Moisture content testing.pdf

Assistant Professor cum Junior Scientist em Bihar Agricultural University, Sabour
1 de Apr de 2023

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Moisture content testing.pdf

  1. PRINCIPLES AND PROCEDURES of Seed moisture TESTING Prof. Kumari Rajani Department of Seed Science & Technology Bihar Agricultural University Sabour, Bhagalpur-813210
  2.  A small change in seed moisture content has a large effect on the storage life of the seeds  Seeds may sprout or molds may develop at high levels of moisture, and the seeds may lose viability in a few days  Therefore it is important to know the moisture content in order to make a reasonably accurate prediction of the possible storage life of each seed sample stored Why is it important to determine moisture content? Prof. Kumari Rajani, DSST, BAU, Sabour
  3.  Seed moisture content is one of the most important factor influencing seed quality and seed storability  The seed moisture content is the amount of water present in the seed  It is usually expressed in percentage and calculated either on wet or dry weight basis  In Seed Testing Laboratory, it is estimated on wet weight basis Prof. Kumari Rajani, DSST, BAU, Sabour Seed Moisture Testing
  4. The optimum method for moisture testing depends upon: 1. Chemical composition of seed 2. Seed structure 3. Moisture content level 4. Degree of accuracy and precision required 5. Constraints of time 6.Technical expertise and cost The ideal methods could be:  Adopted to all seeds  Measures moisture content from 0 to100 percent  Reproducible  Require less training  Low in cost Prof. Kumari Rajani, DSST, BAU, Sabour
  5. It is impossible to combine all these. However, in order to measure the moisture content of seeds, methods can be broadly grouped in two categories: a) Direct method b) Indirect method Prof. Kumari Rajani, DSST, BAU, Sabour
  6. “The seed moisture content is measured directly by removing moisture and then by measuring weight loss” 1. Oven-drying method 2. Phosphorus pentaoxide method 3. Desiccation method 4. Vacuum drying method 5. Distillation method 6. Karl Fisher's method 7. Direct weighing balance 8. Microwave oven method Direct method Prof. Kumari Rajani, DSST, BAU, Sabour Hot Air-Oven method is most commonly used because it is economical, requires simple equipment and little technical expertise, and can be used with any kind of seeds at any moisture content
  7. Commonly used methods are based on electrical property of seed. An electrical current unit, resistance or capacitance, is measured and then converted into moisture content These are not so accurate method and measures do not give moisture content of the seed directly Estimation is approximate, but convenient and quick in use These are frequently used at seed processing plants Indirect method Prof. Kumari Rajani, DSST, BAU, Sabour
  8. Quick, convenient and non-destructive method Moisture determination is approximate (Not precise) Moisture is determined by electrical conductivity or electrical resistance of seed (moisture content is directly proportional to the resistance and dielectric constant of the seed sample) Moisture determination by Moisture Meter Prof. Kumari Rajani, DSST, BAU, Sabour Widely used method to measure seed moisture in field and during processing of seed Needs calibration for each species
  9.  Hot Air-oven methods: commonly used for moisture determinations  The air ovens are electrically heated and the air within them is at atmospheric pressure and is circulated by convection with the help of fan or mechanical means  The basic reference method for the introduction of a new species and methods into the Rules is the low- constant temperature oven method Basic Reference Method for Determination of Moisture Content Prof. Kumari Rajani, DSST, BAU, Sabour
  10. Constant Temperature Oven Method 1. High-ConstantTemperature Oven Method Temperature : 130–133°C Duration : 4 h ±12 min for Maize 2 h ± 6 min for Other Cereals 1 h ± 3 min for Other Spp. 2. Low-Constant Temperature Oven Method  Temperature and Duration: 101–103°C for 17 ±1 h  The RH of the laboratory should be ≤70% during moisture testing  Suitable for seed species with high oil/volatile content Ex: Onion, Soybean, Groundnut, Mustard, Chilli, Cotton, Linum, Castor, Til
  11. The methods prescribed are designed to reduce oxidation, decomposition or the loss of other volatile substances while ensuring the removal of as much moisture as possible Principle for Determination of Moisture Content Prof. Kumari Rajani, DSST, BAU, Sabour
  12. Grinding mill Hot Air-Oven Moisture Containers Glass Tin A glass desiccators with silica gel Analytical balance Materials Required for Moisture Determination
  13. The submitted samples must be sealed in moisture proof container or polythene bags of ≥700 gauge Size of submitted sample: 100 g: for species that have to be ground 50 g: for all other species Seed should not be exposed in environment for more than 2 minutes The oven must be electrically heated 30 minutes before keeping the samples The determination must be carried out in duplicate on two independently drawn working samples Important facts to be remembered… Prof. Kumari Rajani, DSST, BAU, Sabour
  14. The weight of sample depends on the diameter of the containers used: Diameter >5 cm and <8 cm: 4.5 ±0.5 g Diameter ≥8 cm: 10.0 g ±1.0 g Containers must be of metal dishes or glass dishes with lids (non-corrodible materials) The desiccator must contain an effective desiccant i.e. silica gel The balance must be capable of weighing to an accuracy of at least ±0.001 g or 1mg Prof. Kumari Rajani, DSST, BAU, Sabour
  15.  The necessity for grinding depends on factors such as seed size and seed coat permeability to water  Large seeds: cereal seed, beans, and peas  Small seeds: do not require grinding  In case of high moisture content or an extremely hard seed coat, which may prevent grinding: breaking or cutting the seed into pieces ≤7 mm across is permissible  The grinding mill must be made of non-absorbing material and easy to clean Test Necessity for Grinding Prof. Kumari Rajani, DSST, BAU, Sabour
  16. Procedures of Moisture Determination (Hot Air-Oven Method)
  17. Label moisture containers and lid with the same specification weigh moisture containers with lid (M1) Weigh seed samples according to the diameter of the container (weighing should be upto 3 decimal places) Weigh moisture container with seed samples and lid (M2) Keep in heated oven at set temperature for the time required for the species Take out from oven and keept in desiccator for 45 minutes Weigh moisture container with seed samples and lid (M3) Calculate moisture content and report Prof. Kumari Rajani, DSST, BAU, Sabour
  18. The moisture content as a percentage by weight must be calculated to three decimal places for each replicate by following formula: M2-M3 Moisture Content (%) = X 100 M2-M1 Where, M1: weight in grams of the container and its cover M2: weight in grams of the container, its cover and seed sample before drying, and M3: weight in grams of the container, its cover and seed sample after drying Calculation and Expression of Results Prof. Kumari Rajani, DSST, BAU, Sabour
  19. Groundnut (>17%) and paddy (>13%):  Take two subsamples, each weighing 25±1 g are placed in weighed containers  The two subsamples, in their containers, are then dried at 130°C for 5 to 10 min  The partly dried material is then kept exposed in the laboratory for at least 2 h Very moist seed of Zea mays (>25% moisture content):  The seed is spread in a layer not deeper than 20 mm and dried at 65–75°C for 2–5 h Other species with a moisture content >30%: Samples should be dried overnight in a warm place If pre-drying is obligatory… Prof. Kumari Rajani, DSST, BAU, Sabour
  20.  After predrying, the subsamples are reweighed in their containers to determine the loss in weight (Considered as S1)  The second stage drying (S2) of sample should be carried out by following routine air-oven method Original moisture content of the sample should be calculated as a percentage by following formula: S1 X S2 Moisture Content (%) = (S1 + S2) - 100 Where, S1: moisture lost in the first stage drying S2: moisture lost in the second stage drying The result of a moisture content test must be reported in % upto one decimal place Prof. Kumari Rajani, DSST, BAU, Sabour
  21. Maximum Seed Moisture Percent for Storage under Ambient Condition and Vapour Proof Container Crops Ambient storage Vapour proof container Paddy 13 8 Barley, Wheat, Triticale, Maize, Sorghum, Pearl millet, Minor Millets, Oat,Teosinte 12 8 Soybean 12 7 Mesta 10 8 Berseem, Luncerne 10 7 Cotton 10 6 Black gram, Bengal Gram, Cowpea, Green gram, Horse gram, Indian bean, Khesari, Lentil, Mothbean, Pea, Pigeon pea, Cluster Bean, Rice bean, Sunhemp 9 8 Rajmash (French bean), Linseed, Safflower, Sunflower, Jute 9 7 Groundnut, Niger, Sesame 9 5 Rapeseed 8 7 Castor, Mustard, Taramira 8 5 Tobacco 5-6 Prof. Kumari Rajani, DSST, BAU, Sabour