Physical, Engineering and Bio-Chemical Properties of Tamarind Fruit, Pulp and Its Seeds

Sreedevi M.S¹ , Rajkumar P¹ , Palanimuthu V² , Ganapathy S¹ , Surendrakumar A³ , Geethalakshmi I¹

¹Department of Food Process Engineering, AEC and RI,TNAU, Coimbatore-641003, Tamilnadu, India

²AICRP on PHET, GKVK Campus, UAS, Bengaluru-560065, Karnataka, India

³Department of Farm Machinery and Power Engineering, AEC and RI, TNAU, Coimbatore 641003, Tamilnadu, India

Corresponding Author Email: minchu1011@gmail.com

DOI : http://dx.doi.org/10.53709/ CHE.2020.v01i01.012

Abstract

TamarindusindicaL., is a multipurpose long-lived tropical fruit tree used primarily for its fruits, which are eaten fresh or processed, used as a seasoning or spice, or the fruits and seeds are processed for non-food uses. The knowledge about physical and bio-chemical properties like size, weight, moisture content, protein content, and carbohydrate content of any biomaterial is essential to desigh its equipment for processing and value addition. The tamarind fruit pulp has a complex chemical composition. It is characterized by the presence of the low amount of water (26.86 %), a high amount of carbohydrates (54.67 %), protein (4.96 %) and fibre (6.49 %) like other fruits, which make it a good source of nutrients for human. Fruit composition also depends on locality. The intrinsic value of raw tamarind can be further enhanced through value addition activities. There is a good market for these processed products in both domestic and international markets.

Keywords

fruit, hull, pulp, quality parameters, seeds

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1. INTRODUCTION

Tamarind is a hardwood tree scientifically known as Tamarindusindica. In the eighteenth century, Linnaeus named it asTamarindusindica, inspired by the Arabic name Tamar-I-hind, which means date of India [13]. It is a medium-sized bushy tree with evergreen leaves and pods characterized by long and brown shells withfleshy, juicyand sticky pulp, i.e., the tamarind fruit. Tamarind has many valuable properties and both rural and urban population has utilized virtually every part of the tree. Tamarind contains high levels of tartaric acidproviding not just a zing to the taste buds.

Tamarind tree goes through growth, maturation and ripening stages before being ready for harvesting. Tamarind pulp shows a change in color during the different developmental stages and the pulp shrinks due to loss of moisture and becomes sticky. As the pods mature, the shell develops into a brown color, the pulp turns sticky and brown or reddish-brown and the seeds become harder and darker. When it fully ripens, the shells become brittle and easily broken. A tamarind tree takes more than seven years to start fruiting and 10-12 years to produce fruits.

Processing of tamarind fruit increases shelf life and income to the growers and processors. The postharvest handling practices like harvesting, drying, dehulling, deseeding, packaging and storage played an important role in maintaining quality and extending shelf life of pulp and its products. The knowledge about physical and bio-chemical properties like size, weight, moisture content, protein content, and carbohydrate content of any biomaterial is essential to design its equipment for processing, storage, and value addition. Quality differences in fruits are often detected by difference in density. The marketability and acceptability of any fruits depends on its biochemical characteristics and its composition.

Keeping above points in view, the present investigation of“Studies on physical, engineering and biochemical properties of tamarind fruit, pulp and its seeds” was undertaken. This study was conducted to investigate the physical, engineering and biochemical properties of unshelled, shelled and seed of raw and ripe tamarind fruit.

2. MATERIALS AND METHODS

The materials used and methods adopted for conducting various experiments pertaining to the object of the research work are as detailed below. The research on “Studies on physical, engineering and biochemical properties of tamarind fruit, pulp and its seeds” was carried out in the AICRP on Post-Harvest Engineering and Technology (PHET), University of Agricultural Sciences, Gandhi Krishi Vignana Kendra (GKVK), Bengaluru during the year 2019-2020.The methods used for analysis of physical, engineering and bio-chemical properties of tamarind fruits are presented systematically.

2.1 Material

For the present study, local tamarind variety was procured from tamarind traders at Chinthamani, Chikkaballapur district, Karnataka collected during the harvest season between December-March and the samples were then taken to AICRP on PHET laboratory. In the laboratorythe fruits were selected according to degree of maturation and absence of injuries. Subsequently, the pulp of the fruits weremechanically processed, packed and stored in zip-lock plastic bags for further laboratory analysis. The chemicals used for analysis in this study were of analytical grade.

2.2 Physical and Engineering properties of tamarind fruit

The following physical and engineering properties of tamarind fruit were determined using standard procedures are as detailed below.

2.1.1 Size

The tri-axial linear dimensions viz., major axis (length), minor axis (width) and intermediate axis (thickness) were carried out on 50 randomly chosen unripe tamarind (UT) fruits, ripe tamarind (RT) fruits and tamarind seeds (TS)using a digital Vernier caliper (Make: Mitutoyo, China; Model: CD-8 VC) having an accuracy of 0.01 mm.

2.1.2 Shape

The shape of the tamarind fruit and seed was also found to be different from various locations. Actually tamarind fruit is an irregular shape in nature. The mean values of 50 observations for geometric mean diameter (Dg)and sphericity index (Φ) of UT fruits, RT fruits and TSwere calculated by using the following relationships (Mohesenin, 1986) :

1. INTRODUCTION

2. MATERIALS AND METHODS

2.1 Material

2.2 Physical and Engineering properties of tamarind fruit

The following physical and engineering properties of tamarind fruit were determined using standard procedures are as detailed below.

2.1.1 Size

2.1.2 Shape

Dg= 〖(LxBxT)〗^(1/3)

Φ  =Dg/L

Where,
L =Length of the fruit / seed, mm
W = Width of the fruit / seed, mm
T =Thickness of the fruit / seed, mm

2.1.3 Mass

The mass of single tamarind fruit was measured by electronic weighing balance (Make: Adam Equipment co ltd., Miton Keynes, UK: least count 0.001g) and value of each tamarind fruit was recorded for 50 fruits to get average mass of single tamarind fruit. The mass of the whole fruit, pulp, fibre and seeds were obtained by individual direct weighing on electrical weighing balance.

2.1.4Bulk density

Bulk density of tamarind fruit was determined by using a cube box having a volume of 1000 cm³. The samples were filled in a box of standard size and top surface was leveled off. Then the samples were weighed using an electronic weighing balance [25].

The bulk density was calculated as:

Where,

ρ_b= Bulk density, Kg/m³

m = Mass of fruit, Kg

v_c = Volume of the container , m³

2.1.5True density

The true density is defined as the ratio between the mass of tamarind fruit and true volume of the tamarind fruit. It was determined using the toluene displacement method. Toluene was used in the place of water to avoid absorption by the fruits. The volume of toluene displaced was found by immersing a weighed quantity of tamarind in the toluene.

The true density was calculated as:

Where,

ρ_t= True density, Kg/m³

m = Mass of fruit, Kg

v_f = Volume of fruit , m³

2.1.6 Porosity

Porosity was calculated as the ratio of the difference between the true and bulk density to the true density value and expressed in percentage. The porosity of the of UT fruits, RT fruits and TSwere computed using the formula given below and expressed in per cent.

The porosity was calculated as:

Where,

= Porosity, per cent

ρ_b= Bulk density, kg/m³

ρ_t = True density, kg/m³

2.1.7Angle of repose

The angle of repose is the angle made by tamarind with the horizontal surface when piled from a known height. One bag of tamarind fruit was piled over a horizontal surface slowly from a height of 50 cm. The slant height of the pile was measured at different places and the average value was taken. It was found by measuring the height and diameter of the fruits heaped in natural piles.

The angle of repose was calculated as:

Where,

θ = Angle of repose, degree

H = Height of pile, cm

D = Diameter of the pile, cm

2.1.8Coefficient of friction

The static co-efficient of friction of tamarind fruits was determined against four different surface materials namely; glass, plywood, mild steel and aluminium sheetwere determined by using a simple set-up described by [35]. The static angle of friction was calculated when the tamarind fruits just began to slide over a plane surface.

The coefficient of friction was calculated as:

Where,

Coefficient of static friction

= Tilt angle of inclined surface at which grain mass started sliding, degree.

2.1.9Colour

Tristimulus colour measurements of unripe and ripe tamarind fruit and its pulp were made using Spectrophotometer (Make: Konica Minolta Instruments, Osaka, Japan; Model – CM5). It is a light weight, compact Tristimulus colour analyzer for measuring reflected-light colour. It combines advanced electronic and optical technology to provide high accuracy and complete portability. Using an 8 mm diameter (measuring area) diffused illumination and 0º viewing angle, the instrument takes accurate colour measurements instantaneously and the readings are displayed. The colour of the samples were measured in CIELAB (L*, a*, b*) coordinate system, where L* value indicates lightness of the sample; a* value indicates greenness (-) or redness (+) of the sample; and b* value indicates blueness (-) or yellowness (+) of the sample. Three readings were taken for each sample and the mean values were reported.

2.2 Bio chemical properties of tamarind fruit pulp

The following standard procedures were adopted for the proximate analysis of tamarind fruit pulp, an experimental sample extracted under optimum conditions during this study. All the analysis was done in triplicates and the mean values were recorded.

2.2.1 Moisture content

The moisturecontent of tamarind fruit and its parts (fibre, hull, seed and pulp) were determined according to electric hot air oven method of AOAC(2009). 10 g of sampleswere taken in to non-corrosive metal dishes with lid and the exact weight was noted down (W₁). The sampleswere dried in a hot air oven at 105±2 ^oCfor 24 hours. After taking out from the oven, the samples were cooled in a dessicator and weighed. The samples were again kept in the oven, heated for 2 h, cooled and recorded the weight. This procedure was repeated till a constant weight ( ) of the sample was attained. The average moisture content on the wet basis of the samples was calculated using the following equation. The mean of 3 such readings were recorded as the average moisture content of the sample.

The moisture content of the sample was calculated as:

x 100

Where,

W₁ = Initial weight of the sample, g

W₂ = Final weight of the sample, g

2.2.2 Ash content

For determination of ash content of tamarind pulp, standard method of AOAC (2009) was followed. Approximately 2 g of the moisture free powder sample of tamarind pulp was weighed, transferred in to pre-weighed porcelain crucible and charred using gas flame till smoke ceases. The crucible was then transferred to muffle furnace maintained at 550±5 °C to burn off all organic material that does not volatilize at that temperature. The resultant thus obtained is called ash. The crucible was then cooled in dessicator and weighed.

The percent ash content was calculated as:

x 100

Where,

W₁ = Weight of the sample

W₂ = Weight of empty crucible

W₃ = Weight of crucible + ash

2.2.3pH

For determining the pH of fruits and vegetables and their products, a pH 4 would be sufficient. Standardized the pH meter using this buffer and checked the pH of the tamarind pulp.

2.2.4Total Soluble Solids

Total soluble solids (TSS) of tamarind pulp was recorded by using an ERMA Hand Refractometer (0-32 °Brix) and the results were expressed in °Brix.10 g oftamarind pulp was mashed with 20 ml of distilled water to juice. Before measurement, the accuracy of refractometer was checked by using distilled water and calibrated. After proper cleaning with tissue paper, few drops of extracted juicewas placed on the prism, and the readings recorded were expressed in °Brix.

2.2.5Ascorbic acid

Tartaric Acid content of the sample was estimated by using AOAC (2009). Tartaric acid content of the sample was expressed as mg/100g. 10g of the pulp sample was blended with reasonable amount of 0.4% oxalic acid and then filtered by Whatman No.1 filter paper. The filtrate volume was completed to 250 ml with 0.4% oxalic acid. 20 ml of the filtrate was pipettes into a beaker and then titrated with dye solution (0.2g 2.6-dicholorophenol- indophenol dissolve in 500ml solution) to a faint pink color.

The ascorbic acid content was calculated as:

x 100

The dye strength was determined by taking 5ml of standard ascorbic acid (0.05g ascorbic acid /250ml 10%oxalic acid solution) in a beaker and titrate with dye solution to faint pink color.

2.2.6Titrable Acidity

It is necessary to determine titrable acidity of a given food sample to ensure the presence of acid in terms of predominant acid present in it. The predominant acid present in the tamarind is the tartaric acid and the acid content was determined as per AOAC (2009). Ten grams of homogenized sample was taken and made up to 100 ml volume in a volumetric flask. The contents were then filtered through Whatman no.1 filter paper; an aliquot of 10 ml was taken for titration against 0.1 N NaOH using phenolphthalein indicator and light pink colour as end point, to estimate titrable acidity in terms of tartaric acid.

Factor for acidity: One ml. of N/10 NaOH = 0.0075g of tartaric acid.

The titrable acid content was calculated as:

x 100

2.2.7Reducing sugars

The reducing sugars were determined by the method of AOAC (2009). 10 grams of sample was taken in 250 ml volumetric flask. To this, 100 ml of distilled water was added and the contents were neutralized by 1 N sodium hydroxide solution using 1-2 drops of phenolphthalein indicator. Then two ml of 45 per cent lead acetate was added to it. The contents were mixed well and kept for 10 minutes. Two ml of 22 per cent potassium oxalate was added to it to precipitate the excess of lead. The volume was made to 250 ml with distilled water and solution was filtered through Whatman No. 4 filter paper. This filtrate was used for determination of reducing sugars by titrating it against the boiling mixture of Fehling ‘A’ and Fehling ‘B’ solutions (5 ml each) using methylene blue as indicator and formation of brick red precipitate as an end point. Keeping the Fehling’s solution boiling on the heating mantle carried out the titration. The results were expressed on per cent basis.

2.2.8 Total sugars

For inversion at room temperature, a 50 ml aliquot of clarified deleaded solution was transferred to 250 ml volumetric flask, to which, 10 ml HCl was added and then allowed to stand at room temperature for 24 hrs. It was then neutralized with 0.1 N sodium hydroxide solution using 1-2 drops of phenolphthalein indicator. The volume of neutralized aliquot was made to 250 ml with distilled water. This aliquot was used to determine total sugars by titrating it against the boiling mixture of Fehling ‘A’ and Fehling ‘B’ (5 ml each) using methylene blue as an indicator of a brick red end point. The volume was made up to the mark and determined the total sugar as invert sugars. The results were expressed on per cent basis.

2.2.9 Crude fat

Fat was estimated as crude ether extract of the dry material. The dry sample (3-5 g) was weighed accurately in a thimble and plugged with cotton. The thimble was then placed in the Automatic Soxhlet Apparatus (Make: Pelican Equipments, Chennai; Model: SOCS PLUS) and extracted with anhydrous ether for about 1:30 h. The ether is then evaporated and the flask with the residue dried in an oven at 80-100 , cooled in a dessicator and weighed.

The crude fat content was calculated as:

2.2.10 Crude Protein

The protein content was determined from the estimated organic nitrogen content by Micro-Kjeldahl method. The Automatic Nitrogen/Protein Estimation System (Make: Pelican Equipments, Chennai, India; Model: KEL PLUS) was used for crude protein estimation. The nitrogenous compounds present in the sample were converted into ammonium sulphate by boiling with concentrated sulphuric acid. The ammonium sulphate formed was decomposed with an alkali (NaOH) and the ammonia gas liberated was absorbed in excess of the standard solution of acid which was then back titrated with standard alkali to estimate nitrogen content. The nitrogen value was multiplied by 6.25 to obtain the protein content.

The nitrogen percent was calculated as:

Where,

N = Normality of standard HCl solution;

W = Weight of sample

Protein content was estimated by conversion of nitrogen percentage to protein as follows:

Protein % = N% x conversion factor (6.25)

2.2.11Crude fiber

Crude fiber was estimated by following the standard AOAC method (2009). 2 g moisture free, fat free dried sample was transferred to 250 ml conical flask. Then 200 ml of 1.25 % sulphuric acid was boiled and transferred to the flask containing fat free sample, connected with reflux water condenser and heated, so that contents of the flask begin to boil within one minute. The flask was rotated frequently and boiling was continued for 30 minutes. The flask was then removed and the content was filtered through ash less filter paper in a funnel and washed with boiling water. The residue was then returned back into the flask with 200 ml of 1.25 per cent NaOH. The flask was immediately connected with reflux condenser and boiled for 30 minutes. The flask was removed and the content was filtered through ash less filter paper. Residue was washed thoroughly with water, transferred to the silica crucible and dried at 105±1 °C in hot air oven to constant weight. After cooling in dessicator, the weight of crucible with residue was recorded. The crucible was then transferred to muffle furnace at 550 °C until all carbonaceous matter was burnt. After ashing, crucible was cooled in dessicator and reweighed.

Crude fibre content was calculated as :

x 100

Where,

W = Weight of sample

W₁ = Weight of the crucible + weight of treated sample after oven drying, g

W₂ = Weight of the crucible + weight of sample after ashing, g

2.2.12Carbohydrates

The available carbohydrate content in food sample was determined by the method of difference. The total carbohydrate content was obtained by calculation as the difference between the sum of the other major ingredients, namely moisture, ash, crude fiber, crude protein and fat from 100.

Carbohydrate content = 100 – (% moisture + % crude protein + % crude fiber + % crude fat + % ash)

2.3 Statistical analysis

Data was stored in spreadsheets using the MS office Excel software system version 2017. Calculation of descriptive statistics (average mean values, standard deviation values and range of parameters) was performed for each parameter.

3.RESULTS AND DISCUSSION

The results obtained from the present investigation and relevant discussions have been summarized under following heads:

3.1 Physical and engineering properties of tamarind fruit

3.1.1 Physical and engineering properties of whole tamarind fruit (unripe and ripe), pulp and seeds

The physical and engineering properties of UT fruits, RT fruits, tamarind fruit pulp and TS such as; size (length, width, and thickness), mass, shape (geometric mean diameter and spericity index)were studied and the results were presented in Table 1. The mean values of 50 observations for the length, widthand thickness,geometric mean diameter, sphericity index and weight of single fruit of the unripe tamarind fruits were found to be 101.27 mm, 21.68 mm, 15.68 mm, 36.45 mm, 0.35 and26.40 g, respectively. For design and development of any processing machine the length, width and thickness of tamarind are important. Length is highly influenced by nutrition available for the plant and management practices that also influence directly the length of the pod and thickness of pods might be due to inherent genetic variations among the genotypes. The difference in tamarind fruit’s length, width, and thickness may be attributed to genetic difference [34],[17 ].

The average length,width, thickness, geometric mean diameter, sphericity index and weight of single fruit of the whole ripe tamarind fruits were found to be 53.46 mm, 20.18 mm and 13.71 mm, 15.15 mm, 0.28 and 5.47 g, respectively.) [28 ], [10] and [19] reported similar values for tamarind fruits.The shape is inherited and also affected by the environment.Curved, semi curved and straightfruit shapes were similar to the findings by [2] but [14] reported curved and the straight pod shapes. The shapes are affected by the seed number and seed shapes which are influenced by its genetics.

The average length, width, thickness, geometric mean diameter and sphericity index of the ripe tamarind fruits (without husk and with seed) were found to be 71.74 mm, 15.52 mm and 9.40 mm, 10.68 mm and 0.15, respectively.

The average length, width, thickness, geometric mean diameter and sphericity index of the ripe tamarind fruits (without husk and seed) were found to be 56.82 mm, 14.61 mm and 0.96 mm, 0.84 mm and 0.01, respectively.

The mean values of length, width, thickness, geometric mean diameter and sphericity index of the tamarind seeds were found to be13.62 mm, 9.33 mm, 6.70 mm, 0.85mm and 0.06, respectively. [23][3][36][6][10] studied length, width, thickness, geometric mean diameter and sphericity index of tamarind seed and recorded slightly similar values for tamarind and velvet tamarind seeds.The tamarind seeds presented various shapes, oval shaped seeds predominated.

[37] also reported that the number of seeds per pod ranged from 5-7 while this study depicted seed range of 1-12 per pod. This is highly influenced by nutrition available for the plant and the management practices that also influence directly the length of the pod. The difference in seed number may be attributed to the difference in length of pod and ovule fertility [34] [17]. [14] recorded seed shape of quadrant, bowl shape and but from the studies seed shapes of ovate and D shapes were observed. The shape is inherited and also affected by the environment

Table.1. Physical and engineering properties of unripe,ripe tamarind fruit and seeds

All values are means of triplicate determinations ± standard deviation (SD)

3.1.2 Gravimetric and frictional properties of dehulled and hulled tamarind fruit and seeds

The gravimetricproperties (bulk density, true density and porosity) and frictional properties (angle of repose and static co-efficient of friction) fordehulled and hulledtamarind fruitwere studied and the results were presented in Table 2a and 2b. The mean values of bulk density, true density, porosity and angle of repose for whole tamarind fruit (with hull and seed)were observed to be 404.66 kg/m³, 785.23 kg/m³ 48.37 %, and 32.22˚, respectively. [28],[19] and [10] reported slightly similar average values for bulk density, true density and porosity of tamarind fruit and velvet tamarind fruits, respectively.

The average values of coefficient of friction for whole tamarind fruit (with hull and seed) were found to be 0.75, 0.79, 0.90 and 0.76; for glass, aluminium, stainless steel and plywood surfaces, respectively. Among the average values of coefficient of friction, the maximum value of 0.90 was obtained for the stainless less steel surface followed by aluminium. The higher value of coefficient of friction for tamarind fruits shows that these surfaces exert more friction to tamarind whereas minimum friction was experienced on glass surface.It is recommended to use stainless steel as construction material in the manufacture of process components to easy movement of products along its surface. Similar trend of values for coefficient of static friction on different surfaces of materials were recorded by [19] and [10].

The average values of bulk density, true density and porosity of tamarind fruit (without hull and with seed) were found to be 714.00 kg/m³, 1077.40 kg/m³ and 33.68 per cent, respectively. The coefficient of friction for tamarind fruit (without hull and with seed) on different surfaces namely; glass, aluminium, stainless steel and plywood, was recorded with an average value of 1.11, 1.37, 1.08 and 1.20, respectively.

The average values of bulk density, true density and porosity of tamarind pulp (without hull and seed) were found to be 116.08kg/m³, 166.45kg/m³ and 29.61 per cent, respectively.The average values of bulk density, true density and porosity of tamarind seeds were found to be 97.02 kg/m³, 127.60 kg/m³ and 23.78 per cent, respectively.

Table. 2a. Gravimetric properties of dehulled and hulled tamarind fruit, pulp and seeds

Particulars	Whole Tamarind fruit with hull and seed	Tamarind fruit without hull and with seed	Tamarind fruit without hull and seed (pulp)	Tamarind seed
Bulk Density (Kg/m³)	404.66±5.68	714.00±45.21	116.08±0.98	97.02±0.12
True Density (Kg/m³)	785.23±36.48	1077.40±58.37	166.45±18.8	127.60±7.79
Porosity (%)	48.37±2.91	33.68±3.54	29.61±8.63	23.78±4.77

* All values are means of triplicate determinations ± standard deviation (SD)

Table. 2b. Frictional properties of dehulled and hulled tamarind fruit and pulp

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* All values are means of triplicate determinations ± standard deviation (SD)

**3.1.3 Physico-chemical composition of tamarind fruit**

Physico-chemical composition of tamarind fruit was found to be 38% pulp, 34% seed, 22% hull and 6% fibre and the results were presented in Fig.1.The research findings were in agreement with [7], [32] and [29]. [3] investigated and reported that after hot air drying weight of fruit (pulp, weed, shell etc) followed a declining trend with decrease in moisture content of the tamarind fruit. Tamarind fruit (pod) weight is directly correlated with pulp weight and seed number. Tamarind pulp weight is factor of management practices given to the tree. The variations in the pulp, seed, shell, and vein weight was due to their genotypic differences. The difference in shell weight can be clearly attributed to the difference in size of the fruit. The difference in fibre weight may be due to the differences in vascular tissue development rate in fruits [17]. The difference in seed weight may be attributed to the difference in the number and size of seeds. Pulp weight is a factor of management practices given to the tree.

Fig.1. Physico-chemical composition of tamarind fruit

Colour	L*	a*	b*
Unripe tamarind fruit	40.30±1.72	-4.85±0.45	11.08±0.80
Unripe tamarind pulp	64.98±5.21	-2.75±0.50	16.22±4.70
Ripe tamarind fruit	39.31±1.11	7.71±0.37	11.35±0.31
Ripe tamarind pulp (inner surface)	52.12±3.11	4.44±2.72	9.59±3.29
Ripe tamarind pulp (outer surface)	34.59±0.34	13.32±0.83	11.62±0.62
Tamarind seed	30.17±0.12	5.12±0.97	2.78±0.34

All values are means of triplicate determinations ± standard deviation (SD)

3.1.5 Physical properties of unripe tamarind fruit

In Table (4), the average moisture content, TSS and pH of unripe tamarind fruits was recorded as 70.30 (%wb), 2.23 ⁰B and 2.34, respectively. The average values of bulk density, true density and porosity of unripe tamarind fruitswere found to be365.32 kg/m³, 492.33 kg/m³ and 25.82%, respectively. The acid fruits did not differ with sweet tamarinds in sugar content. Tamarind is sour due to high acid content, mainly tartaric acid and ascorbic acid that can mask sugars in the pulp [20].

Table.4. Physical properties of unripe tamarind fruit

Particulars	Average
Moisture content (% wb)	70.30±2.68
TSS (⁰B)	2.23±0.06
pH	2.34±0.01
Bulk Density (Kg/m³)	365.32±18.25
True Density (Kg/m³)	492.33±10.50
Porosity	25.82±2.12

All values are means of triplicate determinations ± standard deviation (SD)

3.2 Bio-chemical analysis of tamarind

The biochemical properties of ripe tamarind fruit pulp (local variety) namelymoisture content, ash, pH, TSS, ascorbic acid, titrable acidity, reducing sugars, total sugars, crude fat, crude protein, crude fibre and carbohydrates were studied and the results are presented in Table 5.

3.2.1 Moisture content

It could be observed from the data presented in Table 5 that the moisture content of tamarind and its parts was recorded 26.86 (%wb) forwhole tamarind fruit (with hulland seed),29.38 (%wb) for tamarind fruit (without hull and with seed), 39.77 (%wb) for pulp (without hull and seed), 28.40 (%wb) for hull, 15.37 (%wb) for fibre and 18.57 (%wb) for seed. [26], [15] and[24] reported similar values ranged between 17.80-35.80%. While [22], [33] and [31] documented the values ranged between to be 13.60-20.90 %, this is greatly lower than the values reported by the above mentioned authors. The variation in moisture content of tamarind could be due to the storage and environmental conditions.

3.2.2Ash

The ash represents total content of minerals in a food. The ash content of tamarind fruit pulp was found to be 3.99%, this value falls within the range of the results obtained by [26], [9], [15] and [16], who reported a range of 2.6-3.9%. However, the values obtained in the present study were higher than those reported by [1], [24] and [31], who reported the values ranged from 2.01-2.90 %. The variation in ash content could be attributed to the difference in environmental factors (Land types).

3.2.3 pH

The pH of tamarind fruit pulp was found to be 2.39. The result of the present study was found slightly lower when compared with those obtained by [12], [1] and [27] who reported value ranged between 2.5-3.15. The reduction of pH leads to inhibition of food spoilage microorganism’s growth, hence extending the shelf life of tamarind fruit and its products like juice, vinegar and pickles. The acid content of tamarind is worthy feature because, of its association with oil content and fatty acid contents of its fruits and seeds.

3.2.4 Total soluble solids (TSS)

In the present study, the total soluble solids of tamarind fruit pulp was 10.50 ⁰B, which was relatively lower than the values documented as 18 to 48 ⁰B by [30], [33] and [8]. Globally, climatic conditions have also been known to influence the chemical composition of food crops. The tamarind fruit has been defined as bitter sweet fruit due to its high content of tartaric acids and sugars reducing combined, it is also said that it is the acidest and sweetest fruit at the same time.

3.2.5 Ascorbic acid

The ascorbic acid content of tamarind fruit was found to be 3.23 mg/100g, which is relatively similar to the value 3.0 mg/100g reported by [9], [15] and [16]; also higher than the result 1.4 mg/100g reported by [1]. Ascorbic acid (Vitamin C) contributes to the nutritional value of fruits juices and is essential water–soluble vitamin. It had been reported that the health benefits of ascorbic acid from tamarind fruit pulp includes treatment of common cold, boosting the immune system, lowering hyper tension, healing of wounds and controlling the symptoms of asthma.

3.2.6 Titrable acidity

The titrable acidity of tamarind fruit pulp was recorded as 10.19 %as tartaric acid, which is in the range documented by [18] from Pakistan and he found that in sour tamarind the tartaric acid content varied from 8.4-12.4% and also [13] opined that the most outstanding characteristic of tamarind is its sweet acidic in taste. In addition the value isrelatively higher than the documented values ranged between 4.04-4.14 % by [22], [33] and [8]. Different genotypes of tamarind fruits may be particularly sour or particularly sweet tastes. Hence it is not surprising that different authors have reported wide variations in the tartaric acid and sugar contents of tamarind pulp.

3.2.7 Reducing sugars

The reducing sugar content of tamarind fruit pulp was observed and recorded as 15.03 %, slightly similar values were reported by [22], [33], [8] and [11] and the values ranged from 15.24 to 16.20 %. [21] studied the reducing sugar content of tamarind fruit pulp and was found to be in the range of 16.60-17.70 %. The increase or decrease in sugar content might be due to slow hydrolysis of polysachharides, acids and pectic substances into simpler substances like sugar [5].

3.2.8 Total sugars

It was observed from the data that the total sugar content of tamarind fruit pulp was 22.05 %. Slightly similar result for total sugars (18.92-20.40) was recorded by [22], [8] and [11]. 21.40 to 30.85 % of total sugar content in different tamarind varieties was reported by [13].

3.2.9 Crude Fat

From the table 5, tamarind fruit pulp was found to contain low contents of crude oil as 0.1%. Similar values of crude fat were reported by Coronel (1991) and Shah (2014). The observed values were lower than those of [26], [15], [16], [24] and [27] as0.6-4%.Tamarind fruit pulp is relatively poor in oil, which is greenish in colour and liquid at room temperature. The variation of these values could be attributed to the genetic variations.

3.2.10 Crude Protein

The protein content of tamarind fruit pulp was found to be 4.9 %, which is slightly higher than the reported value of 3.1 % by [26], [16] and [31]. In addition, the values were lower than that of [24] and [1], who reported a protein content of 5.44% and 5.3%, respectively. The difference in protein content of tamarind fruit pulp is probably associated with difference in environmental conditions in different areas.

3.2.11 Crude Fibre

The average value of crude fiber of tamarind fruit pulp was found to be 6.49 % as shown in Table (5) which was relatively higher than the values5.2-5.6 % documented by [26], [16], [27]; [31] and greatly lower than the values recorded as 8.04-13.05%, reported by [1] and [24].

3.2.12 Carbohydrates

As shown in Table (5), the carbohydrate content of tamarind fruit pulp was calculated as 54.67 %, which was in close agreement to those reported by [26] and [16] and lower than that of [24], who reported a value of 55%. [31] reported 67.4 % of carbohydrates of ripe tamarind fruit.The greater amount of carbohydrate in tamarind fruit pulp can encourage its utilization in many fermented products such as vinegar production.

Table.5. Biochemical properties of tamarind pulp

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Physical, Engineering and Bio-Chemical Properties of Tamarind Fruit, Pulp and Its Seeds