Department of Fruit Processing, Federal College and Institute for Viticulture and Pomology, Klosterneuburg, Austria.
TU Wien, Institut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften, Vienna, Austria.
J Sci Food Agric. 2024 Dec;104(15):9630-9639. doi: 10.1002/jsfa.13787. Epub 2024 Aug 1.
Identifying the best strawberries to produce colour stable nectars is a priority for the juice industry. Although riper strawberries produce nectars with better colour stability, variability between cultivars means that surface colour cannot be used as a single quality attribute to determine stability. Conductivity and bio-impedance measurements can be used to differentiate ripeness of strawberries. The commercially available PEF Control System (ELEA) can measure cell disruption by measuring conductivity at different frequencies. Updated software measured strawberry conductivity at 121 frequencies between 100 Hz and 1 MHz to determine whether conductivity at these frequencies could differentiate ripeness, and be compared with the colour acceptance and stability of nectars produced from these strawberries.
A high-low ratio (HLR) was calculated by dividing the conductivity at frequency 1 MHz by conductivity at 1 kHz. HLR could be used to separate five strawberry ripeness stages, with decreasing HLR associated with increasing ripeness. HLR was then compared with the colour of nectars produced from these strawberries. Although there was a good correlation between HLR and an acceptable colour to consumers on initial production (r = -0.823, P < 0.001) and after 12 weeks of storage (-0.759, P < 0.001), cultivars differed greatly in both HLR and colour stability. Additionally, HLR had a strong correlation with firmness.
The PEF Control System could be used to differentiate ripeness of strawberries by HLR, and therefore was associated with colour stability. However, no additional information on colour stability was gained from conductivity beyond what could already be deduced from differentiating ripeness based on surface colour. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
为了果汁行业的发展，确定生产颜色稳定的果汁的最佳草莓品种是当务之急。尽管成熟度较高的草莓制成的果汁颜色稳定性更好，但不同品种之间的差异意味着表面颜色不能作为单一的质量属性来确定稳定性。电导率和生物阻抗测量可用于区分草莓的成熟度。市售的 PEF 控制系统（ELEA）可以通过测量不同频率的电导率来测量细胞破碎程度。更新的软件以 121 种频率（100 Hz 至 1 MHz）测量了草莓的电导率，以确定这些频率的电导率是否可以区分成熟度，并与这些草莓制成的果汁的颜色接受度和稳定性进行比较。
通过将 1 MHz 频率的电导率除以 1 kHz 的电导率，计算出高低比（HLR）。HLR 可用于分离五个草莓成熟度阶段，HLR 越低与成熟度增加相关。然后将 HLR 与这些草莓制成的花蜜的颜色进行比较。尽管 HLR 与初始生产时消费者可接受的颜色（r = -0.823，P < 0.001）和 12 周储存后的颜色（r = -0.759，P < 0.001）之间存在良好的相关性，但品种之间在 HLR 和颜色稳定性方面存在很大差异。此外，HLR 与硬度有很强的相关性。
PEF 控制系统可以通过 HLR 来区分草莓的成熟度，因此与颜色稳定性有关。然而，除了根据表面颜色区分成熟度之外，电导率并不能提供有关颜色稳定性的任何额外信息。 © 2024 作者。该论文发表于《食品科学杂志》，由 John Wiley & Sons Ltd 代表化学工业协会出版。
