microbial inactivation and sensory properties of rennet cheese whey in comparison with conventional pasteurization batch processes. Ultrasonication treatments had no impact on reduction of any group of studied microorganisms. Microbial inactivation caused by thermo-sonication treatments with pre-heating to 35 °C or 45 °C increased with nominal power input and/or exposure times and was probably due to the heat improved ultrasonic cavitation. Thermo-sonication treatments at nominal power input (400 W) and preheating to 55 °C were the most effective resulting in greater microbial reduction compared to that observed by simulating pasteurization processes, but occurred probably due to developed heat solely. Sensory properties after ultrasonication and thermo-sonication were considerably improved in comparison with that after simulated pasteurization processes. Mouth feel of whey samples was considerably better, there was no occurrence of sediment and colour remained unchanged in almost all samples.
To obtain mass transfer coefficients of three baby food mixtures on cereal basis in a tunnel dryer, Bi-G drying correlation can be used. Experimental moisture content values for three mixtures at ...three different air temperatures (60, 80 and 100 degree C) and air velocities (0.5, 1.0 and 1.5 m/s) during tunnel drying were collected. Effective moisture diffusivities coefficients were calculated in two ways and for mixtures 1, 2 and 3 and ranged between 1.51 x 10 super(-8) to 52.7 x 10 super(-8) m super(2)/s, 1.05 x 10 super(-8) to 64.9 x 10 super(-8) m super(2)/s and 0.107 x 10 super(8-) to 53.1 x 1O super(-8) m super(2)/s, respectively. At lower drying temperature, moisture diffusivities values calculated in two ways agreed better than at higher temperature. The influence of baby food composition on mass transfer parameters was observed.
High power ultrasound (HPU) represents a non-thermal processing method that has been rapidly researched and used in the last 10
years. The application of power ultrasound offers the opportunity to ...modify and improve some technologically important compounds which are often used in food products. One of them is starch. The aim of this research was to examine the effect of the high power ultrasound of 24
kHz frequency on rheological and some physical properties of corn starch. Various ultrasound treatments were used; an ultrasound probe set with different intensities (34, 55, 73
W
cm
−2) and treatment times (15 and 30
min) and ultrasound bath of 2
W
cm
−2 intensity and treatment times (15 and 30
min). Rheological parameters, turbidity and swelling power of corn starch suspensions were determined for native and ultrasonically treated corn starch suspensions. Differential scanning calorimetry was used in order to examine the pasting properties of corn starch. The results have shown that the ultrasound treatment of corn starch distorts the crystalline region in starch granules. The results of differential scanning calorimetry measurements have shown a decrease in enthalpy of gelatinization. A significant decrease in consistency coefficient (
k) has also been observed. The consistency coefficient decreases stepwise jointly with the increasing ultrasound power. The increase in the swelling power is associated with water absorption capacity and corn starch granules solubility, respectively.
Texture is an important propertiy of extruded snack products, and depended on extrusion process conditions, raw material properties and various ingredients properties as well. The main purpose of ...this research was, using twin-screw extrusion, to manufacture a direct expanded extrudate based on mixtures of corn flour and whey protein concentrate with acceptable textural properties. Mixtures were made of corn flour and three different concentrations of whey protein concentrate (7,5 %, 15 %, 22,5 %). Materials were processed in co-rotating twin-screw extruder APV Baker, MPF 50.15 under input conditions: water intake was 10,08 L/h, 12,18 L/h, 14,28 L/h, screw speed was 300 rpm; expansion temperature was 130 °C; feed rate was 70 kg/h. Textural properties: breaking strength index and expansion ratio were determined. Breaking strength index had largest value for the sample with 22,5 % of whey protein concentrate and water intake of 14,28 L/h. Sample with 7,5 % of whey protein concentrate and 10,08 L/h had largest expansion ratio. Calculated textural properties confirmed validity of samples. This results suggest that enrichment of extrudates with wpc addition up to 22,5 % to improve their nutritional value as well as their textural characteristics can be accomplished. Validation of direct expanded extrudates in dependence of its textural properties have shown validity and justification of this research.
Effects of the addition of rice starch and dietary fibres (pectin and Fibrex) on the porosity of basic frying mixture formulations (corn flour, salt, spices) and oil uptake of coated chicken meat ...have been evaluated. Porosity of the fried breaded chicken meat was calculated from particle and bulk density. Pore size and particle size distribution were determined using microscopy image analysis and particle density by mercury intrusion porosimeter (MIP). Since there is a wide range of particle diameters, significant differences in pore size distribution were found. Also, pore structure appeared to be affected by oil absorption. Mercury entrapment in pores decreased significantly during 8 min of frying. The obtained results show that porosity of the samples is different for different frying mixture formulations and indicate that there is a difference in the extent of oil uptake for different formulations due to film forming capabilities of dietary fibres (pectin and Fibrex).
A newly developed Biot number–Dincer number correlation was applied to determine moisture transport parameters of broccoli drying. Broccoli florets were dried in a single layer with suction flow ...changing the temperature and flow of drying air. Experimental dimensionless moisture content data were used to calculate the drying coefficients and lag factors, which were then incorporated into the analytical model for slab geometry. In a relatively simple manner, Biot number, effective moisture diffusivity and mass transfer coefficient were computed and ranged between 0.2272–0.3030, 3.5780
×
10
−6–16.6670
×
10
−6
m
2
s
−1 and 1.9215
×
10
−4–8.7256
×
10
−4
m
s
−1, respectively. Effective moisture diffusivities calculated by newly developed equation which incorporated lag factor and drying coefficient differed from literature values. Experimental and predicted moisture profiles showed an excellent agreement for all drying conditions with mean errors ranging from ±1.26% to ±5.57%.
Production of extrudates from cereals is an often-used technological process in today’s world food industry. Extrudates from corn flour produced using the twin-screw extrusion process and enriched ...with whey protein concentrate represent high-quality source of proteins and fats. Whey protein concentrate (WPC) as a valuable source of proteins and minerals is one of the highest-quality components for possible extrudate enrichment. In this paper, the influence of various WPC addition and some extrusion process parameters such as feed moisture content (
) on physicochemical properties of directly expanded corn flour extrudates manufactured in twin-screw co-rotating extruder was investigated. Whey protein concentrate was added in the following ratios 7.5%, 15% and 22.5% and water in 10.08, 12.18 and 14.28 L/h. Final composition of products is determined with measuring of protein, fat and water shares, water absorption index (WAI) and water solubility index (WSI). With added WPC and with increase of water volume flow, there was a significant rise in total protein, fat and water content in final products, as well as lowering of WSI and rising of WAI indexes. The statistical analysis of the obtained data shows that the lowest WSI and the highest WAI had samples with the largest share of WPC (22.5%) and water volume flow of 14.28 L/h. Colour is measured for each sample, and results were represented with hue angle (
H
), chroma (
C
) and lightness (
L
) values. Process parameters, WPC and
influence the increase of saturation of C and lightness of L colour value, while H value stays unchanged. Mean value of H was 90.14 ± 1.06, which corresponds to dominance of yellow colour of samples.
Texture and pasting properties of ultrasonically treated corn starch Herceg, I.L.,University of Osijek (Croatia). Faculty of Food Technology; Jambrak, A.R.,University of Zagreb (Croatia). Faculty of Food Technology and Biotechnology; Subaric, D.,University of Osijek (Croatia). Faculty of Food Technology ...
Czech Journal of Food Sciences,
01/2010, Volume:
28, Issue:
2
Journal Article
Peer reviewed
Open access
The effects of high power ultrasound of 24 kHz and ultrasound bath of 24 kHz frequency on the textural and pasting properties of corn starch suspensions was examined. Suspensions were treated with ...different intensities and treatment times (15 min and 30 min) using an ultrasound probe set and bath. The treatments with high power ultrasound probes caused a significant lowering of the starting gelatinisation temperatures of corn starch. The ultrasound treatment caused disruption of starch granules by cavitational forces and made the granules more permeable to water. The highest viscosity was observed for the treatment with 300 W probe. A significant increase in solubility in water (20 deg C) was observed, being caused by the disruption of starch granules and molecules by ultrasound treatment. When applying more powerful ultrasound, starch granules, specifically in the amorphous region, are much more mechanically damaged. The texture profile analyses of the starch gel prepared from the suspensions that had been treated with ultrasound probe presented higher hardness and higher values of adhesiveness and cohesiveness when compared with untreated suspensions or those treated with ultrasound bath. Micrography showed an obvious impact of ultrasound on the structure of starch granules. Ultrasound treatment ruptures and mechanically damages the starch granules causing collapse of cavitation bubbles which induces high pressure gradients and high local velocities of the liquid layers in their vicinity.
High power ultrasound (HPU) represents a non-thermal processing method that has been rapidly researched and used in the last 10 years. The application of power ultrasound offers the opportunity to ...modify and improve some technologically important compounds which are often used in food products. One of them is starch. The aim of this research was to examine the effect of the high power ultrasound of 24 kHz frequency on rheological and some physical properties of corn starch. Various ultrasound treatments were used; an ultrasound probe set with different intensities (34, 55, 73 W cm−2) and treatment times (15 and 30 min) and ultrasound bath of 2 W cm−2 intensity and treatment times (15 and 30 min). Rheological parameters, turbidity and swelling power of corn starch suspensions were determined for native and ultrasonically treated corn starch suspensions. Differential scanning calorimetry was used in order to examine the pasting properties of corn starch. The results have shown that the ultrasound treatment of corn starch distorts the crystalline region in starch granules. The results of differential scanning calorimetry measurements have shown a decrease in enthalpy of gelatinization. A significant decrease in consistency coefficient (k) has also been observed. The consistency coefficient decreases stepwise jointly with the increasing ultrasound power. The increase in the swelling power is associated with water absorption capacity and corn starch granules solubility, respectively.
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