DO NOT COPY. Effects of roasting time of sorghum grains on the phenolic concentration, antioxidant activity and colour of their flours

Transcription

1 Effets of rosting time of sorghum grins on the phenoli onentrtion, ntioxidnt tivity nd olour of their flours Ollekn J. Adeowle, John R.N. Tylor nd Henriëtte L. de Kok Deprtment of Consumer nd Food Sienes, University of Pretori, Privte Bg X20, Htfield 0028, South Afri

2 Bisuits, red nd kes An importnt stple food rop in Afri nd Asi Wide vilility t n ffordle prie Puffed sorghum Drought-tolernt Sorghum Potentil helth enefits Beverges Instnt porridge flours 2

3 Whole grin Tnnin-rih Tnnin-free Milling or Deortited grin Therml proessing Development of off-flvour Hmmer mill Sorghum flour t storge OR Mortr nd pestle Sorghum flour 3

4 Chemil omponents of erel grins influening the pereived flvour Voltile ompounds Free mino ids, smll peptides Sugrs Phenoli ompounds Free ftty ids, lipids Heiniö (2003) 4

5 TERMINATION STAGE Forming non-rdils speies (Seondry oxidtion produts) vi.. Retion of two rdils Lipid utoxidtion yle Free rdils Fts/ oils Peroxides Ftty ids INITIATION STAGE Forming free rdils y Temperture, metl ions (Fe 2+ ), light, moisture PROPAGATION STAGE Forming different ftty id rdil nd peroxide vi Retion with O 2 5

6 Wy forwrd? Rosting Dry therml proessing Therml proessing Wet (hydro) therml proessing Mironiztion Mirowving Autolving Cooking Boiling Stem ooking Extrusion ooking 6

7 Ojetive To determine the effets of rosting time of sorghum grins on totl phenoli ontent, ntioxidnt tivity nd olour of flours from whole nd deortited grins, inluding tnninrih nd tnnin-free sorghum types. 7

8 Tnnin-rih Whole grins Experimentl design Sorghum grins Rosting T 0 = Rw (unrosted) T 1 = 150 C, 10 min T 2 = 150 C, 15 min T 3 = 150 C, 20 min T 4 = 150 C, 25 min Milling (500 µm sieve size) Tnnin-free Deortited grins (82 % extrtion) Anlyses Totl phenoli ontent- Spetrophotometri method Antioxidnt tivity-abts method Colour-Colorimetri method Flour 8

9 Lipid-rih setion Polyphenols-rih site Stylr re Strh grnules Epirp Mesorp Cross ells Tue ells Corneous/Vitreous/ Horny Endosperm STARCHY ENDOSPERM F`loury endosperm ` PERICARP (BRAN) GERM Hilum Aleurone lyer (prt of endosperm) Su-leurone (prt of endosperm) Test (su-ot) Sutellum Plumule Emryoni xis Rdil Longitudinl setion of sorghum kernel (Adpted from Tylor nd Belton, 2002) 9

10 Ft ontent (%) 4.5 Effet of rosting time of tnnin-rih nd tnnin-free sorghum grins on the ft ontent of whole nd deortited flours Rosting time (min) Vlues for the sme olour rs with different letters, differ signifintly (p< 0.05) d d Tnnin-rih whole Tnnin-rih deortited Tnnin-free whole Tnnin-free deortited 10

11 Effet of rosting time of tnnin-rih nd tnnin-free sorghum grins on the totl phenoli ontent of whole nd deortited flours Totl phenoli ontent (mgce/g) Rosting time (min) Vlues for the sme olour rs with different letters, differ signifintly (p< 0.05) Tnnin-rih whole Tnnin-rih deortited Tnnin-free whole Tnnin-free deortited 11

12 Antioxidnt tivity (µmolte/g) Effet of rosting time of tnnin-rih nd tnnin-free sorghum grins on the ntioxidnt tivity of whole nd deortited flours e d d Rosting time (min) Vlues for the sme olour rs with different letters, differ signifintly (p< 0.05) Tnnin-rih whole Tnnin-rih deortited Tnnin-free whole Tnnin-free deortited 12

13 Mehnism for lipid-peroxyl rdil nd ntioxidnt ROO* + AH ROOH + A* A* + ROO* ROOA A* + A* A A Stle ompound 13

14 Effet of rosting time of tnnin-rih nd tnnin-free sorghum grins on olour of whole nd deortited flours Vlues for the sme olour rs with different letters, differ signifintly (p< 0.05) Tnnin-rih whole Tnnin-rih deortited Tnnin-free whole Tnnin-free deortited 14

15 Effet of rosting time of tnnin-rih sorghum on olour of whole nd deortited flours Whole Deortited Rw 10 min 15 min 20 min 25 min 15

16 Effet of rosting time of tnnin-free sorghum on olour of whole nd deortited flours Whole Deortited Rw 10 min 15 min 20 min 25 min 16

17 Conlusions Aknowledgement Rosting sorghum grin n potentilly inrese the shelf-life of sorghum flour. Shelf life test will e onduted Rosting sorghum grin hs no effet on the olour of flours Sensory tests will e onduted Deortition proess n redue itterness nd stringent tste Sensory evlution will e onduted Rosting sorghum t 150 for 10 min is the most effetive regime 17

18 Future works: The effet of the extent of mirowve energy (36, 54, 72 nd 90 kj) on sorghum grins on the : Physiohemil properties (free ftty ids ontents, TPC, ntioxidnt tivity nd olour) Funtionl properties (wter sorption index, wter soluility index nd psting hrteristis) of resultnt flours 18

19 Aknowledgements UP Postgrdute ursry for OJ Adeowle for sponsoring the onferene ttendne of OJ Adeowle. for use of filities nd equipment for mirowve proessing. for grnting study leve to OJ Adeowle 19