George Srzednicki

The Change of Total Anthocyanins in Blueberries and Their Antioxidant Effect After Drying and Freezing

This study examined the effects of freezing, storage, and cabinet drying on the anthocyanin content and antioxidant activity of blueberries (Vaccinium corymbosum L). Fresh samples were stored for two weeks at 5°C while frozen samples were kept for up to three months at −20°C. There were two drying treatments, one including osmotic pretreatment followed by cabinet drying and the other involving only cabinet drying. Total anthocyanins found in fresh blueberries were 7.2 ± 0.5 mg/g dry matter, expressed as cyanidin 3-rutinoside equivalents. In comparison with fresh samples, total anthocyanins in untreated and pretreated dried blueberries were significantly reduced to 4.3 ± 0.1 mg/g solid content, 41% loss, and 3.7 ± 0.2 mg/g solid content, 49% loss, respectively. Osmotic treatment followed by a thermal treatment had a greater effect on anthocyanin loss than the thermal treatment alone. In contrast, the frozen samples did not show any significant decrease in anthocyanin level during three months of storage. Measurement of the antioxidant activity of anthocyanin extracts from blueberries showed there was no significant difference between fresh, dried, and frozen blueberries.

Effects of drying treatments on the composition of volatile compounds in dried nectarines

The effects of drying treatments including dryer type, drying conditions, and sample preparation on the composition of volatile compounds in two cultivars of dried Australian nectarines were investigated in this study. A cabinet dryer, a tunnel dryer, and a heat pump dryer were evaluated. The sample preparation included halving or slicing the fruit to different slice thickness and in different directions. The volatile compounds in fresh and dried nectarines were isolated using Likens Nickerson simultaneous distillation and extraction technique and identified by gas chromatography. The results indicated that a heat pump dryer was the best system for preservation of volatile compounds in sliced dried fruit in terms of lactones and terpenoids followed by cabinet dryer and tunnel dryer.

Drying of Beef in Superheated Steam

Two drying treatments were applied to slices of beef: superheated steam and hot air. Drying kinetics and quality attributes such as color, water activity, and peroxide value were investigated for different drying conditions (drying medium temperature 130, 160, or 180°C; flow rate of the drying medium of 35, 45, or 55 kg/h; and sample thickness 3 mm, 6 mm, 9 mm, or minced beef). The experimental results show that superheated steam drying generally leads to shorter residence times in the dryer when the moisture content needs to be decreased below 8%. Superheated steam drying distinguishes itself by longer constant rate periods, lower critical moisture contents, and higher drying rates for the falling rate period compared to air drying. Reducing the sample thickness or increasing the transferred heat, by increasing the temperature or velocity of the drying medium, result in accelerating the drying process. Temperatures above 160°C, however, cause changes within the and its surface and prevent the bound moisture from getting to the meats surface to evaporate. This so-called case-hardening effect is worse for air drying than for superheated steam drying and results in even longer drying times and higher final moisture contents. Superheated steam drying reduces the water activity faster than air drying at the beginning of the drying process, but the same values are reached at the end of the drying run. Furthermore, the study proves that the absence of oxygen during superheated steam drying leads to prevention or minimization of lipid oxidation reactions, thus resulting in low peroxide values. Undesired quality changes like off-flavors and off-odors hardly develop during superheated steam drying even at high temperatures and long drying times.

DRYING OF HIGH MOISTURE CONTENT PADDY IN A PILOT SCALE TRIANGULAR SPOUTED BED DRYER

From the successful drying of paddy in a lab-scale triangular spouted bed (TSB), a pilot scale unit with a capacity of 500kg/batch was constructed and used to dry paddy of high moisture contents. The drying tests showed that air temperatures of up to 160°C in the first stage, followed by a lower temperature of 80–100°C in the second stage, can be used to dry paddy from more than 25% down to around 15% (w.b.) without significantly changing grain quality in terms of head rice recovery. Moisture distribution in the pilot-scale TSB was observed to be satisfactorily uniform.

Effects of High-Temperature Drying on Physicochemical Properties of Various Cultivars of Rice

Abstract Three varieties of paddy rice, namely Langi and Amaroo from Australia and Chainart I from Thailand, were dried from high initial moisture content of about 27% down to 13–14% wet basis using a two-stage drying system. A fluidized bed dryer reduced the moisture content down to 18%. Drying experiments were carried out at 100, 125, and 150°C. Further moisture content reduction down to 14% was achieved by shade drying. As a result of these treatments, head rice yield increased proportionally with the drying temperature. In contrast to that, the yellowness, measured by colorimeter in terms of b value, showed an opposite trend. Starch characteristics were studied by Rapid Visco Analyser (RVA), x-ray diffraction, and differential scanning calorimetry (DSC). Pasting properties were affected by the drying temperature. The peak viscosity and break down were decreasing with the increase of drying temperature in all varieties while the setback values were increasing in Langi and Amaroo only. All starch samples displayed the typical A type x-ray diffraction pattern. The apparent crystallinity determined by x-ray diffraction was reduced with increasing drying temperature. The gelatinization peak shifted to higher temperature while the endothermic enthalpy of gelatinization decreased with increasing drying temperature.

OPTIMIZING CONDITIONS FOR HEAT PUMP DEHYDRATION OF LACTIC ACID BACTERIA

ABSTRACT Heat pump dryers were studied as an alternative to freeze drying for dehydration of lactic acid bacteria for starter cultures. Factors investigated were bacterial growth phase, addition of dehydro-protectants, drying conditions, drying media and storage life of the dried bacteria. The main criterion for evaluation was the activity of the dried product. Results indicated that single dehydro-protectants were not able to give high activities, but suitable combinations were found giving results at least equal to freeze-drying. Nitrogen purging was found to give a significant improvement in activity.

Corn, Rice, and Wheat Seed Drying by Two-Stage Concept

Corn, rice, and wheat seeds with an initial moisture content (IMC) of 20–25% wb were dried to moisture content below 18% wb at 40–80°C in a fluidized bed dryer (FBD) and spouted bed dryer (SBD) and the seeds with IMC 18% wb were dried to below 14% wb at air temperatures 18–30°C and relative humidity 60–70% by an in-store dryer (ISD). As a result, it appears that a two-stage drying concept is feasible in drying high-moisture-content seeds due to the high germination rate of dried seeds. Nonetheless, the drying temperature must be carefully selected. A drying temperature of 40°C was clearly safe for all samples, whereas more than 90% of wheat seeds still germinated after drying at 60°C in FBD. Furthermore, drying seeds with IMC 18% wb by ISD was safe under specified drying conditions.

Seed Drying in Fluidized and Spouted Bed Dryers

This study was conducted in order to provide information on drying behavior of seed destined for reproduction of corn, wheat, and rice. Drying experiments were conducted in a fluidized bed dryer (FBD) with corn, rice, and wheat and in spouted bed dryer (SBD) with wheat and rice at temperatures between 40 and 80°C. The experimental data were fitted into four thin-layer drying models by a least squares method. As a result, Pages model and a two-compartment model were the best-fitted models. However, due to the limitation of these models, Pages model and the two-compartment model were modified by adding the drying temperature term. Subsequently, these models could adequately predict the drying curves under a wider range of temperatures with root mean square (RMS) of the difference between model-predicted and experimental values of less than 0.035.

Effects of high-temperature drying on the flavor components in thai fragrant rice

ABSTRACT The effects of high-temperature drying on Thai Jasmine rice were investigated. Paddy was first rewetted and then dried using a two-stage drying process, involving a fluidized bed at high temperature, followed by shade drying (ambient air drying). Three high drying temperatures: 100, 125, and 150°C were studied. Volatile compounds were extracted by distillation and extraction in a Likens and Nickerson apparatus, and analyzed by gas chromatography–mass spectrometry. A total of 94 volatile compounds were identified. These included 21 alcohols, 19 aldehydes, 14 ketones, 12 acids, 9 heterocyclic compounds, 8 hydrocarbons, 5 esters, and 6 miscellaneous compounds. 2-Acetyl-1-pyrroline, a major constituent of volatiles in fragrant rice was identified and tended to increase in concentration with increasing drying temperature. The three different drying temperatures used in the fluidized bed dryer were found to have an effect on the volatile components of Thai Jasmine rice. The increase in drying temperature contributed to the formation of new compounds, as well as the loss of other desirable volatiles.

Comparison Between Fluidized Bed and Spouted Bed Drying for Seeds

Fluidized bed dryers (FBDs) and spouted bed dryers (SBDs) are considered efficient dryers for drying seeds from high moisture content (MC; 20–25%wb) to medium MC (≈18%wb). In this work, a number of drying experiments and seed quality tests were conducted using rice and wheat seeds in order to compare the FBD and SBD with regard to drying rate, product quality, and specific energy consumption. It was found that FBD was better in terms of a faster drying rate and SBD was better in terms of specific energy consumption. However, it could not be clearly concluded which dryer provided a better product quality in terms of germination percentage.