The LPP had an extraction rate comparable to the SPP, showing that the particle size had no significant effect on the extraction rate. In summary, when using WPP for antioxidant extraction, higher TEY, TPY, and TPC can be achieved by increasing the extraction temperature, time, and solvent ratio. The DSA was independent of the extraction time and solvent ratio but decreased with the increase in extraction temperature. The two groups of peel particles, with average particle sizes of 0.60 and 0.38 mm, respectively, had no significantly different effects on the extraction of phenolics with varied extraction temperature, time, and solvent ratio. The highest TEY, TPY, and TPC obtained were 57.83%, 12.80%, and 22.06%, respectively. The DSA ranged from 5.37 to 6.35 g g-1. The results indicated that extraction of phenolics from peel particles, produced by grinding to less than 0.6mm with a large cutting head, at a temperature of 20°C for 6 min using a solvent ratio of 4:1 could be the most economical and sustainable approach for industrial-scale production. The chromatogram obtained from the HPLC, showing the peaks of major compounds in the peel extract, including gallic acid, ellagic acid, punicalagin , and punicalagin , is shown in Figure 2.5 a. The contents of the four major phenolic compounds produced by the five groups of extraction conditions are shown in Figure 2.5 b. The gallic acid content significantly improved, from 0.17 to 0.29 mg g-1 , with the increase in solvent ratio from 1:1 to 4:1. Except for the group with a 1:1 solvent ratio , the gallic acid contents obtained with the other groups with different solvent ratios varied from 0.27 to 0.35 mg g-1 and were not significantly different, regardless of the time and temperature. The ellagic acid content varied from 0.77 to 1.51 mg g-1, with no significant differences among groups G3, G4, and G5. The solvent ratio mostly influenced punicalagin. At the same extraction conditions, the punicalagin content increased from 2.13 to 4.48 mg g-1 when the solvent ratio increased from 1:1 to 8:1. In addition to the solvent ratio ,snap clamps ABS pvc pipe clip the extraction time and temperature affected the extraction of punicalagin , which can be seen from the increased punicalagin content from 7.51 mg g-1 to 9.17 mg g-1 .

The punicalagin purity ranged in order of G2 > G4 > G5 > G3 > G1, and the corresponding values were 88.99%, 88.27%, 87.73%, 87.64%, and 85.93%, respectively. Qu et al. compared the gallic acid, punicalagin, punicalagin , and ellagic acid concentrations of different pomegranate products. The results presented in this study showed significantly higher retention of punicalagin than the pomegranate peel extract using dried peel particles used by Qu et al. . The WPP extraction in this study also achieved slightly higher phenolic concentrations compared to Langers 100% pomegranate juice. To study the effects of drying, DPP was produced using HA drying and IR drying, and the peel compositions and phenolic extraction conditions were compared between DPP and WPP. The compositions of WPP and DPP on a dry basis are shown in Table 2.5 Composition of fresh and hot-air dried pomegranate peel. . The WPP had higher contents of protein, ash, and crude fat than the DPP. The loss of these contents was reduced by avoiding the drying process. On the other hand, the HA DPP maintained higher total dietary fiber at 25.44%, and the ratio of insoluble dietary fiber to soluble dietary fiber was 8.84. This was higher than the values for WPP, which maintained 17.19% TDF and an IDF/SDF ratio of 4.93. Morais et al. compared the compositions of raw, freeze-dried, and oven-dried papaya peels. They reported similar findings for the differences in fiber content, but the differences were not statistically significant. Figure 2.6 shows the TEY, TPY, DSA, and color characteristics of IR DPP, HA DPP, and WPP. The DPP resulted in significantly lower TEY, TPY, and TPC than the WPP. The DSA values were similar for both DPP and WPP at about 6.41 g g-1. In other words, extraction from WPP resulted in 10% more extract yield and 2.5% more TPY with similar DSA compared to DPP. Loizzo et al. investigated the phytochemical contents of extracts from fresh and processed peel and pulp. Compared to steamed, baked, and microwaved pulp, extraction with fresh pulp achieved up to 0.9% higher TEY and twice the TPC. Their results demonstrated that extraction with fresh peel or pulp could reduce the phytochemical loss that occurs during the drying process. Similarly, Mphahlele et al. compared the bio-active compounds in fresh peel and hot-air dried peel at 40°C, 50°C, and 60°C. As for color, extraction of WPP achieved significantly higher L* , a* , b* , and C* values.

The results demonstrated statistically higher retention of L* and a* values using WPP. According to Cadena et al. , changed color characteristics indicate the formation of caramel-colored pigments resulting from nonenzymatic processes, which are related to lower sensory acceptance. Therefore, extraction from WPP could be a more suitable method for the extraction of polyphenols for use in food product development and supplementation. PCA was applied to explore the interdependence among variables. Observations consisted of the average sub-sampling results from the 30 aforementioned extraction conditions at different extraction times, temperatures, and solvent ratios. Four vectors were estimated based on the eigenvectors of the correlation matrix of four variables: total extract yield , total phenolic yield , total phenolic content , and DPPH scavenging activity . The eigenvalues of F1 to F4 were 2.548, 0.899, 0.544, and 0.008, and the first three PCs accounted for 63.70%, 22.48%, and 13.61% of the sample variance, respectively, and represented 99.79% of the total variance in cumulation . Biplots of the observations and variables show the data distributions of F1-F2 and F1-F3. Confidence ellipses with 99% confidence intervals were used for each set of experiment groups, and no outliers were detected. PCA weighting scores of the four measured variables are listed in Table 2.6. For instance, TEY and TPC were positively correlated with the F1 axis, whereas TPY and DSA were negatively correlated. In addition, TEY and TPY were positively correlated with the F2 axis, while DSA was negatively correlated with the F3 axis. Figure 2.7 also shows the data distribution for F1-F2 and F1-F3. For instance, the data point with a higher F1-axis value had higher TPC, which was extracted at 60°C for 6 min using a solvent ratio of 8:1. This was following the experimental results, indicating that PCA can be applied for future condition prediction. Extraction of bio-active compounds from waste fruit peel is an efficient approach to improve food system sustainability and industry profitability.

This study developed a novel green process for antioxidant extraction from wet pomegranate peel and investigated the effects of extraction conditions on polyphenol yield and quality, including phenolic composition, DPPH scavenging activity, and color characteristics. PCA condensed the multivariable analysis into three factors, which explained 99.79% of the variance and could be suitable for future process development. Three parameters, including drying preparation, extraction temperature, and solvent ratio, significantly influenced the extraction rate. Considering water usage and energy consumption, WPP extraction at 20°C for 6 min with a solvent ratio of 4:1 is recommended as an economic and sustainable process, resulting in 10.53% total phenolic yield with 88.93% punicalagin purity. Overweight is raising concern worldwide due to its high prevalence and various adverse health outcomes. According to a report from World Health Organization, an adult with Body Mass Index between 25.0 to 30.0 is defined as overweight, and over 1.9 billion adults worldwide were overweight in 2016, accounting for 39% of the population . Being overweight can further induce obesity when BMI increased beyond 30.0. These two statuses are major risk factors of physical and mental illness. Wilson et al. conducted 44-year follow-up research on 5209 participants aged 30 to 62 years from the Framingham cohort . Results showed that being overweight was related to elevated cardiovascular risks, including hypertension , angina pectoris , and coronary heart disease . Calle and Kaaks reviewed obesity and obese-related epidemiological studies. An increased risk of cancers was noted from 1.2-2 folds, including colorectal, endometrial, kidney, and oesophageal cancer . BeLue et al. studied the relation between mental healthiness and overweight in youth aged 12 to years in different races and ethnicity . Their results revealed that overweight white and Hispanic youth possessed a higher percentage of self-reported depression, anxiety,greenhouse snap clamps and other mental and behavioral problems. Various causes contributed to being overweight. Among them, a calorie-dense and nutrient-poor diet is a major contributor along with a lack of exercise. Standard American Diet is a typical western diet that includes excess natural and added carbohydrates, fats, and sodium while lacking in consumption of fruits, vegetables, and whole grains . Improving the diet pattern for weight control is in need. Diet with the addition of phytochemicals, such as polyphenol, demonstrated positive health outcomes on weight management. Studies have suggested that polyphenol modulated the plasma and hepatic cholesterol in a few possible mechanisms, including inhibiting enzymes related to intestinal carbohydrate digestion and glucose absorption , inhibiting pancreatic lipase activity and fat absorption from the intestine , promoting β-oxidation of fatty acids , increasing bile excretion to eliminate the cholesterol , and regulating the gut microbiota towards a leaner composition .

Pomegranate peel is a common underused fruit by-product from the juicing process and consists of up to 53.01% of the fruit weight . The high molecular weight polyphenols in the pomegranate peel are the major high-value phytochemicals and have been proven associated with reduced risks of chronic diseases , including type 2 diabetes and cardiovascular diseases . Among all the polyphenols in pomegranate peel, gallic acid , ellagic acid , punicic acid, and punicalagin-α, -β are responsible for most health benefits . It was worth noting that punicalagin is unique in pomegranate peel and demonstrated the greatest antioxidant activities with abundant hydroxyl groups, which can trap peroxyl radicals to reduce oxidation . Therefore, pomegranate peel is a promising source for polyphenols. By far, nearly all the studies of health benefits in pomegranate peel utilized liquid extractable polyphenol. Limited research focused on the pomegranate peel as a whole. Labib and Hossin characterized the effects of pomegranate peel powders and extracts on obese hypercholesterolemic rats solely from anthropometric and serum lipid. Insights of hepatic lipid profile were missing and the regulating mechanisms were not investigated in their study . Moreover, research has shown that the polyphenol and fiber in the food matrix might have a synergistic effect to promote health . Therefore, the objectives of this research were to compare the hypolipidemic properties of PPP and PPE and investigate the regulating mechanisms by supplementing the high-fat diets with different percentages of PPP and PPE to male Syrian hamsters. Pomegranate peel of Wonderful variety was collected from a juicing plant located in Buttonwillow, California in October of 2017. The peel was processed based on Wu et al. . In summary, the peel was sliced and ground into particles less than 0.6 mm. Then extract was obtained by mixing the peel particles with 4 times of water at 20 ⁰C for 6 mins, then filtered before administration to the hamsters. The male Syrian hamster was used since it possessed similarities of hepatic cholesterol and bile acid metabolism with humans compared to other rodents . The compositions of peel powder and extract were listed in Table 2.5. The study was approved by the Animal Care and Use Committee, Western Regional Research Center, USDA, Albany, CA, USA. 45 male golden hamsters were acclimatized for 2 weeks. They were fed with Purina Rodent Laboratory Chow and individually raised in a 20−22 °C environment with relative humidity at 60 %, and 12 h alternating light/dark cycle. After that, 45 hamsters were randomly divided into five groups for each diet as indicated in. A high-fat diet with 20% fat energy intake was set as a control group. 5 and 10% of lyophilized PPP were supplemented into the HF diet ad libitum to evaluate the dose effects. In correspondence, 2.5 and 5% of lyophilized PPE addition were applied to investigate the effect of supplementation form. In this way, LP/LE group contained nearly 8.68 mg soluble phenolic compounds per kg body weight, and HP/HE group doubled the content. These dosages corresponded to approximately 70 mg and 140 mg per day in a 60 kg human according to the Km factor ratio of 5 and 37 for hamsters and humans , respectively .