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ThesisItem Embargo Development of process protocol for the production of powder from stevia (stevia rebaudiana)(Punjab Agricultural University, 2023) Kalsi, Baldev Singh; SandhyaStevia rebaudiana leaves, renowned for their natural sweetness, have gained prominence as a healthier alternative to artificial sweeteners. The present research explores various aspects of Stevia leaf processing such as drying, extraction, and grinding, with a vision of optimizing both quality and efficiency. The fresh stevia leaves were dried using different methods: sun drying, convective drying (30-80°C), microwave drying (180 to 900 W) and multistage/hybrid drying: convective pre drying at 50 °C until reaching moisture content of 0.18 g/g, 0.43 g/g and 1.50 on dry basis (db) and then microwave finishing drying at power levels of 360, 540, and 720 W. The Artificial Neural Network (ANN) exhibited a reasonably good fit across all drying conditions to predict drying kinetics, surpassing the maximum R2 range and minimum χ2 and RMSE from the mathematical model. The multistage drying done at 1.50g/g-540W achieved the lowest total color difference (ΔE) value i.e 1.97 compared to other methods, indicating minimal color alteration. Furthermore, ascorbic acid content showed maximum retention after multistage drying at conditions of 1.50g/g-540W (23.50 mg/100g), followed by 1.50g/g-720W (23.04 mg/100g). Further, the total phenolic content also showed excellent results, with multistage drying at 1.50g/g-720W yielding the highest value (58.88 mg GAE/g), followed by 1.50g/g-540W (58.26 mg GAE/g). Additionally, very high antioxidant activity (78.67 %) was retained at the multistage drying at 1.50g/g-540W. The multistage drying at 1.50g/g-540W was selected as best drying as it not only significantly reduced drying time but also preserved the quality and bioactive compounds of Stevia leaves. A lab scale ohmic heating setup was also developed for extracting stevioside and bioactive compounds from dried leaves. The optimization of the ohmic heating assisted-extraction was executed using response surface methodology with temperatures (40-70°C), time (5-15 min) and solvent/ leaf powder ratio (10:1-30:1 ml/g) as independent parameters. The optimized conditions observed were 51.02˚C for 10.297 minutes using Solvent/leaf powder ratio of 30:1 ml/g for maximum stevioside, total phenolic content and antioxidant activity with overall desirability of 0.91. The innovative ohmic heating extraction method proved highly efficient, achieving an approximately 50% higher extraction efficiency for natural compounds from Stevia leaves compared to conventional thermal extraction. Besides enhancing the yield of valuable components, the novel approach also reduces processing time. After considering both visual decolorization and the impact on important quality parameters, the extract decolorized with 1g of activated carbon per 100 ml of stevia extract was deemed the most optimal choice. To combat the hygroscopic nature of Stevia extract powder, inulin (10% w/v) was introduced as an encapsulating agent before the spray drying process. The resulting spray-dried powder displayed favorable characteristics, ensuring improved stability. Moreover, successful crystal formation of stevia powder was achieved using Erythritol. The developed process demonstrated economic viability. In conclusion, this comprehensive study resulted in a process protocol for development of powder from stevia leaves keeping in view consumer preferences.ThesisItem Open Access Development of a prototype for shelf life enhancement of guava juice using manothermosonication(Punjab Agricultural University, Ludhiana, 2019) Kalsi, Baldev Singh; SandhyaInvestigation was carried out to study the effect of ultrasound in combination with temperature and pressure treatment on the juice of guava (variety: Arka Amulya). For experiments, a pressurizing system was designed in CREO 3.0 software and constructed from the local market of Ludhiana. The juice samples were exposed to manothermosonication at combinations of three temperatures (40, 60 and 800C) and three pressure levels (100, 200, and 300 kPa) for three holding times (2, 6, and 10 min). Response surface methodology (RSM) was applied to optimize the conditions of the manothermosonication of guava juice. The main criteria for constraints optimization were minimum color change, pH, total plate count, total mold/ yeast and maximum ascorbic acid, total soluble solids, titratable acidity and overall acceptability. The juice samples treated under optimized conditions for manothermosonication were packed in two packaging material (glass and PET bottles) and stored at ambient and refrigerated conditions. The juice samples were also treated with ultrasonication and thermosonication for storage and their physicochemical, phytochemical, microbial anyalysis and sensory evaluation was done at regular intervals of 7 days. The optimized conditions for manothermosonication obtained were: Heating temperature= 63.810C, Pressure= 184.16 kPa and holding time = 2 minutes for each process. The highest microbial inactivation and retention of TSS and color (*L-value) along with highest overall acceptability score was observed in manothermosonicated samples. Thus, results showed that guava juice manothermosonicated and packed in glass bottles have better quality and a shelf life of six weeks under refrigerated conditions.ThesisItem Open Access Development of a prototype for shelf life enhancement of guava juice using manothermosonication(Punjab Agricultural University, Ludhiana, 2019) Kalsi, Baldev Singh; SandhyaInvestigation was carried out to study the effect of ultrasound in combination with temperature and pressure treatment on the juice of guava (variety: Arka Amulya). For experiments, a pressurizing system was designed in CREO 3.0 software and constructed from the local market of Ludhiana. The juice samples were exposed to manothermosonication at combinations of three temperatures (40, 60 and 800C) and three pressure levels (100, 200, and 300 kPa) for three holding times (2, 6, and 10 min). Response surface methodology (RSM) was applied to optimize the conditions of the manothermosonication of guava juice. The main criteria for constraints optimization were minimum color change, pH, total plate count, total mold/ yeast and maximum ascorbic acid, total soluble solids, titratable acidity and overall acceptability. The juice samples treated under optimized conditions for manothermosonication were packed in two packaging material (glass and PET bottles) and stored at ambient and refrigerated conditions. The juice samples were also treated with ultrasonication and thermosonication for storage and their physicochemical, phytochemical, microbial anyalysis and sensory evaluation was done at regular intervals of 7 days. The optimized conditions for manothermosonication obtained were: Heating temperature= 63.810C, Pressure= 184.16 kPa and holding time = 2 minutes for each process. The highest microbial inactivation and retention of TSS and color (*L-value) along with highest overall acceptability score was observed in manothermosonicated samples. Thus, results showed that guava juice manothermosonicated and packed in glass bottles have better quality and a shelf life of six weeks under refrigerated conditions.
