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Title:Impact of novel thermal and non-thermal processing on nutritional value and overall quality of papaya and strawberry nectars and their respective blends
Author(s):Swada, Jeffrey
Director of Research:Engeseth, Nicki J.
Doctoral Committee Chair(s):Cadwallader, Keith
Doctoral Committee Member(s):Lee, Youngsoo; Morris, Scott
Department / Program:Food Science & Human Nutrition
Discipline:Food Science & Human Nutrition
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Synergistic Relationships
Antioxidant Capacity
Papaya and Strawberry
Enzymatic Activity
Nutrient Content
Thermal and Non-Thermal Processing
Abstract:Papaya and strawberry are notable for their rich nutrient contents and high antioxidant activities. Though consuming these fruits on their own contribute to a healthy lifestyle, combinations of fruits, such as papaya and strawberry nectar blends, can result in an even greater synergistic impact on human health. Availability of these fruits, however, is limited; both have extremely short shelf lives and tend to be seasonal fruits, resulting in over 50% of fruit not reaching consumers due to softening and molding during harvesting and shipping. In addition, deleterious enzymes naturally present in fruits, such as pectin methylesterase (PME) in papaya and peroxidase (POD) in strawberry, can lead to reduced consumer acceptance if not reduced to low enough concentrations through processing. To extend shelf lives and combat these deteriorative enzymes, traditional thermal processing is often employed. This technique is able to sufficiently reduce enzyme activity; however, it results in undesirable nutrient and quality loss. As a result, the impact of different novel thermal and non-thermal techniques, i.e., ultra high temperature (UHT), high pressure processing (HPP) and irradiation on papaya and strawberry nectars and their respective blends were explored. Traditional thermal processing resulted in the greatest reduction in ascorbic acid and carotenoid concentration, with moderate impact on antioxidant capacity. UHT had moderate effects on ascorbic acid content and antioxidant capacity and resulted in the greatest retention in carotenoid concentration, with observed synergistic relationships for ascorbic acid and antioxidant capacity. HPP had minimal impact on antioxidant capacity in strawberry nectar, but resulted in the greatest overall retention of ascorbic acid at 20oC. Irradiation had moderate effects on ascorbic acid and carotenoid concentration, with the greatest overall increase in antioxidant capacity. Both anergetic and additive relationships for ascorbic acid were observed in nectar blends after irradiation, with anergetic, additive, and synergistic relationships for antioxidant capacity. As treatment intensity increased, across all techniques, carotenoid concentration decreased followed by an observed increase in carotenoid concentration as well as an upward trend in antioxidant capacity due to nutrient release from the fruit matrix; this was explained by fruit structure softening and confirmed through TEM imaging of papaya and strawberry pulp structure. Traditional thermal and UHT processing were both able to sufficiently reduce PME activity and prevent gel formation in papaya nectar when processed at 110oC for 5 minutes and 110oC for 1-3 seconds, respectively. PME reduction in nectar blends was enhanced by anergetic relationships after UHT at 80oC. Irradiation was unable to prevent gel formation in papaya nectar. The 50P:50S blend processed at 10 kGy, however, was the only blend to show irradiative prevention of gel formation. An increase in POD activity, coupled with synergistic relationships makes UHT undesirable for strawberry nectar. HPP of strawberry nectar at elevated temperatures and pressures had similar reductions in POD activity as irradiation at 5 kGy. Anergetic relationships for POD activity in nectar blends after irradiation resulted in enhanced reduction in POD activity. Processing strawberry for 2 minutes at all temperatures examined, resulted in similar, but slightly greater reductions in POD activity than either HPP or irradiation. Findings suggest that novel thermal and non-thermal techniques result in enhanced nutrient retention and antioxidant capacity in papaya and strawberry nectars compared to traditional thermal processing. For both PME and POD, traditional thermal processing was most effective at inactivation, with UHT sufficiently reducing PME activity in papaya nectar and both HPP and irradiation reducing POD activity in strawberry nectar similarly to traditional thermal processing at low temperatures. Blending of papaya and strawberry nectars mainly resulted in desirable synergistic nutrient retention and antioxidant capacity increase, and anergetic reduction in enzymatic activity.
Issue Date:2015-04-10
Rights Information:Copyright 2015 Jeffrey Swada
Date Available in IDEALS:2015-07-22
Date Deposited:May 2015

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