Electric field applications on dried key lime juice quality with regression modeling

Abstract

Key lime (Citrus aurantifolia L.) is an important source of juice and vitamins. A continuous nonthermal juice pasteurizer (CNTJP) using electric field with alternating current was designed and constructed. The effect of electric field was investigated on dried (black) lime juice using voltage gradients (X1) of 24–88 V/cm and mass flow rates (X2) of 12–50 kg/hr. The treated juice was evaluated for physicochemical properties, phytochemical compounds with antioxidant capacity, and microbial quality. The results showed that there were no significant effects (p > .05) between CNTJP treatment and both the thermal treatment and the control sample regarding the total soluble solids and pH values. However, the titration acidity value of dried juices in thermal treatment was significantly higher (p < .05) compared to the control and CNTJP samples. There was a significant difference (p < .05) between CNTJP samples and both the control and the thermal treatment samples regarding the total phenolic content, ascorbic acid content, and antioxidant activity (1,1‐diphenyl 2‐picrylhydrazyl). Also, the results showed that coliform bacteria, yeast, and mold were not capable of growing in control samples (fresh juice) or all samples treated by CNTJP treatments or thermal treatments. However, the total viable count of CNTJP samples varied between 1.93 and 4.79 (Log10 CFU/mL), whereas the total viable counts of the control sample and thermal treatment were 5.99 and 3.82 (Log10 CFU/mL), respectively. At the optimum conditions of mass flow rate of 28.24 kg/hr and voltage gradient of 82.38 V/cm, the highest electrical conductivity was 0.65 S/m. Practical applications Nonthermal, high‐throughput pasteurization systems are highly desirable as alternatives to overcome the negative effects of thermal pasteurization. Electric field (EF) is one potential alternative technology. Although this study did not focus on effectiveness of log reduction of pathogens, EF resulted in fewer pathogenic indicators than nontreated dried lime juice. Electric field did demonstration superiority over thermal pasteurization for maintaining total phenolic content, ascorbic acid, and antioxidant activity in dried lime juice. Maximizing healthy characteristics of fruit juice during pasteurization can lead to a product with a higher retail value than traditional thermal processing. This potential higher economic value for EF‐treated juice could offset implementation and processing costs. The EF system described in this study can be readily scaled up by having parallel lines of size similar to this study or by increasing the tubing and electrode sizes or both.

Effect of batch infrared extraction pasteurizer (BIREP)‐based processing on the quality preservation of dried lime juice

“…These results were in agreement with Altemimi et al. (2018) who found that the increase of acidity due to thermal treatment could be ascribed to the distribution of intracellular components. In addition, this result reported that pH, total soluble solids, and titratable acidity of lime juice samples were within the limits of the institute of standards and industrial research of Iran (ISIRI) (2013) and GCC Standardization Organization (GSO) (2018).…”

“…In contrast, the titration acidity of dried juices in thermal treatments was slightly higher significant (p < .05) at 1.12 relative to control samples and BIREP juice samples. These results were in agreement with Altemimi et al (2018) who found that the increase of acidity due to thermal treatment could be ascribed to the distribution of intracellular components.…”

“…The DPPH solution consisted of 25 mg of DPPH radical dissolved in 50% v/v methanol, with a vortex used for gentle mixing. Pasteurized juice (0.1 ml) was added to 3.9 ml of the freshly prepared DPPH solution, mixed, and stored in the dark for 25 min at room temperature (Altemimi, Ali, Al‐HiIphy, Lightfoot, & Watson, 2018). The 517 nm wavelength absorbance measured with the spectrophotometer was used to calculate antioxidant activity based on the DPPH radical scavenging activity using the following formula.…”

Ifs and buts of non-thermal processing technologies for plant-based drinks’ bioactive compounds

“…All these new non-thermal technologies allow working at environmental temperatures (20–25 °C), providing products safe from a microbiological point of view, with an extended shelf-life and improved sensory and nutritional features, while minimizing the use of additives (Altemimi et al, 2018; Picart-Palmade et al, 2019). These effects are achieved by the inactivation of enzymes (Cortés et al, 2005) and reductions of the bacterial load higher than 5 decimal logs (Food and Drug Administration, 2009).…”

Impact of Non-Thermal Technologies on the Quality of Nuts: A Review

“…In nuts, roasting (in oil or air-oven), pasteurization or blanching are the most used heat treatments [ 19 ]. However, although these heat treatments are effective in eliminating the microorganisms present in dried fruits, they entails a loss of sensory and nutritional quality [ 20 , 21 ].…”