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" The Impact of Modification Technologies on the Physicochemical, Rheological and Thermal Characteristics of Selected Improved Non-waxy Rice Flours "
Nwankpa, Chijioke Anthony
Ngadi, Michael O.
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Latin Dissertation
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English
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| Record Number
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1111897
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TLpq2506255516
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| Main Entry
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Ngadi, Michael O.
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Nwankpa, Chijioke Anthony
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| Title & Author
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The Impact of Modification Technologies on the Physicochemical, Rheological and Thermal Characteristics of Selected Improved Non-waxy Rice Flours\ Nwankpa, Chijioke AnthonyNgadi, Michael O.
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| College
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McGill University (Canada)
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| Date
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2019
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2019
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| Degree
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Ph.D.
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| Page No
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222
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| Abstract
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Physical modification of rice flour plays a pivotal role in the adoption and utilization of non-waxy rice cultivars. Understanding and optimizing the impact of applying physical modification techniques holds the potential of enhancing food security in non-waxy rice producing communities through the development of acceptable novel rice-based products. This study investigated the impact of selected modification technologies on the physicochemical, rheological and thermal characteristics of non-waxy rice flours. Structural, rheological, thermal, functional and physicochemical properties of flours from seven non-waxy rice cultivars were studied by different techniques namely X-ray diffractometry, rheometry and differential scanning calorimetry (DSC). Physicochemical properties varied for all the samples studied. Protein content ranged between 8.47 to 9.24%, while amylose content was between 25.90 and 30.85%. Relative crystallinity degree (%) of rice flours were significantly different, with the values ranging from 15.63–23.40%. Water holding capacity of rice flours ranged from 1.13–1.49 g/g. A strong negative correlation (0.965) was observed between the water holding capacity (WHC) of the rice flours and amylose contents. Oil holding capacity (OHC) of the tested flours ranged from 0.93 -1.27 g/g. A strong positive correlation (0.965) was observed between the OHC of the rice flours and their amylose contents. Glass transition temperature (Tg) values ranged between 45.43–72.57 °C. Onset of gelatinization (To), gelatinization peak,(Tp) and gelatinization conclusion, (Tc) temperatures values ranged from 56.70–81.27 °C, 62.91–87.57 °C and 72.47–89. 87 °C, respectively. Enthalpy of gelatinization, ΔH values was between 0.38–7.46 J/g. Non-waxy rice flours were treated at different combinations of temperatures (85, 100 and 115 °C), times (1, 2 and 3 hr) and adjusted moisture content (25, 30 and 35 %). Processing temperature and moisture content during the heat-moisture treatment significantly (P < 0.05) influenced the physicochemical, thermal and rheological properties of the rice flours. Variation of the moisture contents and processing temperatures during heat-moisture treatment (HMT) led to a 3.75% reduction in the protein contents of the flour. Increase in processing temperature led to an increase in the WHC of the rice flours. Increasing processing temperature during the thermal treatment led to at least 20% increase in the WHC of the flours. OHC properties reduced from 1.28–1.20 g/g, when the moisture content was increased during HMT. Lightness (L*) of heat-moisture treated SAH 177 flour was at least 4–6.25% less than the native flour. A 1.5 °C decrease in gelatinization temperature (Tp) was observed for every percent increase in moisture content. Moisture content during HMT and ΔH were inversely associated. A 1 J/g reduction in the enthalpy of gelatinization for every percentage increase in the moisture content was observed during the HMT process. G', reduced from (63.86 Pa) to (5.84 Pa), as moisture contents were increased from 25 to 35% during HMT. G'', values reduced from 17.21 to 4.97 Pa, as the processing temperature increased from 85 to 115 °C. Regression models developed for predicting the WHC, OHC, L*, b*, Tp and ΔH of the rice flours during HMT had a high R2 of at least to the 80% significance. Rheological, textural and color properties of rice puddings made from heat-moisture treated rice flours were assessed. G' and G'' values of the pudding samples made from the heat-moisture treated flours were (0.44- 1121 Pa) and (0.18–79.50 Pa), respectively, while the G' and G'' ranges of the puddings made from the control flours were (1.70–1034 Pa) and (0.15–101.50 Pa), respectively. Puddings exhibited thixotropic behavior with G' > G'' at the studied frequencies (10–100 Hz). Hardness (0.04–0.16 N), gumminess (0.01–0.15 N) and chewiness (0.01–0.15 N) of puddings made from heat-moisture treated flours was higher than the hardness (0.14–0.26 N), gumminess (0.12–0.22 N) and chewiness (0.12–0.21 N) properties of the puddings made from the control rice flours. HMT significantly (P < 0.05) influenced the overall color (ΔE) of the rice puddings. Application of the heat-moisture treated rice flours increased the ΔE values of the puddings. Physicochemical, rheological and thermal studies were carried out on microwave processed nonwaxy rice flours. Variation of the moisture contents, processing time and power during microwave treatment significantly (P < 0.05) influenced the amylose content, viscosity, hardness, OHC and WHC of the non-waxy rice flours. OHC properties increased from 1.28–3.10 g/g, while WHC increased from 1.22–3.50 g/g during microwave treatment indicating moisture and time effects. However, interestingly the first 15 sec of microwave treatment saw at least a 23.58% reduction in the oil and water holding properties of the rice flour. The application of this microwaved rice flours with reduced oil and water holding capacities on quality properties of air fried chicken breast cuts were evaluated. Porosity ranges for the samples coated with untreated rice flour was 25.17–88.90%, while samples coated with microwaved rice flours ranged from 13.99–77.38%. The application of microwaved treated rice flours increased the coating pick up and cooking yield of the fried samples. Other properties of the fried samples such as texture, moisture content, oil content, and color were significantly (P < 0.05) influenced by the flour treatment. Ultrasonication was used to investigate the effect of varying amplitudes over time at different moisture contents on non-waxy rice flour characteristics. Variation of the moisture contents, processing time and amplitude during ultrasound treatment significantly (P < 0.05) influenced the amylose content, swelling power, oil and water holding properties of the non-waxy rice flours. Amylose contents increased with ultrasonication time. The lowest swelling power was found in the untreated rice flour samples while the highest water holding properties were obtained in the flour samples treated under ultrasonication having around 24.59 and 58.20% water increase at amplitude levels of 20 and 30%, respectively, compared to the untreated sample. Other properties of the non-waxy rice flour such as protein contents, rheological and thermal were significantly (P < 0.05) influenced by ultrasonication treatment. Finally, a comparative analysis was performed to evaluate the application of untreated, microwave and ultrasound treated non-waxy rice flours on the quality of air-fried chicken samples. The effective moisture diffusivity for the untreated coated, ultrasound coated, and microwave coated ranged between 5.68 × 10−5 to 12.14 × 10−5, 4.90 × 10−5 to 8.01 × 10−5 and 5.36 × 10−5 to 6.34 × 10−5 m2/s, respectively, and the R2 values ranged between 0.89 and 0.98. Increased activation energy for moisture loss was observed in the samples coated with untreated rice flours, while the lowest activation energy for oil uptake was observed in samples coated with ultrasound treated rice flour.
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Chemistry
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Dielectric properties
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Food science
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Microwaves
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Polymers
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Rice
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