Quality and handling shelf life of macadamia styles and quality - mark penter

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  • 1. Optimisation of Kernel Storage Parameters and the Prediction of ShelfLife for South African Macadamia Kernel M.G. Penter, F.J. Kruger and A.D. Sippel Agricultural Research Council - Institute for Tropical and Subtropical Crops P/Bag X11208, Nelspruit, 1200, South Africa
  • 2. Background South African Industry Export value for 2011 $ 103 660 000 R850 000 000Slide Compliments of Rudolf Badenhorst
  • 3. BackgroundSlide Compliments of Rudolf Badenhorst
  • 4. BackgroundSlide Compliments of Rudolf Badenhorst
  • 5. BackgroundSA Macadamia Tree Age Distribution (%) 13.4 18.8 0 - 5 yrs 6 - 10 yrs > 11 yrs 31.5 Unknown 36.3Slide Compliments of Andrew Sheard
  • 6. Background 2012 2017 2022 34 500 t 41 800 t 50 000 t ?Slide Compliments of Derek Donkin
  • 7. Introduction• Consequences of rapid industry growth include: – NIH spending longer periods on the ground – NIS being held on farm for longer periods – NIS being held longer at processors – Extended harvesting season (‘Beaumont’) – Processed kernel being held for longer periods
  • 8. Introduction• Industry needs information: – Extended shelf life (optimised storage) – Accurate sell-by dates – Export kernel required to have peroxide < 3meq/kg
  • 9. Quality parameters• Peroxide• Breakdown products of peroxides
  • 10. Peroxide production
  • 11. Factors promoting peroxide formation• Oxygen• Lipoxygenases• Light• Metals (iron, manganese, copper)• Water• Heat• Time (maturity, NIS holding period)• Oil exposure to oxygen
  • 12. Storage trials• Procure commercially packed kernel (nitrogen flushed, vacuum packed, 5.68kg)• Examine the effect of: – Storage period – Storage temperature – Style – Seasonality• Use peroxide analysis to monitor quality (react with iodide, titrate iodine with Na2S2O3)
  • 13. Early season Mid season Late season-5C RT -5C RT -5C RT 5C 15C 5C 15C 5C 15C 6, 12, 18, 24 months 6, 12, 18, 24 months 6, 12, 18, 24 months 0, 2, 4, 6, 8, 12, 16, 20 weeks on shelf 0, 2, 4, 6, 8, 12, 16, 20 weeks on shelf 0, 2, 4, 6, 8, 12, 16, 20 weeks on shelf Peroxide analysis Peroxide analysis Peroxide analysis
  • 14. Early season kernel stored 6 months 14 12 10Peroxide value (meq/kg) 8 6 4 2 0 E 6m 0w E 6m 2w E 6m 4w E 6m 6w E 6m 8w E 6m 12w E 6m 16w E 6m 20w -5˚C S1 -5˚C S5 5˚C S1 5˚C S5 15˚C S1 15˚C S5 Ambient S1 Ambient S5
  • 15. Mid season kernel stored 6 months 14 12 10Peroxide value (meq/kg) 8 6 4 2 0 M 6m 0w M 6m 2w M 6m 4w M 6m 6w M 6m 8w M 6m 13w M 6m 16w M 6m 20w -5˚C S1 -5˚C S5 5˚C S1 5˚C S5 15˚C S1 15˚C S5 Ambient S1 Ambient S5
  • 16. Mid season kernel stored 6 months 14 12 10Peroxide value (meq/kg) 8 0.24 0.12 0.12 6 0.12 12.83 0.12 4 2 0 M 6m 0w M 6m 2w M 6m 4w M 6m 6w M 6m 8w M 6m 13w M 6m 16w M 6m 20w -5˚C S1 -5˚C S5 5˚C S1 5˚C S5 15˚C S1 15˚C S5 Ambient S1 Ambient S5
  • 17. Late season kernel stored 6 months 14 12 10Peroxide value (meq/kg) 8 6 4 2 0 L 6m 0w L 6m 2w L 6m 5w L 6m 8w L 6m 12w L 6m 20w -5˚C S1 -5˚C S5 5˚C S1 5˚C S5 15˚C S1 15˚C S5 Ambient S1 Ambient S5
  • 18. Late season kernel stored 6 months 14 12 10Peroxide value (meq/kg) 8 2..51 9.73 0.25 0.25 7.14 0.37 0.87 3.25 0.12 6 7.99 5.12 7.60 4 2 0 L 6m 0w L 6m 2w L 6m 5w L 6m 8w L 6m 12w L 6m 20w -5˚C S1 -5˚C S5 5˚C S1 5˚C S5 15˚C S1 15˚C S5 Ambient S1 Ambient S5
  • 19. For kernel stored 6 months• Ambient temperature not sufficient for late season kernel – requires storage temperatures of 15˚C or less• Data variability is of concern – arises from small quantities of poor kernel in otherwise good batches
  • 20. Early season kernel stored 12 months 14 12 10Peroxide value (meq/kg) 8 6 4 2 0 E 12m 0w E 12m 2w E 12m 4w E 12m 6w E 12m 8w E 12m 12w E 12m 16w E 12m 20w -5˚C S1 -5˚C S5 5˚C S1 5˚C S5 15˚C S1 15˚C S5 Ambient S1 Ambient S5
  • 21. Mid season kernel stored 12 months 14 12Peroxide value (meq/kg) 10 8 6 4 2 0 M 12m 0w M 12m 2w M 12m 4w M 12m 6w M 12m 8w M 12m 12w M 12m 16w M 12m 20w -5˚C S1 -5˚C S5 5˚C S1 5˚C S5 15˚C S1 15˚C S5 Ambient S1 Ambient S5
  • 22. Late season kernel stored 12 months 16 14 12Peroxide value (meq/kg) 10 8 6 4 2 0 L 12m 0w L 12m 2w L 12m 4w L 12m 6w L 12m 8w L 12m 12w L 12m 16w L 12m 20w -5˚C S1 -5˚C S5 5˚C S1 5˚C S5 15˚C S1 15˚C S5 Ambient S1 Ambient S5
  • 23. For kernel stored 12 months• Style 5 is of concern, particularly at ambient temperatures• Late season style 5 at all temperatures except - 5˚C approach 3meq/kg after 5 months on the shelf• Style 5 to be consumed within 3 months of repacking or held below 0˚C if longer shelf life is required• Mid season kernel appears to be of better quality than early or late season kernel
  • 24. Early season kernel stored 18 months 12 10Peroxide value (meq/kg) 8 6 4 2 0 E 18m 0w E 18m 2w E 18m 5w E 18m 8w E 18m 12w E 18m 16w E 18m 20w -5C S1 -5C S5 5C S1 5C S5 15C S1 15C S5 Ambient S1 Ambient S5
  • 25. Mid season kernel stored 18 months 12 10Peroxide value (meq/kg) 8 6 4 2 0 M 18m 0w M 18m 2w M 18m 4w M 18m 6w M 18m 8w M 18m M 18m M 18m 12w 16w 20w -5C S1 -5C S5 5C S1 5C S5 15C S1 15C S5 Ambient S1 Ambient S5
  • 26. Late season kernel stored 18 months 12 10Peroxide value (meq/kg) 8 6 4 2 0 L 18m 0w L 18m 2w L 18m 4w L 18m 6w L 18m 8w L 18m 12w L 18m 16w L 18m 20w -5C S1 -5C S5 5C S1 5C S5 15C S1 15C S5 Ambient S1 Ambient S5
  • 27. For kernel stored 18 months• Style 5 again cannot be held at ambient temperature – not even for mid season harvest• For both style 1 and 5, 15˚C is inadequate for storing late season kernel if 5 months shelf life is required in retail packs
  • 28. Predicting shelf life
  • 29. Rancimat• Also known as: – Swift test – Accelerated oxidation test• Principle: – At elevated temperatures and oxygen levels, poor samples with existing oxidative damage will degrade rapidly
  • 30. Effect of style and harvest time on Rancimat induction period 50 45 40Induction period (hours) 35 30 25 20 15 10 5 0 Style 1 Style 5 Style 1 Style 5 Style 1 Style 5 Early season Mid season Late season Style and harvest timing
  • 31. Rancimat• The rancimat test predicts: – Kernel quality and shelf life declines as season progresses – Style 5 has lower storage potential than style 1• Is this prediction accurate?
  • 32. Conclusions• Style 5 kernel has lower storage potential than style 1 kernel (assume this applies to all styles with fractured kernel• For vacuum packed bulk kernel: – For storage periods of up to 12 months, ambient temperature is not suitable – For storage periods of 18 months temperatures of 15˚C may not be adequate
  • 33. Conclusions• Kernel quality declines as season progresses and there may be small quantities of poor kernel in early season batches – Is there old kernel picked up in the early season? – Is late season kernel spending longer on the orchard floor / drying bins?• Rancimat may be able to predict shelf life – further work required to correlate induction times and shelf life
  • 34. Thank You• SAMAC• ARC• Bioservices cc• Elvis Nkwana and Yvonne Nxundu