Novel processing techniques and spinach juice: Quality and safety improvements

Abstract

In this study, the combined effect of ultrasound (US) and pulsed electric field (PEF) techniques was analyzed for the quality improvement and microbial safety of spinach juice. The spinach juice was treated with US at frequency of 40 kHz, radiating power of 200 W below 30 ± 2°C temperature for 21 min in ultrasonic bath cleaner, and PEF treatment (pulse frequency: 1 kHz, flow rate: 60 mL/min, temperature: 30 ± 2°C, time: 335 µs, electric field strength 9 kV/cm) was done. In results, the combined (US-PEF) treatment attained the highest value of minerals and total free amino acids as compared to US or PEF treatment alone. US-PEF treatment significantly reduced the total plate count (3.83 to 1.97 log CFU/mL), E. coli/Coliform (1.90 to 0.75 log CFU/mL) and yeast and mold (4.23 to 2.22 log CFU/mL). Fouriertransform infrared spectroscopy (FT-IR) spectra showed that all nonthermal treatments led to a higher concentration of carbonyl compounds rather generate new carbonyl compounds. US-PEF treatment significantly reduced the particle size. The rheology of spinach juice was drastically changed by all nonthermal techniques, indicating non-Newtonian modal accompanied by a decrease of consistency index (K), apparent viscosity (η), and increase of flow behavior (n). Overall, the improved quality of spinach juice shows the suitability of both technologies for industrial applications despite the variations in rheological properties.Practical Application: Nowadays, nonthermal technologies like US and PEF are being used to enhance the nutritional quality and stability of different fruits and vegetable juices. The current research shows that US-PEF application can enhance the free amino acids and mineral contents while significantly decrease microbial activities and particle size. The rheology of spinach juice can be dramatically changed, through the reduction of consistency index (K), apparent viscosity (η) and elevation of flow behavior (n). The results of this research proposed that US-PEF treatment can be a more suitable nonthermal application to enhance the quality of spinach juice at an industrial scale.

Probing the combined impact of pulsed electric field and ultra‐sonication on the quality of spinach juice

“…We aim to investigate the combined impact of PEF and US treatment on the quality of spinach juice to define the best processing conditions to ensure the best quality of spinach juice. The combined impact of US and PEF processing on microbiological analysis in spinach juice was already published in our article (Manzoor, Ahmed, et al., 2020).…”

Efficient utilization of date palm waste for the bioethanol production through Saccharomyces cerevisiae strain

“…The infrared spectra analysis also identified the vibration signs of biofuel from the waste date palm. The results revealed that wave numbers 2,900 and 3,300 cm −1 link to CH and OH molecule groups, respectively (Boulal et al., 2016; Manzoor et al., 2019, 2020; Mehani et al., 2013).…”

Effect of dielectric barrier discharge plasma, ultra‐sonication, and thermal processing on the rheological and functional properties of sugarcane juice

“…Ultrasound is an inexpensive technique that reduced energy consumption, as well as processing time (Manzoor et al., 2019; Rahaman et al., 2019; Siddeeg et al., 2019a). The influence of ultrasound on the freshness of liquid juices has been studied in spinach juice (Manzoor et al., 2020), blackberry juice (Cervantes‐Elizarrarás et al., 2017), pear juice (Saeeduddin et al., 2016), and strawberry juice (Bhat & Goh, 2017). The outcome of these investigations is to maintain the quality of juices without losing its bioactive compounds and inactivate pathogenic microbes.…”