Rheological Properties of Starch and Whey Protein Isolate Gels

The paste viscosity of starches Amioca (~0.5% amylose), native corn (~27% amylose), Hylon VII (~70% amylose), tapioca (~19% amylose), and their whey protein isolate (WPI; 50/50) mixtures at varying solid concentration of 2.5, 5, 10, 15 and 20% were determined. At higher gel concentration (20%) during the cooling cycle, WPI paste measured by rapid visco-analyser (RVA) showed a tremendous increase in viscosity over that of the micro visco-amylograph (MVA), 5784 and 184 cP, respectively. RVA gels had a more uniform network of coarse particles (~250—500 nm) than the fine structures (~50 nm) in those of the MVA. Inclusion of WPI reduced the paste viscosity of all starches by at least 50%, except for Hylon VII at 20% solid concentration. The strength of Hylon VII and corn starch gels was reduced by WPI. In contrast, gels of WPI/tapioca ( G' = 45.4 Pa) and WPI/amioca ( G' = 18.3 Pa) had similar rheological properties as their pure starch control ( G' = 47.4 Pa and G' = 15.3 Pa for Tapioca and Amioca, respectively).

The Effect of Oral Processing on the Viscosity of Thickened Drinks for Patients With Dysphagia

Objective

To determine whether a gum-containing thickener maintains its viscosity better during oral processing than a completely starch-based thickener.

Methods

Thirty-five healthy volunteers participated in a double-blind, cross-over study. Artificial tap water was thickened to honey-like consistency (effective viscosity of 1,300±100 mPa·s at a shear rate of 50 per second at 20℃) with a starch-based thickener (SB) or a gum-containing thickener (GC). Bolus viscosity was determined after standardized oral processing of the thickened water by the subjects for 10 and 20 seconds. Significant effects were determined by ANOVA analysis and pairwise comparisons.

Results

Both thickeners were susceptible to breakdown during oral processing. However, GC-thickened water retained its viscosity significantly better than SB-thickened water.

Conclusion

The presence of gums has a protective effect on the starch hydrolysis by salivary amylase in thickened drinks, which may facilitate safer swallowing.

Effect of human saliva on the consistency of thickened drinks for individuals with dysphagia

BACKGROUND

Thickening of foods and fluids is commonly used in the management of dysphagia to reduce the risk of aspiration. The use of starch-based thickeners is established. However, the use of gums in thickeners is gaining interest as they are resistant to salivary amylase, which may promote safer swallowing.

AIMS

To compare the effect of human saliva on the consistency of drinks thickened with a gum-containing (GC) thickener with that of drinks thickened with four starch-based (SB) thickeners.

METHODS & PROCEDURES

Three drinks (artificial tap water, hot coffee and full-fat milk) were thickened to custard consistency with the different thickeners. Compression force and amount of thin liquid formed were determined after 10 and 50 min of contact with human saliva with standardized amylase activity and compared with a control inoculated with water.

OUTCOMES & RESULTS

Drinks thickened with GC thickener were significantly less sensitive to thinning by human saliva compared with drinks thickened with all four SB thickeners (p < 0.05). Moreover, incubation of SB-thickened drinks with human saliva resulted in the formation of at least 10 g of decantable liquid, while for GC-thickened drinks, almost no liquid was formed.

CONCLUSIONS & IMPLICATIONS

These results show that GC thickeners contain their consistency better in contact with human saliva than SD thickeners. This may enhance the swallowing safety of people with dysphagia.

Conversion of paper sludge to ethanol. I: Impact of feeding frequency and mixing energy characterization

In this paper, conversion of paper sludge to ethanol was investigated with the objective of optimization of the overall operation costs. Experimental work was undertaken to optimize cellulase loading, and to determine mixing energy requirements. It was found that decreasing feeding frequency (feed additions per residence time) allows the cellulase loading to be decreased at least two fold with no decrease in cellulose conversion but also entails mixing a slurry of higher solids content and lower conversion at the beginning of the operating cycle. The viscosity of paper sludge slurries was found to increase exponentially with decreasing conversion and increasing solid content. In particular, the viscosity (V) was described well by equation V = e(kX-X )(0)(S-S)(0)+C (V viscosity (cp), X conversion, S solid content (g/L), k, X (0), S (0), C are empirical parameters). Added costs associated with operating at low feeding frequencies (including higher mixing energy and higher capital costs for the motor and for sludge hold tasks) were found to be small compared to the economic benefits resulting from reduced cellulase loading.

Effect of Formulation and Manufacturing Parameters on Process Cheese Food Functionality—I. Trisodium Citrate

The objective of this research was to use a Rapid Visco Analyzer to study the effect of natural cheese age, trisodium citrate (TSC) concentration, and mixing speed on process cheese food (PCF) functionality. In this study 3 replicates of natural cheese were manufactured, and a portion of each cheese was subjected to 6 different PCF manufacturing treatments at 2, 4, 6, 12, and 18 wk of ripening. These treatments were factorial combinations of 3 levels of TSC (i.e., 2.0, 2.5, and 3.0%) and 2 mixing speeds during manufacture (450 and 1,050 rpm). Functional properties of the PCF evaluated included manufacturing properties [apparent viscosity after manufacture (VAM)], unmelted textural properties (firmness), melted cheese flow properties [hot apparent viscosity (HAV)], and cheese thickening during cooling [time at 5000 cP (T5)]. All 4 parameters (VAM, firmness, HAV, and T5) were significantly affected by natural cheese age and mixing speed, whereas VAM, HAV, and T5 were also significantly influenced by the amount of TSC. The VAM and firmness decreased as cheese age increased, whereas T5 values increased as cheese age increased. Similarly, VAM, HAV, and firmness values increased because of the increased mixing speed, whereas T5 values decreased. The age x mixing speed interaction was significant for VAM and firmness. The age x concentration of the TSC interaction term was significant for VAM, whereas the age x age x TSC concentration term was significant for HAV. The results demonstrate that natural cheese age, mixing speed during manufacture, and concentration of TSC have a significant impact on process cheese functionality.

Comparison of Pilot-Scale and Rapid Visco Analyzer Process Cheese Manufacture

Numerous formulation and processing parameters influence the functionality of process cheese. A small-scale manufacturing and analysis method could be used to evaluate the influence of formulation parameters and processing conditions on the functionality of process cheese. The objective of this study was to compare process cheese produced on a small-scale (25 g) in a Rapid Visco Analyzer (RVA) to process cheese produced on a pilot-scale (4.5 kg) in a Blentech twin-screw pilot-scale cooker (BTS). Three replicates of pasteurized process cheese (PC) and pasteurized process cheese food (PCF) were produced in an RVA and in a BTS. Texture profile analysis (TPA) and the RVA melt test were performed on all PC and PCF produced. There was a significant replication effect on TPA-hardness and hot apparent viscosity of the PC and PCF produced in the RVA and the BTS. The PC and PCF produced in the RVA had significantly higher TPA-hardness and hot apparent viscosity compared with PC and PCF produced in the BTS. The RVA manufacturing time (short vs. long) did not have a significant effect on TPA-hardness values for PC or PCF. However, the long manufacturing time significantly increased hot apparent viscosity for PC and PCF. The RVA was successfully used to manufacture process cheeses; however, differences in the manufacturing profiles and type of cooker influenced the functional properties of the process cheese.