Quality Characteristics of Pre-treated Yam Chips Produced from Irradiated Yams

Aims: The objective of this research was to study the effect of irradiation on some quality characteristics of yam chips produced from irradiated yam tubers.
Study Design: In this study, irradiated yam (Lariboko) was processed into yam chips and quality characteristics (moisture, texture and colour) of the frozen yam chips evaluated over 4 weeks storage period.
Place and Duration of Study: This study was carried out at the Radiation Technology Centre of BNARI and Food Research Institute of CSIR, between November 2011 to September 2013.
Methodology: Yam samples were irradiated at 0Gy (control), 120Gy and 200Gy at the Gamma Irradiation Facility (GIF) of the Biotechnology and Nuclear Agriculture Research Institute (BNARI), Accra at the rate of 0.3927kGy/hr. Irradiated yam samples were washed and peeled. The mid sections of the tubers were diced into chips (1 x 1 x 7cm) and divided into 3 groups. Each group was dipped into 0.1% Citric Acid (CA), 0.1% Sodium Metabisulphite (SMBS) and Blanched (BLA) in boiling water for 1min. The treated samples were vacuum packed and blast frozen to Maxi chill (-26ºC) for 1½ hours and then stored in a freezer at - 20ºC. Moisture was determine by air-oven method (AOAC), tristimulus colour L*a*b* was measured, and TX plus Texture Analyzer (Gallenkamp hotbox oven, UK) used to determine the texture characteristics.
Results: Gamma irradiation doses significantly affected (P=.000) the hardness of the yam chips and only affected the surface elasticity in the 2nd and 3rd weeks of storage. There was a low negative correlation (R = -.095) between hardness and surface elasticity of the treated samples at the various doses. Irradiation did not have a significant effect on the Lightness, L*colour index of the yam chips produced, however L* for the irradiated samples was relatively higher compared to the un-irradiated samples. Irradiation also affected the moisture contents of chips treated with both CA and SMBS significantly (P<.05).
Conclusion: Combination treatment of gamma irradiation at an optimum dose of 120Gy with chemical treatments with SMBS or CA is recommended for the processing of yams into chips all year round.