Kafirin protein from sorghum: Its application as a fruit coating and new challenges S. Buchner-Rech, A. Minnaar, C. Erasmus
© CSIR Contributions to knowledge on kafirin EU INCO (ENVIROPAK), 2001 – 2004: Kafirin protein (extraction & application) for the preparation of packaging films (extrusion and film blowing); free standing films; and edible coatings (export fruits & nuts) 1 MSc. & 1 PhD degree from ENVIROPAK CSIR co-investment - ENVIROPAK, MSc. & PhD degrees CSIR investment - Prolamin extraction optimisation, coatings for other fruits, PCT patent application (Prolamin films/coatings)
© CSIR Kafirin and its benefits It’s the alcohol-soluble protein in sorghum grain Sorghum is indigenous to Africa Kafirin is abundant - extracted from grain proc. waste, BSG, by-product stream, bioEtOH production Kafirin is hydrophobic – H 2 O barrier Non-allergenic, natural biopolymer, biodegradable
© CSIR Successful kafirin applications Applied only at research level Fruit coatings to extend shelf life of export pears (CSIR, UP) Free standing films with gas and moisture barrier properties (UP, UEA, CSIR, SIK) Inclusion of anti-fungal agents in films (SIK) Biodegradability of kafirin films (CSIR, UP) Film blowing, biomedical foam formation, extruded plastic packaging (IMCB, SIK)
© CSIR Application 1: Kafirin coatings to extend the quality of exported pears - Pears exported from SA to Europe - Refrigeration maintains fruit quality (↓ ripening rate) - Plastic packaging – creates MA (↓respiration & transpiration) - Stem-end shrivelling & quality loss can occur during export and distribution - Coatings create MA, ↓ ripening rate, ↓ packaging waste Why develop coatings for pears?
© CSIR Requirements of a fruit coating Act as gas and moisture barrier ↓ packaging waste Leave appearance, odour and taste of pears unaffected
© CSIR Experimental plan: Effect of kafirin coating on pear quality during storage at 20°C
© CSIR Appearance of coated and uncoated pears prior to ripening at 20°C 11
© CSIR Quality of coated and uncoated pears ripened at 20°C for 24 days
© CSIR Transverse section of the skin of an uncoated pear – SEM (X 1.100) Pear cuticle
© CSIR Transverse section of skin of coated pear (3% kafirin) – SEM picture
© CSIR Gas exchange mechanisms of an uncoated pear (SEM)
© CSIR Pear skin surface of a coated pear (3% kafirin coating) Reduced amount of surface cracks
© CSIR Lenticel of a coated pear, covered with a 3% kafirin coating
© CSIR Respiration rate mg CO 2 kg -1 h -1 Respiration rate of coated and uncoated pears during storage at 20°C for 24 days
© CSIR Shrivelling on coated pears after 10 day storage at 20°C
© CSIR Conclusions on kafirin coatings for pears Kafirin coating can reduce quality loss without refrigeration and plastic packaging Kafirin coating provides sufficient gas barrier properties to reduce pear ripening Colour change delay (due to ↓ metabolism) possibly misleading to consumers Ethanol in coating solution may increase skin shrivelling when fruit are not coated directly after harvest
© CSIR Points to consider before researching kafirin further Zein (the prolamin protein from maize) + kafirin = homologues Zein - well researched (past 50 years) & commercially available Zein tested successfully (research level) as: - drug delivery system, electro-spun fibres, tissue engineering scaffolding BUT zein not industrially applied, lack of consistency in zein quality between batches
© CSIR Immediate challenges around kafirin Because IP on pilot-scale prolamin extractions belongs to CSIR, we should: - Produce pure (>95%) kafirin repeatably on large scale - Understand factors that influence kafirin protein properties (for selection of new applications) Because - Kafirin hydrophobicity > zein - Kafirin digestibility < zein Kafirin possibly better biomaterial than zein
© CSIR Protein purification Kafirin for new applications: Current and future investigations Biomaterial for novel applications Protein structure Functional properties Material properties Modification for specified function ? PhD study
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