Quality and Sensory Evaluation of Fruits and Vegetables
Aim of Experiment: To observe the quality
and sensory parameters of fruits and vegetables.
Objective:
·
Determination of Total Soluble
Solids (TSS).
·
Determination of Acidity
·
Determination of Physiological Weight loss
·
Determination of moisture
content
· Determination of sensory parameters of product.
Total Soluble Solid (TSS):
The average moisture content in fresh fruits and vegetables varies from 60 to 96 percent. Among the various constituents present in fresh fruits and vegetables, some of them are soluble in water. The water-soluble substances are minerals, acids, sugars, a few proteins and some vitamins. The estimation of total soluble constituents gave the approximate amount of water-soluble substance present in the sample. Among the various soluble substances, the number of sugars is 80-85 percent. The TSS value is roughly considered to be the number of sugars and soluble content which can be determined by Hand Refractometer or Digital Refractometer.
Materials Required:
Hand Refractometer of 0-20 range (works on the principle of total
refraction of the plant product) or
Digital Refractometer of 0-85 range, juice,
muslin cloth or tissue paper and glass rod.
Procedure:
1. For calibrating the refractometer use clean distilled water.
2. Once the instrument is
calibrated the juice of the test material is to be put on prism for determining the TSS.
3. For calibrating the instrument put a few drops of distilled water on the specimen chamber of the refractometer with the help of a clean glass
rod.
4. Fold back the cover of the refractometer lightly. Look through an eye-piece with a projection inlet facing towards light. (Hand
Refractometer). Read and record the point where the boundary where the boundary line of the shaded area intersects with the unshaded
area on the scale.
5. If necessary rotate eyepiece either for clear reading. The reading should be zero. If the reading
is not zero, set it to zero with a scale correction knob.
6. Now place three to four
drops of test solution on the dry clean surface of the prism. Record the reading
in the same manner as
that of distilled water.
7. Clean the specimen chamber
with a muslin cloth.
For Digital Refractometer follow the procedure up to step 3. Set it to zero. Then add one drop of juice where the water was put
previously and take the reading. Wash with distilled water and clean properly.
Acidity:
The titrable acidity content of fruit/ vegetable pulp was calculated by using
the procedure given by Ranganna (1979) which includes the use of the following reagents:
i.
0.1 N Standard
NaOH solution
ii.
1% phenolphthalein solution
Five grams of pulp was macerated in pestle mortar and diluted with a small
amount of distilled water. Then it
was filtered through muslin cloth. The volume was made up to 50 ml and 5 ml aliquot was taken for titration
against N/10 sodium hydroxide (NaOH) solution using phenolphthalein indicator. The appearance of pink color was
considered as the end-point. The result was calculated by the formula:
Acidity analysis by titration method
Physiological loss in weight (PLW)
Materials Required: Electrical Weighing Balance, Fresh fruits
The weighing balance was used to record the weight of fruits. The fresh weight of five fruits were measured and kept in storage. After one week again the final weight is measured. The percent physiological loss in weight was calculated by using the following standard procedure (AOAC, 2000) mentioned below.
Materials Required: Hot
air oven, fruits, Weighing balance
Procedure:
The weighing balance was used to record the weight of fresh fruits. The fresh weight of five fruits were measured and kept in a hot air oven. After the removal of fruits from oven again the final weight is measured. The percent moisture content was calculated by using the following standard procedure (AOAC, 2000) mentioned below.
Sensory Evaluation:
Organoleptic parameters are judged by appearance, feel and visual methods
using 9-point scale (Lawless
and Heymann,2010). Though sophisticated and highly sensitive
instruments are now available, the importance of sensory analysis has
significantly increased. Most instrumental analysis have come to realize
that only through
the co-ordination of instrumental
and sensory analysis can optimal information be obtained (Jellinek, 1985).
Hence following sensory
qualities were estimated.
Colour, taste, flavour and overall acceptability of the fruits were
evaluated by a 9-point Hedonic scale given by Amerine et al. (1965)
for use of 10 semi-trained panelists as follows:
|
Attributes |
Score |
|
Like extremely |
9 |
|
Like very much |
8 |
|
Like moderately |
7 |
|
Like slightly |
6 |
|
Neither like nor dislike |
5 |
|
Dislike slightly |
4 |
|
Dislike moderately |
3 |
|
Dislike very much |
2 |
|
Dislike extremely |
1 |
