Processing Characteristics and Utilization of Germinated Lentil for Product Development
Date
2024-05-21
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Degree Level
Doctoral
Abstract
Lentils (Lens culinaris Medikus) is among the oldest crops, consumed by humans since ancient civilization and are known for its affordability in terms of protein, carbohydrates and other vital micro-nutrients. The presence of bioactive compounds make them highly nutritive; however, they also contain antinutrients some of which can be easily removed or reduced by simple processes. Germination improves the bioavailability of nutritional compounds, along with removal of antinutritional compounds. The optimum number of days for germination of green and red lentils (CDC Greenland and CDC Maxim) was investigated, based on the highest value total phenolic compounds (TPC), total antioxidant activity (TAA) and in vitro starch digestibility (SD). The TPC and TAA increase until 5 days of germination and tended to decline on day 6 of germination. The SD increased steadily, even after 5 days of germination. However, the increase was much less after germinating for 4 days. Therefore, lentil after 5 days of germination was selected for further studies and utilization.
Germinated lentil was dried using a pulsed-mode, microwave-vacuum drying (MVD) technique, for 2 s, 5 s and 8 s of microwave pulse level (rated capacity, 2000 W) at 0, 15 and 45 kPa vacuum pressure to understand the effect of microwave and vacuum on drying kinetics and energy consumption. Overall, the Modified Page model II showed the highest R2 and lowest RMSE values. The drying rate constant k and effective moisture diffusivity (Deff) increased with increased microwave pulse and vacuum pressure level, resulting in reduction of drying time. The optimization of processing parameters for pulse-mode, microwave-vacuum drying of germinated lentil was based on the total phenolic content (TPC), total antioxidant activity (TAA) and in vitro starch digestibility (SD). In vitro starch digestibility increased significantly with increased microwave pulse level. The TPC and TAA may vary distinctively with changing varieties of selected lentils. Vacuum pressure levels did not significantly (p>0.05) affect any responses. Green lentil can be dried at 8 s microwave pulse and 45 kPa vacuum pressure and red lentils can be dried at 5.5 s microwave pulse and 42.19 kPa vacuum pressure.
Dried germinated green and red lentil flours were extruded with corn flour using a single-screw extruder. Response surface methodology was employed to study the effect of moisture, percent blend of lentils and screw speed at 150 ̊C barrel temperature on expansion ratio (ER), extrudate density (ED), hardness (HD), water absorption index (WAI), water solublility index (WSI), TPC, TAA and SD. The percentage of germinated lentil flour in the blend had more significant effects on the response variables as compared to moisture and screw speed. Optimum process parameters were observed at 20% blend, 19.5% moisture and 147 rpm screw speed for germinated green lentil extrudates, whereas 20.7% blend of germinated red lentil flour, 19.7% moisture and 141 rpm screw speed for germinated red lentil extrudates.
The technoeconomic analysis (TEA) of germinated, lentil-based, extruded products was carried out. Extrusion of germinated red lentil was more profitable (3.8%) and had shorter break-even point (BEP of 949.3 t/h) as compared to germinated green lentils. Net present value (NPV) and internal rate of return (IRR) for red lentil type was higher than green lentil type, CAD $ 392612.9 and 21% respectively. Germination of lentil followed by microwave vacuum drying (MVD) and extrusion can enhance the nutritive value and can be utilized in new product development.
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Keywords
Lentil, germination, microwave-vacuum drying, extrusion, technoeconomic analysis
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Chemical and Biological Engineering
Program
Biological Engineering