M. N. Eshtiaghi

High electric field pulse pretreatment: potential for sugar beet processing

Abstract The application of high intensity electric field pulses (HELPs) on the cell disintegration of sugar beet cells was investigated. HELP treatment (20 pulses, ∼2.5 kV / cm , 5 μF , 1–6 Hz) rapidly performed disintegration of sugar beet cell membranes in 20 s or less. In particular, field strength (1.2–2.5 kV/cm) and pulse number (1–200) had a key influence on the disintegration. Apart from the conventional thermal cell disintegration (at 75–80°C) followed by extraction, it is possible to extract sugar beet after HELP-pretreatment at ambient temperatures. HELP permeabilized sugar beet can be completely depleted of sucrose after one or two pressing steps (at 2 or 5 MPa, respectively) by adding water (less than 40% of the raw material weight) between the pressings. The HELP-treated and subsequently pressed pulp showed higher dry matter (∼30% dry matter) than the conventionally heat extracted and pressed pulp (∼15% dry matter) which provides a significant reduction in process time and energy requirement during dehydration of the extracted cossets.

Comparison of pretreatment methods on water and solid diffusion kinetics of osmotically dehydrated mangos

Abstract This study compared mass transfer during osmotic dehydration (OD), as well as some quality indices, of untreated mango samples to those pretreated by applying high intensity electric field pulses (HELPs), high pressure (HP) or supercritical carbon dioxide having the same initial cell disintegration index ( Z p ) in the range 0.50–0.58. HELP and HP pretreated samples had a higher water loss (WL) and higher solid gain (Sg) than the untreated samples. Applying supercritical carbon dioxide did not improve water loss but facilitated higher sugar gain (8–42%) than in the other pretreated samples. HP and supercritical carbon dioxide pretreatments increased the red intensity ( a values) of the mangos. The breaking force of HELP and HP pretreated samples increased with OD time.

HIGH HYDROSTATIC PRESSURE THAWING FOR THE PROCESSING OF FRUIT PREPARATIONS FROM FROZEN STRAWBERRIES

Abstract High hydrostatic pressure thawing (600 MPa, 25 and 50°C, 15 min) of frozen strawberries was applied as a pretreatment in the thermal processing of strawberry preparations when comparing this process with thawing of strawberries at atmospheric pressure prior to thermal processing (92°C, 20 min) increases in sucrose uptake were observed for strawberry slices (21%) as well as for whole fruit (140%) reaching maximum sucrose contents of 45.6±2.4°Brix and 34.7±0.9°Brix respectively. In addition high pressure treatment of strawberries proved sufficient to reduce total microbial counts by two log cycles.

Effects of combined high pressure and heat treatment on the reduction of peroxidase and polyphenoloxidase activity in red grapes

Abstract The effects of high hydrostatic pressure treatment (100 to 600 MPa) coupled with heat treatment (0 to 60 °C) on the inactivation of peroxidase (POD) and polyphenoloxidase (PPO) in red grapes (Vitus viniferd) have been studied. The examination of the complex interactions between pressure and temperature has been carried out using a central composite rotatable design (CCRD). The response surfaces show that the lowest activity of POD (55.75%) and PPO (41.86%) was found to be at 60 °C at 600 MPa and 100 MPa, respectively.

Inactivation of Lemon Pectinesterase by Thermosonication

The combined effect of ultrasound and temperature (thermosonication) on the inactivation of lemon pectinesterase was examined. The experiments were separated into two groups. The first ones were performed at 40°C-90°C, ambient pressure with ultrasonication of 20 kHz. The other ones were carried out at 40°C-90°C without ultrasonication. After heating at 50°C with the ultrasonic treatment for 63 min, the residual activity was 83% decreased whereas without the ultrasound the residual activity was only 30% decreased. The D-values show that the combination treatment has more influence on the inactivation of pectinesterase.

Preliminary study for bioconversion of water hyacinth (Eichhornia crassipes) to bioethanol.

The effect of physical (subcritical water) and chemical (acid and alkali) pretreatment on conversion of lignocellulose (cellulose, hemicellulose) in water hyacinth (WH) was investigated. The highest sugar content in acid pretreated samples was observed in WH treated with 3% H2SO4 solution (up to 18.16% w/w). Alkali treatment had nearly no effect on conversion of lignocellulose in WH to sugar. Combinations of acid or alkali pretreatments with enzyme treatment resulted in drastic increase of sugar in samples (up to 31.2 and 22.9 % w/w, respectively). In addition, increasing the applied enzyme concentration from 0.8% w/w (on dry WH basis) to 4% further increased the sugar content in the sample (up to 50.5% w/w). Subcritical water (SCW) (200°C and 10 min) and subsequent enzyme treatment resulted up to 17% w/w sugar in samples. Bioethanol concentration during fermentation (at 30°C) of pretreated sample using Saccharomyses cerevisae increased with increasing the fermentation time. After 3 days fermentation, up to 60% of sugar in the sample was converted in ethanol.

Optimization of Subcritical Ethanol Extraction for Xanthone from Mangosteen Pericarp

 Abstract—Mangosteen pericarp has been used for long time as traditional medicine. One of main active ingredient in mangosteen pericarp is xanthone. Xanthone has remarkable effects on cardiovascular, antiviral, and anti-inflammatory. Subcritical ethanol extraction (Sc-ethanol) was employed to extract xanthone from dried mangosteen pericarp and compared with maceration and soxhlet extraction. The Sc-ethanol was applied by various temperature (80, 120 and 160 o C), ethanol concentration (50, 72.5 and 95%) and extraction time (10, 20 and 30 min.) for 1:20 of sample to solvent ratio. The Box-Behnken design was applied to investigate the optimum condition of Sc-ethanol extration. The optimum conditions from Box-Behnken design to obtain the highest xanthone were determined at the optimum conditions as following; temperature 160 o C, extraction time 30 min in 95% ethanol. The results presented that for maceration, soxhlet and Sc-ethanol extractions in 0.5 h, the extracted xanthones were 28.31, 31.26 and 57.42 mg/g of dried mangosteen pericarp respectively.

Effect of Various Pulsed Electric Fields Conditions on Extraction of Sugar from Sugar Beet

The effects of pulsed electric field (PEF) on the cell disintegration of sugar beet were studied. Field strength (0.5kV/cm to 6kV/cm), pulse number (1 to 100 pulses) and capacity of capacitors (0.5 F to 32 F) were evaluated on degree of cell disintegration and consumed energy in PEF treatment. The field conditions of 1 and 2 kV/cm, 8 F with 20 and 10 pulses respectively disintegrated the cell membrane in less than 1 minute. The most important parameters during cell permeabilization were the total energy input followed by field strength. At energy input of 3.2 kJ/kg, the higher the field strength resulted the higher cell permeabilization. Mass transfer with determination of sugar and ion leaching for PEF pretreated sugar beets at room temperature were compared to moderate and high heat treatment (50, 75 and 80C, 15minutes). Comparison between PEF pretreatment and conventional thermal cell disintegration (average 75C) method showed that high values of sugar may extracted after PEF pretreatment (2kV/cm, 8µF) at ambient temperature while 75C or more with long time thermal duration is needed to achieve the same extracted sugar. In addition, the energy consumption for thermal treatment is approximately 20 times more than PEF pretreatment. Optimization of field condition (Field strength, capacity of condensers, and number of pulses) as well as treatment chamber conditions are very important factors to achieve high yield of sugar from sugar beet when using PEF. Keywords: Nonthermal, Pulse electric fields, Sugar beet, Cell disintegration