STUDIES ON POST HARVEST PROCESSING OF GARLIC
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Date
2013
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Publisher
MPUAT, Udaipur
Abstract
Garlic (Allium sativum L.) has been used as a food, a condiment and
medicinal purposes for over many centuries. The combination of allin and
allinase present within the mesophyl cells of garlic cloves produces allicin and
other thiosulphonates, which are responsible for typical garlic flavour. Garlic
processing involves unit operations such as curing, grading, storage, bulb
breaking, clove separation, peeling, dehydration, product development and
packaging. The separation and peeling of garlic cloves requires special care
and skill due to its typical physical characteristics and presence of essential
volatile oils in the epidermal cells. Looking in to the increasing demand of
garlic and its products in domestic and export market, the present
investigation was taken to study on the post harvest processing of garlic.
The average initial moisture content and bulk density were observed to be 198.5
kg water per kg of dry matter and 332.2 kg/m3, respectively. Sphericity of garlic clove
was ranged from 0.38 - 0.48. Survey study on the existing methods of garlic
processing revealed that most of the farm practices are performed with traditional
methods. The garlic bulb breaker was found to be used for separation of cloves for
seed purpose or further processing. It was found to work satisfactorily with clove
separation efficiency of 93%. The existing garlic peeler was observed unsatisfactory
as there was crushing/ bruising of cloves. The 30 min heating at 70 oC in cabinet tray
dryer was found to be the best among chemical treatment, hydrothermal and thermal
treatments as minimum time (12.10 min) for peeling of garlic cloves was required.
Preliminary trials on clove peeling were conducted to optimise the process
parameters on the basis of maximum peeling recovery and peeling efficiency with
minimum damage of cloves. The optimized attributes viz. diameter of peeling chamber (130 mm), air jet pressure (10 kg/cm2) and air jet position (60 mm) were
taken to develop batch type clove peeler for peeling of 500 g garlic cloves with the
assistance of compressed air. The extensive trails for performance evaluation of
developed garlic clove peeler were conducted and found that developed peeler
worked satisfactory with peeled recovery of 94.8 % and peeling efficiency of 97.6 %
for 70 seconds peeling time.
The drying time required to reach the safe moisture level (7.5 % db)for unpeeled
and peeled garlic cloves was found to be 50 and 40 h in open Sun and 33 and 28.5 h in solar cabinet drying, respectively. The convective drying behaviour of dehydrated
garlic cloves at drying air temperature of 40, 50 and 60oC and velocities of 1.0, 1.5
and 2.0 m/s were studied. The drying time ranged from 570 to 1200 min and entire
drying was taken place in falling rate period. Moisture diffusivity was found to vary
in the range of 3.03- 8.64×10-10 m²/s. The garlic slices were also dehydrated in
fluidized bed dryer at air temperature of 40, 50 and 60oC with air velocity of 3.0 m/s.
The drying time for garlic slices was found to be 306, 274 and 180 min. Freeze dryer
required 48 h for garlic slice drying to the safe moisture content (7.8 %) at freezing
temperature - 40°C.
The L value and flavour strength of fresh garlic was recorded to be 72.64 and
0.66, respectively. The L value and flavour strength was observed to be 52.32 & 0.17,
58.72 & 0.19, 64.79 & 0.30, 66.42 & 0.27 and 68.23 & 0.41 for the garlic samples
dehydrated in open sun, solar, convective, fluidized bed and freeze drying method,
respectively. The water activity of garlic cloves and slices dehydrated in different
drying methods varied between 0.25 and 0.29. For garlic paste, the flavour strength
was found to be 0.65, 0.49, 0.46, 0.45 and 0.44 at interval of 0, 30, 60, 90 and 120
days, respectively. The colour, flavour and overall acceptability of the garlic paste,
dehydrated cloves and powder was found to be satisfactory up to the storage period of
90, 120 and 90 days, respectively. Technology packages for production of garlic
paste, flakes and powder was developed. The developed Process Technology was
observed to be techno-economic feasible. The cost of production of garlic paste and powder was worked out to be Rs 38.15 and 141.16 per kg, respectively.
Description
STUDIES ON POST HARVEST PROCESSING OF GARLIC
Keywords
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Citation
Champawat and Sharma, 2013