Description:
The idea of publishing a special issue on proteins and enzymes was conceived during the 18th International Drying Symposium (IDS2012) held in the historical city of Xiamen, China (November 11-15, 2012). It appeared to us that a number of scientists and engineers were enthusiastically undertaking research in various aspects of drying of proteins and enzymes. Professors Arun Mujumdar and Sakamon Devhastin encouraged me to explore the possibility of bringing at least one special issue that would depict contemporary research undertakings in the broader theme involving proteins and enzymes. We were somewhat unsure in the beginning whether or not the required number of high quality mansucripts could be garnered for one issue in the time constraint we had in mind. Editorial
Description:
The effect of moisture content on the thermal properties of rice embryos was investigated using differential scanning calorimetry (DSC). A long grain hybrid rice variety (Jinyou 974) grown in Hunan Province of China was selected in this investigation. The temperature scanning tests were carried out from 20°C to 180°C at different heating rates from 2°C/min to 20°C/min. Consistently higher values of glass transition temperature (Tg) were measured when higher heating rates were used during DSC measurements at every set of moisture contents. The Tg values decreased from (65.28±0.38)°C to (31.08±0.26)°C with increase in moisture content from (10.7±0.3)% to (22.0±0.7)% (w/w). The analysis of variance and the regression analysis showed that both the linear function and Gordon Taylor model can adequately represent the variation of Tg with moisture content (R2 > 0.96).
Description:
To examine the effect of protein adsorption on the fat-water interface on the surface composition of spray-dried particles, whey, hydrolyzed whey, and soy protein isolate emulsions were prepared at three different protein to fat ratios of 1:1, 1:5, and 1:10 and spray dried. Non-hydrolyzed whey protein isolate (WPI) and the more hydrolyzed whey protein solutions at 20.2% degree of hydrolysis (DH) had significantly lower surface tension values with fat than without fat. The correlation between the reduction of surface tension value of an emulsion and the increase in protein surface composition of powder particles was observed for WPI and HWP406 but was not observed for the other protein isolate types. It was clear that the spray-dried emulsions had fat as the dominant component on the surface of the powder particles and that the amount of protein on the surface became severely depressed at higher fat addition levels. In terms of its powder morphology, the unique powder structures such as the indentations and folds usually found on the surface of protein containing powders were not evident because they were compromised by the presence of high surface fat. The powder with higher surface fat had more crumpled particle structures and dimpled surfaces.
Description:
The influence of spray-drying conditions, inlet air temperature (130 degrees C to 200 degrees C), outlet air temperature (38 degrees C to 65 degrees C), drying medium (air and nitrogen) and milk-derived protectants (10%, 15%, and 25% lactose; 5% and 10% sodium caseinate; 10%, 25%, and 35% lactose: sodium caseinate (Lac: NaCas, 3:1)) on the survival of Lactococcus lactis ssp. cremoris was studied using a laboratory-scale spray dryer. An inlet air temperature of 130 degrees C and 65 degrees C as the outlet air temperature maintained high survival of the bacteria without sacrificing low moisture content. Inlet air temperature, previously considered to have no significant effect, was shown to play an important role in the survival of bacteria during spray drying. A mixture of Lac:NaCas (3: 1) showed a better protective effect on the survival of bacteria than lactose and sodium caseinate individually, and this effect increased with increasing amount of protectant. The results were generalized by substituting whey protein isolate for sodium caseinate. Finally, the positive effect of elimination of oxygen was demonstrated both by replacing air with nitrogen and adding ascorbic acid as an oxygen scavenger to improve survival of the bacteria. Adding an oxygen scavenger would be a better candidate for industrial application considering the potential high cost of manufacturing if nitrogen was used as the atomization and/or drying medium.
Description:
The objective of the study was to determine optimum inlet and outlet air temperatures of spray process for producing co-microcapsules containing omega-3 rich tuna oil and probiotic bacteria L. casei. These co-microcapsules were produced using whey protein isolate and gum Arabic complex coacervates as shell materials. Improved bacterial viability and oxidative stability of omega-3 oil were used as two main criteria of this study. Three sets of inlet (130 degrees C, 150 degrees C, and 170 degrees C) and outlet (55 degrees C, 65 degrees C, and 75 degrees C) air temperatures were used in nine combinations to produce powdered co-microcapsule. The viability of L. casei, oxidative stability of omega-3 oil, surface oil, oil microencapsulation efficiency, moisture content, surface elemental composition and morphology of the powdered samples were measured. There is no statistical difference in oxidative stability at two lower inlet air temperatures (130 degrees C and 150 degrees C). However, there was a significant decrease in oxidative stability when higher inlet temperature (170 degrees C) was used. The viability of L. casei decreased with the increase in the inlet and outlet air temperatures. There was no difference in the surface elemental compositions and surface morphology of powdered co-microcapsules produced under these nine inlet/outlet temperature combinations. Of the range of conditions tested the co-microcapsules produced at inlet-outlet temperature 130-65 degrees C showed the highest bacterial viability and oxidative stability of omega-3 and having the moisture content of 4.93 +/- 0.05% (w/w). This research shows that powdered co-microcapsules of probiotic bacteria and omega-3 fatty acids with high survival of the former and high stability against oxidation can be produced through spray drying.
Description:
The objective of the study was to determine optimum inlet and outlet air temperatures of spray process for producing co-microcapsules containing omega-3 rich tuna oil and probiotic bacteria L. casei. These co-microcapsules were produced using whey protein isolate and gum Arabic complex coacervates as shell materials. Improved bacterial viability and oxidative stability of omega-3 oil were used as two main criteria of this study. Three sets of inlet (130 degrees C, 150 degrees C, and 170 degrees C) and outlet (55 degrees C, 65 degrees C, and 75 degrees C) air temperatures were used in nine combinations to produce powdered co-microcapsule. The viability of L. casei, oxidative stability of omega-3 oil, surface oil, oil microencapsulation efficiency, moisture content, surface elemental composition and morphology of the powdered samples were measured. There is no statistical difference in oxidative stability at two lower inlet air temperatures (130 degrees C and 150 degrees C). However, there was a significant decrease in oxidative stability when higher inlet temperature (170 degrees C) was used. The viability of L. casei decreased with the increase in the inlet and outlet air temperatures. There was no difference in the surface elemental compositions and surface morphology of powdered co-microcapsules produced under these nine inlet/outlet temperature combinations. Of the range of conditions tested the co-microcapsules produced at inlet-outlet temperature 130-65 degrees C showed the highest bacterial viability and oxidative stability of omega-3 and having the moisture content of 4.93 +/- 0.05% (w/w). This research shows that powdered co-microcapsules of probiotic bacteria and omega-3 fatty acids with high survival of the former and high stability against oxidation can be produced through spray drying.
Description:
Drying kinetics of low molecular weight sugars such as fructose, glucose, sucrose and organic acid such as citric acid and high molecular weight carbohydrate such as maltodextrin (DE 6) were determined experimentally using single drop drying experiments as well as predicted numerically by solving the mass and heat transfer equations. The predicted moisture and temperature histories agreed with the experimental ones within 6% average relative (absolute) error and average difference of +/- 1degreesC, respectively. The stickiness histories of these drops were determined experimentally and predicted numerically based on the glass transition temperature (T-g) of surface layer. The model predicted the experimental observations with good accuracy. A nonsticky regime for these materials during spray drying is proposed by simulating a drop, initially 120 mum in diameter, in a spray drying environment.
Description:
The glass transition temperature and the second transition (the endothermic change between the glass transition and melting temperatures) of fructose were studied. The thermal history strongly affected both transitions of fructose. Storage for 10 days at 22degreesC increased the dynamic glass transition temperature from 16 to 25degreesC and decreased the second transition of fructose from 110 to 98degreesC in the first differential scanning calorimetric (DSC) scan. The amplitude of the second transition increased slightly with storage time and reached 260% of the first transition for vacuum oven dried samples. The effect of thermal history on the glass transition temperature of fructose can be removed by scanning the sample in a DSC to 130degreesC. The effects of water content, glucose and sucrose on the two transitions were also investigated.