School of Food Science and Engineering, South China University of Technology, Guangzhou, Guangdong, 510640, China.
Overseas Expertise Introduction Center for Discipline Innovation of Food Nutrition and Human Health (111 Center), Guangzhou, 510640, China.
J Food Sci. 2020 Apr;85(4):1018-1026. doi: 10.1111/1750-3841.15107. Epub 2020 Mar 28.
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). Fourier-transform 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.
在这项研究中，分析了超声（US）和脉冲电场（PEF）技术的联合效应，以提高菠菜汁的质量并确保其微生物安全性。将菠菜汁在频率为 40 kHz、辐射功率为 200 W 的超声浴清洁器中处理 21 分钟，温度低于 30 ± 2°C，然后进行 PEF 处理（脉冲频率：1 kHz、流速：60 mL/min、温度：30 ± 2°C、时间：335 µs、电场强度 9 kV/cm）。结果表明，与单独的 US 或 PEF 处理相比，联合（US-PEF）处理获得了最高的矿物质和总游离氨基酸值。US-PEF 处理显著降低了总平板计数（从 3.83 降低至 1.97 log CFU/mL）、大肠杆菌/大肠菌群（从 1.90 降低至 0.75 log CFU/mL）和酵母和霉菌（从 4.23 降低至 2.22 log CFU/mL）。傅里叶变换红外光谱（FT-IR）谱表明，所有非热处理都导致了更高浓度的羰基化合物，而不是产生新的羰基化合物。US-PEF 处理显著减小了颗粒尺寸。所有非热技术都极大地改变了菠菜汁的流变学性质，表明非牛顿模式伴随着稠度指数（K）、表观粘度（η）的降低和流动行为指数（n）的增加。总体而言，尽管流变学性质存在差异，但菠菜汁的这种质量提高表明这两种技术都适合工业应用。
实际应用：如今，超声和 PEF 等非热技术被用于提高不同水果和蔬菜汁的营养质量和稳定性。当前的研究表明，US-PEF 应用可以提高游离氨基酸和矿物质含量，同时显著降低微生物活性和颗粒尺寸。菠菜汁的流变学性质可以通过降低稠度指数（K）、表观粘度（η）和提高流动行为指数（n）而显著改变。本研究结果表明，US-PEF 处理可以作为一种更合适的非热应用，在工业规模上提高菠菜汁的质量。
