IDLI

Idli  is a type of savory rice cake, originating from South India, popular as a breakfast food in Southern India. The cakes are made by steaming a batter consisting of fermented black lentils (de-husked) and rice. The fermentation process breaks down the starches so that they are more readily metabolized by the body.

Fermentation of idli batter results in both leavening caused by the generation of carbon dioxide as well as an increase in acidity. This fermentation is performed by lactic acid bacteria especially the heterofermentative strain Leuconostoc mesenteroides and the homofermentative strain Enterococcus faecalis (formerly classified as Streptococcus faecalis). Heterofermentative lactic acid bacteria such as L. mesenteroides generate both lactic acid as well as carbon dioxide whereas homofermentative lactic acid bacteria only generate lactic acid.

Both L. mesenteroides and E. faecalis are predominantly delivered to the batter by the black gram. Both strains start multiplying while the grains are soaking and continue to do so after grinding.

L. mesenteroides tolerates high concentrations of salt unlike most other bacteria. Hence the salt in the batter and the ongoing generation of lactic acid both suppress the growth of other undesirable micro-organisms.

Objective

  1. To optimize and formulate the fermented dehydrated idly premix.

2. To study the fermentation of idli batter at different temperature range and time.

3.

Problem Statement:

Already in market, there are various brands which sales the idli/ dosa instant premix like gits, katdare, etc. but these premixes are not fermented. These are only rice flour and black gram dhal flour with excessive amount of leavening agents like baking soda (Sodium bicarbonate), baking powder (Sodium hydrogen bicarbonate; baking soda + edible acids like tartaric acid), for puffiness of idli. Baking soda can be harmful to our health if taken into large doses or for a long time. About 5% leavening agents used in idli premixes which are not fermented.

Being food technologist; it is task for me to standardize and formulate the fermented dehydrated idly premixes.

Material

  1. Raw material :
    • Rice
    • black gram dhal
  2. Instruments:
    • Incubator
    • Weighing balance
    • Digital Thermometer.
    • Digital pH meter.
    • Hot air oven
  3. Glassware’s and utensils:
    • Burette stand
    • burette
    • Beakers
    • Measuring cylinder
    • Measuring cups.

Methodology

After the discussion with Mr. dixit, we were decided that; first we are going to standardization of general recipe of idli batter and study the fermentation of idly batter at various time and temperature.

Firstly, I was studied literature about idli and fermentation; and went through using these information.

I. FERMENTATION:

I. A. FIRST TRIAL:

27 and 28 November 2023

Generally, for idli and dosa batter rice to dehusked black gram dhal ratio is 2:1 ideal. First step of idli making is soaking of rice and black gram dhal for at least 4 hrs to maximum 12 hrs; I was following the measurements used in research paper. In that they used 1:3 to 1:4 w/v ratio of rice or dhal: water. but I used 1:2 w/v.

Soaking:

  1. Rice (60 gm) in 120 ml of water.
  2. black gram dhal (30gm) in 60 ml of water
  3. Soaking time: 14 hrs.

After 14 hrs of soaking;

Grinding seperately with soaking water: rice was coarsely grinded and black gram dhal was finely grinded,

Mixing together,

Kept for fermentation at room temperature (Soil lab’s incubator we cants used for fermentation due to contamination and second incubator which is used for curd formation their was problem in it.

Observation:

  1. The batter was not fermented due to atmosphere change (rainy and cloudy weather) and contaminated after 10-12 hrs.)
  2. Black gram dhal soaks more water than rice that means water absorption capacity of black gram dhal is higher than rice.

Then I will decide to control the temperature of incubator (used for curd formation) manually using hot water and thermometer.

II. B. SECOND TRIAL:

29 and 30 November 2023

Soaking:

(Rice or Black gram dhal: water:: 1:3 w/v)

1.Rice 60 gm in 180 ml of water)

2. Black gram dhal 30 gm in 90ml of water

3. Soaking time : 4 hrs

Grinding separately with soaking water: rice was coarsely grinded and black gram dhal was finely grinded .

Mixing together:

Fermentation in incubator: at 30 degree , by controlling manually using hot water and thermometer.

Sr. no.Time intervalBurette readingMeanAcidity in K2CO3 gm/ 100 gm of sampleAcidity in molpH
1.Initial1.2, 1.11.150.3170.0001156.98
2.After 10 hrs4.9, 4.74.81.320.0004804.98
3.After 12 hrs5.3, 5.55.41.480.0005404.93
fig. Fermentation data at 30 degree.

Fig., Ckecking titrable acidity.

After checking titrable acidity and pH; remained idly batter was used for idli making. Idli was prepared after 14 hrs. of fermentation. Salt was added to it Idli batter was poured in pre-greased idli mold and steamed for 10-15 mins.

Note: Leavening agents like baking powder or baking soda were not used

Observation:

  1. Controlling temperature of incubator by hot water and thermometer was too difficult because there were various fluctuations in temperature.
  2. The mold which is used for idli steaming has not small holes.
  3. Batter consistency was thin (more amount of water).
  4. Idli was too much sour (due to overfermentation 14 hrs).
  5. Idli was not good in taste and texture (does not fluffy or spongy).

I. C. THIRD TRIAL:

02 December 2023

From above observation I understood that the amount of water we used in batter should be low. I discussed with Mr. Dixit sir and we decided that; water used for soaking of rice and black gram dhal will be 1:1w/v and 1:2w/v respectively.

Soaking :

(Rice : water :: 1:1 and Black gram dhal: water :: 1:2)

  1. Rice: 60 gm in 120 ml of water
  2. Black gram dhal : 30 gm in 60 ml of water
  3. Soaking time: 6 hrs.

Grinding separately with soaking water; rice was coarsely grinded and black gram dhal was finely grinded,.

Mixing together.

Fermentation in incubator at 35 degree

Observation: Readings of titrable acidity and pH were not taken due to temperature fluctuations caused by incubator maintenance by FabLab department.

I. D. FORTH TRIAL:

06 December 2023

I studied some research papers on idli and discussed with Mr. dixit sir and we decided to determine the moisture content in rice and black gram dhal after and before soaking to understand the what amount of water exactly used in batter. also we decide to drain out the soaking water from rice and black gram dhal and additionally add necessary amount of water during grinding.

I was determined the moisture content dry ingredients that is rice and dehusked black gram dhal also wet ingredients (after soaking ) that is soaked rice and black gram dhal.

Sr. no.Ingredient Moisture Content (%)
1.Dry rice12.27
2.Dry black gram dhal12.8
Fig. moisture Content

Fig., Moisture Content of dry rice and Black gram dhal

Soaking:

  1. Rice 60 gm in 100 ml of water.
  2. Black gram dhal 30 gm in 100 ml of water.
  3. Soaking time: 12 hrs.

Fig., Soaking

Draining:

  1. Water was drained from rice and dhal after 12 hrs of soaking by using strainer.
  2. Drained water was measured using measuring cup (Measuring cylinder not available in food lab)
sr. no.IngredientWeight before soaking.Weight after soakingDrained waterMoisture content after soaking
1.Rice60 gm77 gm 85 ml33.06 %
2.Black gram dhal30gm 53 gm75 ml57.17 %
Fig., Water absorption of rice and black gram dhal

fig., Draining using strainer

Grinding:

  1. Soaked rice was grinded coarsely with 30 ml of water.
  2. Soaked black gram dhal was grinded finely with 60 ml of water.

Fig., Grinding of Soaked rice and black gram dhal

Mixing together:

Fig., Mixed batter

Fermentation: at 40 degree in incubator

Sr. no.Time IntervalBurette reading Acidity in K2CO3 gm/ 100 gm sampleAcidity in molpH
1.Initial1.40.1120.000146.45
2.3 hrs2.40.66240.000245.40
3.6 hrs4.11.13160.000415.13
4.7 hrs4.71.29720.000475.02
fig. Fermentation data at 40 degree

I.E. TRIAL FIFTH:

08 and 09 December 2023

Soaking:

  1. Rice 60 gm in 100 ml of water.
  2. Black gram dhal 30 gm in 100 ml of water.
  3. Soaking time: 12 hrs.

Draining:

Grinding:

  1. Soaked rice was grinded coarsely with 30 ml of water
  2. Soaked black gram dhal was grinded finely with 60 ml of water.

Mixing together:

Fermentation at 35 degree in incubator

Sr. no.Time IntervalBurette reading MeanAcidity in K2CO3 gm/ 100 gm sampleAcidity in molpH
1.Initial1.3,1.21.250.99360.0001256.70
2.7 hrs4.9, 5.04.951.36620.0004954.80
3.9 hrs5.6, 5.75.651.55940.0005654.25
fig. Fermentation data (titrable acidity )at 35 degree

II. Sensory evaluation of idli prepared with batter fermented at various time and temperature and having different level of Baking soda:

11 and12 December 2023

II. A. Fermentation at 300C (steaming without leavening agent):

  1. Soaking:

Rice: 80 gm

Black gram dhal: 40 gm

Soaking Time: 12hrs.

2. Grinding: Grinding separately.

Added water in soaked rice during grinding: 40ml.

Added water in soaked black gram dhal during grinding: 80 ml.

3. Mixing together:

Prepared batter: 240 gm

240 gm of sample divided into two: Sample A (120g) and Sample B (120gm).

4. Fermentation:

Sr. no.SampleFermentation TemperatureFermentation Time
1Sample A300C 10hrs
2Sample B300C 12hrs
Fig., Fermentation of batter at 300C

5. Steaming:

Sr. no.Sample Addition of salt in batterAddition of water in batterAddition of leavening agent into batterCooking time
1.A1 gm15 ml10 min
2.B2gm15 ml10 min
Fig., Steaming of idli.

6. Sensory evaluation:

Sensory assessment is a scientific approach for evoking, measuring, and interpreting products reactions as experienced via the senses of sight, smell, touch, taste and hearing. On a 9-point hedonic scale, 8 semi-trained panel members comprised of DIC members of the Vigyan Ashram, Pabal, evaluated freshly prepared Idli developed with batter which is fermented at different time with same temperature, for sensory characteristics like appearance, color, taste, flavor, texture, and overall. Products were rated on a 9-point hedonic scale with associated descriptive words ranging from 9 (very like) to 1 (strongly detest).

Sensory score:

  1. Dislike extremely
  2. Dislike very much,
  3. Dislike moderately,
  4. Dislike slightly,
  5. Neither like nor dislike,
  6. Like slightly,
  7. Like moderately,
  8. Like very much,
  9. Like extremely.
Sr. no,Sample ColorAromaTextureTasteMouthfeelOverall acceptability
1A7.427.143.1465.715.88
2B7.427.4256.4276.65
Fig., Sensory evaluation

7. Observations:

  1. As leavening agents (baking soda) was not added into batter, the texture of idli was not good (as per sensory evaluation).
  2. Sample B was salty in taste, as we added 2gm salt in 100 gm of batter.
  3. Sample B which fermented at 300C for 12 was better, having 6.65 Overall acceptability than sample A having 5.88 overall acceptability.

15 and 16 December 2023

II. B. Fermentation at 300C (steaming 1 mol leavening agent):

1.Soaking :

Rice: 120 gm

Black gram dhal: 60 gm

Soaking Time: 12hrs.

2. Grinding:

Grinding separately.

Added water in soaked rice during grinding: 60 ml

Added water in soaked black gram dhal during grinding: 120 ml.

3. Mixing together:

Prepared batter: 370 gm

370 gm of sample divided into three: Sample A (120g), Sample B (125gm) and Sample C (125gm).

4. Fermentation: at 300C

Sr. no.SampleFermentation
Temperature
Fermentation
Time
Burette
reading
Acidity in
K2CO3 gm/ 100 gm sample
Acidity in molpH
1Sample A300C 10hrs4.91.35240.000493.86
2Sample B300C 12hrs5.31.46280.000533.75
3.Sample C300C 14 hrs5.71.57320.000573.66
Fig., Fermentation of batter at 300C

5. Steaming:

In fermented idli batter 1 mol baking soda is added

Sr. no.Sample Addition of salt in batterAddition of water in batterAddition of
NaHCO3/ 120 gm batter
Cooking time
1.A2gm15 ml0.987915 min
2.B2gm15 ml1.068615 min
3.C2 gm15 ml 1.887815 min
Fig., Steaming of idli.

6. Sensory evaluation:

Sensory evaluation is carried out by 9 point hedonic scale.

Sr. no,Sample ColorAromaTextureTasteMouthfeelOverall acceptability
1A6.87.27.46.46.46.8
2B7.67.67.67.277.24
3C5.86.47.46.66 6.44
Fig., Sensory evaluation

7. Observations:

  1. Sample B was good which was fermented at 300C for 12 hrs. (acidity 1.46 gm K2CO3 / 100 gm of sample), having 7.24 overall acceptability.
  2. Proportion of Baking Soda (1 mol) was more in batter that result in yellowish color of idli and slightly flavor of baking soda.
  3. Proportion of water was slightly more.

20-21 December 2023

II.C. Fermentation at 350C (Steaming with 0.75 mol baking soda)

1.Soaking :

Rice: 120 gm

Black gram dhal: 60 gm

Soaking Time: 12hrs.

2. Grinding:

Grinding separately.

Added water in soaked rice during grinding: 60 ml

Added water in soaked black gram dhal during grinding: 120 ml.

3. Mixing together:

Prepared batter: 370 gm

370 gm of sample divided into three: Sample A (120g), Sample B (125gm) and Sample C (125gm).

4. Fermentation: at 350C

Sr. no.SampleFermentation
Temperature
Fermentation
Time
Burette
reading
Acidity in
K2CO3 gm/ 100 gm sample
Acidity in molpH
1Sample A350C 9hrs5.11.40760.000514.91
2Sample B350C 11hrs5.41.49040.000544.76
3.Sample C350C 13 hrs5.71.57320.000574.59
Fig., Fermentation of batter at 300C

5. Steaming:

In fermented idli batter 0.75 mol baking soda is added

Sr. no.Sample Addition of salt in batterAddition of water in batterAddition of
NaHCO3/ 120 gm batter
Cooking time
1.A1gm15 ml0.176715 min
2.B1gm15 ml0.680415 min
3.C1 gm15 ml 1.1715 min
Fig., Steaming of idli.

6. Sensory evaluation:

Sensory evaluation is carried out by 9 point hedonic scale.

Sr. no,Sample ColorAromaTextureTasteMouthfeelOverall acceptability
1A
2B
3C
Fig., Sensory evaluation

7. Observations:

24-25 December 2023

II.D. Fermentation at 400C (Steaming with 0.50 mol Baking Soda)

1.Soaking :

Rice: 120 gm

Black gram dhal: 60 gm

Soaking Time: 12hrs.

2. Grinding:

Grinding separately.

Added water in soaked rice during grinding: 60 ml

Added water in soaked black gram dhal during grinding: 120 ml.

3. Mixing together:

Prepared batter: 370 gm

370 gm of sample divided into three: Sample A (120g), Sample B (125gm) and Sample C (125gm).

4. Fermentation: at 400C

Sr. no.SampleFermentation
Temperature
Fermentation
Time
Burette
reading
Acidity in
K2CO3 gm/ 100 gm sample
Acidity in molpH
1Sample A400C 8hrs4.91.35240.000494.83
2Sample B400C 9hrs5.31.46280.000534.33
3.Sample C400C 11hrs5.71.57320.000574.17
Fig., Fermentation of batter at 300C

5. Steaming:

In fermented idli batter 0.50 mol baking soda is added

Sr. no.Sample Addition of salt in batterAddition of water in batterAddition of
NaHCO3/ 120 gm batter
Cooking time
1.A2gm15 ml0.987915 min
2.B2gm15 ml1.068615 min
3.C2 gm15 ml 1.887815 min
Fig., Steaming of idli.

6. Sensory evaluation:

Sensory evaluation is carried out by 9 point hedonic scale.

Sr. no,Sample ColorAromaTextureTasteMouthfeelOverall acceptability
1A6.87.27.46.46.46.8
2B7.67.67.67.277.24
3C5.86.47.46.66 6.44
Fig., Sensory evaluation

7. Observation

30 -31 December 2023

II.E. Fermentation at 400C (with 0.25 mol baking soda)

1.Soaking :

Rice: 120 gm

Black gram dhal: 60 gm

Soaking Time: 8 hrs.

2. Grinding:

Grinding separately.

Added water in soaked rice during grinding: 60 ml

Added water in soaked black gram dhal during grinding: 120 ml.

3. Mixing together:

Prepared batter: 430 gm

370 gm of sample divided into three: Sample A (140g), Sample B (145gm) and Sample C (14 5gm).

4. Fermentation: at 400C

Sr. no.SampleFermentation
Temperature
Fermentation
Time
Burette
reading
Acidity in
K2CO3 gm/ 100 gm sample
Acidity in molpH
1Sample A400C 8hrs5.20.43520.000524.66
2Sample B400C 9hrs5.41.49040.000544.34
3.Sample C400C 11hrs.5.81.60080.000584.08
Fig., Fermentation of batter at 300C

5. Steaming:

In fermented idli batter 0.25 mol baking soda is added

Sr. no.Sample Addition of salt in batterAddition of water in batterAddition of
NaHCO3/ 120 gm batter
Cooking time
1.A1gm10 ml0.176915 min
2.B1gm10 ml0.680415 min
3.C1gm10 ml 1.1715 min
Fig., Steaming of idli.

6. Sensory evaluation:

Sensory evaluation is carried out by 9 point hedonic scale.

Sr. no,Sample ColorAromaTextureTasteMouthfeelOverall acceptability
1A
2B
3C
Fig., Sensory evaluation

7. Observations:

2-4 January 2024

II.F. Fermentation at 400C (With 0.12 mol baking soda)

1.Soaking :

Rice: 120 gm

Black gram dhal: 60 gm

Soaking Time: 12hrs.

2. Grinding:

Grinding separately.

Added water in soaked rice during grinding: 60 ml

Added water in soaked black gram dhal during grinding: 120 ml.

3. Mixing together:

Prepared batter: 370 gm

370 gm of sample divided into three: Sample A (120g), Sample B (125gm) and Sample C (125gm).

4. Fermentation: at 400C

Sr. no.SampleFermentation
Temperature
Fermentation
Time
Burette
reading
Acidity in
K2CO3 gm/ 100 gm sample
Acidity in molpH
1Sample A400C 8hrs5.11.40760.000513.86
2Sample B400C 9hrs5.31.46280.000533.75
3.Sample C400C 11 hrs5.61.54560.000563.66
Fig., Fermentation of batter at 400C

5. Steaming:

In fermented idli batter 0.12 mol baking soda is added

Sr. no.Sample Addition of salt in batterAddition of water in batterAddition of
NaHCO3/ 120 gm batter
Cooking time
1.A1gm10ml0.1015 min
2.B1gm 10ml0.1015 min
3.C1 gm 10ml 0.1115 min
Fig., Steaming of idli.

6. Sensory evaluation:

Sensory evaluation is carried out by 9 point hedonic scale.

Sr. no,Sample ColorAromaTextureTasteMouthfeelOverall acceptability
1A
2B
3C
Fig., Sensory evaluation

7. Observation:

5-6 January 2024

II.F. Fermentation at 400C (With 0.20 mol baking soda)

1.Soaking :

Rice: 120 gm

Black gram dhal: 60 gm

Soaking Time: 12hrs.

2. Grinding:

Grinding separately.

Added water in soaked rice during grinding: 60 ml

Added water in soaked black gram dhal during grinding: 120 ml.

3. Mixing together:

Prepared batter: 370 gm

370 gm of sample divided into three: Sample A (120g), Sample B (125gm) and Sample C (125gm).

4. Fermentation: at 400C

Sr. no.SampleFermentation
Temperature
Fermentation
Time
Burette
reading
Acidity in
K2CO3 gm/ 100 gm sample
Acidity in molpH
1Sample A400C 8hrs5.21.43520.000524.60
2Sample B400C 9hrs5.51.5180.000554.52
3.Sample C400C 11 hrs5.71.57320.000574.48
Fig., Fermentation of batter at 400C

5. Steaming:

In fermented idli batter 0.20 mol baking soda is added.

Sr. no,Sample ColorAromaTextureTasteMouthfeelOverall acceptability
1A
2B
3C
Fig., Sensory evaluation

7. Observation:

  1. From above readings of sensory evaluation, it is observed that the idli prepared with 0.20 mol baking soda was good in taste, texture and had no flavour of baking soda.

III. Dehydration of Prepared idli batter:

III. A. FIRST TRIAL