Postharvest Drying and Storage of Horticultural Seeds and Their Marketing. Ing. Johan Van Asbrouck Centor Group

Transcription

1 Postharvest Drying and Storage of Horticultural Seeds and Their Marketing Ing. Johan Van Asbrouck Centor Group

2 EVERYBODY TALK ABOUT, WANTS, SPEAKS, NEEDS, IMPROVES, LOOKS AFTER, STORES, MAINTAINS, SELL, QUALITY SEEDS But what are they really doing?

3 STARTING BY THE BEGINNING Good quality foundation seeds

4 Good Quality Foundation Seed Good germination, vigorous Homogeneous in field emergence Induced heterogeneity by the males As little pathogens as possible Color coding Genetic purity

5 PROFESSIONAL SEED PRODUCTION

6 Seed Production Outstanding soil preparation Perfect planting Fast and homogeneous emergence Weed and pest control Adding nutrients Irrigation

7 SEED HARVESTING AT THE RIGHT MOMENT

8 Harvesting Correct maturity Correct harvesting, no seed damage No contamination by harvesters

9 SEED RECEPTION AND PROCESSING

10 Seed reception & processing Drying the seeds to final SMC Quality control aspects Storage in quality warehouses (cool or conditioned rooms) Cleaning and upgrading Free from insects and/or diseases

11 SEED STORAGE AND PACKAGING

12 Seed reception & processing Final quality control Storage in quality warehouses Packaging at low SMC in sealed bags Correct labeling (cool or conditioned rooms)

13 Foundation seeds Seed production Seed harvesting Seed reception Seed processing Seed storage Seed packaging Did we not do everything we could to get a perfect seed quality? SO, WHAT ELSE CAN WE DO?

14 Seeds are often dried in the sun, but this cannot reduce the seed MC to low levels if ambient RH is high.

15 Selling OP seeds in Nepal

16 Displaying seed packages in the sun in the tropics

17 DOES ANYONE KNOW HOW MUCH TIME IS GOING FROM THE MOMENT THE SEEDS ARE HARVESTED TILL THEIR RECEPTION IN THE WAREHOUSE? One day, 2-3 days, a week?

18 What is the impact of this gap? Assume that we do harvest rice seeds in Thailand. Seed moisture content after harvesting 25% Temperature during harvesting 30 C Period from farm to warehouse 1 day Period in warehouse before starting to dry 1 day Initial germination of the seeds 95% (duration of classical drying 3-4 days?) Germination 2 days later (Ellis and Roberts equation, cfr later) 67%

19 Some more examples Rice: 25%SMC - 30 C 95% germ 2 days 67% germ Soy: 18%SMC - 30 C 95% germ 3 days 90% germ Cabbage : 25%SMC - 25 C 99% germ 1 day 96% germ Onion: 22%SMC - 25 C 90% germ 4 days 51% germ

20 The biggest and most cost effective improvements can be made in these small area s (periods) where we do not have full control such as: Between harvesting and warehouse After sun drying Storage of seeds at the retail level THE WEAKEST LINKS

21 Seed Drying and Storage Key to a Profitable Seed Business Especially in the Subtropics

22 Seed Storage and Seed Quality Harrington s rule James rule Bradford s metronome rule Ellis & Roberts equation Walters lag time

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26 Ellis & Roberts equation(1980) v = final viability (expressed as NEDs or probits) after p days storage. p = storage time (days) m = % moisture content (fresh weight basis) t = temperature ( C) K i = initial viability of the seed lot at p = 0 days (seed lot constant) K E = species-specific overall aging constant C W = species-specific moisture content constants C H and C Q = species-specific temperature constants

27 Into practice Use the website of the Royal Botanic Gardens, Kew Predict storage time Predict final viability Estimate moisture content to give viability at known temperature Estimate temperature to give viability at known moisture content

28 Seed Storage and Seed Quality Using KEW gardens website:

29 Pepper seed longevity in relation to RH

30 Walters Lag time Loss of Viability Shows a Threshold Pattern In many cases, seeds tend to survive well during storage for a period of time, then die over a relatively shorter period, but the relationships with MC and temperature are the same. Walters et al. (2010) Plant Science 179: UCDAVIS

31 Effect of the initial water content in the air Understanding the reality is a necessary key towards controlling and improving it

32 Relation RH and Seed moisture (vegetables) RH / MC Beet Cabbage Carrot Sweet Corn Cucumber Lettuce Onion Pepper Tomato Water melon

33 Relation RH and Seed moisture (agro) RH / MC Rice (milled) Soy Sorghum Wheat (durum) Pop corn (shelled)

34 Relationship between seed moisture (water) content and erh MC (%DW) 1- X 440 ln(1 RH 1.1 t Manual determination using saturated salt solutions Manual determination using non-saturated salt solutions Automated determination Approximation: Cromarty s equation for seed drying (Cromarty et al., 1990) X = Seed oil content (proportion of dry weight); t = temperature ( C). Need to know X: Calculator available on-line - Seed Information Database (SID) Presentation Dr. Fiona Hay

35 CIBSE Psychometric chart Moliere diagram Temperature/RH Relationships

36 CIBSE Psychrometric chart The difference between these two environments is equal to the difference of the two equilibrium RH

37 Europe versus Asia The minimum SMC obtained in drying with heated air (40 C) is related to the esmc. This SMC will effect the longevity. Imagine we store the seeds (after drying) in sealed bags and at a temperature of 20 C. The starting seed quality would be 95% what would be the time we could store these seeds before they would drop below 80% germination? Europe/Asia after drying esmc storage time For rice: 3.5% / 8.5% 4% / 10% 73 year / 9 months For soy: 3.4% / 8.2% 4% / 9% 15 year / 7 months For chili 3.2% / 7.7% 4% / 9% 8 year / 5 months For onion 3.4% / 8.3% 4% / 9% 9 year / 7 months

38 Moisture level determines physiological reactions, physical properties Lipid oxidation Enzyme activity Germination Freezing injury Recalcitrant seeds are desiccation intolerant Intermediate seeds survive partial drying Orthodox seeds are desiccation tolerant Recalcitrant - die Orthodox longevity (glassy state) Intermediate - die Orthodox max longevity? Presentation Dr. Fiona Hay

39 RICE viability study A theoretical study on seed moisture content and storability through the equations of Roberts & Ellis using the KEW website

40 SMC (in % fresh weight) RH and Temp e-curves for Rice 30.0 Asian conditions: 20 C and 80% RH -> equilibrium 14% SMC C 10 C 15 C 20 C 25 C 30 C 35 C 40 C % 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% RH (in %)

41 Rice Longevity Ellis & Roberts Temp ( C) % SMC % germ time 30 days 90 days 180 days 270 days 360 days 20 6% 99% 0% 0% 0% 0% 0% 20 6% 90% 0% 0% 0% 1% 1% 20 6% 80% 0% 0% 1% 1% 1% 20 6% 70% 0% 0% 1% 1% 3% 20 C, 6%SMC & 90% germ 20 10% 99% 0% 0% 1% 2% 3% 20 10% 90% 1% 3% 7% 11% 16% 20 10% 80% 1% 5% 11% 18% 25% 20 10% 70% 3% 7% 16% 24% 31% 20 14% 99% 1% 5% 22% 52% 80% 20 14% 90% 6% 23% 58% After 1 year 86% = 2% germ 97% 20 14% 80% 10% 35% 71% 93% 99% 20 14% 70% 14% 44% 80% 96% 100% 20 C, 14%SMC & 90% germ After 1 year = 89% germ 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 30 days 90 days 180 days 270 days 360 days 99% 90% 80% 70% 99% 90% 80% 70% 99% 90% 80% 70% 6% 6% 6% 6% 10% 10% 10% 10% 14% 14% 14% 14%

42 Drying in General An overview at the situation, today

43 Sun Drying Using the sun as a drying source Shade Drying Protecting the seeds from direct sunlight

44 Static Drying Systems Equilibration is the key word Silo Drying Huge volumes in a batch system

45 Box Dryers Volume combined with throughput Continuous dryers Conventional continuous systems

46 Batch drying systems Medium and small sized system

47 Silica gel types A widely used system (often as a one-time-use system Dried Rice A natural desiccant

48 Heating versus conditioning What system would give me the needed drying and for what cost?

49 Heating versus conditioning Heat source as a method of reducing the relative humidity of the drying air Using air conditioning systems as a method to reduce the relative humidity of the drying air Using adsorption is another system, but this system is in fact a special form of an air conditioning system

50 Classical versus fluidized bed systems Sieve bed characteristics Classical drying systems Fluidized bed systems A fluidized system is often realized by working with a high initial pressure and having a drop in pressure just before the seedbed. Therefore the speed increase of the air will result in a higher lifting capacity

51 Mesh sieves 70-80% throughput V1=V2 Perforated plate % throughput V1 = V2 Triangular wire %Throughput V2>> V1

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53 Some important aspects of seed drying Drying Speed - Technical Pellet (coating) seed germ Drying speed is linked to the migration speed of the water in the seed Migration speed depend on different internal and external parameters External parameters are the temperature and the differential in RH (and in a lesser extend the difference in pressure) Maximum drying speed = maximum temperature (seed dependent) + 0% RH air Minimum drying speed = no difference in RH between seed /air (RH equilibrium) Controlled drying = Controlled setting of % RH air

54 What are the characteristics and differences with other absorbents THE UNIQUENESS OF THE DRYING BEADS

55 Disruptive Technologies The idea of installing telephones in every city is idiotic... Why would any person want to use this ungainly and impractical device when he can send a messenger to the telegraph office and have a clear written message sent to any large city in the US? This 'telephone' has too many shortcomings to be seriously considered as a means of communication. The device is inherently of no value to us. (Western Union) With thanks to Dr. Michael Reid

56 Zeolite Crystals Micro-porous materials Uniform pore dimensions Thermally & Mechanically stable Selective for water Micro-porous materials Absorption till 30 % of their weight in water Strong binding Adsorption heat generated Non toxic, food grade SPECIFIC PORE SIZE FOR WATER (3Å) NO SIZE CHANGES BETWEEN DRY AND WET STAGE Ceramic product Crystalline structure

57 % moisture absorbtion at 20% RH % moisture absorbtion at 100% RH Comparison with Other Absorbents 14.0% 12.0% 10.0% 8.0% 6.0% 4.0% 2.0% 0.0% 0 5 Days 10 Beads Silica gel 20.0% 18.0% 16.0% 14.0% 12.0% 10.0% 8.0% 6.0% 4.0% 2.0% 0.0% Hours B 1 B 2 B 3

60 % moisture absorbtion at 20% RH % moisture absorbtion at 100% RH Comparison with Other Absorbents 20.0% 18.0% 16.0% 14.0% 12.0% 10.0% B1 8.0% 14.0% B2 6.0% 4.0% 2.0% 0.0% 12.0% 10.0% 8.0% 6.0% 4.0% 2.0% B: drying beads S: silica gel 1,2,3 re-uses 0.0% Days 10 Beads Silica gel Hours B3 S1 S2 S3

61 % moisture absorbtion at 100% RH % moisture absorbtion at 20% RH Comparison with Other Absorbents 14.0% 12.0% 10.0% 8.0% 6.0% 4.0% 2.0% 0.0% 20.0% 18.0% 16.0% 14.0% 12.0% 10.0% 8.0% 6.0% % 8 10 Days 2.0% 0.0% Beads Silica gel Hours B 1 B 2 B 3

62 % moisture absorbtion at 20% RH % moisture absorbtion at 100% RH Comparison with Other Absorbents The repeated use of baked rice one time Silica gel few times Drying beads lifetime 14.0% 12.0% 10.0% 8.0% 6.0% 4.0% 2.0% 0.0% 0 5 Days 10 Beads Silica gel 20.0% 18.0% 16.0% 14.0% 12.0% 10.0% 8.0% 6.0% 4.0% 2.0% 0.0% Hours B 1 B 2 B 3

63 Conclusions Drying Beads Small pore size Only water molecules No polymerization during heating Regeneration temperature > 200 C Pores do remain open - Identical capabilities Most efficient at lower RH levels Silica Gel Big pore size Many molecules (water, esters, alcohols ) Polymerization during heating Regeneration temperature <125 C Pores are clogging up - Reduced capabilitie Most efficient at higher RH levels

64 The impact of drying capacity on quality and storage of seeds DRYING BEADS & SEED QUALITY

65 Easy Seed Drying & Seed Storage

66 RH (%) RH Reduction Beads absorb water extremely rapidly RH air during cucumber trial on 6 November 2008 control T1 T2 T3 T :52 15:21 15:50 16:19 16:48 17:16 17:45 18:14 18:43 19:12 19:40 20:09 20:38 Time

67 24 % 12 % 6 %

68 This can be very nice but what would a farmer think? Would it make a real difference?

69 Field trials soil test 0 months

70 Field trials soil test Chili 4 months 18 days

71 Field trials soil test chili 6 months

72 Open storage vs. bead storage of onion seeds in Nashik, India % 9 5 Open bags With beads Stored for 1 year by farmers Seed MC reduced by 4% with beads. % Germination decreased by 45% in open bags. Courtesy of Dr. Keshavulu Kunusoth, ANGRAU, Hyderabad, India

73 Another tool DrumDry DrumDry is a seed storage system using drying beads to maintain a low SMC (RH), a metal drum to store seeds easily and at ambient temperatures with silica-gel as an RH indicator

74 Molds, diseases, aflatoxins, insects Roberts EH (1972) Viability of Seeds

75 Storage Insect Control using Drying Beads Six months storage Without beads 69% infestation With beads 0% infestation Courtesy of Dr. Keshavulu Kunusoth, ANGRAU, Hyderabad, India