charanjit kaurJYOTI NISHAD2019-05-242019-05-242018http://krishikosh.egranth.ac.in/handle/1/5810104421t-10042Citrus peel (CP) is an important byproduct of fruit processing industry and well-recognized source of phenolics and flavonoids known to possess health-promoting antioxidant properties including anti-carcinogenic, anti-inflammatory, anti-aging, and cardioprotective. The disposal of CP has considerable constraints due to both economic and environmental factors. Considering the high added value of the compounds that can be recovered from CP, it has promising potential uses: in the food industry, cosmetic and pharmaceutic industries. However, in many cases, these uses are still not economically sustainable. Extraction of phenolics and flavonoids from CP and their evaluation in the food matrix for imparting oxidative stability would be an appropriate valorization approach for functionalization of food. Against this background, the major objective of the present study was extraction, characterization, and functionalization of phenolic compounds from citrus peel. Sixteen pummelo genotypes were characterized for their physicochemical, biochemical, functional and sensory quality. Results suggested pummelo selection 8 (PS-8) with high peel percentage and good availability of polyphenolic compounds to be used for extraction. Thus, CP from three species included Citrus sinensis (sweet orange cv. Malta), Citrus paradisi (grapefruit cv. Redblush), and Citrus maxima (pummelo genotype PS-8) was chosen as experimental material. The extraction for the phenolics was achieved using ultrasound (UAE) and enzyme (EAE) assisted process. The extraction techniques were optimized using Box-Behnken design of response surface methodology (RSM) for the recovery of total phenolic content (TPC) and total flavonoid content (TFC) from the peel. The optimized conditions for UAE of sweet orange, grapefruit and pummelo were obtained at 35, 33.12 and 35 min extraction time, 70.89, 71.11 and 70% amplitude and a solvent–solid (SS) ratio of 40, 39.63 and 40 mL/g, respectively. Moreover, the optimized conditions for EAE were 4.87, 4.81 and 4.8 h extraction time, 0.84, 0.9 and 0.85% enzyme concentration and 30.94, 40 and 35 mL/g SS ratio for sweet orange, grapefruit and pummelo respectively. Similar values of experimental and predicted TPC and TFC at optimized conditions indicates the suitability of the quadratic model in optimizing the extraction parameters. The characterization of extracts suggested EAE as the most efficient process in extracting bioactive compounds in comparison to UAE and conventional solvent extraction (CSE). Phenolic profiling exhibited the presence of varietal difference and treatment effect on different phenolic compounds, naringin being the predominant phenolic followed by phloridzin dihydrate in all the three citrus species. The extract from EAE of grapefruit peel shown the presence of highest TPC and AOX activity (3387 mg GAE/100g and 215.73 µmol TE/g resp.) which was nearly 1.6 fold higher than the UAE. Evaluation of the citrus peel phenolics (CPP) in preventing oxidation in food matrices high in fat content viz. mustard oil and meatballs, demonstrated significant antioxidant efficacy of the phenolic rich extract. For incorporation in mustard oil, the extract was formulated in a nano-emulsion using ultrasonication. The process variables viz. amplitude, emulsifier and sonication time were optimized using RSM considering particle size as the response. Optimization and validation of the quadratic model revealed 9.49 min of sonication at 30.12% amplitude and 0.52% span 80 to be best to yield a nano- emulsion with a minimum droplet size of 29.73 nm. Further, the formulation was added in mustard oil in different concentrations ranging from 100-400 ppm and compared for its efficiency against its non-encapsulated counterparts (100-400 ppm) and TBHQ (200 ppm). Results of accelerated storage studies revealed that phenolics in nano-emulsion form produced more potent antioxidants than non-encapsulated ones, and the efficiency in extending the shelf life of mustard oil was on par with the TBHQ. The use of CPP in meatballs along with Nutmeg (NM) extracts showed the active synergistic effect as demonstrated by high antioxidant activity in a binary mixture (NM-CP), exceeding the expected values indicating possible interactive synergism. NM-CP was evaluated at two concentrations 0.5% (NMCP) and 1.0% (NMCP1). Meatballs with added salt (MS) and control (without any salt and antioxidant) served as control. Binary mixture (NM-CP) at 1% showed a stronger inhibitory effect on lipid oxidation in comparison to the individual extract NM and CP. However, with respect to protein oxidation, effects of both concentrations (NMCP and NMCP1) were found to be at par. Color, flavor and sensory scores further confirmed the efficacy of NM-CP in extending the storage life of frozen meat. Nearly 70% reduction in oxidation rate can be achieved in meatballs during frozen storage by using NM-CP. Furthermore, CPP was vacuum infused into ash gourd cubes for functionalization. Optimization of vacuum impregnation process (2.21 min blanching time, mbar vacuum pressure and 28.18 min vacuum time) was able to increase 300% phenolics in ash gourd. Overall, the present study demonstrates that EAE is an effective method for extraction of CPP. Further, the CPP has potential industrial relevance as an antioxidant for functionalization of food commodities. Keywords ; Antioxidant, Citrus, Enzyme extraction, Nanoemulsion, Ultrasonicationen-USnullThesis