What Is the Active Ingredient in Passionflower Extract and Its Uses?

Passionflower (Passiflora edulis) extract is rich in organic acids, pectin, flavonoids, amino acids, alkaloids, lutein, beta-carotene, vitamins, and trace elements [1]. Passionflower fruits have a fragrant aroma and are often referred to as “the most aromatic fruit in the world.” Their primary aromatic components include ethyl butyrate, ethyl caprylate, propyl acetate, 1-hexanol, and α-terpineol [2]. Although passion fruit has a low yield and few processed commercial products, its intense aroma and rich content of bioactive compounds have led to its increasing application in food products.

This paper reviews the functional active components and processing status of passion fruit, focusing on the processing of juice, vinegar, and wine, as well as the extraction and activity studies of pectin, flavonoids, anthocyanins, and dietary fiber from passion fruit pulp, peel, and leaves. The aim is to provide a reference for future passion fruit processing and active component extraction.

1 Functional Active Components and Effects of Passion Fruit

The pulp, peel, and leaves of passion fruit contain various bioactive compounds, but the content of these bioactive components varies among different parts. Pectin, polysaccharides, polyphenols, and flavonoids are distributed in both the pulp and peel [3], while vitamins, amino acids, and various macro- and trace elements are primarily found in the pulp [4]; the main active components in passion fruit leaves are flavonoid compounds [5].

These bioactive substances possess significant medicinal value. For example, mice fed a high-fat diet supplemented with passion fruit peel powder exhibited improved insulin sensitivity, enhanced blood glucose balance, increased intestinal insulin secretion, and a sense of satiety, thereby serving as a food for lowering blood sugar and a weight-loss agent [6].

Consuming passion fruit peel powder can induce sedation in mice and reduce weight gain [7]. Marques et al. [8] investigated the effects of passion fruit peel powder combined with dietary therapy on plasma cholesterol levels in HIV patients with lipid metabolism disorders. After 30 days of treatment, total cholesterol and triglyceride levels were significantly reduced; after 90 days, low-density lipoprotein cholesterol levels decreased, while high-density lipoprotein cholesterol levels increased, with effects superior to those of dietary therapy alone. These findings indicate that consuming 30 g of passion fruit peel powder combined with dietary adjustments for 90 days can effectively improve the structure of total cholesterol in plasma and reduce triglyceride concentrations.

Additionally, extracts from passion fruit peel and leaves have been shown to inhibit spoilage bacteria. For example, a study [9] demonstrated their effective inhibitory effect on Fusarium moniliforme in Panax notoginseng roots.

1.1 Pectin

Pectin is widely present in plant fruits, roots, stems, and leaves. Pectin accounts for 10% of the dry fruit peel of passion fruit and has lipid-lowering, anticancer, weight-loss, and hemostatic effects [10]. In food processing, it can be used as a thickener, stabilizer, and emulsifier [11]. Currently, the demand for pectin is growing both domestically and internationally, with China's annual production amounting to approximately 3,000 tons. Research [12] indicates that feeding mice pectin extracted from passion fruit peel reduces colonic mucosal damage and, to some extent, lowers the incidence of ulcerative colitis, thereby demonstrating significant potential for further exploration.

1.2 Dietary Fiber

Dietary fiber is divided into two major categories: soluble dietary fiber and insoluble dietary fiber. Research [13] indicates that total dietary fiber accounts for 73% of the dry weight of passion fruit peel, with 60% being insoluble dietary fiber. Dietary fiber has various functions, including anti-diarrheal effects, cancer prevention, detoxification, weight control, and blood sugar reduction [14-15]. Mice fed with modified passion fruit fiber showed reduced levels of serum total cholesterol, triglycerides, and malondialdehyde, while high-density lipoprotein cholesterol, alanine transaminase, alanine aminotransferase, glutathione peroxidase, and superoxide dismutase activity increased, while the water content of mouse feces increased, indicating its excellent lipid-lowering, liver-protective, and laxative effects [16].

1.3 Flavonoid Compounds

Previous studies have shown that flavonoids in passion fruit possess multiple functions, such as: the total flavonoid extract from passion fruit peel can effectively inhibit nitrosamine synthesis and remove sodium nitrite [17]; Compared with vitamin C at the same concentration, it exhibits better scavenging effects on free radicals such as ·OH and O.[18].

Anzoise et al. [19] demonstrated that passionflower extracts possess anti-inflammatory effects, effectively treating colitis in mice and alleviating colitis-related symptoms, and speculated that the main components responsible for the anti-inflammatory effects are flavonoids and vitexin. Araujo et al. [20] analyzed the anti-mycobacterial activity and anti-inflammatory effects of flavonoids extracted from passionflower based on their inhibition of nitric oxide and tumor necrosis factor-α production and their antioxidant potential, and proposed that flavonoids in passionflower have potential for treating tuberculosis.

Additionally, there are numerous studies on the anxiolytic effects of passionflower: Ayres et al. [21] found that flavonoid glycosides in two different subpopulations of passionflower leaf extracts exhibit anxiolytic, antidepressant, and sedative effects; Zhao Ruirui [22] proposed that the n-butanol extract of passionflower leaves (mainly containing linarin and isomaringin) exhibits significant anxiolytic activity; Zou Jiangbing et al. [23] used fluorescence quantitative PCR to demonstrate that the ethanol extract of purple passionflower leaves can upregulate the expression levels of GA BAA receptor α2 and α3 subunit mRNA expression levels in the brain tissue of mice with elevated anxiety, demonstrating significant anxiolytic effects. In summary, the bioactive potential of flavonoids in passionflower is promising and warrants further investigation.

2 Processing and Comprehensive Utilization of Passion Fruit

2.1 Passion Fruit Beverage Processing

Passion fruit has a fragrant aroma, high acidity, and natural pigments in purple, yellow, and green. The fruit peel accounts for approximately 50% of the fruit, and the juice accounts for approximately 30%. Due to the relatively low overall juice content and high acidity of passion fruit compared to common fruits, it is often blended with other fruits and vegetables during processing to produce fruit and vegetable products with excellent color, aroma, taste, and comprehensive nutrition. Currently, passion fruit processing is primarily focused on related beverage production.

2.1.1 Juice Beverages

Passion fruit has high acidity but is rich in aromatic compounds, making its juice alone difficult for consumers to accept. Therefore, it is often blended with other fruits and vegetables to prepare composite fruit and vegetable juices, resulting in beverages with both good flavor and texture. For example, Jian Shaofen et al. [24] used a ratio of 5:2:3 (by volume) of sand orange juice, passion fruit juice, and water chestnut juice, added 10% white sugar and 0.05% citric acid, to produce a composite fruit and vegetable juice beverage with natural aroma and color, uniform texture, and a refreshing taste.

Ye Lizhu [25] utilized passion fruit to compensate for the mild flavor of cucumber, mixing 12% passion fruit juice with 28% cucumber juice, adding 10% white sugar and 0.6% sodium citric acid, to produce a passion fruit-cucumber composite juice. Passion fruit has thick peel and contains a large amount of seeds in its juice, with a fresh fruit juice yield of approximately 40% [26]. Considering its low juice yield, blending it with other high-yield fruits and vegetables is a viable strategy to leverage strengths and mitigate weaknesses, thereby enhancing the overall utilization of fruits and vegetables.

During juice processing, juice stability is one of the key issues of concern to researchers, directly affecting the sensory quality of juice. Nie Qiang et al. [27] compared the effects of composite thickening agents (xanthan gum, pectin, and sodium carboxymethyl cellulose) with single thickening agents on juice stability, demonstrating that composite thickeners are more effective than single thickeners. They also found that when the centrifugal rate of passion fruit juice beverage treated with composite stabilizers was reduced to 2.1%, the juice stability was high. The aforementioned studies primarily focused on improving juice yield and stability, with little consideration given to the retention rate of nutrients and the impact on flavor after thermal sterilization of juice beverages. Ma Weihong et al. [28] found that passion fruit juice beverages subjected to 95°C sterilization for 10 minutes and stored at room temperature or 36°C all exhibited severe deterioration in sensory quality. Currently, non-thermal processing technologies such as ultra-high pressure, high-pressure pulsing, ultra-high pressure carbon dioxide, and ultrasound have reached a relatively mature stage. Future research should explore the application of these non-thermal technologies in passion fruit juice beverage production to ensure effective sterilization while maintaining the excellent sensory and flavor qualities of passion fruit juices and beverages.

2.1.2 Fruit Vinegar

Fruit vinegar is a clear, transparent product with a rich fruit aroma, pure vinegar scent, and attractive color, produced through fermentation by yeast and acetic acid bacteria. It contains phenolic compounds, flavonoids, and vitamins, and has strong antioxidant and health-promoting effects [29]. Passion fruit has low sugar content and high acidity, making it difficult to ferment directly into fruit vinegar. Typically, sugar must be added, or it is used as an ingredient in a blend with high-sugar fruits to ferment composite fruit vinegar. For example, Pan Yanli et al. [30] used banana and passion fruit as main ingredients to ferment fruit vinegar, with a ratio of banana : passion fruit : water of 80 : 1 : 10 (g : g : mL), with a sugar content of 20%, and inoculated with mixed yeast at 1.6 × 10⁶ CFU/mL. Fermentation was conducted at 24°C until the alcohol content reached 7%; then, 5% acetic acid bacteria were added, and fermentation was continued at 32°C for 9 days before filtration, yielding banana passion fruit composite fruit vinegar.

Wang Zhi-jiang et al. [31] used passion fruit juice : yam juice = 1 : 2 (volume ratio), with an alcohol fermentation process of initial sugar content 20%, inoculation of 0.02% yeast, fermentation at 20°C for 84 hours until alcohol content reached 7%; Then, 9% acetic acid bacteria were inoculated, and the mixture was fermented at 32°C for 8 days, yielding a composite fruit vinegar with natural color and a full-bodied taste. Considering the high acidity and rich flavor of passion fruit juice, it can be used as an acidity regulator in fruit vinegar production or to adjust flavor and enhance fruit aroma.

2.1.3 Fruit wine

Passion fruit juice undergoes enzymatic hydrolysis, blending, fermentation, clarification, and sterilization processes to produce high-quality and nutrient-rich fruit wine [32]. Due to its high acidity, passion fruit juice is more suitable for producing dry-style fruit wine and is typically blended with other fruits for composite fermentation. Pan Yanli et al. [33] blended snow lotus fruit and passion fruit, fermented them using white pear yeast and active dry yeast, and found that when the pH of the blended juice was 4.0 and the initial sugar addition was 25%, fermentation at 25°C yielded a blended fruit wine with an alcohol content of 12.8%. Kong Danqi [34] found that mixing 25% passion fruit juice with 75% sweet orange juice, diluting it to a juice content of 30%, adding white sugar to achieve a soluble solids content of 22% and a pH of 3.8, then adding 80 mg/L of sulfur dioxide, followed by inoculation with QA-23 wine dry yeast and mixed fermentation at 20°C for 11 days, resulting in a fruit wine with a harmonious taste.

Generally, when making fruit wine from passion fruit, due to the high pectin content in the fruit pulp, enzymatic hydrolysis is required beforehand. Additionally, controlling sugar content in the fermented fruit wine is crucial: on one hand, high residual sugar levels may result in lower alcohol content; on the other hand, high residual sugar provides energy for contaminants, accelerating wine spoilage. Therefore, it is generally advisable to keep the residual sugar content of dry fruit wines below 4 g/L [35]. Additionally, while citric acid in passion fruit can enhance the flavor of fruit wine and has color-preserving, antibacterial, and preservative effects, high acidity may impair enzymatic hydrolysis and fermentation efficiency, so it is often necessary to blend with other fruits or vegetables to control acidity.

2.2 Extraction of Functional Components

If passion fruit peel is used solely as feed processing raw material or the waste residue from fruit pulp processing is discarded, it would result in significant resource waste. To enhance its comprehensive utilization value, researchers [36] have reported on the integrated utilization of passion fruit pulp, peel, and leaves, primarily focusing on the extraction of pectin, dietary fiber, pigments, and antioxidant compounds from the peel and leaves.

2.2.1 Pectin Extraction

Currently, the main methods for extracting pectin include acid extraction, alkali extraction, enzymatic extraction, ion exchange, microwave extraction, ultrasonic extraction, supercritical fluid extraction, and high-pressure pulsed electric field extraction [37].

(1) Enzymatic extraction is the most commonly used method. Liu Yunhua et al. [38] used a composite of three enzymes—cellulase, hemicellulase, and ligninase—to extract pectin from passion fruit peel. Under conditions of a liquid-to-solid ratio of 6:1 (mL/g), pH 4, 40°C, and 3.5 hours, achieving a maximum pectin extraction yield of 2.63%. Enzymatic extraction increased the extraction rate by 40% compared to traditional chemical methods [39], but it is time-consuming and energy-intensive.

(2) Acid extraction method. A mixture of hydrochloric acid and 30% citric acid was used as the extraction solution. Under conditions of a solid-to-liquid ratio of 45:1 (mL/g), pH 1.5, and 65.5°C, the pectin yield was 10.98% [40]. but the acid method produces a large amount of waste liquid, increasing processing costs and causing environmental pollution.

(3) Microwave-assisted extraction. Under conditions of 687 W power, pH 1.75, and a liquid-to-solid ratio of 20:1 (mL/g), the extraction time can be shortened, and the pectin extraction rate can be improved [41].

Therefore, in subsequent stages, the above two or more methods can be combined to enhance pectin extraction efficiency from passion fruit, making the extraction process more time-efficient and labor-saving, thereby maximizing economic benefits and increasing the added value of passion fruit.

2.2.2 Extraction of Dietary Fiber

Most studies have employed enzymatic methods to extract dietary fiber from passion fruit. Chen Liangyun [42] used acid enzyme and chemical methods to extract dietary fiber from passion fruit, finding that the acid enzyme method yielded higher extraction rates, water-holding capacity, and adsorption properties compared to the chemical method, and that D301R anion exchange resin demonstrated excellent decolorization effects. Jiang Linlan et al. [43] used an acid enzyme method to extract soluble dietary fiber from passion fruit. When the solid-to-liquid ratio was 1:40 (g/mL), the addition of heat-resistant α-amylase was 5.00 U/g, citric acid solution concentration of 0.18%, and at 80°C, the extraction rate of soluble dietary fiber reached 13.82%. Cheng Mingming et al. [44] first enzymatically hydrolyzed passion fruit peel powder with α-amylase and papain at a mass ratio of 1:1, followed by ultrasonic treatment at 355.5 W and 37.3 °C for 32.8 minutes to enhance the extraction rate of insoluble dietary fiber, with a final dietary fiber yield of 53.07%.

2.2.3 Extraction of flavonoid compounds

Passion fruit pulp contains 9 flavanol monomers (afrutin glucoside and its derivatives, catechin glucoside and its derivatives, etc.) and 9 proanthocyanidins (procyanidin dimers and trimers, cyanidin dimers and trimers, procyanidin dimers, etc.), accounting for 59.4% and 40.6% of the total, respectively [45]. Yang Dan et al. [46] optimized the extraction process of total flavonoids from purple passion fruit peel using response surface methodology. The results showed that at 75.97°C, using 58.70% ethanol for extraction for 0.5 hours, 11.70 mg/g of total flavonoids could be obtained.

2.2.4  Extraction of anthocyanins

Anthocyanins possess multiple functions, serving as natural colorants, antioxidants, and free radical scavengers. Most fruit peels contain higher anthocyanin content than fruit juice. Compared to anthocyanin-rich fruits such as blueberries, mulberries, and grapes, passion fruit peels have a higher anthocyanin content, primarily consisting of cyanidin, peonidin, and pelargonidin [47]. Extracting anthocyanins from the peel can enhance their comprehensive utilization rate. Currently, the main method used is alcohol extraction. For example, Peng Bin et al. [48] used an extraction method to extract pigments from passion fruit juice, with the optimal process being: juice to 95% ethanol ratio of 1:5 (by volume), extracted at 60°C for 10 minutes. Zeng Shaoxiao et al. [49] used 86% ethanol as the extractant, under conditions of a solid-liquid ratio of 1:36 (g/mL), extraction temperature of 31°C, and extraction time of 120 minutes, the extraction yield of passiflora fruit peel anthocyanins reached 13.7236 mg/g.

3 Conclusions and Outlook

Currently, in terms of processing, passion fruit products primarily consist of composite beverages such as juice, vinegar, and wine to mitigate their high acidity and enhance palatability. In terms of bioactivity, extracts from various parts of passion fruit exhibit anti-inflammatory, anxiolytic, sedative, laxative, and lipid-lowering effects. In terms of functional compound extraction, all parts of passion fruit contain various bioactive components; however, most studies have focused on pharmacological activity research, with limited exploration of extraction methods. The extraction rate directly determines the potential for development and utilization, leaving significant room for further exploration in this area.

Future research can be directed toward four key areas:

(1) In the fresh food sector, research should be strengthened on preservation methods and quality changes during storage to identify an optimal storage and preservation method, reduce fruit rot rates, and enhance economic benefits.

(2) In processing, studies should explore the effects of processing methods on microbial content, endogenous enzymes, sensory quality, and nutritional value to meet safety, hygiene, and health standards while extending product shelf life. Particular attention should be given to the effects of thermal processing on characteristic aromatic compounds and flavor, to better preserve their rich aroma. This not only benefits passion fruit processing but also enables the development of natural flavor agents using passion fruit as a flavor base for fruit and vegetable products.

(3) In the field of deep-processed products, functional products such as ready-to-eat, “zero-additive,” and dietary fiber-containing extracts can be developed. The optimal conditions for utilizing dietary fiber in various types of foods can be explored to enrich product varieties and meet the current demand for convenient, leisure, and nutritious foods, thereby expanding the market and utilization rate of passion fruit.

(4) In terms of pharmacological activity, although functional components in passion fruit have been proven to possess significant pharmacological activity, the mechanisms of most of these effects remain unclear. Further research should be conducted to investigate the structural characteristics of various passion fruit extracts and their regulatory mechanisms in specific pathological conditions, elucidate the therapeutic effects of specific compounds, and expand the application of passion fruit extracts in pharmaceuticals.

In summary, through continuous in-depth research, the comprehensive utilization rate of passion fruit can be improved, expanding its application scope in food, pharmaceuticals, health products, and feed, thereby enhancing economic benefits.

References

[1]  Wang Qinfeng, Zhang Rulian, Xu Li, et al.  HPLC determination of lutein and β-carotene in Passiflora edulis leaves [J].  Journal of Tropical Crop Science, 2016,  37(3):  609-614.

[2] JANZANTTI N S, MONTEIRO M. Changes in the aroma of organic passion fruit (Passiflora edulis, Sims f. flavicarpa, Deg.) during ripeness [J].  LWT-Food Science and Technology, 2014, 59(2): 612-620.

[3] Wen Liangjuan, Mao Huijun, Zhang Yuancun, et al. Analysis of components in passion fruit peel and its antioxidant activity [J]. Food Science, 2008, 29(11): 54-58.

[4] Chen Zeqiong, Liao Bin, Zhuang Zonghao. Nutritional components and comprehensive utilization of passion fruit juice, peel, seeds, and seed oil [J]. Guangzhou Food Industry Science and Technology, 1992(1): 25-28.

[5] Zou Jiangbing, Kong Qiuling, Chen Longhao, et al. Determination of total flavonoids in leaves of purple-fruited passion fruit from different origins [J]. Pharmaceutical Guide, 2012, 31(3): 348-349.

[6] LIMA G C, VUOLO MM, BATISTA A G, et al. Addition of passion fruit peel to the diet of high-fat diet rats improves insulin sensitivity, increases incretin and hypothalamic satiety signals [J]. Feed Expo, 2016(9): 44-44.

[7] FIGUEIREDO D A F, PORDEUS L C M, PAULO LL, et al. Effects of Passiflora edulis bark flour on food intake, body weight, and behavioral response of rats [J]. Revista Brasileira de Farmacognosia, 2016, 26(5): 595-600.

[8] MARQUES S D S F, LIBONATI R M F, LUO R, et al. Evaluation of the effects of passion fruit peel flour (Passiflora edulis, fo. flavicarpa) on metabolic changes in HIV patients with lipodystrophy syndrome secondary to antiretroviral therapy [J].  Brazilian Journal of Pharmacognosy, 2016, 26(4): 420-426.

[9] Cen Chuny, Xie Qiul, Su Qiyong, et al. Study on the inhibitory effect of passion fruit extract on the root rot fungus of Panax notoginseng[J]. Chinese Journal of Tropical Agriculture, 2015(4): 76-79.

[10] Zhang Lifen, Wu Qian, Chen Fusheng, et al. Research progress on the structure, function, and methods of modified pectin [J]. Grain and Oil, 2015(1): 1-5.

[11] Xie Mingyong, Li Jing, Nie Shaoping. Research and application progress of pectin [J]. Chinese Journal of Food Science, 2013, 13(8): 1-14.

[12] Chen Yingshan. Extraction of Pectin from Purple Passion Fruit and Its Activity in Preventing Ulcerative Colitis [D]. Guangzhou: South China University of Technology, 2014: 50-61.

[13] Cheng Mingming, Huang Wei. Study on the Process of Extracting Water-Insoluble Dietary Fiber from Passion Fruit Peel Using Ultrasound-Assisted Enzymatic Alkali Method [J]. Guangdong Agricultural Sciences, 2017, 44(5): 118-125.

[14] Wang Yanli, Liu Ling, Sun Hui, et al. Study on the Microstructure and Functional Characteristics of Dietary Fiber [J]. Chinese Food Additives, 2014(2): 98-103.

[15] Liu Yingli, Xie Liangxu, Ding Li, et al. Effects of wheat bran dietary fiber on the functional properties of pork myofibrillar protein gel [J]. Food Science, 2016, 37(19): 15-23.

[16] Cheng Mingming, Huang Wei. Lipid-lowering, liver-protecting, and laxative functions of dietary fiber in passion fruit peel [J]. Food Science, 2017, 38(11): 202-207.

[17] Feng Jinan, Huang Haiying, Zhao Liping, et al. Extraction process of total flavonoids from passion fruit peel and its inhibition of nitrosation reaction [J]. Spectroscopy Laboratory, 2013, 30(3): 1179-1184.

[18] Tao Yongyuan, Shu Kangyun, Dong Hongli, et al. Extraction and antioxidant activity of flavonoids from Passiflora. Food Research and Development, 2014(17): 25-29.

[19] ANZOISE M L, MARRASSINI C, BACH H, et al. Beneficial properties of Passiflora caerulea on experimental colitis [J]. Journal of Ethnopharmacology, 2016, 194: 137-145.

[20] ARAUJO M H D, SILVA I C V D, OLIVEIRA P F D, et al. Biological activities and phytochemical profile of Passiflora mucronata from the Brazilian restinga [J]. Rev. Bras. Farmacogn, 2017, 27: 702-710.

[21] AYRES A S F S J, ARAJO LL S D, SOARES T C, et al. Comparative central effects of the aqueous leaf extract of two populations of Passiflora edulis [J].   Brazilian Journal of Pharmacognosy, 2015, 25(5): 499-505.

[22] Zhao Ruirui. Study on the anti-anxiety active components of Passiflora mu-cronata leaves [D]. Guangzhou: South China University of Technology, 2011: 35-47.

[23] Zou Jiangbing, Yuan Jin, Jiang Linlan. Anti-anxiety effects and mechanisms of Passiflora edulis leaf extract [J]. Pharmaceutical Guide, 2015, 34(2): 166-169.

[24] Jian Shaofen, Zhang Shaoping, Pan Huanhua. Formulation and Processing Technology of a Composite Fruit and Vegetable Juice Beverage from Sand Orange, Passion Fruit, and Water Chestnut [J]. Anhui Agricultural Sciences, 2017, 45(7): 70-72.

[25] Ye Lizhu. Optimization of the Processing Technology for a Passion Fruit and Cucumber Composite Beverage [J].  Journal of Ningde Normal University: Natural Science Edition, 2014, 26(3): 276-279.

[26] Huang Guoqing, Xiao Zai Jun, Liang Xiaoying, et al. Research on the processing technology of passion fruit juice [J]. Food Science, 2006, 27(8): 187-190.

[27] Nie Qiang, He Ren, Huang Yongchun, et al. Optimization of Stabilizer Formulation for Passion Fruit Juice Beverage Using the Simplex Center of Gravity Method [J]. Anhui Agricultural Sciences, 2016(9): 109-111.

[28] Ma Weihong, Lao Yongda, Zhong Ruimin, et al. Study on Flavor Stability and Aroma Retention of Passion Fruit Juice Beverage [J]. Food Research and Development, 2017, 38(21): 6-9.

[29] Xiang Jinle, Luo Lei, Guo Xiangfeng, et al. Progress in the functional research of fruit vinegar [J]. Food Science, 2013, 34(13): 356-360.

[30] Pan Yanli, Yang Changpeng, Huang Xia, et al. Study on the Fermentation Process of Banana Passion Fruit Vinegar [J]. Food Industry Science and Technology, 2014, 35(2): 150-153.

[31] Wang Zhijiang, Zhou Yuhua, Chen Wanling, et al. Development of a passion fruit and yam composite fruit vinegar [J]. Chinese Condiments, 2015, 40(2): 96-99.

[32] Guo Zhengzhong, Huang Xingyuan, and Cai Guanying. Fermentation process study of passion fruit wine [J]. Brewing, 2017, 44(4): 96-98.

[33] Pan Yanli, Huang Youqin, Huang Xia, et al. Study on the Double Yeast Fermentation Process of Snow Lotus Fruit-Passion Fruit Composite Fruit Wine [J]. Chinese Brewing, 2011, 30(8): 175-178.

[34] Kong Danqi. Preliminary Study on the Brewing Process of Passion Fruit Wine [J]. Shandong Chemical Industry, 2016, 45(13): 49-53.

[35] Gao Chen-zhe. Research on the Brewing of Red Raspberry Wine and the Application of Ultra-High Pressure Technology [D]. Harbin: Northeast Agricultural University, 2017: 10.

[36] Li Liping. Research Progress on the Comprehensive Utilization of Passion Fruit [J]. Anhui Agricultural Sciences, 2012, 40(28): 13840-13843.

[37] Gao Jian, Ma Lushang, Hu Jianjun, et al. Research Progress on Pectin Extraction Technology [J]. Food Industry Science and Technology, 2014, 35(6): 368-372.

[38] Liu Yunhua, Huang Wei, Guo Meiyuan, et al. Study on the Composite Enzyme Extraction Process of Pectin from Passion Fruit Peel [J]. Food Industry Science and Technology, 2017, 38(18): 117-128.

[39] VASCO-CORREA J, ZAPATA A D Z. Enzymatic extraction of pectin from passion fruit peel (Passiflora edulis f. flavicarpa) at laboratory and bench scale [J]. LWT-Food Science and Technology, 2017, 80: 280-285.

[40] Chen Yingshan, Jiang Linlan. Response surface optimization of mixed acid extraction of pectin from passion fruit peel[J]. Food Industry Science and Technology, 2013, 34(12): 261-266.

[41] Huang Yongchun, He Ren, Ma Yuefei, et al. Study on Microwave-Assisted Extraction of Pectin from Passion Fruit Peel [J]. Food Science, 2007, 28(9): 161-164.

[42] Chen Liangyun. Preparation Process and Properties of Dietary Fiber from Purple Passion Fruit Peel [D]. Guangzhou: South China University of Technology, 2013: 75-76.

[43] Jiang Linlan, Zhang Fengjin, Chen Liangyun, et al. Optimization of the acid enzyme extraction process for soluble dietary fiber from passion fruit peel using response surface methodology [J]. Chinese Journal of Experimental Pharmacology, 2015, 21(9): 31-34.

[44] Cheng Mingming, Huang Wei. Study on the process of extracting water-insoluble dietary fiber from passion fruit peel using ultrasonic-assisted enzyme-alkali method [J]. Guangdong Agricultural Sciences, 2017, 44(5): 118-125.

[45] GARCA-RUIZ A, GIRONES-VILAPLANA A, LEN P, et al. Banana Passion Fruit [Passiflora mollissima (Kunth) L. H. Bailey]: Microencapsulation, Phytochemical Composition, and Antioxidant Capacity [J]. Molecules, 2017, 22(1): 1-12.

[46] Yang Dan, Mo Xuchuan, Tan Liqing, et al. Optimization of the extraction process for total flavonoids from purple passion fruit peel using response surface methodology [J].  Journal of Guilin Normal University, 2017, 31(5): 100-103.

[47] Zhu Hui. Study on the Flavonoid Components of Passion Fruit and the Peptide Components of Harbin Red Sausage [D]. Suzhou: Soochow University, 2015: 26-27.

[48] Peng Bin, Kong Xianglong, Zheng Baodong. Study on the Extraction Process of Pigments from Passion Fruit Juice [J]. Fujian Light Industry and Textiles, 2010(9): 36-41.

[49] Zeng Shaoxiao, Peng Bin, Chen Jie, et al. Optimization of Passion Fruit Peel Anthocyanin Extraction Process Using Response Surface Methodology [J]. Chinese Journal of Food Science, 2014, 14(1): 104-113.