目的：果胶是天然的杂多糖，因其独特的凝胶特性和健康益处在食品、生物医药等领域用途非常广泛，需求量大。果胶主要来自植物基材料，目前商业果胶绝大多数是从柑橘果皮、苹果渣中提取。因此，充分利用区域优势农产品资源，加强废弃物利用、开发果胶具有很大的商业价值。新疆是中国籽用南瓜最大产地，南瓜籽加工产生的皮瓤副产品数量巨大（约为种子产量的49倍），目前资源利用率低，浪费严重。本课题组前期分析显示南瓜皮瓤富含果胶，因此，本研究以籽用南瓜副产物为原料，以得率为标准优化不同的果胶提取工艺，同时为比较籽用南瓜果胶含量，对富含果胶的甜菜废渣、番茄皮废渣进行了同步处理、提取果胶；并分析了提取果胶的总糖、半乳糖醛酸、分子量等理化性质，表征了籽用南瓜果胶的吸附能力、乳化能力、抗氧化能力等功能属性，为籽用南瓜果胶进一步商业化开发的可行性提供充分的参考依据。

方法：本研究聚焦籽用南瓜副产物，选用甜菜和番茄皮渣作为对照，采用传统酸加热提取（AHE）、超声辅助热酸提取（UAHE）、微波辅助热酸提取（MAHE）和超声微波热酸提取（UMAHE）四种工艺提取籽用南瓜果胶（SP）、甜菜皮渣果胶（BP）和番茄皮渣果胶（TP）。通过单因素实验比较不同来源的果胶得率优化提取工艺。进一步运用响应曲面法优化UMAHE参数，对比探索其对提升籽用南瓜果胶得率的影响。进而对优化工艺提取的不同果胶理化性质和功能特性进行了详细表征，并市售果胶(CAP)进行了比较分析，以获得具有优异理化性质和功能特性的高得率籽用南瓜果胶。

结果：（1）对比不同提取工艺的最适条件下SP得率，UMAHE-SP的得率最高为33.38 %。AHE-SP的优化得率为9.49 %，优于BP（8.8 %）和TP（4.15 %）；UAHE-SP的优化得率为12.85 %，低于BP（25.79 %）和高于TP（5.5 %）；MAHE-SP的优化得率为9.66 %，低于BP（26.43 %）和高于TP（7.64 %）；而UMAHE-SP的最优参数为超声功率51 %、时间15 min、微波功率77 %、时间5 min，得率为33.38 %，虽然略低于BP的36.76 %，但显著高于TP的17.52 %。SP在各类提取技术中均呈现出稳固的竞争优势，尤其在采用UMAHE时，尽管其提取效率相较于BP略低，但仍维持在一个相当高的水准，此结果凸显了UMAHE作为高效提取SP的显著潜力。

（2）UMAHE-SP是具有高半乳糖醛酸（51.25 %）、总糖（44.19 %）、蛋白质（10.26 %）和低还原糖（5.41 %）的优质低脂籽用南瓜果胶。其平均分子量最小（371.976 kDa），且比CAP更低，在水中溶解性更高。UMAHE-SP 的低中性糖（20.43 %）使其具有较短侧链提升其凝胶能力。SP、BP和TP在相同工艺下SEM表面形态呈现相同的特征。多种提取方式所带来的表面侵蚀使得UMAHE提取的SP、BP和TP表面网状结构有更多的凹陷和皱纹。通过FT-IR分析进一步证明提取得到的SP均为低酯果胶。

（3）不同工艺的SP稳定性均优于其它果胶。UMAHE-SP在模拟胃液与小肠中展现出卓越的吸附性能，亚硝酸盐和胆固醇吸附量分别高达1.37 mg/g、1.30 mg/g和9.51 mg/g和15.69 mg/g，显著优于BP、TP和CAP。其同样表现出强的持水力与持油力，分别达12.30 g/g与23.01 g/g，与BP、TP和CAP相比，持水、持油力提升显著。1 %（m/v）的UMAHE-SP与MAHE-SP均有优异发泡特性，MAHE-SP和UMAHE-SP发泡能力和稳定性分别达到了44 %、36 %和39 %、27 %，超越相同工艺下的BP、TP和CAP。2 %（m/v）的AHE-SP和UMAHE-SP乳化能力分别为36.67 %与34 %，UMAHE-SP乳化稳定性达最大值59.03 %，显示出UMAHE-SP卓越的乳化性能。UMAHE-SP的DPPH清除率46.53 %，ABTS清除率5.60 %，Fe³⁺还原能力30.96 %，具备最优异的抗氧化性能。SP均表现出最强的α-葡萄糖苷酶抑制能力且UMAHE-SP 抑制酶活能力高达11.89 %。综上，UMAHE-SP在多方面的性能评估中展现出了显著优势，充分验证其在食品行业和降血糖领域的应用潜力和卓越的性能优势。

结论：基于响应面法优化UMAHE工艺得到最高得率的籽用南瓜果胶(SP)。UMAHE-SP是具有优质理化性质的小分子低脂籽用南瓜果胶。其表面网状结构有较多的凹陷和皱纹且在多方面的功能特性评估中展现出了显著优势，充分验证籽用南瓜果胶商业化利用潜力巨大。

Purpose:Pectin is a natural heteropolysaccharide,which is widely used in food,biomedicine and other fields because of its unique gel properties and health benefits. Pectin is mainly derived from plant-based materials,and most of the commercial pectin is extracted from citrus peel and apple residue. Therefore,it is of great commercial value to make full use of regional superior agricultural resources,strengthen waste utilization and develop pectin. Xinjiang is China's largest seed-used pumpkin production,pumpkin seed processing produces a large number of skin and flesh byproducts (about 49 times the seed production),the current resource utilization rate is low,serious waste. The previous analysis of our research group showed that seed-used pumpkin skin is rich in pectin. Therefore,this study focused on seed-used pumpkin by-products as raw materials and optimized different pectin extraction processes according to the yield standard. Meanwhile,in order to compare the pectin content of seed-used pumpkin,the waste residues of beet and tomato peel,which are rich in pectin,were simultaneously treated and extracted pectin. The physical and chemical properties of pectin such as total sugar,galacturonic acid and molecular weight were analyzed,and the functional properties of seed-used pumpkin pectin such as adsorption capacity,emulsification capacity and antioxidant capacity were characterized,which provided sufficient reference for the feasibility of further commercial development of seed-used pumpkin pectin.

Methods:This study focused on seed-used pumpkin by-products,using beet and tomato peel as controls. Seed-used pumpkin pectin (SP),beet peel pectin (BP) and tomato peel pectin (TP) were extracted by conventional acid heating extraction (AHE),ultrasonic assisted hot acid extraction (UAHE),microwave assisted hot acid extraction (MAHE) and ultrasonic microwave hot acid extraction (UMAHE). The optimal extraction technology of pectin from different sources was compared by single factor experiment. Further,the response surface method was used to optimize UMAHE parameters,and the influence of UMAHE parameters on seed-used pumpkin pectin yield was explored. The physical and chemical properties and functional properties of different pectin extracted by optimized technology were characterized in detail,and the commercially available pectin (CAP). was compared to obtain the seed-used pumpkin pectin with high yield and excellent physical and chemical properties and functional properties.

Results:(1) The UMAHE method significantly outperformed the AHE,UAHE,and MAHE techniques concerning the yield of extracted seed-used pumpkin pectin. Specifically,the optimized parameters for AHE-based seed-used pumpkin pectin extraction comprised an 80°C water bath temperature sustained over a duration of 40 minutes. For UAHE,the peak performance was attained with a citric acid solution at pH 1.5,a solid-to-liquid ratio set at 1:35,an ultrasonic power level of 50 %,and a 15-minute interval of ultrasonic disruption. In the case of MAHE,the ideal settings involved a microwave power of 77 % administered over a 5-minute irradiation period; however,it is noteworthy that these optimal conditions can vary depending on the specific pectin source. Following the application of response surface methodology for refinement,the UMAHE process yielded remarkable pectin recovery rates:33.38 % for seed-used pumpkin,36.7 % for beet peel,and 17.5 % for tomato peel,respectively.

(2) UMAHE-SP is a high-quality low-fat seed-used pumpkin pectin with high galacturonic acid (51.25 %),total sugar (44.19 %),protein (10.26 %) and low reducing sugar (5.41 %). It has the smallest average molecular weight (371.976 kDa) and is lower than CAP and more soluble in water. The low neutral sugar (20.43 %) of UMAHE-SP gives it a shorter side chain to enhance its gel capacity. The SEM surface morphology of SP,BP and TP showed the same characteristics under the same process. The surface erosion of SP,BP and TP extracted by UMAHE resulted in more depressions and wrinkles. FT-IR analysis further proved that the extracted SP was low ester pectin.

(3) The SP stability of different processes is better than other pectin. UMAHE-SP showed excellent adsorption properties in simulated gastric juice and small intestine,with the adsorption capacity of nitrite and cholesterol up to 1.37 mg/g,1.30 mg/g,9.51 mg/g and 15.69 mg/g,respectively,significantly superior to BP,TP and CAP. It also showed strong water holding capacity and oil holding capacity,up to 12.30 g/g and 23.01 g/g respectively. Compared with BP,TP and CAP,the water holding capacity and oil holding capacity increased significantly. 1% (m/v) of UMAHE-SP and MAHE-SP have excellent foaming characteristics,MAHE-SP and UMAHE-SP foaming capacity and stability reached 44%,36%,39%,27%,surpassing BP,TP and CAP under the same process. The emulsification capacity of AHE-SP and UMAHE-SP of 2% (m/v) was 36.67% and 34%,respectively,and the emulsification stability of UMAHE-SP reached the maximum value of 59.03%,indicating the excellent emulsification performance of UMAHE-SP. The DPPH clearance rate of UMAHE-SP was 46.53 %,the ABTS clearance rate was 5.60 %,and the Fe³⁺ reducing capacity was 30.96 %. SP showed the strongest α-glucosidase inhibition ability and UMAHE-SP inhibited enzyme activity up to 11.89%. In summary,UMAHE-SP has shown significant advantages in various performance evaluations,fully verify its application potential and excellent performance advantages in the food industry and the field of hypoglycemia.

Conclusion:The SP with the highest yield was obtained by optimizing the UMAHE process based on the response surface method. UMAHE-SP is a small molecule low fat seed-used pumpkin pectin with high quality physical and chemical properties. The surface network structure of pumpkin pectin has more depressions and wrinkles,and it shows significant advantages in many functional characteristics evaluation,which fully verifies the commercialization potential of pumpkin pectin for seed use.

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