Effect of high pressure processing, browning treatments, and refrigerated storage on sensory analysis, color, and polyphenol oxidase activity in pawpaw (Asimina triloba L.) pulp

Accepted Manuscript Effect of high pressure processing, browning treatments, and refrigerated storage on sensory analysis, color, and polyphenol oxidase activity in pawpaw (Asimina Triloba L.) pulp Lin Zhang, Shun Dai, Robert G. Brannan PII:

S0023-6438(17)30502-9

DOI:

10.1016/j.lwt.2017.07.023

Reference:

YFSTL 6382

To appear in:

LWT - Food Science and Technology

Received Date: 31 May 2017 Revised Date:

14 July 2017

Accepted Date: 15 July 2017

Please cite this article as: Zhang, L., Dai, S., Brannan, R.G., Effect of high pressure processing, browning treatments, and refrigerated storage on sensory analysis, color, and polyphenol oxidase activity in pawpaw (Asimina Triloba L.) pulp, LWT - Food Science and Technology (2017), doi: 10.1016/ j.lwt.2017.07.023. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Effect of High Pressure Processing, Browning Treatments, and Refrigerated Storage on

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Sensory Analysis, Color, and Polyphenol Oxidase Activity in Pawpaw (Asimina Triloba L.)

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Pulp

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Lin Zhang, Shun Dai, and Robert G. Brannan*

6 School of Applied Health Sciences and Wellness

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Ohio University

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E170 Grover Center

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Athens, OH 45701

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United States

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740.593.2879 (phone)

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740.593.0289 (fax)

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*Author to whom correspondence should be addressed ([email protected])

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Abstract

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This study compared the effects of high pressure processing (HPP), treatments (pasteurization,

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ascorbic acid, and steviosides), storage time (1 day, 15 days, 30 days, and 45 days at 4 °C) on the

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polyphenol oxidase (PPO) activity, color, and sensory analysis of pulp from pawpaw fruit. HPP

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significantly decreased but did not completely inhibit PPO activity compared to the processed

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samples. HPP did not affect significantly any of the twelve sensory attributes. PPO activity and

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all color measurements were affected significantly by refrigerated storage. PPO activity declined

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after day 1 of refrigerated storage and remained unchanged thereafter. The untreated samples

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exhibited a significant change in all color values to varying degrees during the 45 day storage

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period, but this effect during storage was not observed in the samples that were pasteurized or

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treated with stevia or ascorbic acid. There was no difference between the PPO activity of the

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untreated pulp and the pulp treated with steviosides and pasteurization, however, the pawpaw

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pulp to which steviosides were added were perceived to be about 60% sweeter and 50% more

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bitter. HPP is a promising technology for shelf life extension of fresh-packaged pawpaw pulp.

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KEYWORDS: Pawpaw, Browning, Polyphenol oxidase (PPO), High pressure processing (HPP),

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Steviosides,

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1. Introduction The pawpaw (Asimina triloba L.), a fruit that is cultivated in eastern North America

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(Layne, 1996; Pomper & Layne, 2010), belongs to the tropical Annonacea fruit family even

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though it grows in temperate climates (Callaway, 1990). The pawpaw fruit ripens in late summer

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and early fall and appears kidney shaped, light green to yellow, with a size that varies from 5 cm

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to 20 cm long (Callaway, 1990). The ripe fruit has a complex sweet, tropical fruity, and slightly

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fermented aroma, and intense flavors of banana and mango (Brannan, Salabak, & Holben, 2012;

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Goodrich, Zjhra, Ley, & Raguso, 2006; McGrath & Karahadian, 1994). The texture is described

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as soft, custard or avocado-like (Brannan et al., 2012; McGrath & Karahadian, 1994; Pomper et

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al., 2008). No comprehensive nutritional analysis of the pawpaw has been performed recently.

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The nutritional content of pawpaw that includes the skin was performed (Peterson, Simmons, &

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Cherry, 1982), but this study must be discounted because the skin usually is not considered part

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of the edible portion of the fruit. What can be gleaned from pawpaw pulp without skin shows

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that 100 g pulp contains 64 kcal energy (US Department of Agriculture, 1963), about 75%

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moisture and 20% soluble sugar content depending on the state of ripeness (Brannan, R. G., T.

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Peters, & S. T. Talcott, 2015; McGrath & Karahadian, 1994), less than 1 g of lipid and 1-5 g

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protein (McGrath & Karahadian, 1994; Peterson et al., 1982; US Department of Agriculture,

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1963).

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The pawpaw fruit is highly susceptible to enzymatic discoloration, which is mainly

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attributable to polyphenol oxidase (PPO) activity (Fang, Wang, Xiong, & Pomper, 2007). PPO

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catalyzes colorless o-diphenol in the pulp to the formation of o-quinones that generate dark

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melanin after polymerization (Yoruk & Marshall, 2003). Therefore, the level of PPO activity

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plays a role in the discoloration rate of food. The PPO activity in fruits in general and fruits from

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the Annonacea family can be influenced by multiple factors, including fruit variety (Falguera et

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al., 2012; Fang et al., 2007), pH (Chaves, De Souza Ferreira, Da Silva, & Neves, 2011; Fang et

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al., 2007; Guerrero-Beltrán, Barbosa-Cánovas, Moraga-Ballesteros, Moraga-Ballesteros, &

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Swanson, 2006; Lima De Oliviera, Guerra, Sucupira Maciel, & Souza Livera, 1994; Yoruk &

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Marshall, 2003), addition of chemical inhibitors (Barba, Criado, Belda-Galbis, Esteve, &

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Rodrigo, 2014; Chaves et al., 2011; Guerrero-Beltran, Barbosa-Canovas, & Swanson, 2004;

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Siddiq, Cash, Sinha, & Akhter, 1994; Sun et al., 2008), and storage time (Campos-Vargas et al.,

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2008).

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High pressure processing (HPP) uses high hydrostatic pressure to pasteurize and inactivate enzymes such as PPO. Research comparing HPP to thermal pasteurization suggests

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that HPP preserves nutrients, flavor, and color but may not be as effective for enzyme

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degradation and microbial inactivation (Sevenich, Rauh, & Knorr, 2016; Zhao, Zhang, & Zhang,

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2017). Research on fruits processed by HPP often have shown a significant reduction of PPO

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activity when the pressure of HPP is over 500 Mpa (Asaka & Hayashi, 1991; Barba et al., 2014;

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Dajanta, Apichartsrangkoon, & Somsang, 2012; Guerrero-Beltran et al.; Sulaiman & Silva, 2013;

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Woolf et al., 2013), but the result is not universal (Rastogi, Raghavarao, Balasubramaniam,

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Niranjan, & Knorr, 2007). PPO inactivation by HPP may be enhanced with the application of

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chemicals. For example, peach puree treated with ascorbic acid before HPP (517 MPa at 25 °C

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for 20 min) treatment inactivates more than 95% of the PPO (Guerrero-Beltran et al., 2004).

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Similarly, the addition of 2.5% (w/v) stevia addition before HPP (500 MPa at 25 °C for 15 min)

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resulted in a 98% reduction of PPO activity in a mixed papaya, mango and orange puree (Barba

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et al., 2014). Because the pawpaw ripens quickly, changes to texture, color, and flavor limit its usage.

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High pressure processing causes minimal changes in the fresh characteristics of foods and is

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especially beneficial for heat-sensitive products like the pawpaw. We hypothesize that the

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pawpaw would be a suitable candidate for this process. The objective of this study was to assess

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the effect of HPP, addition of chemical inhibitors (ascorbic acid and steviosides), and storage on

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PPO inhibition, pulp color, and sensory analysis of pawpaw fruit.

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2. Materials and Methods

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2.1. Materials

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Pawpaw samples of variety Shenandoah were donated and manually harvested from Fox Paw Ridge Farm, Cincinnati, Ohio. Each individual fruit was selected by hand for ripeness by

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Dr. Ron Powell, a pawpaw expert who owns of Fox Paw Ridge Farm and is the president of the

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North American Pawpaw Growers Association. The whole pawpaw fruits were labeled,

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numbered, and transported back to Athens in coolers on ice.

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Experimental design and sample preparation

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Immediately after harvest and transport, the weight, length, width, skin and pulp color,

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sugar content (oBrix), and hardness were measured for each individual pawpaw fruit. The skin

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and seeds were removed from the pulp manually. The pulp obtained from individual fruits from

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each variety was pooled and divided into four equal portions. One lot was treated with 0.18%

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(w/w = 0.18 g powder/ 100 g pawpaw pulp) steviosides (Hard Rhino U.S.A., Phoenix, AZ) based

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on previous research (Barba et al., 2014), another lot treated with 400 mg/kg +99% L-ascorbic

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acid powder (Fisher Scientific, PA), and one other lot received a 60 ℃ water bath for 30 min in

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sealed polyethylene/nylon FoodSaver 27.94-cm bags. The remaining pulp was not chemically or

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thermally treated. Pulp from each of the four lots was assigned randomly into prelabeled bags,

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each representing a treatment group according to the 4 x 2 x 4 full-factorial design described

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later. The bags, polyethylene/nylon FoodSaver 27.94-cm bags (Jarden Corp., Rye, NY) with an

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oxygen transmission rate of 6.7 cc/m2/24 h/23°C/0% RH, were sealed under vacuum using a

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VACMASTER vacuum sealer (Overland Park, KS). All individual bags of pulp were stored at 4

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°C for not longer than 12 h until they were transported to the HPP facility where half of the

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samples were subjected to HPP as described below.

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2.2. HPP treatment

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The samples were transported to the HPP facility (Sandridge Food Corporation, Medina, OH, U.S.A.) on ice. The HPP samples were subjected to 600 MPa of pressure at ambient

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temperature (4 °C) for 76 s as recommended by previous research (Asaka & Hayashi, 1991;

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Barba et al., 2014; Dajanta et al., 2012; Guerrero-Beltran et al., 2004; Woolf et al., 2013). The

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samples sealed in the bags were transferred into iced water immediately after pressurization.

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Upon return from the HPP facility, samples designated as 1 day were analyzed for color and

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immediately transferred to frozen storage (- 40 °C). The remaining samples were stored

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refrigerated (4 °C). At the completion of their designated storage time (15, 30, or 45 days), the

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samples were analyzed for color and transferred to frozen storage (- 40 °C).

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2.3. Hardness, Percent Sugar, Color, and PPO activity determination Hardness and percent sugar (oBrix) of the whole fruit and color of the whole fruit and

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pulp was determined according to previously published methods (Brannan, R.G., T. Peters, & S.

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T. Talcott, 2015).

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Pulp color of the skin and pulp was characterized by using a Colorimeter (BC-10

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Colorimeter, Konica Minolta, NJ). The CIELAB system values (L*, a*, b*) were used to

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calculate the hue angle and chroma based on published methods for pawpaw (Brannan & Wang,

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2017).

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PPO activity was determined from crude enzyme extracts based on published methods for pawpaw (Fang et al., 2007), as follows. Pawpaw pulp was thawed quickly and pulp (2 g) mixed

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with 3 mL of 0.2 mol/L Na2HPO4/NaH2PO4 buffer (pH 6.5) containing 5g/100ml

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polyvinylpolypyrrolidone (PVPP), 2g/100ml Amberlite XAD-4 and 2g/100ml Triton X100. Each

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sample was centrifuged at 18,000 rpm (30065 × g, radius 8.3 cm) for 20 min at 4 °C (Eppendorf

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5417r, Hauppauge, NY). The supernatant, which contained the crude PPO, was kept at 0 °C

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before subjecting to protein and enzyme activity measurements, which were performed on the

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same day as extract preparation. Soluble protein in the supernatant was determined using the

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Lowry protein assay and quantified based on a standard curve prepared from pure albumin. PPO

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activity was measured as the increase in absorbance over time when catechol was added to the

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crude extracts. Absorbance at 420 nm was monitored every 10 s for 60 s.

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2.4. Descriptive Sensory Evaluation

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The nine trained panelists utilized in this study had previously developed the pawpaw lexicon, the standards that describe each attribute, and the procedures for pawpaw sampling

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(Brannan et al., 2012). They received refresher training focused on perception of flavors from the

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complex flavor profile of the pawpaw and re-familiarization with the ballot, attributes, and

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standards. Panelists were presented with 25 g of each sample at room temperature (25oC) in

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white plastic cups labeled with randomly coded with three-digit numbers. Panelists had access to

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ad libitum purified water and unsalted saltine crackers between tastings. Responses were

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recorded by ballots with a 15-cm line scale anchored with standards for each attribute.

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2.5. Statistical Analysis

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ascorbic acid, pasteurization), two levels of HPP processing (none, HPP-processed), and four

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levels of refrigerated storage (1, 15, 30, 45 days) was employed. Sensory analysis utilized a 4 x 2

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full-factorial design because the safety of pawpaw pulp during the extended refrigerated storage

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could not be assured. The main effects and interactions were analyzed statistically using PASW

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Statistics 18 for Windows (Armonk, NY). Analysis of variance (ANOVA) was used to determine

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differences between the means of the main effects at a significance level of p < 0.05. Means was

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separated using the Duncan’s Multiple Range test.

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3. Results and Discussion

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3.1. Characterization of pawpaw fruit

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Descriptive statistics for weight, length, width, skin color, percent sugar, and hardness for

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the 15 fruits utilized for this study are shown in Table 1. The weights of the individual pawpaw

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fruit ranged from 51 to 240 g, 5.5 to 12.5 cm in length, and 4.5 to 7.0 cm in breadth. Although

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skin color, percent sugar and hardness values change as the pawpaw fruit ripens (McGrath &

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Karahadian, 1994), these changes are not reliable indicators of ripeness (Archbold, Koslanund, &

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Pomper, 2003). As shown in Table 1, oBrix, hardness, and skin color reported in this study all

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fall within the ranges that we previously reported for the means of 10 varieties of pawpaw

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(Brannan, R.G. et al., 2015).

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3.2. Sensory Analysis of Pawpaw

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The main effects of treatment (untreated, steviosides, pasteurization, ascorbic acid) but not HPP processing (HPP versus non-HPP) affected the sensory quality of the pawpaw pulp. The

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fact that HPP did not affect significantly any of the twelve sensory attributes agrees with a

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multitude of studies that show that HPP has little or no effect on the sensory quality of a wide

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variety of foods (Wang, Huang, Hsu, & Yang, 2016). Results of this study indicate that banana,

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melon, mango, and papaya flavors predominate and we reported similar results from a previous

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study for a different variety of pawpaw (Brannan et al., 2012). However, differences in the

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intensity of flavor attributes between the current study and our previous study indicate that the

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magnitude of the flavor attributes were lower in the current study and the sweet/bitter intensity

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was 0.6:1 compared to 0.9:1 in the previous study. This suggests that the Shenandoah pawpaw

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variety studied in this study was more bitter and less flavorful. The pawpaw pulp to which

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steviosides were added were perceived to be about 60% sweeter (p < 0.001) and 50% more bitter

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(p < 0.001) than the pulp that was untreated, pasteurized, or had added ascorbic acid. This result

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is not unexpected because steviosides are a well-known sweet tasting compound that can have a

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very bitter aftertaste (Wolwer-Rieck, 2012). The color of the pulp was affected by treatment (p =

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0.018), with panelists perceiving pasteurized pulp as being about 25% more brown compared to

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the pulp that was untreated or contained stevia or ascorbic acid.

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Shown in Table 2, the two-way interaction of treatment and HPP processing did not

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affect the flavor attributes but color, sweetness, and bitterness were affected. There was no

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difference in color between the unprocessed and HPP-processed samples with the exception of

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the ascorbic acid-treated samples, which exhibited a darker color in the unprocessed samples

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than in the HPP-processed samples. Sweetness and bitterness were significantly affected by the

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addition of steviosides, as was observed for the main effects.

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3.3. Effect storage time, HPP-processing, and treatment on pawpaw PPO activity and color

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The main effect of storage time showed that PPO activity and all color measurements

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were affected significantly (p < 0.001) by refrigerated storage. PPO activity was significantly

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higher on day 1 (18.5 ∆ABS/min/g protein) than after 15, 30, or 45 days of refrigerated storage

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(2.2, 0.8, 1.4 ∆ABS/min/g protein, respectively), indicating that PPO activity decreases after day

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1 with no further decline when considered across all inhibitors and processing. These results

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agree with HPP-processed Cherimoya, which like pawpaw an Annonacaeous fruit (Campos-

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Vargas et al., 2008). However, there does not appear to be consensus about the effect of storage

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on PPO activity. For example, a decline in PPO during refrigerated storage has been observed for

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eggplant (Barbagallo, Chisari, & Patane, 2012) although the opposite was observed in pineapple

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(Botrel & Decarvalho, 1993). The color values L*, b*, chroma, ∆E, and hue angle declined and

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a* increased after day 1. These results suggest that as PPO activity declines, the pawpaw pulp

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became darker (lower L*), less vivid (lower chroma), less yellow (lower b* and hue angle), and

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more red (lower hue angle and higher a*).

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The main effect of HPP processing showed that HPP significantly decreased but did not completely inhibit PPO activity (p < 0.001) by 66%, from 8.6 ∆ABS/min/g protein to 2.9

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∆ABS/min/g protein across inhibitors and storage time. This result agrees previous research that

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indicated that HPP has an effect on PPO inhibition in fruit (Dajanta et al., 2012; Guerrero-

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Beltran et al., 2004; Sulaiman & Silva, 2013) and with other that research suggests that

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polyphenol oxidase is resistant to PPO to varying degrees (Guerrero-Beltran, Barbosa-Canovas,

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& Swanson, 2005; Terefe, Buckow, & Versteeg, 2014). The HPP pawpaw was browner as

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indicated the observations that the HPP pulp was significantly darker (lower L*), redder (higher

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a*), and less yellow (lower b*). Similar results were observed in avocado slices and pear fruits

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(Asaka & Hayashi, 1991; Woolf et al., 2013).

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The main effect of treatment (untreated, steviosides, pasteurization, ascorbic acid)

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revealed significance for PPO activity (p = 0.007) and all color measurements (p < 0.002 for all

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variables). There was no difference between the PPO activity of the untreated pulp and the pulp

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treated with steviosides and pasteurization (4.7, 5.5 ∆ABS/min/g protein, respectively). In a

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previous study of pawpaw extracts that were exposed to 60oC for 10 min, an 80% inactivation of

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PPO was observed (Fang et al., 2007). This suggests a protective effect on PPO activity during

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the pasteurization treatment employed on the pulp in this study compared to the more labile PPO

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in extracts. Ascorbic acid (7.8 ∆ABS/min/g protein) produced pulp with significantly higher PPO

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activity (p < 0.007) than the untreated pulp (4.9 ∆ABS/min/g protein). Endogenous ascorbic acid

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in pawpaw (Harris & Brannan, 2009) coupled with the added ascorbic acid could cause it to

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behave as a quinone reducer rather than PPO inhibitor, as has been described in lettuce (Ali, El-

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Gizawy, El-Bassiouny, & Saleh, 2015). Supporting this hypothesis is the observation that the

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color of the ascorbic acid-treated pulp was the least affected compared to the other treatments, as

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shown by a significantly higher brightness (L*), yellow color (b* and hue angle), and vividness

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(chroma) than the untreated pulp.

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3.4. Comparison of the two-way interaction of refrigerated storage time x HPP processing

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The two-way interaction of refrigerated storage and HPP processing was significant for PPO activity (Table 3) and all color measurements (Table 4). As shown in Table 3, a significant

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decrease in PPO activity was observed after day 1 with no further significant changes occurring

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during the refrigerated storage period. At day 1, there was significantly lower PPO activity for

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the HPP-treated samples compared to the non-treated samples. These observations support the

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findings from section 3.2, and a review by Rastogi et al. (2007) shows a similar effect in some

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fruits (apple, grape, avocado, pear) but not others (grape, plum). This indicates that PPO

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inhibition by HPP is species dependent, and pawpaw PPO is reduced by HPP. Although HPP-

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treated samples at day 1 were more red as indicated by significantly higher a* and lower hue

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angle (Table 4), the reduction in PPO activity did not correspond to increased browning as

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observed by the sensory panel or other measures of browning. The low values of PPO activity

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for HPP-treated pawpaw during storage (Table 3) corresponded to a lack of continued PPO-

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induced color change, indicating low residual PPO activity in these samples. The color of the

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HPP-treated pawpaw at days 15, 30 and 45 were darker (L*), more red (a*), less yellow (b* and

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hue angle), less vivid (chroma) compared to day 1 pulp.

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3.5. Comparison of the two-way interaction of refrigerated storage time x treatment

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The two-way interaction of refrigerated storage and processing treatment was significant

for PPO activity (p < 0.001) and all color measurements (p < 0.017). As shown in Table 3, a

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significant decrease in PPO activity was observed after day 1 with no further significant changes

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occurring during storage. The untreated samples exhibited a significant change in all color values to varying

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degrees during the 45 day storage period (Table 4), but this effect during storage was not

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observed in the other treated samples. Assuming the color changes observed in the untreated

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samples was caused by residual PPO, all of the treatments inhibited further PPO-mediated color

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change during the storage period.

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3.6. Comparison of the two-way interaction of treatment x HPP processing

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At day 1 of storage, comparisons of the two-way interaction of processing treatment and HPP for PPO activity and color are shown in Table 2. There were significant differences for PPO

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and all color attributes except for L*. Significant decline in PPO activity was observed in HPP-

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treated samples compared to non-HPP treated samples for the control (85% reduction),

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stevioside-treated (74% reduction), and heat pasteurized (81% reduction) samples. There was no

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significant difference in PPO activity for ascorbic acid-treated samples, suggesting that ascorbic

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acid has a protective effect on PPO activity during high pressure processing. This mirrors a

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conclusion from section 3.3 that in the HPP-treated samples, ascorbic acid could be behaving as

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a quinone reducer as described for lettuce (Ali et al., 2015). Supporting this conclusion is the

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observation that the color of the HPP processed pulp showed a significantly higher redness (a*),

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yellow color (b* and hue angle), and vividness (chroma) than the untreated pulp. However, these

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differences were not observed in the sensory analysis of the pulp.

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4. Conclusion

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Currently the pawpaw fruit industry is very small. Distribution of the whole fruit is challenging due to its perishability. Most pawpaw is sold as frozen pulp, usually for festivals,

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food service, or increasingly for the brewery industry. Results from this research show that HPP

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has potential for processing fresh pawpaw, in spite of the fact that HPP did not completely

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inhibit PPO activity. Storage of HPP-processed pawpaws resulted in no further changes during

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the refrigerated storage period. The objective color measurements of the HPP pawpaw indicated

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that it was browner, however, there was no difference in the sensory perception of the color of

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HPP-treated pawpaw. It appears that PPO activity is not the only determinative factor of

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browning of the pawpaw fruit.

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The other treatment strategies were not as effective at PPO inhibition but did mitigate color changes. The addition of steviosides, a natural sweetener, produced sweeter and more

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bitter pulp that protected the color during extended storage. Before steviosides can become a

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reliable additive to pawpaw, development must focus on mitigating the bitterness of the already-

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bitter pawpaw. Ascorbic acid was employed based on its use in the frozen pawpaw pulp industry,

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but showed mixed results in this study. In HPP-treated samples, it appears to spare PPO

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somehow, but protects the color at the same time. In untreated samples, it protects the color

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during storage.

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The variety used for this study, Shenandoah, is a commercially available cultivar that was

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chosen based on its availability. Although it has been described in marketing materials by

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growers as “one of the most flavorful” varieties, sensory analysis suggests that it was not as

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flavorful and more bitter than a previous variety that was tested. Thus, there may be other

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cultivars that are better suited from a sensory analysis or shelf life point of view. Research on

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other varieties with commercialization potential should focus on varieties that maximize

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sweetness and minimize bitterness, especially if its shelf life can be extended via a process such

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as HPP.

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References

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Ali, H. M., El-Gizawy, A. M., El-Bassiouny, R. E. I., & Saleh, M. A. (2015). Browning inhibition mechanisms by cysteine, ascorbic acid and citric acid, and identifying PPOcatechol-cysteine reaction products. Journal of Food Science and Technology-Mysore, 52(6), 3651-3659. doi: 10.1007/s13197-014-1437-0 Archbold, D. D., Koslanund, R., & Pomper, K. W. (2003). Ripening and postharvest storage of pawpaw. Horttechnology, 13(3), 439-441. Asaka, M., & Hayashi, R. (1991). Activation of Polyphenol Oxidase in Pear Fruits by HighPressure Treatment. Journal of Agricultural and Biological Chemistry, 55(9), 2439-2440. Barba, F. J., Criado, M. N., Belda-Galbis, C. M., Esteve, M. J., & Rodrigo, D. (2014). Stevia rebaudiana Bertoni as a natural antioxidant/antimicrobial for high pressure processed fruit extract: processing parameter optimization. Food Chemistry, 148, 261-267. doi: 10.1016/j.foodchem.2013.10.048 Barbagallo, R. N., Chisari, M., & Patane, C. (2012). Use In Vivo of Natural Anti-Browning Agents Against Polyphenol Oxidase Activity in Minimally Processed Eggplant. In E. Bardone, A. Brucato, T. Keshavarz, S. Pierucci & J. J. Klemes (Eds.), Ibic2012: International Conference on Industrial Biotechnology (Vol. 27, pp. 49-54). Milano: Aidic Servizi Srl. Botrel, N., & Decarvalho, V. D. (1993). Effect of Fruit Weight on the Internal Browning and Quality of Pineapple CV Smooth Cayenne. 1. Polyphenol Oxidase, Peroxidase-Activities and Phenolic-Compounds. Pesquisa Agropecuaria Brasileira, 28(6), 733-742. Brannan, R. G., Peters, T., & Talcott, S. T. (2015). Phytochemical Analysis of Ten Varieties of Pawpaw (Asimina triloba [L.] Dunal) Fruit Pulp. Food Chemistry doi: 10.1016/j.foodchem.2014.07.018 Brannan, R. G., Peters, T., & Talcott, S. T. (2015). Phytochemical analysis of ten varieties of pawpaw (Asimina triloba L. Dunal) fruit pulp. [Article]. Food Chemistry, 168, 656-661. doi: 10.1016/j.foodchem.2014.07.018 Brannan, R. G., Salabak, D. E., & Holben, D. H. (2012). Sensory Analysis of Pawpaw (Asimina triloba) Pulp Puree: Consumer Appraisal and Descriptive Lexicon. Journal of Food Research, 1(1). doi: 10.5539/jfr.v1n1p179 Brannan, R. G., & Wang, G. (2017). Effect of Frozen Storage on Polyphenol Oxidase, Antioxidant Content, and Color of Pawpaw (Asimina Triloba [L.] Dunal) Fruit Pulp. Journal of Food Research, 6(3). Callaway, M. B. (1990). The Pawpaw (Asimina triloba): Frankfort, Ken. : Kentucky State Univ., 1990. Campos-Vargas, R., Defilippi, B. G., Romero Q, P., Valdés G, H., Robledo M, P., & Prieto E, H. (2008). Effect of Harvest Time and L-Cysteine as an Antioxidant on Flesh Browning of Fresh-Cut Cherimoya (Annona cherimola Mill.). Chilean Journal of Agricultural Research, 68, 217-227. Chaves, I. R., De Souza Ferreira, E., Da Silva, M. A., & Neves, V. A. (2011). Polyphenol Oxidase from Atemoya Fruit (Annona Chermola Mill x Annona Squamosa L.). Journal of Food Biochemistry, 35(6), 1583-1592. doi: 10.1111/j.1745-4514.2010.00508.x

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Dajanta, K., Apichartsrangkoon, A., & Somsang, S. (2012). Comparison of physical and chemical properties of high pressure- and heat-treated Lychee (Litchi chinensis Sonn.) in syrup. High Pressure Research, 32(1), 114-118. doi: 10.1080/08957959.2012.664641 Falguera, V., Sánchez-Riaño, A., Quintero-Cerón, J., Rivera-Barrero, C., Méndez-Arteaga, J., & Ibarz, A. (2012). Characterization of Polyphenol Oxidase Activity in Juices from 12 Underutilized Tropical Fruits with High Agroindustrial Potential. Food and Bioprocess Technology, 5(7), 2921-2927. doi: 10.1007/s11947-011-0521-y Fang, C., Wang, C., Xiong, Y. L., & Pomper, K. W. (2007). Extraction and characterization of polyphenol oxidase in pawpaw (Asimina triloba) fruit Journal of Food Biochemistry, 31, 603-620. doi: 10.1111/j.1745-4514.2007.00133.x Goodrich, K. R., Zjhra, M. L., Ley, Courtney A., & Raguso, Robert A. (2006). When Flowers Smell Fermented: The Chemistry and Ontogeny of Yeasty Floral Scent in Pawpaw (Asimina triloba: Annonaceae), 33. Guerrero-Beltrán, J. A., Barbosa-Cánovas, G. V., Moraga-Ballesteros, G., Moraga-Ballesteros, M. J., & Swanson, B. G. (2006). Effect of pH and Ascorbic Acid on High Hydrostatic Pressure-Processed Mango Puree. [Article]. Journal of Food Processing & Preservation, 30(5), 582-596. doi: 10.1111/j.1745-4549.2006.00090.x Guerrero-Beltran, J. A., Barbosa-Canovas, G. V., & Swanson, B. G. (2004). High hydrostatic pressure processing of peach puree with and without antibrowning agents. Journal of Food Processing & Preservation, 28(1), 69-85. Guerrero-Beltran, J. A., Barbosa-Canovas, G. V., & Swanson, B. G. (2005). High hydrostatic pressure processing of fruit and vegetable products. Food Reviews International, 21(4), 411-425. doi: 10.1080/875591205500224827 Harris, G. G., & Brannan, R. G. (2009). A preliminary evaluation of antioxidant compounds,

reducing potential, and radical scavenging of pawpaw (Asimina tribloba) fruit pulp from different stages of ripeness. LWT - Food Science and Technology,

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doi:10.1016/j.lwt.2008.05.006. Layne, D. R. (1996). The pawpaw [Asimina triloba (L) Dunal]: A new fruit crop for Kentucky and the United States. Hortscience, 31(5), 777-784. Lima De Oliviera, S., Guerra, N. B., Sucupira Maciel, M. I., & Souza Livera, A. V. (1994). Polyphenoloxidase Activity, Polyphenols Concentration and Browning Intensity during Soursop (Annona muricata, L.) Maturation. Journal of Food Science, 59(5), 1050-1052. doi: 10.1111/j.1365-2621.1994.tb08187.x McGrath, M. J., & Karahadian, C. (1994). Evaluation of Physical, Chemical, and Sensory Properties of Pawpaw Fruit (Asimina-Triloba) as Indicators of Ripeness. Journal of Agricultural and Food Chemistry, 42(4), 968-974. Peterson, R. N., Simmons, J. G., & Cherry, J. P. (1982). Composition of pawpaw (Asimina triloba) fruit. Annual report - Northern Nut Growers Association, 97-107. Pomper, K. W., Crabtree, S. B., Layne, D. R., Peterson, R. N., Masabni, J., & Wolfe, D. (2008). The Kentucky pawpaw regional variety trial. Journal of the American Pomological Society, 62(2), 58-69. Pomper, K. W., & Layne, D. R. (2010). The North American Pawpaw: Botany and Horticulture Horticultural Reviews (pp. 349-382): John Wiley & Sons, Inc.

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Rastogi, N. K., Raghavarao, K., Balasubramaniam, V. M., Niranjan, K., & Knorr, D. (2007). Opportunities and challenges in high pressure processing of foods. Critical Reviews in Food Science and Nutrition, 47(1), 69-112. doi: 10.1080/10408390600626420 Sevenich, R., Rauh, C., & Knorr, D. (2016). A scientific and interdisciplinary approach for high pressure processing as a future toolbox for safe and high quality products: A review. Innovative Food Science & Emerging Technologies, 38, 65-75. doi: 10.1016/j.ifset.2016.09.013 Siddiq, M., Cash, J. N., Sinha, N. K., & Akhter, P. (1994). Characterization and Inhibition of Polyphenol Oxidase from Pears (Pyrus-Communis L Cv Bosc And Red). [Article]. Journal of Food Biochemistry, 17(5), 327-337. Sulaiman, A., & Silva, F. V. M. (2013). High pressure processing, thermal processing and freezing of ‘Camarosa’ strawberry for the inactivation of polyphenoloxidase and control of browning. Food Control, 33, 424-428. doi: 10.1016/j.foodcont.2013.03.008 Sun, J., Shi, J., Zhao, M., Xue, S. J., Ren, J., & Jiang, Y. (2008). A comparative analysis of property of lychee polyphenoloxidase using endogenous and exogenous substrates. Food Chemistry, 108(3), 818-823. doi: 10.1016/j.foodchem.2007.11.036 Terefe, N. S., Buckow, R., & Versteeg, C. (2014). Quality-Related Enzymes in Fruit and Vegetable Products: Effects of Novel Food Processing Technologies, Part 1: HighPressure Processing. Critical Reviews in Food Science and Nutrition, 54(1), 24-63. doi: 10.1080/10408398.2011.566946 US Department of Agriculture, U. (1963). United States Deptartment of Agriculture Agriculture Handbook No. 8: Composition of foods: raw, processed, prepared. Consumer and Food Economics Research Division, Agricultural Research Service, USDA Retrieved from http://www.library.ohiou.edu/ezpauth/redir/athens.php?http://search.ebscohost.com/login. aspx?direct=true&db=cat00572a&AN=alice.b1876074&site=eds-live&scope=site. Wang, C. Y., Huang, H. W., Hsu, C. P., & Yang, B. B. (2016). Recent Advances in Food Processing Using High Hydrostatic Pressure Technology. Critical Reviews in Food Science and Nutrition, 56(4), 527-540. doi: 10.1080/10408398.2012.745479 Wolwer-Rieck, U. (2012). The Leaves of Stevia rebaudiana (Bertoni), Their Constituents and the Analyses Thereof: A Review. Journal Of Agricultural And Food Chemistry, 60(4), 886895. doi: 10.1021/jf2044907 Woolf, A. B., Wibisono, R., Farr, J., Hallett, I., Richter, L., Oey, I., . . . Requejo-Jackman, C. (2013). Effect of high pressure processing on avocado slices. Innovative Food Science and Emerging Technologies, 18, 65-73. doi: 10.1016/j.ifset.2013.02.011 Yoruk, R., & Marshall, M. R. (2003). Physicochemical properties and function of plant polyphenol oxidase: A review. Food Biochemistry, 27(5), 361-422. Zhao, G. H., Zhang, R. F., & Zhang, M. W. (2017). Effects of high hydrostatic pressure processing and subsequent storage on phenolic contents and antioxidant activity in fruit and vegetable products. International Journal of Food Science and Technology, 52(1), 312. doi: 10.1111/ijfs.13203

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Table 1 Comparison of weight, size, color, percent sugar, and hardness of whole pawpaw fruit from variety Shenandoah (used for this study) to values previously reported. From Brannan and others, 20151 Current Study Mean Max Min Weight (g) 123 ± 62 140 204 84 Length (cm) 8.6 ± 2.0 9.8 11.5 7.9 Height (cm) 5.6 ± 0.9 5.5 6.4 4.6 Skin_L* 61.85 ± 4.35 64.2 69.3 61.4 Skin_a* -8.03 ± 1.67 -6.9 -3.1 -10.2 Skin_b* 31.96 ± 7.79 34.0 41.3 29.6 o Brix 21.2 ± 1.6 24.3 28.0 19.9 Hardness (kg) 0.432 ± 0.284 0.377 0.643 0.198 1 Means calculated from ten pawpaw varieties from the same growing season (Green River Belle, IXL, KSU-Atwood™, Lynn’s favorite, NC-1, Overleese, Quaker’s Delight, Rebecca’s Gold, SAA Zimmerman, Taytwo.).

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Table 2 Polyphenol oxidase activity (∆ABS/min/g protein), color measurements, and sensory analysis of the two-way interaction of processing treatment (no treatment, pasteurization, 0.18% steviosides, 400 ppm ascorbic acid) on pawpaw pulp without and with high pressure processing (HPP). Means within a row with different superscripts are significantly different at p<0.05. Pasteurization No HPP HPP

Steviosides No HPP HPP

Sensory Analysis 3.1 ± 1.2abc 3.6 ± 1.5ab

Color

2.5 ± 0.9c

2.7 ± 0.9bc

Ascorbic Acid No HPP HPP

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Control No HPP HPP

3.3 ± 1.3abc 3.3 ± 0.9abc 3.2 ± 0.8abc

4.0 ± 1.0a

4.8 ± 2.7

4.9 ± 2.8

5.9 ±2.7

6.6 ± 2.0

6.0 ± 3.1

5.5 ± 1.6

6.3 ± 2.4

7.7 ± 2.9

Sweet

2.2 ± 0.6b

2.1 ± 0.9b

2.2 ± 1.5b

1.6 ± 1.5b

3.4 ± 1.9a

3.3 ± 1.1a

2.2 ± 1.1b

2.1 ± 0.6b

Sour

1.5 ±1.1

1.2 ± 1.1

0.7 ± 0.6

1.2 ± 1.1

1.7 ± 1.5

1.9 ± 1.9

0.9 ± 1.1

1.5 ± 1.3

Banana

2.5 ± 1.4

2.6 ± 1.6

2.6 ± 1.2

2.1 ± 1.5

2.2 ± 1.0

2.7 ± 0.9

2.7 ± 1.7

1.9 ± 0.8/

Melon

2.1 ± 1.1

2.4 ± 0.9

2.2 ± 1.1

Mango

2.7 ± 1.3

2.8 ± 1.4

2.5 ± 1.2

Papaya

2.6 ± 1.2

1.7 ± 1.0

2.2 ± 1.3

Tropical

1.2 ± 1.0

1.2 ± 0.9

1.4 ± 1.3

Astringent 3.8 ± 2.1

3.0 ± 1.9

2.8 ± 1.5

Rindy

2.5 ± 1.5

2.9 ± 3.3

Bitter

2.9 ± 2.2b

3.3 ± 2.3b

Color Measurements L*

64.3 ± 1.4

a*

6.3 ± 1.2cd

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2.4 ± 1.2

2.1 ± 0.9

2.3 ± 1.4

2.3 ± 0.9

2.5 ± 1.1

2.6 ± 1.0

2.1 ± 1.1

2.4 ± 1.1

2.3 ± 1.7

1.6 ± 0.9

1.7 ± 1.1

1.9 ± 1.3

2.2 ± 1.4

1.0 ± 0.8

1.7 ± 1.9

1.5 ± 0.8

1.5 ± 1.4

1.1 ± 1.0

2.4 ± 1.9

3.2 ± 2.2

3.4 ± 2.1

2.5 ± 1.4

2.7 ± 2.2

2.8 ± 1.6

2.8 ± 2.8

2.6 ± 2.1

3.6 ± 2.7

3.7 ± 2.1

3.0 ± 1.9

3.4 ± 2.6b

2.2 ± 2.8b

6.1 ± 2.3a

6.3 ± 4.9a

3.1 ± 1.7b

3.1 ± 2.2b

3.4 ± 0.3b

32.1 ± 9.4a

6.2 ± 3.5b

25.1 ± 2.7a

6.5 ± 2.8b

27.6 ± 7.7a 23.4 ± 10.5a

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24.0 ± 5.3a

2.7 ± 1.9

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Polyphenol Oxidase Activity

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Body

59.2 ± 2.4

59.4 ± 2.2

66.6 ± 8.5

61.3 ± 2.5 57.7 ± 22.5 64.0 ± 2.1

6.3 ± 0.8de

3.1 ± 1.1de

10.7 ± 1.6ab

4.9 ± 2.0cde

12.8 ± 3.1a

39.8 ± 0.3a 39.6 ± 2.9a

31.9 ± 3.3c

33.3 ± 1.5bc 35.2 ± 2.3bc 34.7 ± 0.7bc 31.3 ± 2.4c 37.5 ± 3.2ab

Chroma

40.3 ± 0.5a 39.8 ± 3.0ab 32.1 ± 3.3d

35.0 ± 1.0cd 35.6 ± 2.0bcd 37.1 ± 0.7abc 31.4 ± 2.5d 38.3 ± 3.6abc

Hue Angle

80.9 ± 1.6ab 85.3 ± 0.9a

72.1 ± 3.1c

b*

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62.0 ± 1.3

84.5 ± 1.8a

2.1 ± 1.0e

7.6 ± 2.7bc

82.0 ± 3.7ab 69.8 ± 4.8c 86.2 ± 1.5a 78.7 ± 3.1b

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Table 3 Comparison of polyphenol oxidase activity (∆ABS/min/g protein) for the two-way interactions of 1) storage time x high pressure processing (HPP) and 2) storage time x processing treatment (no treatment, pasteurization, 0.18% steviosides, 400 ppm ascorbic acid). Different superscripts within a two-way interaction denote significant differences at p<0.05. Days of Refrigerated Storage 15 30 4.0 ± 2.5c 0.5 ± 0.6c

0.7 ± 0.6c 0.9 ± 0.7c

2.4 ± 1.4c 0.4 ± 0.5c

13.7 ± 11.8y 15.8 ± 10.5y 19.1 ± 15.5yz 25.4 ± 8.5z

3.0 ± 2.1x 1.2 ± 1.2x 2.1 ± 2.3x 2.6 ± 4.1x

1.5 ± 0.2x 0.3 ± 0.2x 0.4 ± 0.2x 1.0 ± 0.5x

1.7 ±0.7x 1.6 ± 1.8x 0.3 ± 0.4x 2.1 ± 1.8x

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27.2 ± 6.6a 9.8 ± 9.6b

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Two-Way Interaction 1) Storage x HPP Control (no HPP) Pulp HPP-treated Pulp 2) Storage x Treatment Control (Untreated) Stevia Pasteurization Ascorbic Acid

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1) Storage x HPP no HPP HPP-treated

Pasteurization

Ascorbic Acid

59.2 ± 2.0xyz 53.6 ± 4.6wxy 55.9 ± 3.4wxyz 54.3 ± 6.6wxyz

60.8 ± 14.6xyz 63.2 ± 4.1yz 60.3 ± 9.6x 59.0 ± 8.6xyz

63.1 ± 1.8yz 61.2 ± 5.7xyz 51.4 ± 7.6wx 48.8 ± 8.0w

63.9 ± 6.3z 56.6 ± 11.9wxyz 57.0 ± 2.2wxyz 55.6 ± 7.1wxyz

8.6 ± 4.1c 13.5 ± 1.6a 13.6 ± 1.9a 12.6 ± 3.7ab

4.8 ± 1.8v 9.9 ± 3.2vwxyz 11.9 ± 2.5wxyz 15.4 ± 0.5z

8.8 ± 4.9vwxy 7.4 ± 6.2vwx 13.5 ± 1.0yz 13.1 ± 7.8xyz

6.9 ± 4.3vw 9.4 ± 4.9vwxy 9.1 ± 2.2vwxy 7.8 ± 1.9vwxy

4.8 ± 3.4v 11.9 ± 2.5x 10.0 ± 6.6vwxyz 8.8 ± 6.8vwxy

36.2 ± 3.2a 27.5 ± 5.3b 26.2 ± 5.4b 24.8 ± 4.4b

39.7 ± 1.8z 35.8 ± 5.7yz 26.4 ± 7.9w 26.9 ± 8.3w

34.9 ± 1.5xyz 30.4 ± 9.2wxy 32.9 ± 1.4wxyz 33.0 ± 4.4wxyz

32.5 ± 2.3wxyz 26.1 ± 3.7w 25.7 ± 4.2w 27.8 ± 5.9wx

34.4 ± 4.2xyz 35.9 ± 2.7yz 35.4 ± 7.5yz 33.0 ± 6.4wxyz

37.5 ± 2.7a 30.8 ± 5.0b 29.6 ± 5.1b 28.1 ± 4.0b

40.0 ± 1.9z 37.4 ± 4.6xyz 29.4 ± 6.5uvw 31.2 ± 7.3uvwx

36.3 ± 1.5xyz 32.6 ± 7.8uvwxy 35.6 ± 1.3xyz 35.7 ± 4.3vwxy

34.8 ± 4.7wxyz 27.9 ± 2.1uv 27.3 ± 4.1v 29.0 ± 5.4uvw

37.4 ± 4.6xyz 37.4 ± 1.4xyz 37.6 ± 5.3yz 35.0 ± 4.4wxyz

76.4 ± 6.9b 63.2 ± 4.5c 61.9 ± 5.4c 62.7 ± 8.7c

83.1 ± 2.6z 73.6 ± 7.2wxyz 63.8 ± 10.5vw 58.8 ± 7.3v

75.8 ± 7.6wxya 70.4 ± 13.9vwxy 67.6 ± 1.8vwx 68.2 ± 6.7vwx

78.3 ± 7.1xyz 73.3 ± 14.4wxyz 70.2 ± 5.0vwxy 73.4 ± 6.1wxyz

82.4 ± 4.6yz 75.0 ± 8.3wxyz 72.6 ± 13.2wxyz 73.5 ± 13.7wxyz

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61.6 ± 2.4a 53.0 ± 6.1b 51.1 ±4.5bc 47.9 ± 5.0c

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L* 1 day 61.9 ± 10.9a 15 day 64.3 ± 4.6a 30 day 61.2 ± 4.8a 45 day 60.9 ± 8.0a a* 1 day 4.1 ± 2.0d 15 day 4.6 ± 2.4d 30 day 8.7 ± 3.9c 45 day 10.0 ± 5.7bc b* 1 day 34.5 ± 4.0a 15 day 36.6 ± 5.1a 30 day 34.0 ± 6.2a 45 day 35.6 ± 3.0a Chroma 1 day 34.8 ± 4.1a 15 day 36.9 ± 5.3a 30 day 35.3 ± 6.1a 45 day 37.3 ± 3.0a Hue Angle 1 day 83.3 ± 2.9a 15 day 83.0 ± 3.0a 30 day 75.1 ± 6.4b 45 day 74.3 ± 8.8b

2) Storage x Treatment Untreated Stevia

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Table 4 Comparison of CIE tristimulous values (L*, a*, b*), chroma, and hue angle for the two-way interactions of 1) storage time x high pressure processing (HPP) and 2) storage time x processing treatment (no treatment, pasteurization, 0.18% steviosides, 400 ppm ascorbic acid). Different superscripts within a two-way interaction for each color variable denote significant differences at p<0.05.

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HIGHLIGHTS: High pressure processing inhibits polyphenol oxidase in pawpaw pulp.

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High pressure processing did not affect any of the twelve sensory attributes.

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High pressure processing is promising for shelf life extension of pawpaw pulp.

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