K. Muthukumarappan

Effects of sonication on the kinetics of orange juice quality parameters.

The effects of sonication on pH, degrees Brix, titratable acidity (TA), cloud, browning index, and color parameters ( L*, a*, and b*) of freshly squeezed orange juice samples were studied. Ultrasonic intensity (UI) levels of 8.61, 9.24, 10.16, 17.17, and 22.79 W/cm2 and treatment times of 0 (control), 2, 4, 6, 8, and 10 min were investigated. No significant changes in pH, degrees Brix, and TA ( p < 0.05) were found. Cloud value, browning index, and color parameters were significantly affected by ultrasonic intensity and treatment time. Changes in cloud value followed first-order kinetics, whereas browning index, L*, a*, and b* values followed zero-order kinetics. Reaction rate constants were linearly correlated ( R2 > 0.90) to ultrasonic intensity.

Rheological Properties of Sonicated Guar, Xanthan and Pectin Dispersions

The influence of high intensity ultrasound on the rheological characteristics of guar, xanthan, and pectin dispersions was investigated. Guar 1%, xanthan 1% and pectin 2% (w/v) dispersions were sonicated at varying intensity levels of 3.7, 6.3, 8.1, and 10.1 W/cm2 for 5 min at 25oC. Significant differences were observed in the rheological characteristics of each sonicated hydrocolloid dispersion studied. Sonication affected the consistency index (k), flow behaviour index (n) and complex power law constants (a and b). No recovery was observed in the structure breakdown after a 24-h storage period. Changes in the rheological properties of guar and pectin dispersions were significantly higher than that of xanthan dispersions.

Textural and Rheological Properties of Processed Cheese

Abstract Cheddar cheeses made from ultra filtered (UF) as well as vacuum condensed milks (CM) containing two protein levels (4.5 and 6.0%) were used to manufacture processed cheeses. These processed cheeses were evaluated for instrumental textural profile analysis (TPA), stress relaxation characteristics using Sintech universal testing machine, and visco elastic characteristics (Elastic modulus-G′ and viscous modulus-G′′) using a Haake Viscometer. A small amplitude oscillatory shear test was employed to assess the visco elastic characteristics. Peleg model and six elements Maxwell model were used to assess stress relaxation characteristics of the cheese. Results indicated that the instrumental TPA hardness of UF2 cheeses made from high protein UF milk was highest (149 N) as compared to cheeses made from low protein UF milk (125 N), high and low protein vacuum condensed milks (103 and 62 N, respectively), and control (53 N). The values of elastic and viscous moduli of cheeses made utilizing high protein UF milk were 3.53 and 2.32 MPa respectively, which indicated its higher viscoelastic nature. The UF2 cheese also showed higher values of modulus of elasticity during stress relaxation (21.8 and 16.2 kPa respectively for Peleg and Maxwell models) and required longer time to relax the given amount of stress as compared to rest of the cheeses. The higher values of hardness and visco-elasticity were attributed to higher protein and lower fat contents in the cheeses. The methods of instrumental texture and rheology evaluation had common outcome for hardness and visco-elasticity of cheeses. Results of stress relaxation tests were more useful to differentiate the cheese characteristics as compared to the results of instrumental TPA and dynamic rheology tests.

Effect of flow agent addition on the physical properties of DDGS with varying moisture content and soluble levels.

Distillers Dried Grains with Solubles (DDGS) is widely recognized as a highly nutritious animal feed ingredient. With the exponential growth of the fuel ethanol industry in the past several years, significant quantities of distillers grains are now being produced. To effectively utilize these feeds in the domestic market, these coproduct streams have to be transported greater distances, and must be stored in various structures until final use. Unfortunately, DDGS flow is often problematic, as it frequently becomes restricted by caking and bridging during storage and transport. This issue may arise from a number of factors, including storage moisture, temperature, relative humidity, particle size, time, or temperature variations. The objective of this study was to examine the effect of various moisture content levels (10%, 15%, 20%, 25%, and 30% d.b.) and calcium carbonate (a common flow agent) levels (0%, 1%, and 2% w.b.) on the resulting physical and flow properties (Carr indices) of DDGS with varying soluble levels (10%, 15%, 20%, and 25% d.b.). The results showed that DDGS flowability declined with increased soluble and moisture content levels. Flow agent (CaCO3) addition did not have a significant effect in improving the flow properties of DDGS. This may have been due to no surface affinity between DDGS and the flow agent particles, or too little inclusion of the flow agent.

Effect of Moisture content and Soluble levels on the Physical and Chemical Properties of DDGS

Over the past few decades, researches concerning handling and storage characteristics of bulk solids have been conducted to a large extent. Distillers Dried Grains with Solubles (DDGS) are a bulk material that has been widely used as a protein source for ruminants and non-ruminants for more than two decades. Distillers’ grains are energy dense as they contain high fat levels. With the exponential growth of the fuel ethanol industry in the past several years, significant quantities of distiller’s grains are now being produced. To effectively utilize these feeds in the domestic market, however, these coproduct streams are increasingly being transported greater distances, and must be stored until final use. DDGS flow is often problematic as it can become restricted by caking and bridging which occurs during transportation and storage. This issue probably results from storage moisture, temperature, relative humidity, particle size, time, or temperature variations. The objective of this phase of the study is to examine the effect of various moisture content levels (10, 15, 20, 25, 30% db) on the resulting physical and chemical properties of DDGS with varying soluble percentages (10, 15, 20, 25% db).

Rheological Properties of Cheddar Cheese During Heating and Cooling

Abstract Rheological properties of different Cheddar cheeses were characterized using a dynamic test. Cheddar cheeses with four fat contents (15.3, 22.8, 37.3, and 45.6% fat in the dry matter—FDM) and two moisture contents (58.1 and 62.4% moisture in non fat portion—MNFP) at 2, 4, 12, and 24 wk old were used in this study. Time sweep mode was used to characterize the elastic (G ′) and viscous (G ″) properties of Cheddar cheese at a constant frequency of 1 Hz and strain 0.5%. G ′ and G ″ of the cheese were determined during heating from 25 to 60°C and cooling from 60 to 25°C. G ′ decreased from 9.0 to 0.07 MPa during heating and increased from 0.07 to 9.0 MPa during cooling of Cheddar cheese. G ″ showed similar trend as that of G ′ although magnitude of change were about one log higher. The reduction in % FDM of Cheddar cheese increased G ′ from 5.5 to 9.0 MPa and increased G ″ from 2.5 to 6.0 MPa at 25°C. A similar trend was observed at other temperatures. Proteolysis during ripening of cheese lead to decrease in G ′ and G ″ value for different fat Cheddar cheese at 60°C but differences were not statistically significant at 25°C. However, G ′ increased for high moisture Cheddar cheese (62.4% MNFP) from 1.6 to 4.4 MPa at 25°C and difference were not significant at 60°C.

STRESS RELAXATION CHARACTERISTICS OF CHEDDAR CHEESE

Stress relaxation experiments were conducted by heating a cheese sample (22 mm diameter and 17.5 mm height) at 40, 50 and 60°C in an aluminum cup whose inner diameter and depth were 22 mm and 17.5 mm, respectively. A plunger of 18 mm diameter, which was attached to an Instron type machine, was allowed to compress the cheese instantaneously to 10% deformation. The relaxation of stress was recorded as a function of time. Cheddar cheeses with four different fat content (15.3, 22.8, 37.3 and 45.6% fat dry matter – FDM) and two different moisture content (58.1 and 62.4% moisture in non fat portion – MNFP) at 2, 4, 12 and 24 weeks were used in this study. Generalized Maxwell and empirical Peleg models were used to characterize the stress relaxation behavior of melted cheese. The effect of fat content, moisture content, and age of cheese on stress relaxation behavior was studied. Peleg model well described the stress relaxation behavior of melted cheese (cheeses above 50°C) and eight element Maxwell model predicted better than three element Maxwell and six element Maxwell models. The stress relaxation experiment differentiated the viscoelastic nature of different cheeses due to reduction of fat content, increase in moisture, increase in melting temperature and age of cheese. Stress relaxation test can be used as a tool to systematically study cheese functionality.

Viscoelastic Properties of Part Skim Mozzarella Cheese: Effect of Calcium, Storage, and Test Temperature

Abstract Part skim Mozzarella cheeses with four levels of calcium (0.65% in control, 0.48% in T 1, 0.42% in T 2, and 0.35% in T 3) were manufactured on four separate occasions. Effect of varying calcium levels on viscoelastic properties of these cheeses was studied. Elastic (G′) and viscous (G′′) modulus were determined on day 1, 7, 15, and 30. Effect of increasing cheese temperature from 25 to 45°C during the test was also determined. Low calcium cheeses (0.35% in T 3 vs. 0.65% in control) had lower value of elastic (0.83 MPa vs. 1.89 MPa) and viscous modulus (0.57 MPa vs. 1.43 MPa). During storage, a decline in viscoelastic properties of the cheese was also noticed. After 30 days of storage, the elastic modulus of control and lowest calcium cheese (T 3) declined from 1.89 MPa to 1.69 MPa and from 0.83 to 0.55 MPa, respectively. Similar reduction in viscous modulus of control and lowest calcium cheeses (T 3) was also noticed after 30 days, i.e., values of G′′ declined from 1.43 to 1.25 MPa in control and from 0.57 to 0.27 MPa in T 3. A decline in elastic as well as viscous modulus with increase in cheese temperature during the test was observed. Values of elastic modulus were always higher than viscous modulus, indicating dominance of elastic nature of Mozzarella cheese. This information would help the manufacturers to produce cheeses with specific functional properties. #Published with the approval of Director of the South Dakota Agricultural Experiment Station as Publication Number 4321 of the Journal Series.

Physical and Chemical Characterization of Fuel Ethanol Coproducts Relevant to Value-Added Uses

ABSTRACT One of the fastest growing industries in the United States is the fuel ethanol industry. In terms of ethanol production capability, the industry has grown by more than 600% since the year 2000. The major coproducts from corn-based ethanol include distillers dried grains with solubles (DDGS) and carbon dioxide. DDGS is used as a livestock feed because it contains high quantities of protein, fiber, amino acids, and other nutrients. The goal of this study was to quantify various chemical and physical properties of DDGS, distillers wet grains (DWG), and distillers dried grain (DDG) from several plants in South Dakota. Chemical properties of the DDGS included crude ash (5.0–21.93%), neutral detergent fiber (NDF) (26.32–43.50%), acid detergent fiber (ADF) (10.82–20.05%), crude fiber (CF) (8.14–12.82%), crude protein (27.4–31.7%), crude fat (7.4–11.6%), and total starch (9.19–14.04%). Physical properties of the DDGS included moisture content (3.54–8.21%), Aw (0.42–0.53), bulk density (467.7–509.38 kg/m3...

Modeling The Flow Properties Of Distillers Dried Grains with Solubles

Distillers dried grains with solubles (DDGS) are an excellent source of energy, minerals, and bypass protein for ruminants, and are also used in monogastric rations as well. With the remarkable growth of the US fuel ethanol industry in the past decade, large quantities of distillers grains are now being produced. DDGS flow is often restricted by caking and bridging during its storage and transportation. In our previous works, it has been found that increased soluble and moisture levels significantly affected the flow properties of DDGS. Currently, however there is no model available to predict the flowability of DDGS. So, the objectives of this study were to thoroughly investigate the data obtained from our previous work using exploratory data analysis techniques, and to develop a comprehensive model to predict the flowability of DDGS. A simple and robust model (R2=0.93; SE=0.12) was developed by combining the important flow properties obtained from both Carr and Jenike tests using dimensional analysis and response surface modeling. The model developed was exclusively based on the DDGS from one ethanol plant. As DDGS flow properties will differ with each plant, it is suggested to use this methodology to develop a similar model to predict the flowability of DDGS for other plants as well.