Antimicrobial Disc Susceptibility Tests for Glucose Oxidase/Catalase System

Whachun Yoo,Arthur G. Rand 한국식품과학회 1995 Food Science and Biotechnology Vol.4 No.4

Steady and Dynamic Rheological Properties of Thickened Beverages Used for Dysphagia Diets

조현문,Whachun Yoo,유병승 한국식품과학회 2012 Food Science and Biotechnology Vol.21 No.6

Thickened beverages prepared with commercial food thickeners are widely used to promote safer and more successful swallowing in patients with dysphagia. In this study, the rheological properties of cold thickened beverages (bottled water, orange juice, apple juice, and whole milk)prepared with a commercially available gum-based food thickener (xanthan-guar gum mixture) marketed in Korea were investigated at 3 different thickener concentrations (2,3, and 4%, w/w). Thickened beverages showed high shearthinning (n=0.12-0.21) behavior with Casson yield stress at all concentrations. Their apparent viscosity (ηa,50),consistency index (K), Casson yield stress (σoc), storage modulus (G'), and loss modulus (G") increased with an increase in thickener concentration. Steady and dynamic rheological parameters also demonstrated greater differences in rheological behaviors between thickened beverages with different thickener concentrations. These results suggest that rheological properties of thickened beverages are strongly affected by thickener concentration and the type of beverage prepared.

Standard Recipes for the Preparation of Thickened Barium Liquids Used in the Diagnosis of Dysphagia

( Jaechun Park ),( Whachun Yoo ),( Byoungseung Yoo ) 한국임상영양학회 2019 Clinical Nutrition Research Vol.8 No.4

Barium sulfate is commonly used to prepare contrast media for videofluorograpy. The flow characteristics of thickened liquids formulated for oropharyngeal imaging are known to be greatly affected by the addition of barium. In this study, thickened barium liquids were prepared by mixing a commercial xanthan gum (XG)-based thickener (Visco-up®) at different concentrations (0.1%-3.0%) with barium powder (Baritop HD®), and differences in the viscosity between thickened non-barium and thickened barium liquids were investigated. In addition, the thickness levels of thickened barium liquids, which are based on the National Dysphagia Diet (NDD) and International Dysphagia Diet Standardization Initiative (IDDSI) guidelines, were classified by measuring the viscosity (NDD) and gravity flow through a syringe (IDDSI) with 0.1%-3.0% thickener concentrations. The apparent viscosity (ηa,50) values of thickened barium liquids were much higher than those of thickened non-barium liquids, indicating that the addition of barium to the XG-based thickener resulted in further thickening. Standard recipes for preparing thickened barium liquids with desirable thickness levels were also established, showing the different thickener concentrations corresponding to the different NDD and IDDSI levels.

Effect of NaCl Addition on Rheological Behaviors of Commercial Gum-Based Food Thickener Used for Dysphagia Diets

Cho, Hyun-Moon,Yoo, Whachun,Yoo, Byoungseung The Korean Society of Food Science and Nutrition 2015 Preventive Nutrition and Food Science Vol.20 No.2

Rheological properties of thickened fluids used for consumption by people with dysphagia (swallowing difficulty) are very sensitive to several factors, such as thickener type, temperature, pH, sugar, protein, and NaCl. In this study, steady and dynamic rheological properties of thickened water samples mixed with five commercial xanthan gum-based food thickeners (A~E) were studied in the presence of NaCl at different concentrations (0.3%, 0.6%, 0.9%, and 1.2%). The magnitudes of apparent viscosity (${\eta}_{a,50}$), consistency index (K), yield stress (${\sigma}_{oc}$), and dynamic moduli (G' and G") showed significant differences in rheological behaviors between thickened samples with various NaCl concentrations. Dynamic moduli values of all thickened samples, except for samples with thickener C, were much higher than those of the control (0% NaCl). All rheological parameter values (K, G', and G") in a thickener A were much higher than those in other thickeners. These results suggest that rheological properties of thickened samples containing NaCl are strongly affected by xanthan gum-NaCl interaction and depended on the type of thickener.

Relationship between Apparent Viscosity and Line-Spread Test Measurement of Thickened Fruit Juices Prepared with a Xanthan Gum-based Thickener

Sung-Gun Kim,Whachun Yoo,Byoungseung Yoo 한국식품영양과학회 2014 Preventive Nutrition and Food Science Vol.19 No.3

The flow behaviors of three thickened fruit juices (orange, apple, and grape juice) prepared with a commercial instant xanthan gum (XG)-based thickener that is marketed in Korea were investigated at different thickener concentrations (1.0%, 1.5%, 2.0%, 2.5%, 3.0%, and 3.5%) and setting times (5 and 30 min) using a rheometer and a line-spread measurement method. The flow distance values measured by the line-spread test (LST) were compared with the apparent viscosity (ηa,50) values measured with a sophisticated computer-controlled rheometer. The ηa,50 values of the juices increased as thickener concentration increased, whereas their flow distances decreased. The ηa,50 values at the 30-min setting time were much higher than those at the 5-min setting time, indicating that the setting time before serving or consuming thickened juices can affect viscosity values. Plots comparing ηa,50 values to LST flow distances revealed strong exponential relationships between the two measures (R<SUP>2</SUP>=0.989 and R<SUP>2</SUP>=0.987 for the 5- and 30-min setting times, respectively). These results indicate that the LST can be a suitable instrument for evaluating the viscosity of thickened fruit juices prepared with different XG-based thickener concentrations and setting times for the dysphagia diet.

Effect of Thickener Type on the Rheological Properties of Hot Thickened Soups Suitable for Elderly People with Swallowing Difficulty

Kim, Sung-Gun,Yoo, Whachun,Yoo, Byoungseung The Korean Society of Food Science and Nutrition 2014 Preventive Nutrition and Food Science Vol.19 No.4

Flow and dynamic rheological properties of hot thickened soups for consumption by the elderly people with swallowing difficulty (dysphagia) were investigated at a serving temperature of $60^{\circ}C$. In this study, sea mustard soup (SMS) and dried pollock soup (DPS), which have been widely known as favorable hot soups provided in a domestic hospitals and nursing homes for dysphagic patients, were thickened with four commercial xanthan gum (XG)-based food thickeners (coded A~D) marketed in Korea. Thickened soups prepared with different thickeners showed high shear-thinning flow behaviors (n=0.15~0.21). Apparent viscosity (${\eta}_{a,50}$), consistency index (K), storage modulus (G'), and loss modulus (G") demonstrated differences in rheological behaviors between the XG-based thickeners. The magnitudes of (G') were much higher than those of (G") over the entire range of frequency (${\omega}$) with the high dependence on ${\omega}$, showing the rheological behavior similar to a weak gel. In general, all rheological parameter values of thickened DPS samples were higher when compared to the thickened SMS samples. These results indicate that flow and dynamic rheological properties of hot thickened soups containing commercial XG-based thickeners are strongly dependent on the type of thickener and soup.

Effect of NaCl Addition on Rheological Behaviors of Commercial Gum-Based Food Thickener Used for Dysphagia Diets

Hyun-Moon Cho,Whachun Yoo,Byoungseung Yoo 한국식품영양과학회 2015 Preventive Nutrition and Food Science Vol.20 No.2

Rheological properties of thickened fluids used for consumption by people with dysphagia (swallowing difficulty) are very sensitive to several factors, such as thickener type, temperature, pH, sugar, protein, and NaCl. In this study, steady and dynamic rheological properties of thickened water samples mixed with five commercial xanthan gum-based food thickeners (A∼E) were studied in the presence of NaCl at different concentrations (0.3%, 0.6%, 0.9%, and 1.2%). The magnitudes of apparent viscosity (ηa,50), consistency index (K), yield stress (σoc), and dynamic moduli (G" and G") showed significant differences in rheological behaviors between thickened samples with various NaCl concentrations. Dynamic moduli values of all thickened samples, except for samples with thickener C, were much higher than those of the control (0% NaCl). All rheological parameter values (K, G", and G") in a thickener A were much higher than those in other thickeners. These results suggest that rheological properties of thickened samples containing NaCl are strongly affected by xanthan gum-NaCl interaction and depended on the type of thickener.

Effect of Thickener Type on the Rheological Properties of Hot Thickened Soups Suitable for Elderly People with Swallowing Difficulty

Sung-Gun Kim,Whachun Yoo,Byoungseung Yoo 한국식품영양과학회 2014 Preventive Nutrition and Food Science Vol.19 No.4

Flow and dynamic rheological properties of hot thickened soups for consumption by the elderly people with swallowing difficulty (dysphagia) were investigated at a serving temperature of 60℃. In this study, sea mustard soup (SMS) and dried pollock soup (DPS), which have been widely known as favorable hot soups provided in a domestic hospitals and nursing homes for dysphagic patients, were thickened with four commercial xanthan gum (XG)-based food thickeners (coded A∼D) marketed in Korea. Thickened soups prepared with different thickeners showed high shear-thinning flow behaviors (n=0.15∼0.21). Apparent viscosity (ηa,50), consistency index (K), storage modulus (G′), and loss modulus (G″) demonstrated differences in rheological behaviors between the XG-based thickeners. The magnitudes of G′ were much higher than those of G″ over the entire range of frequency (ω) with the high dependence on ω, showing the rheological behavior similar to a weak gel. In general, all rheological parameter values of thickened DPS samples were higher when compared to the thickened SMS samples. These results indicate that flow and dynamic rheological properties of hot thickened soups containing commercial XG-based thickeners are strongly dependent on the type of thickener and soup.

Relationship between Apparent Viscosity and Line-Spread Test Measurement of Thickened Fruit Juices Prepared with a Xanthan Gum-based Thickener

Kim, Sung-Gun,Yoo, Whachun,Yoo, Byoungseung The Korean Society of Food Science and Nutrition 2014 Preventive Nutrition and Food Science Vol.19 No.3

The flow behaviors of three thickened fruit juices (orange, apple, and grape juice) prepared with a commercial instant xanthan gum (XG)-based thickener that is marketed in Korea were investigated at different thickener concentrations (1.0%, 1.5%, 2.0%, 2.5%, 3.0%, and 3.5%) and setting times (5 and 30 min) using a rheometer and a line-spread measurement method. The flow distance values measured by the line-spread test (LST) were compared with the apparent viscosity (${\eta}_{a,50}$) values measured with a sophisticated computer-controlled rheometer. The ${\eta}_{a,50}$ values of the juices increased as thickener concentration increased, whereas their flow distances decreased. The ${\eta}_{a,50}$ values at the 30-min setting time were much higher than those at the 5-min setting time, indicating that the setting time before serving or consuming thickened juices can affect viscosity values. Plots comparing ${\eta}_{a,50}$ values to LST flow distances revealed strong exponential relationships between the two measures ($R^2$=0.989 and $R^2$=0.987 for the 5- and 30-min setting times, respectively). These results indicate that the LST can be a suitable instrument for evaluating the viscosity of thickened fruit juices prepared with different XG-based thickener concentrations and setting times for the dysphagia diet.

Effect of Salivary Reaction Time on Flow Properties of Commercial Food Thickeners Used for Dysphagic Patients

( Hwa Young Lee ),( Seung Ro Yoon ),( Whachun Yoo ),( Byoungseung Yoo ) 한국임상영양학회 2016 Clinical Nutrition Research Vol.5 No.1

The effect of human saliva on the flow properties of pudding-like thickened water prepared with commercial food thickeners was investigated, and their viscosity differences were also compared as a function of salivary reaction time (0-60 min after the addition of saliva). Food thickeners used in this study were starch-based (SB), gum-containing starch-based (GSB), and gum-based (GB) commercial thickeners marketed in Korea. GB showed no significant reduction in viscosity upon contact with human saliva during the salivary reaction. In contrast, SB almost completely lost its viscosity shortly after the addition of saliva, and GSB significantly reduced its viscosity after 20 min of reaction time but retained its viscosity. The results of this study indicate that GB can enhance the swallowing safety of dysphagic patients by retaining a stable viscosity level without the reduction of viscosity during consumption of thickened fluids, whereas SB may increase the possibility of aspiration owing to a rapid decrease of viscosity upon contact with human saliva.