Effect of Continuous Flow Microwave and Conventional Heating on the Bioactive Compounds, Colour, Enzymes Activity, Microbial and Sensory Quality of Strawberry Purée

Abstract

The impact of continuous microwave heating (MV) at 90 and 120°C for 10 s and at 80 and 90°C for 7 s, as well as conventional thermal processing (CTP) at 90°C for 15 min, on the quality of strawberry purée was studied. Product quality was determined, covering total polyphenols, anthocyanins, phenolic acids, flavonols and vitamin C content, as well as colour parameters, enzymatic activity, and finally, the sensory and microbiological quality. CTP caused higher degradation of polyphenols (ca. 7 %), anthocyanins (ca. 20 %) and vitamin C (ca. 48 %) compared to MV at 120°C. Changes of the colour of MV-preserved purée were insignificant (dE <2), whereas CTP caused significant changes (dE >3). Only MV at 120°C and CTP effectively decreased the level of total microbial count (<1 log cfu/g), but considering enzymes activity, only CTP was effective, inactivating ca. 98 and 100 % of polyphenol oxidase (PPO) and peroxidase (POD), respectively. The most effective inactivation of PPO (82 %) and POD (88 %) after MV was noted at 120°C, but the best compromise between colour and nutrient preservation and enzyme inactivation was achieved at the MV at 90°C. Considering the obtained results, it can be concluded that the microwave heating better preserved the quality of strawberry puree than conventional heat pasteurization.

Quality and consumer acceptance of radio frequency and traditional heat pasteurised kiwi puree during storage

“…After RF and TP treatment, samples became significantly ( P < 0.05) brighter (higher L * values), and yellower (higher b * values) after processing. It may be caused by the electromagnetic field extraction of chlorophyll from the tissue to intercellular juice (Marszałek et al ., ). With regard to lightness, the L* values of RF‐ and TP‐treated samples had no significant difference after processing.…”

Impact of three warming-up methods on the stability of vitamin C and 5-methyltetrahydrofolate supplemented to apple and carrot purée

“…Vitamin C and 5-methyltetrahydrofolate withstood the treatment without major losses (Table 1). High stability of vitamin C when food is heated by a microwave is in accordance with the result of Benlloch-Tinoco et al (2014), Marszalek et al (2015) and Bureau et al (2015).…”

“…Depending on the heating length and the type of food, vitamins are preserved or lost. For example, only 2% of vitamin C in strawberry pur ee were lost when the pur ee was treated at 90 C for 10 s and 12% when it was heated at 120 C for 10 s under the conditions of Marszalek, Mitek, and Skapska (2015). It was not lost in kiwi pur ee after a treatment at 1000 W for 340 s (Benlloch-Tinoco, Igual, Salvador, Rodrigo, & Martínez-Navarrete, 2014) and to 46% in broccoli which stayed at 1000 W for 5 min (Vallejo, Tomas-Barberan, & Garcia-Viguera, 2002).…”

Innovative Quality Improvement by Continuous Microwave Processing of a Faba Beans Pesto Sauce

“…1c). According to our results, Marszalek et al (2015) found minor color changes in strawberry puree after two continuous MW treatments (90 ± 1°C, at atmospheric pressure or at 120 ± 1°C and 0.35 MPa with a holding time of 10 s). De Ancos et al (1999) also reported that MW heating induced slight color changes in strawberry puree.…”

“…Microwave (MW) pasteurization is a thermal technology considered as an interesting alternative to conventional techniques. MW heating has a number of quantitative and qualitative advantages over conventional heating techniques (Marszalek et al 2015;Bornhorst et al 2017). The main advantage is that heat is generated inside the product itself.…”