Effect Of Drying As A Function Of Moisture On Physical,Textural And Quality Attributes Of Rough And Milled Rice

Increasing demand of food with complex modern technologies for handling,storing and processing strongly requires the information of physical and textural properties to enhance and maintain the quality of rice.Rough rice when harvested normally has a high moisture of 20-25%which requires immediate drying,reducing its mass loss and preventing it to spoil.This situation is more crucial with the areas lying under humid tropical conditions,where moisture and temperature mainly plays an important role deteriorating the quality of rough rice.In farms,mills and commercial warehouses whatever the rice product is,it has to be processed and stored with its desired moisture content.Exact information of physical and textural properties are necessary to be executed for designing the equipment's and machineries being used for harvesting,threshing and other post-harvest practices,which in result can reduce the losses being occurred during improper handling of paddy grains.Keeping the aspects in view,the study was designed to observe the effect of different drying as a function of moisture on quality attributes of rough and milled rice.All experiments were conducted at College of Engineering,Nanjing Agricultural University,the results of conducted experiments are summarized as below.1.Optimisation and mathematical modelling of low temperature drying.The study was conducted to assess the effects of low temperature drying and suggest an optimum condition.Response surface methodology(RSM)with central composite design was employed to study the effects of variables i.e.temperature(X1),time(X2)and air velocity(X3)on responses i.e.head rice yield(HRY),hardness,lightness and cooking time.The experimental data was fitted to quadratic model,studying the relationship between independent and dependent variables.The results revealed that the hardness,lightness and cooking time increased with increasing variables,where for HRY it particularly increased and then decreased.It was observed that temperature had more influence on the quality of rough rice followed by time and air velocity.Results for analysis of variance revealed that the quality aspects of rough rice were significantly(p?0.05)affected by temperature and time,where for air velocity it only significantly affected the hardness.The optimal drying conditions predicted by RSM for variables were 25?,600 min and 1 m s-1 and optimal predicted HRY,hardness,lightness and cooking time were 73.93%,38.28 N,71.40 and 27.58 min respectively.Acceptable values of R2,Adj.R2 and non-significance of lack of fit demonstrated that the model applied was adequate and can be used for optimisation.The study concluded that the RSM with central composite design was successfully used to study the dependence of quality aspects of rough rice at low temperature.2.Effects of different vacuum pressures on cooked freeze-dried rice.The current study was carried out to determine the effect of different freezing temperature(FT)and vacuum pressure(VP)at different boiling temperature(BT)on the rehydration ratio and functional properties of cooked freeze-dried rice.Paddy variety Hua Jing 5 was taken under determination.The rice was cooked using a conventional rice cooker and then kept for freezing at two different temperatures of-15 and-30?.The freezed samples were dehydrated under two different pressure of 7 and 125 Pa using a laboratory freeze-dryer.The freeze-dried samples after dehydration were subjected to different boiling temperatures of 70,80 and 90?respectively.The statistical design was subjected to randomized complete block design(RCBD),replicated thrice.The results of the current study revealed that the process indicators had significantly(p?0.05)affected the rehydration ratio,texture,lightness and moisture absorption of the cooked rice.The interaction between treatments were also observed to be statistically different.The mean average values of rehydration ratio for FT at-15 and-30?were observed to be 157.68 and 171.64%respectively,for VP at 7 and 125 Pa the rehydration ratio was observed to be 169.37 and 159.94%respectively and for BT at 70,80 and 90? the mean average values were observed to be 145.07,164.65 and 184.25%respectively.The average mean texture for cooked rice at-15 and-30? FT;7 and 125 Pa and 70,80 and 90?was observed to be 1.41 and 1.27 N;1.28 and 1.40 N and 1.58,1.28 and 1.15 N respectively.The average mean lightness for cooked rice at-15 and-30? FT;7 and 125 Pa and 70,80 and 90? was observed to be 77.37 and 83.52;81.67 and 79.22 and 77.57,80.41 and 83.35 respectively.The average mean moisture content for cooked rice at-15 and-30? FT;7 and 125 Pa and 70,80 and 90? was observed to be 73.43 and 75.90%;75.32 and 74.01%and 72.52,74.88 and 76.60%respectively.The study from the present research concluded that a significant variation was observed among the parameters when subjected to different treatments.3.Optimisation and mathematical modelling of physico-engineering properties.The study was conducted to investigate the effects of indicators(temperature and time duration)on physico-engineering properties of two different paddy varieties using RSM.A mathematical model was used to predict length,width,thickness,TKW,bulk density,true density,porosity and hardness as affected by temperature and time each with five levels.Higher values of R2 and Adj.R2,non-significance of lack fit and significance of F-test demonstrated the suitability and accuracy of the model when tested for both Nanjing 9108 and Wuyunjiang varieties.The results revealed that the responses were significantly affected by the indicators and can be predicted by temperature and time duration.Central composite design of the RSM was successfully used to study the dependence of physico-engineering properties of paddy.This useful information can be implemented and utilized by the rice processing industries.4.Effect of moisture content on husked and de-husked rice varieties.The study aimed to assess the physical and engineering properties of husked and de-husked paddy of two different varieties i.e.Nanjing 9108 and Wuyunjiang as a function of moisture(i.e.10,15,20,25 and 30%).The results revealed that length,width,thickness,geometric mean diameter,arithmetic mean diameter,square mean diameter,equivalent diameter,surface area,volume,sphericity and aspect ratio for husked and de-husked paddy for both varieties increased with increasing moisture,while sphericity and aspect ratio decreased for de-husked paddy varieties.Thousand kernel weight,bulk density,true density and toughness increased with increasing moisture while porosity and hardness decreased with increasing moisture in husked and de-husked paddy for both varieties.The study concluded that the changes with respect to moisture between husked and de-husked paddy were statistically different(p?0.05),whereas both varieties(Nanjing 9108 and Wuyunjian)when compared were also statistically different from each other(p<0.05).5.Fracture resistance of paddy as influenced by various factors.Mechanical properties as force and deformation curve while performing post-harvest operations are important to be determined for predicting the extent of damage being occurred.This study was carried out by determining rupture force and energy of three different rice varieties i.e.Nuo gao,Nanjing 9108 and Hui dao 5 hao.Paddy grains were quasi-statically loaded at four levels of moisture(8%,13%,18%and 23%)on horizontal and vertical orientations at two different loading rates of 5 and 10 mm min-1.Experimental design was subjected to randomized complete block design with 10 replications.The results revealed that average values of force under 5 and 10 mm min-1 loading rates with increasing moisture content decreased from 57.74 to 33.99 N,49.91 to 37.99 N and 48.54 to 32.37 N at horizontal orientation,whereas for vertical orientation it decreased from 27.19 to 15.83 N,25.86 to 16.54 N and 25.47 to 13.88 N for Nuo gao,Nanjing 9108 and Hui dao 5 hao respectively.Average values of rupture energy under 5 and 10 mm min-1 loading rates with increasing moisture content increased from 22.62 to 28.40 mJ,19.11 to 26.93 mJ and 17.35 to 23.45 mJ at horizontal orientation,whereas for vertical orientation it increased from 8.24 to 15.58 mJ,7.51 to 14.25 mJ and 6.96 to 12.34 mJ.Values of rupture force and energy were observed higher for Nuo gao,followed by Nanjing 9108 and Hui dao 5 hao,whereas for loading rate they were greater under 5 mm min-1.Influence of moisture,variety,orientation,loading rate and their interactions when observed were also statistically(p?0.05)different under quasi-static compressive load.The results further concluded that paddy at horizontal orientation was more flexible as compared to vertical orientation.6.Evaluation of physico-mechanical properties grown in humid subtropical region.The study was carried out to assess the variation in physico-mechanical properties of thirteen different paddy cultivars grown in humid subtropical region of eastern China.The results revealed that parameters when assessed were statistically different(p?0.05)from each other.The average values of different paddy for length,width,thickness,geometric mean diameter,arithmetic mean diameter,square mean diameter,equivalent diameter,surface area,volume,sphericity,aspect ratio,thousand kernel weight,bulk density,true density,porosity,hardness and toughness(for both horizontal and vertical orientations)were observed to be 7.93 mm,3.32 mm,2.26 mm,3.84 mm,4.51 mm,2.56 mm,3.64 mm,46.53 mm2,29.75mm3,0.49%,0.42,28.64 g,568.31 kg m-3,1225.20 kg m-3,54%,46.09 N,14.75 N,16.06 mJ and 6.90 mJ respectively.A wide variation was observed for each parameter while comparing different cultivars with each other,this wide variation in result will negatively affect the performance of the equipment's and machineries being used for post-harvest practices.The study concludes that different cultivars when determined acquires significant differences,which information by industries while designing equipment's and machineries and for users for implementing them is necessary.7.Mechanical characteristics of rice straw as influenced by various factors.The study was carried out to assess the mechanical characteristics of rice straw as effected by different variety,moisture content and loading rate.Three different rice varieties i.e.Yue76,Qianjindao and Yue61 when harvested were brought to College of Engineering,Nanjing Agricultural University for experimentation.Mechanical properties of rice straw were evaluated at all three internodes(IN1,IN2 and IN3)down from ear,and were subject to two different moisture contents(11 and 18%)and two different loading rates(10 and 20 mm min1).The experimental design was subjected to randomized complete block design,replicated thrice.The results revealed that the rice straw parameters and their interactions were significantly affected(p?0.05)by different moisture content,variety and loading rate.The average values obtained were significantly different from each other,the average values for shear strength were observed to be 14.18,9.95 and 11.99 MPa,for specific shearing energy the average values were observed to be 17.30,13.34 and 15.93 mJ mm-2,for bending strength the averages values were observed to be 11.33,7.40 and 9.54 MPa and for young's modulus the average values were observed to be 1.06,0.73 and 0.99 GPa for Yue76,Qianjindao and Yue61 varieties respectively.The study revealed that shear strength and specific shearing energy increased with increasing moisture content and loading rate,while the bending strength and young's modulus decreased with increasing moisture content and loading rate at IN1,IN2 and IN3 for all varieties.It was observed that for different moisture content,variety and loading rate the shear strength and specific shearing energy increased toward third internode(IN3),while the bending strength and young's modulus increased towards first internode(IN1).The outcomes of current study revealed a wide variation between the parameters observed for rice straw,it therefore from this study is highly recommended to assess the mechanical characteristic of rice straw before designing and judging the equipment's and machineries being used for post-harvest operations.