ID: 2171

• Title:
  INFLUENCE OF PULSED ELECTRIC FIELD (PEF) AND RAW MATERIAL COMPOSITION ON ACRYLAMIDE CONTENT AND CRISPINESS OF FRIED SWEET POTATO CHIPS
  
  Authors:
  

  Kirchner, Madita - Elea Vertriebs- und Vermarktungsgesellschaft mbH, 49610 Quakenbrück, Germany
  Hill, Kevin - Elea Vertriebs- und Vermarktungsgesellschaft mbH, 49610 Quakenbrück, Germany
  Siemer, Claudia - Elea Vertriebs- und Vermarktungsgesellschaft mbH, 49610 Quakenbrück, Germany
  Weisz, Ute - University of Bonn, Institute for Nutritional and Food Sciences, 53115 Bonn, Germany
  Töpfl, Stefan - Elea Vertriebs- und Vermarktungsgesellschaft mbH, 49610 Quakenbrück, Germany

  
  
  Abstract:
  The aim of this study was to determine the impact of Pulsed Electric Fields (PEF) and raw material composition on the quality of sweet potato chips. Crispiness as one of the most important sensory properties of snack products and further parameters like fat content and color were analyzed. Acrylamide as a product of the Maillard reaction is an unwanted process contaminant due to its genotoxic properties. The chips were produced without PEF (control) or with different treatment intensities. The PEF system provides high-voltage exponential decay, monopolar pulses with an interval of 0.5 s (2 Hz) and pulse duration of 40 µs. The pulses were applied to the raw material in a batch chamber consisting of two parallel stainless-steel electrodes. The applied field strength and specific energies were 1 kV/cm and 0.3 kJ/kg to 3 kJ/kg, respectively. An enzymatic test was used to measure the release of sugars from the sweet potato slices in the washing water. To investigate the effects of different raw material compositions, sweet potatoes of the same variety were stored for four months while trials including analyses of the raw material and the chips were conducted once a month.
  
  Texture analysis showed that chips produced with PEF had a significant higher crispiness. Significantly lower fat absorption of the chips pre-treated with PEF was observed after frying. Both can be attributed to the softening effect that PEF has on plant tissue, resulting in a facilitated cutting behavior. The smoother sweet potato slice surface enables a reduction of adhered fat and less starch loss. Gelatinized starch is important for the crispiness of chips and does not absorb fat. PEF treated chips were preferred based on their sensory attributes indicated through Duo-Trio and Paired Comparison Tests (n = 71). Storage led to a reduction in the starch content of the raw sweet potatoes, resulting in chips with higher fat content and lower crispiness. The analysis of the washing water showed that the PEF treatment led to an enhanced release of reducing sugars, which are precursors of acrylamide. When aiming for the same moisture content as in non-PEF-treated chips, chips produced with high PEF treatments (> 1 kJ/kg) required longer frying times, causing less favorable L*a*b* color values and higher acrylamide contents. This can be attributed to the altered mass transfer of PEF treated chips which further leads to an enhanced crust formation and therefore slower water evaporation towards the end of the frying process. Low specific energy inputs (0.3 kJ/kg), however, required shorter frying times and were advantageous for color values and in some cases for the acrylamide content. Since PEF-treated chips are crispier, a higher moisture content can be targeted while keeping the same crispiness as for chips produced without PEF. This allows a reduction of frying time and diminished Maillard reaction. Despite a rise in reducing sugars over the storage period, no significant changes in acrylamide content were observed comparing the samples from different months. Texture analysis of raw sweet potatoes showed that the softening effect of PEF leads to less variations in hardness, which enables a more consistent chip production quality over the duration of storage.
  
  Combined with processing benefits such as lower cutting losses and less knife wear, PEF is a promising technology for improving sweet potato chip production and quality. This study has shown that due to the altered structural properties, adjustments of the frying process are crucial to use the full potential of PEF. To confirm the benefits so far observed, further analysis of the frying behavior of PEF- and non-treated sweet potato chips must be conducted on industrial scale.
  
  
  
  Keywords:
  
  
  Refs:
  
  
  Topic 1:
  10. Food safety and food preservation
  
  Topic 2:
  13. Pulsed power devices and methods