Browsing by Author "Josip Simunovic, Committee Member"

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Development and Characterization of Spray Dried Sweetpotatoes
(2005-12-18) Grabowski, Julie Ann; Josip Simunovic, Committee Member; Chrisopher Daubert, Committee Member; Van-Den Truong, Committee Chair
Sweetpotatoes are a nutritious vegetable rich in calories, vitamins, minerals, and biologically active phytochemicals. However, the consumption of sweetpotatoes has been declining. Very few sweetpotato product choices exist for consumers beyond the raw root. Furthermore, special storage and handling requirements for sweetpotatoes have proven to be a challenge to incorporating this healthy vegetable into processed food products. Therefore, a need exists to develop alternative processing methods to produce a functional and stable form of sweetpotatoes that is readily available for the food processing industry. One strategy is to convert sweetpotato puree into a dried powder to be used as a functional ingredient in different food systems. Spray drying, which has been used for commercial production of several fruit and vegetable powders, has not yet been applied to sweetpotato processing. Several methods of producing a functional powder in an efficient manner were investigated since spray drying has never been applied to sweetpotato puree. The high viscosity of sweetpotato puree was anticipated to be a challenge in pumping and atomization during the spray drying process. Moreover, the sticky behavior due to high sugar content in sweetpotato puree may affect spray drying efficiency. Many spray dried products make use of a drying aid such as maltodextrin in order to increase the glass transition temperature and reduce stickiness thus facilitating product recovery. These pre-drying treatments of viscosity reduction and maltodextrin addition, as well as drying temperature, were expected to have effects on the physicochemical characteristics of the final spray dried powder. Thus, model-fitting using response surface methodology was performed to examine the effects of the pre-drying treatments and spray drying conditions on the moisture content, color, water absorption, solubility, particle size, bulk density, and glass transition temperature of the spray dried powder. Elevated temperature and the action of amylase proved to be effective in reducing puree viscosity. Furthermore, pre-treatment with alpha-amylase resulted in dried powders with a lower glass transition temperature and smaller particle size. The addition of maltodextrin significantly increased powder solubility, altered the hue value, and raised the glass transition temperature of the powder. Sound models were developed for some attributes while further study is needed to accurately develop prediction models for other powder characteristics. Difficulty existed in determining the optimal drying conditions for sweetpotatoes as the best finished product characteristics for dried sweetpotato powders are dependent on the finished product application. However, spray drying sweetpotatoes with a combination of amylase treatment and maltodextrin created a quality powder balancing all functional characteristics. To better determine potential applications of powders produced with various levels of amylase and maltodextrin, nutrient composition and rheological properties of the powders in solution were examined and compared to sweetpotato puree. Many of the characteristic sweetpotato nutrients such as beta-carotene and ascorbic acid were severely reduced during the spray drying of sweetpotato puree. Further isomerization of beta-carotene also occurred during dehydration. In addition to thermal degradation of components, the addition of maltodextrin as a drying aid diluted the amount of nutrients in the resulting powder. Rheological characterization of the powders found the viscosity of the reconstituted solutions was much lower than that of the puree at the same solid concentration. However, the reconstituted sweetpotato slurries did behave similarly to pregelatinized starch solutions. Spray dried sweetpotato powders have been developed to become a functional ingredient in foods by enhancing natural color, flavor, and functionality. Overall, results show that good quality sweetpotato powders can be produced using this drying method. Despite the need for further increased nutrient retention, these powders have the potential to be a good source of beta-carotene and minerals as well as used in food systems as a thickener. As product developers research ways to improve food products, sweetpotato powders could potentially be used in dry mixes, soups, beverages, and other food and nutraceutical products. Furthermore, additional research could optimize the physicochemical characteristics for a specific product application.
Residence Time Distribution of Multiple Particles in Four Configurations of Holding Tubes
(2004-11-15) Tanyel, Zeynep; Andrey Kuznetsov, Committee Member; Saad Khan, Committee Member; K.P. Sandeep, Committee Chair; Josip Simunovic, Committee Member
Residence time distributions of multiple particles (as affected by process and system parameters) were investigated during non-Newtonian tube flow. Process parameters included flow rate, particle type, carrier fluid viscosity, and particle concentration. The system parameter of interest was the holding tube configuration. Polystyrene and acrylic particles were used as model food particles. Digital imaging analysis was used to obtain residence time data of particles. A novel type of holding tube (chaotic holding tube) was constructed. Comparisons among the straight, single helical, double helical, and chaotic holding tube were performed in terms residence time distribution (RTD) of particles. In addition, the effect of inclination angle (0 ° and 45 °) of the chaotic holding tube was investigated. It was found that the narrowest RTD of particles was obtained in the single helical holding tube. RTstd in the chaotic holding tube was greater than that in the single helical holding tube, but lower than those in the straight and double helical holding tubes. The most significant process parameter affecting RTD was flow rate. The effect of flow rate was more pronounced for high density (acrylic) particles. Carrier fluid viscosity, particle type, and particle concentration did not have significant effects on the overall RTstd. Trends observed in the chaotic holding tube were similar to those observed in the single helical holding tube. However, there were some cases where use of chaotic holding tube resulted in narrower RTD of particles. Changing the inclination angle from 0 ° to 45 ° in the chaotic holding tube resulted in wider RTD of both types of particles.
Thermal Processing of Sour Cream using Continuous Flow Microwave Heating - Feasibility Study
(2007-07-26) Settle, David William; Josip Simunovic, Committee Member; Jonathan C. Allen, Committee Member; Leon Boyd, Committee Member; Arthur P. Hansen, Committee Chair
The purpose of this research was to develop a sour cream that could withstand the effect of UHT continuous microwave processing. The major benefit to the manufacturer of the UHT processing would be extended shelf-life, especially in conjunction with asceptic packaging. This would result in less spoilage, thus increased profits. This becomes increasingly important as sour cream increases in popularity and is sold and marketed at greater distances from the point of processing One major problem with UHT processing of acidic dairy products is that high temperatures cause milk proteins to aggregate, especially at pH's around the pI (isoelectric point) of casein. Fouling (or burn-on) of the heat-exchanger tube walls is another factor that excludes the use of UHT processing to sterilize sour cream. The proper formulation of sour cream with the use of stabilizers such as starch and gelatin can also minimize aggregation, reduce syneresis, and increase the viscosity of the final products. The addition of gelatin is often used in sour cream formulations as it increases water binding, whey retention, and adds to mouthfeel, and gives the final product sheen-like appearance. In order to characterize the performance and functionality of sour cream under continuous flow microwave thermal processing conditions, seven sour cream formulations with different gelatin and starch content were produced and processed. Yield stress and viscosity tests were performed and compared to rheological tests performed on commercial brands to determine if they were within the upper and lower commercially accepted limits. Viscosities were dynamically measured with the Stresstech. Dielectric properties of the sour cream samples were also analyzed. Dielectric measurements were taken at 5#176; C intervals. Microwave processing was performed using a 5 kw microwave system. Processing was performed at an output power of 3 kilowatts at 915 MHz at flow rate of 4 liters per minute to determine dielectric properties and estimate the need for formulation adjustments. Rheological analysis of the seven NCSU sour cream formulations showed no correlations between stabilizer levels and yield stress or viscosity. Measurement of time and temperature data showed that variations were present and that processing conditions had an influence on the rheological behavior of the sour creams. Because of this, a single formulation could not be determined as optimal. All seven formulations were more viscous than the commercial brands tested but had lower yield stresses. Also, none of the seven formulations had visual casein aggregation. Rheological analysis of the seven formulations indicated that UHT continuous microwave processing was feasible using any of the formulations. This new process will allow sour cream to be ascetically packaged which had never been done. Aseptic packaging would allow manufactures to increase profit margins by reducing spoilage and eliminate refrigeration costs.