Changes in Quality Attributes of Strawberry Purees Processed by Power Ultrasound or Thermal Treatments

Abstract

The effect of thermal and ultrasound treatments on the physicochemical properties (pH, total soluble solids, titratable acidity, electrical conductivity, viscosity and color attributes), bioactive compounds (ascorbic acid, total pheolics and total anthocyanins) and antioxidant activity of strawberry puree was investigated. No significant difference in pH, total soluble solids and titratable acidity was observed among the treated and control samples whether thermal or ultrasound treatments were used. Ultrasound treatments significantly increased the electrical conductivity, while significantly reducing the viscosity of strawberry puree samples. Ultrasound treatments were found to better maintain or increase the bioactive compounds and the color attributes compared to the thermally treated samples. Ultrasound treatments significantly increased the radical scavenging activity compared to that of the control sample except when the ultrasound treatment was carried out at 0.42 W/mL for 20 and 30 min. These results indicate that ultrasound treatments can greatly improve the quality of strawberry puree.Keywords: power ultrasound, thermal treatment, strawberry puree, antioxidant activity, phenolic, anthocyanin IntroductionStrawberry (Fragaria × ananassa Duch.) is a soft, juicy and palatable berry available during the spring-summer period.Strawberry is highly appreciated for its excellent organoleptic properties such as red color, smooth texture, and exquisite taste and flavor. It is also a good source of micronutrients and phytochemical compounds particularly ascorbic acid, anthocyanins and phenolic compounds (Cao et al., 2012). Strawberry is mostly consumed fresh but it is also processed into jams, juice, canned products and added into dairy products such as yoghurt (Terefe et al., 2010).Unfortunately, it is a readily perishable fruit because it is susceptible to fungal attacks and physical damage (Lara et al., 2004). Therefore, it is essential to find a suitable method to extend its shelf-life and maintain its quality for better commercialization.To date, thermal treatment is the most commonly used technology to inactivate enzymes and destroy microorganisms.However, it also brings about undesirable changes in the food properties, such as loss of nutrients and changes in color, flavor and texture. Therefore, there is a need to develop alternative methods which enhance microbiological stability and to better preserve the nutrients of strawberry. It is expected that ultrasound as one of the novel non-thermal processing technologies can be used as an alternative of the thermal processing (Tiwari et al., 2009c). In general, ultrasound in 20_ 1000 KHz range can be divided into two zones namely: (1) high frequency (100 _ 1000 kHz) low energy ultrasound, (2) low frequency (20 _ 100 kHz) high energy power ultrasound (Golmohamadi et al., 2013). When power ultrasound propagates in liquid, cavitation bubbles are generated due to rapid change in pressure. Collapse of these bubbles in the subsequent compression cycles of ultrasonic ...

Effects of high‐power ultrasound on microflora, enzymes and some quality attributes of a strawberry drink

“…observed that the anthocyanin content decreased by 5% in blackberry juice treated at 20 kHz, 100% amplitude and 25 °C for 10 min. Cheng et al . also reported a decrease of about 10% in anthocyanin content in strawberry puree treated at 20 kHz, 30% power and 40 °C for 10 min.…”

“…Ultrasound is a new type of non‐thermal processing technology. According to its frequency and power, it has been divided into two ranges: low‐frequency (20–100 kHz), high‐power (10–1000 W cm −2 ) ultrasound and high‐frequency (1–10 MHz), low‐power (<1 W cm −2 ) ultrasound High‐power ultrasound (HPU) has been identified as a potential technology to meet the FDA requirement of a 5 log 10 reduction in pertinent microorganisms occurring in fruit juices Besides, ultrasound has been reported to reduce enzyme activities, ameliorate viscosity and turbidity and improve quality parameters of juice effectively Therefore this technology has been used in carrot juice tomato juice apple juice and orange juice To the best of our knowledge, only a few researchers have studied the effect of ultrasound on strawberry juice They focused on the effects of ultrasound on the anthocyanin content, color, antioxidant capacity and microorganism inactivation of strawberry juice. However, these experiments were carried out at a fixed ultrasound power with a limited treatment time gradient.…”

Changes in Bioactive Compounds Concentration and Physicochemical Properties of Mango Smoothies Treated by Ultrasound

“…Interestingly, there is controversial information related to the effects of US in physicochemical parameters of fruit-based beverages. On one hand, it has been reported that pH, TA and TSS values of different fruit juices were not affected after sonication process (Tiwari et al, 2008;Cheng et al, 2014;Abid et al, 2013;Adekunte et al, 2010). However, Bermudez-Aguirre and BarbosaCánovas (2012) observed significant changes in pH and TA after US processing of whole milk and pineapple, grape, and cranberry juices.…”

“…In this respect, ultrasound (US) technology has received special attention because it can be cheap, simple, environmental-friendly, and effective treatment in extending shelf-life of beverages, particularly when it is combined with mild heat (thermosonication) (Abdullah, 2014). Some authors have demonstrated that US processing caused minimal impact on quality parameters and great retention of health related compounds in orange, guava, and strawberry juices, purple cactus pear, and soymilk (Abdullah, 2014;Cheng et al, 2014;Fahmi et al, 2012;Sakhale et al, 2012;Ribeiro et al, 2014;Chauhan and Patil, 2013). However, information about the effects of US treatment together with the application of mild heat on physicochemical properties and health-related compounds of mango smoothies is not available.…”

Stability, Antioxidant Capacity and Degradation Kinetics of Pelargonidin-3-glucoside Exposed to Ultrasound Power at Low Temperature

“…Non-thermal processing can reduce microbial load, and avoid at the same time undesirable changes on food nutrients [2]. Cao et al [3] found that ultrasound treatment at a frequency of 40 kHz inhibited the decay of strawberry fruit and maintained a significant higher level of vitamin C. Cheng et al [4] observed that sonicated samples showed better retention or preservation of phenolic compounds when compared to heat-treated samples. However, recent studies have manifested that some non-thermal pasteurization alternatives may lead to the loss of vitamin C, anthocyanins, lycopene, carotenoids and flavonoids under extreme conditions.…”