Physicochemical and Rheological Characterization of Malaysian Rice Flours and Starches

Physicochemical and rheological properties of flours and starches from nine Malaysian rice varieties (seven MR and two MRQ) were investigated. The physicochemical properties determined were swelling power (SP), carbohydrate leaching (CL), gelatinization, pasting, and textural characteristics, whereas the rheological properties studied were steady and dynamic shear. The varieties can be classified into low, intermediate and high amylose (AM) rice and also into intermediate and high-gelatinization temperature (GT). The varieties can be clearly grouped into MR and MRQ varieties based on setback (SB) and final (FV) viscosities and textural analysis. MRQ possessed greater SB, FV and gel hardness but lower gel adhesiveness, whereas, MR varieties showed the opposing results. An increase in AM increased the SB, FV, gel hardness, apparent viscosities(ηa) at and above 8% and 6% for flours and starches, respectively), and, storage modulus (G’), loss modulus (G”), complex modulus (G*) and complex viscosity (η*), but decreased the SP, To, Tp, Tc, enthalpies (ΔH), peak viscosity (PV), breakdown (BV), gel adhesiveness, and tan δ. ηa of the flours and starches increased with increasing solid concentrations and the viscosities depended on concentration regimes. Close-packing concentration was observed at concentration ranges of 6.4-8.7% (w/w) and 3.4-4.7% (w/w) in both flour and starch pastes, respectively. Cross-over concentration in the viscosity of the flour (5.6–7.9%, w/w) and starch (2.3–3.4%, w/w) pastes between high (MR) and low (MRQ) swelling varieties was found to occur at around the close-packing concentration. G’, G”, G* and η* increased whereas tan δ decreased with storage. Dynamic viscoelastic measurements of the starch and flour pastes before and after cooling indicated strong gel characteristics, with MRQ giving stronger and elastic gels. Cox-Merz rule was applicable in the rice starch only at certain concentrations. However, η* could provide a reasonable estimate of ηa. The interplay of starch granular properties and AM contents primarily influence the physicochemical and rheological characteristics of rice flours and starches, whereas the presence of flour components especially proteins significantly influenced the flour properties. MRQ34 exhibited interesting properties that possessed similar characteristics to the high AM variety (MRQ74). Strong correlation observed between the physicochemical (SP, FV, hardness and adhesiveness) and rheological (ηa, G’, G”, G* and η*) characteristics provide a means of predicting of the physicochemical properties via rheological methods and vice versa

Functional properties of whey protein concentrate texturized at acidic pH: effect of extrusion temperature

Reactive supercritical fluid extrusion (RSCFX) process at acidic condition (pH 3.0) was used to generate texturized whey protein concentrate (TWPC) and the impacts of process temperature on product's physicochemical properties were evaluated. TWPC extruded at 50 and 70 °C formed soft-textured aggregates with high solubility than that extruded at 90 °C that formed protein aggregates with low solubility. Total free sulfhydryl contents and solubility studies in selected buffers indicated that TWPC is primarily stabilized by non-covalent interactions. Proteins texturized at 90 °C showed an increased affinity for 1-anilino-naphthalene-8-sulfonate (ANS) and a decreased affinity for cis-parinaric acid (CPA), indicating changes in protein structure. Water dispersion of TWPC at room temperature showed thickening function with pseudoplastic behavior. Secondary gelation occurred in TWPC obtained at 50 and 70 °C by heating the cold-set gels to 95 °C. TWPC texturized at 90 °C produced cold-set gels with good thermal stability. Compared to control, TWPC formed stable oil-in-water emulsions. Factors such as degree of protein denaturation and the balance of surface hydrophobicity and solubility influenced the heat- and cold-gelation and emulsifying properties of the protein ingredients. TWPC generated by low and high temperature extrusions can thus be utilized for different products requiring targeted physicochemical functionalities

Alternative Dietary Fiber Sources from Kenaf (Hibiscus cannabinus L.) Seeds and Their by-Products

This study evaluates the macronutrients and Dietary Fiber (DF) of kenaf seeds and their secondary by-products to promote food sustainability and support the zero-waste concept. The first part concentrates on macronutrients and potential DF sources of kenaf seeds and their by-products, i.e., kenaf seed meals and dregs. Following this, the DF from the most probable source was fractionated to quantify its composition. The results showed that the macronutrients of kenaf seeds are comparable to other commercial oilseeds such as soybean, almond, and hemp seeds. Additionally, the secondary by-products could be reused as DF sources. It was found that the kenaf seed by-products had 20.63–35.08% DF contents which were comparable to soybean by-products. Moreover, the fractionation of DF from kenaf seed dregs showed that the DF comprised 1.86%, 1.01%, 6.33%, and 66.33% (dry basis) of acid-soluble pectin, calcium-bound pectin, alkali-soluble hemicellulose, and cellulose, respectively. The soluble (pectins and hemicelluloses) and insoluble (cellulose) fractions are related to the modulation of gut microbiota which have similar potential to conventional prebiotics and an excellent role in bodyweight management, respectively. These findings provide useful information for researchers and industries to venture into alternative DF sources from kenaf seeds as a value-add ingredient for functional food applications

Development of Jackfruit Crackers: Effects of Starch Type and Jackfruit Level

Crackers are one of the convenient and inexpensive snacks that have high market potential.  Most of the commercial crackers are carbohydrate-rich and normally considered as a low value-added product.  In this study, innovative value added crackers made of jackfruit were developed.  The effect of starches (sago and cassava) and levels of jackfruit (30 and 50%, w/w) on characteristics of the crackers were investigated.  Physicochemical properties of the products at each predetermined processing steps (steaming, drying and frying); bulk density, expansion ratio, color and carotenoid contents were measured.  A decrease in jackfruit level resulted in crackers with lower bulk density (0.26 to 0.41 g/cm3) and higher volume expansion ratio (2.84 to 4.66 cm3).  Blending the cassava and sago starch at 1:1 ratio resulted in lower bulk density and higher expansion ratio compared to crackers made with a single type of starch.  The L* and b* values decreased with drying and frying process, indicative of Maillard reactions.  The higher L* value was influenced by the starch content, while higher jackfruit led increased the b* values, attributed to the presence of pigments in the fruit.  Total carotenoid contents of fried crackers increased following steaming process, ranging from 0.061 to 0.199 mg/100g and samples made with blend of sago and cassava has the highest carotenoid contents.  A jackfruit level of 30% (w/w) made with blend of sago and cassava starches (1:1) produced fried crackers with the most acceptable physicochemical characteristics.  Crackers with improved nutritional value can be developed by incorporating jackfruit, thus expanding the conventional use of the fruit

Effects of brine concentration, thickness and microwave finish drying on the textural characteristics of buffalo jerky

Jerky, a ready-to-eat snack, known for its high protein and low-fat content. Current methods used in jerky processing take 6-10 hours in a conventional oven, dehydrator or smokehouse. In this study, whole buffalo meat was sliced to 5mm and 6mm and cured in three different salt concentrations of 1.0%, 1.5% and 2.0% for 24 hours at 4°C. The effects of microwave finish drying (5, 10 and 15 seconds) were examined after samples were dried in a convection oven for three hours. Cured buffalo slices showed significant (p<0.05) lower initial moisture content compared to uncured slices. This is due to the effect of salt which increased the protein solubility thus reducing its moisture content. Buffalo jerky treated with 2.0% salt showed the lowest final moisture content and the highest weight loss. Analysis of the texture characteristics showed that lower salt content and higher microwave duration produced softer buffalo jerky. The colour analysis of dried buffalo jerky implied that altering salt concentration and drying treatment did not give negative impact to the colour. Thus, microwave finish drying is capable of producing a good buffalo jerky without jeopardizing its quality

Effect of storage temperature on the antioxidant properties of active bilayer polyethylene/soy protein isolate (PE/SPI) film

Polyethylene (PE) is considered to be one of the most widely used plastic in the world due to its vast array of applications depending on the particular type. It is well known that petroleum-based plastic is a good material for food packaging for its good mechanical properties. Meanwhile, biopolymer films have poor mechanical and water barrier properties compared to conventional plastics. Soy protein isolate (SPI) with mangosteen pericarps extract (MPE) was laminated on PE film to form a bilayer film with antioxidant property. The PE/SPI film was stored at two different temperatures; 25°C and accelerated temperature at 40°C for 9 weeks. The color and opacity of the film increased significantly (P ≤ 0.05) after 9 weeks observation. There is no change in the morphology of the film after 9 weeks stored at both temperatures. The antioxidant properties of film were measured by total phenolic content (TPC) and 2,2-diphenyl-1- picrylhydrazyl (DPPH) scavenging assay for each week interval. The antioxidant activities of films decreased significantly (P≤0.05) throughout the storage time at both temperatures. Higher temperature also reduced the antioxidant properties of bilayer film significantly (P ≤ 0.05). Addition of mangosteen pericarps extract contributes to the enhanced antioxidant properties of bilayer film

Optimization of mixing parameters on techno-functional properties of fenugreek gum-soy protein isolate dispersion

Fenugreek (Trigonella foenum-graecum L.) gum (FG) has been identified as a hydrocolloid, with promising emulsifying and stabilizing properties. In an emulsion-based food system, these properties dramatically increased when FG was mixed with soy protein isolate (SPI). Nevertheless, it is highly dependent on mixing parameters such as FG:SPI ratio, pH, and temperature, and it is currently not well understood. The objective of this study was to determine the effects of FG:SPI ratio (3:1 - 1:1), pH (3 - 9), and temperature (65 - 85 °C) on techno-functional properties (flow properties, emulsifying properties, and turbidity) of the FG-SPI dispersion, to reveal the optimum mixing parameters. A response surface regression modeling demonstrated that the quadratic effect of the FG:SPI ratio had significantly (p<0.05) increased the flow properties of the dispersion. However, the interaction between FG:SPI ratio and temperature or pH gave the opposite effect. The FG:SPI ratio had the most significant (p<0.05) increasing effect on both emulsifying properties and turbidity. Conversely, the emulsifying properties were determined to decrease with the interaction effect of FG:SPI ratio and pH. The optimized mixing parameters were recorded at FG:SPI ratio of 2.6:1, pH of 3.0, and temperature of 70 °C, with apparent viscosity (0.19 Pa.s), emulsion stability (100%), and turbidity (2.91, Abs600) values were within the predicted ranges. The present findings provide an excellent opportunity to advance the use of FG-SPI dispersion in related to emulsion-based food products

Effect of addition of resistant starch on oxidative stability of fried fish crackers as influenced by storage temperatures and packaging materials

The aim of the present work was to investigate the effect of the addition of resistant starch (unmodified potato starch) on physicochemical properties and lipid stability of fried fish crackers packed in two types of packaging. Fish crackers added with one part of resistant starch were prepared, packed into two types of packaging with four different layers of packaging material; (i) polyethylene terephthalate-polyethylene-aluminium-linear low density polyethylene and (ii) oriented polypropylene-polyethylene-metallized polyethylene terephthalate-linear low density polyethylene and stored at 25, 40 and 60°C for 12 weeks. The linear expansion and oil absorption of the fried fish cracker were 58.00 ± 3.46% and 12.60 ± 1.34% respectively. Physical analyses showed an increase in moisture contents (from 2.75-3.47% to 4.08-4.54%), water activities (0.297 to 0.436aw) and a* and b* values (5.27 to 9.14% and 21.09 to 25.27%, respectively), while a decrease in L* value (from 63 to 58%), hardness (from 2.110 to 1.117 kg) and crispiness (from 12.46 to 8.18 kg/sec) throughout 12 weeks of storage at all temperatures tested. The lipid yield of the crackers increased during the storage time and the concentrations of conjugated dienes and thiobarbituric acid reactive substances showed a gradual increase and decrease, respectively. These results showed that the fried fish crackers in the storage study had undergone lipid oxidation where physical and chemical deterioration were observed and measured. In conclusion, the addition of one part of resistant starch in crackers has given positive effect on the stability of the resulting fried fish crackers

Characterization of heat-moisture treated Dioscorea alata purpurea flour: impact of moisture level

Purpose: Edible bird’s nest (EBN) has been considered as one of the nutritious foods and was also claimed to aid in digestion problems. Potential prebiotic of the EBN for gut health by the presence of glycan within the complex structure of the EBN glycoprotein to date has not been reported. The gut health can contribute to the overall consumers’ health in the improvement of the gut beneficial bacterial growth. In this study, the potential prebiotic of the EBN was conducted using a simulation of in vitro human colon model system. Methods: The EBN-extracted glycan and EBN glycoprotein (crude sample) were digested using in vitro oral, gastric and duodenal model system. Prebiotic activities of the undigested EBN glycan and EBN glycopeptide compounds were studied with the fructooligosaccharide as a positive control, using inoculum of 10% (w/v) faecal bacteria in the in vitro fermentation system. Result: The fermentation of EBN glycan and EBN glycopeptide had shown significant increases of the gut beneficial bacteria and was comparable with fructooligosaccharide fermentation, with each sample presented different profiles of bacterial growth. The fermentation of EBN glycan and EBN glycopeptide demonstrated an increase in the total short-chain fatty acid production, particularly acetate, propionate and butyrate. Conclusion: These findings suggested that the EBN can be functioned as a natural prebiotic upon consumption, thus providing apotential as prebiotic ingredients

Dough rheology and physicochemical properties of steamed buns fortified with cross-linked rice starch

Although fibre is associated with numerous health effects, daily fibre consumption is less than recommended. Fibre-enriched food is desirable to overcome this problem and resistant starch (RS) has potential as fibre ingredient. The objective of the research was to study the effect of cross-linked (CL) rice starch (RS type 4) at different levels (0%, 15% and 30%) on dough rheology, physicochemical and sensory acceptance of steamed bun. CL rice starch was produced by cross-linking rice starch with combination of 12% sodium trimetaphosphate and sodium tripolyphosphate for 3h at 45°C under alkaline condition. The dough of steamed bun was characterized by Farinograph and Extensograph, whereas cooked steamed bun was characterized by total dietary fibre, protein, moisture, textural properties, colour and sensory acceptance. Incorporation of CL rice starch in wheat flour lowered the strength, extensibility and quality of dough. The quality of dough was positively correlated with the protein content, indicating lower gluten formation in fortified SB. Total dietary fibre of steamed bun increased significantly with increasing CL starch in the order: 30CL (2.44%) > 15CL (1.33%) > 0CL (0.75%). Hardness and yellowness of steamed bun incorporated with CL rice starch reduced significantly. SB with 15% CL rice starch showed similar sensory acceptability with control SB. The study suggests that CL rice starch at 15% is suitable to increase fibre in steamed bun with little effects on the appearance and sensory attributes