alexa Preparation and Quality Evaluation of Dehydrated Carrot and Onion Slices

ISSN: 2157-7110

Journal of Food Processing & Technology

  • Research Article   
  • J Food Process Technol 2017, Vol 8(9): 692
  • DOI: 10.4172/2157-7110.1000692

Preparation and Quality Evaluation of Dehydrated Carrot and Onion Slices

Naimish Gupta and Shukla RN*
Department of Food Process Engineering, Sam Higginbottom University of Agriculture Technology & Sciences, Allahabad, Uttar Pradesh, India
*Corresponding Author: Shukla RN, Department of Food Process Engineering, Sam Higginbottom University of Agriculture Technology & Sciences, Allahabad-211007 Uttar Pradesh, India, Tel: 09412397290, Email: [email protected]

Received Date: Aug 07, 2017 / Accepted Date: Aug 28, 2017 / Published Date: Sep 04, 2017

Abstract

Studies were conducted to determine the effect of different drying temperatures on the carrot and onion slices that were blanched with hot water and potassium meta bisulphite (KMS) then dipped in 0.25% for 20 min. Pre-treated to drying carrot and onion slices were dehydrated in cabinet tray dryer at four different temperatures viz. 50°C, 60°C, 70°C and 80°C. Dehydrated products were then packed in LDPE and stored at ambient temperatures. The products were analysed for physico-chemical, microbial and sensory attributes at regular interval of 0 days, 15 days and 30 days during one-month storage period, the results were compared with the control sample. It was observed that moisture content and rehydration ratio increased during storage period but moisture content showed decreasing trend with increasing temperatures. There was decrease in β-carotene, Vitamin A content and organoleptic properties. However, no significant effect on ash content was observed during storage. The treated samples showed better nutritive value than the control sample. Finished product had no mould count which means the product remained microbiologically sterile during entire storage period. It was observed that the products dehydrated at 50°C and 60°C were best among all the samples.

Keywords: KMS; Blanching; Tray drying; Dehydration ratio; Rehydration ratio; Low density polyethylene

Introduction

Vegetables constitute an important item of human diet. They are plant or parts of plant that are used as food. Vegetables are important in improving the acceptability of the meal, because of innumerable shades of colour, flavour and texture they contribute. The minimum daily requirement of vegetable is about 284 g per head i.e., 20 percent of the total food requirement of an adult, it is more in case of vegetarians. India is one of the horticulturally rich countries of world taking second position next to china with regard to vegetable production. About 46.97 million tonnes of fresh fruits and 110.67 million tonnes of vegetables are grown in nearly 9 million hectares. Only 70 percent of horticultural crops are effectively utilized and 30 percent of these account for postharvest losses.

Drying is one of the most relevant and challenging processes of food industry, since a great number of food products are subjected to at least one drying step during its production. Dehydration or drying of foods is described as any process that involves thermal removal of volatile substances to obtain a dry solid [1]. The main purposes of drying crops are to increase its shelf life, to better its quality, to simplify the handling, storage and transport of the products and also to prepare the product to subsequent processes. Moringa Oleifera is native to some parts of Africa and Asia and it is the sole genus in the flowering plant family Moringaceae. Moringa is full of nutrients and vitamins and is good for both human and animal consumption. It is also a useful source of medicines. Drying of Agricultural crops is done in most farms by sun-drying. This results into contamination by insects and dust. Therefore, there is need to introduce the use of mechanical dryers provided that the nutritional characteristics would be retained better than using sun-drying method [2].

Being seasonal, as well as perishable due to high moisture content, carrots and onion are available in plenty only at a particular period of the years. During the peak season, due to abundant supply of carrots and onion the selling price becomes too low, leading to heavy losses to the growers. To preserve the carrots over a period of long time for use during off-seasons, dehydration is one of the most important methods, because it lowers the cost of packaging, storage and transportation by reducing both the weight and volume of the final product [3].

Carrot (Daucus carota) is an important vegetable, which has high nutritional value and utility. Carrot belongs to the family Umbelli ferae, genus Daucus, species Carota, and is one of the important root crops cultivated throughout the world for its fleshy edible roots cool season root vegetable grown extensively in various countries particularly during winter season in tropical regions. It finds wide application in day to day use for making carrot juice, carrot powder, terminated carrot sweetmeats, soups, stews carrot flakes etc. Carrot is known for its nutrient content viz., carotene and carotenoids, besides appreciable amounts of vitamins B1, B2, B6 and B12 vitamins and minerals. Hence, carrots occupy an important place in root vegetables for their multifaceted application, which in turn, results in the development of various processing operations for making different products and/or to extend shelf-life. Fresh carrots cannot be stored for more than 3-4 days under ordinary conditions, but shelf-life can be extended to 7-8 months if stored in crates covered with perforated plastic film at 0°C and 93-96 per cent relative humidity [4].

Onion belongs to the lily family amaryllidaceae, genus allium, species a. cepa, such as garlic and leeks. Dehydrated onion can be presented in powder, chunks, granules or slices. Its applications consider manufacturing of condiments, dehydrated or added to rehydrated meals. Dehydrated onion is used as condiment and flavouring agent in manufacturing of tomato ketchups, sauces, salad, pickles, chutneys, meat sausages, masala bread and buns, breakfast foods, etc. Dehydrated garlic is used for aids in digestion and for absorption of food having antiemetic and antiseptic properties and in some medicinal formulations. Allium crops are the most indispensable vegetable crops used as condiments in most Ethiopian cuisine. Among them, onion rightly called “queen of kitchen”, belongs to the family Alliaceae and considered as one of the most important vegetable and spice crops produced in large scale in Ethiopia and cultivated during the dry and rainy seasons [5].

Methodology

Collection of carrot and onion samples

Properly matured carrots were selected for the purpose. Carrots and onions should not have blemish on surface or any mechanical damage. Damaged carrots and onions may lead to contamination. Unripe carrots and onions might affect the moisture loss in process so they were not used.

Slices: Carrot and onion slices for blanching and further process. Main purpose of slices was to give carrots and onions a uniform shape and size throughout experiment.

Pre-treatment

Blanching: Principle for blanching is to inactivate the enzyme present in food commodity. Time and temperature combination for carrots and onions is 95°C for 2-3 minutes. Carrots and onions was tied in muslin cloth and dipped in 95°C for 2-3 minutes. After blanching they was cooled to room temperature. Free surface moisture was removed by sieving. In blanching of carrots and onions, leaching was found along with enzyme inactivation. So, slight weight loss obtained.

Potassium meta bisulphite (KMS): Carrot and onion was dipped in 0.25% KMS by weight for 20 mins. KMS was used as a preservative and thus increases the shelf life of slices.

Cabinet tray drying: Tray drying was done to dehydrate carrot and onion slices for different dehydration temperatures was taken as 50°C, 60°C, 70°C and 80°C.

Collection of dried carrots and onions: Dried carrots and onions was collected and thus packaged in LDPE.

Physico-chemical analysis

Moisture content (%): Moisture was determined according to the hot air oven method described by AOAC [6].

equation

Where,

W=weight of empty petri plate, g

W1=weight of petri plate + slice before drying, g

W2=weight of petri plate + slice after drying, g

Total ash content (%): The ash was estimated according to the method described by Ranganna [7].

equation

Where,

W=weight of sample, g

W1=weight of crucible, g

W2=weight of crucible + Ash, g

Dehydration ratio: Dehydration ratio was calculated by taking the weights of sample before drying and the weight of sample after drying [8].

equation

Where,

W2=Weight of sample after drying

W1=Weight of sample before drying

Rehydration ratio: Dehydrated slices were evaluated for rehydration ratio to find the reconstitution of dried sample using the following formula [7].

equation

Where,

W2=Weight of rehydrated sample, g

W1=Weight of the dehydrated sample, g

Beta carotene content and vitamin A (μg/100 g): Reagents: Acetone, anhydrous sodium sulphate, petroleum ether. 5 g of fresh sample was taken and crushed in 10-15 ml acetone, adding few crystals of anhydrous sodium sulphate, with the help of pestle and mortar. The supernatant was decanted into the beaker. The process was reported twice and transferred the combined supernatant to a separatory funnel, adding 10-15 ml petroleum ether and mix thoroughly. Two layers was separated and the lower layer was discarded and upper layer was collected in a 100 ml with petroleum ether and optical density was recorded using petroleum ether as blank [9].

Calculation:

equation

Vitamin A content: The vitamin A was estimated according to the method described by Suman and Kumari [10].

equation

Microbiological analysis

Dehydrated carrots and onions have too low moisture content to support even the growth of moulds. If, however these products become moistened above the minimum of microbial growth, growth was flow. A little moistening was permit only the growth of moulds. Moulds are thus most common and most important cause of spoilage.

Results And Discussions

The result obtained from the present investigation as well as relevant discussion have summarized under following:

Effect of temperature on moisture content (%) of dehydrated carrot slices during storage period

The product was prepared by processing it by different temperatures followed by storage at ambient temperature. Moisture content was calculated on the 0th day. The effect of storage condition on the moisture content was evaluated after every 15 days during a period of one month. The results showed that moisture content decreased with the increase in temperature as there is more evaporation of the moisture at higher temperature. Also, the moisture content increased during the storage period, the reason may be due to the ingress of moisture through the packaging material. The results obtained are shown in Table 1, the highest moisture content for carrot was 5.21% present in sample dehydrated at 50°C and lowest i.e., 4.98% was recorded in the sample dehydrated at 80°C [11].

Moisture Content (%) of Carrot
Temperature Control Sample Treated Sample
0 day 15 days 30 days Mean 0 Day 15 Days 30 Days Mean
50ºC 4..85 5.06 5.27 5.06 5.21 5.4 5.62 5.41
60ºC 4.77 4.98 5.21 4.98 5.13 5.35 5.54 5.34
70ºC 4.71 4.91 5.16 4.92 5.07 5.26 5.48 5.27
80ºC 4.65 4.85 5.09 4.86 4.98 5.17 5.39 5.18
Mean 4.74 4.95 5.18   5.09 5.29 5.50  
Result S S S   S S S  
S. Ed. (±) 0.025 0.058 0.037   0.009 0.018 0.006  
C.D.at 5% 0.052 0.123 0.078   0.019 0.038 0.012  

Table 1: Effect of temperature on moisture content of dehydrated carrot slices during storage period.

Effect of temperature on moisture content (%) of dehydrated onion slices during storage period

The product was prepared by processing it by different temperatures followed by storage at ambient temperature. Moisture content was calculated on the zeroth day. The effect of storage condition on the moisture content was evaluated after every 15 days during a period of one month. The results showed that moisture content decreased with the increase in temperature as there is more evaporation of the moisture at higher temperature. Also, the moisture content increased during the storage period, the reason may be due to the ingress of moisture through the packaging material. The results obtained are shown in Table 2, the highest moisture content for onion slices was 7.87% present in sample dehydrated at 50°C and lowest i.e., 7.73% was recorded in the sample dehydrated at 80°C.

Moisture Content (%) of Onion
Temperature Control Sample Treated Sample
0 day 15 days 30 days Mean 0 Day 15 Days 30 Days Mean
50°C 7.23 7.44 7.67 7.44 7.87 8.07 8.28 8.07
60°C 7.18 7.38 7.61 7.39 7.83 8.02 8.24 8.03
70°C 7.13 7.36 7.59 7.36 7.78 7.96 8.19 7.97
80°C 7.08 7.31 7.55 7.31 7.73 7.91 8.15 7.93
Mean 7.15 7.37 7.60   7.80 7.99 8.21  
Result S S S   S S S  
S. Ed. (±) 0.035 0.024 0.006   0.042 0.007 0.037  
C.D.at 5% 0.075 0.050 0.013   0.090 0.014 0.038  

Table 2: Effect of temperature on moisture content of dehydrated onion slices during storage period.

Effect of temperature on ash content (%) of dehydrated carrot slices during storage period

The ash content was obtained by incineration of the sample at 550°C in muffle furnace, at this high temperature all the organic component in the samples burn out and inorganic component is left. The results obtained are given in Table 3, the results showed that there was difference in ash content of sample treated at different temperatures. During storage, the ash content decreased slightly, this may be due to the increase in moisture content with the increase in storage period. The highest ash content in carrot was present in the sample dehydrated at 50°C i.e., 0.47% and lowest ash content 0.44% was found in the sample dehydrated at 80°C [12].

Ash Content (%) of Carrot
Temperature Control Sample Treated Sample
0 Day 15 Days 30 Days Mean 0 Day 15 Days 30 Days Mean
50°C 0.28 0.27 0.26 0.27 0.47 0.46 0.45 0.46
60°C 0.27 0.26 0.25 0.26 0.46 0.45 0.44 0.45
70°C 0.26 0.25 0.24 0.25 0.45 0.44 0.43 0.44
80°C 0.25 0.24 0.23 0.24 0.44 0.43 0.42 0.43
Mean 0.26 0.25 0.24   0.45 0.44 0.43  
Result S S S   S S S  
S. Ed. (±) 0.007 0.007 0.005   0.008 0.008 0.004  
C.D. at 5% 0.016 0.014 0.010   0.016 0.017 0.008  

Table 3: Effect of temperature on ash content of dehydrated carrot slices during storage period.

Effect of temperature on ash content (%) of dehydrated onion slices during storage period

The ash content was obtained by incineration of the sample at 550°C in muffle furnace, at this high temperature all the organic component in the samples burn out and inorganic component is left. The results obtained are given in Table 4, the results showed that there was difference in ash content of sample treated at different temperatures. During storage, the ash content decreased slightly, this may be due to the increase in moisture content with the increase in storage period. The highest ash content in onion was present in the sample dehydrated at 50°C i.e., 0.43% and lowest ash content 0.40% was found in the sample dehydrated at 80°C.

Ash Content (%) of Onion
Treatments Control Sample Treated Sample
0 Day 15 Days 30 Days Mean 0 Day 15 Days 30 Days Mean
50°C 0.24 0.23 0.22 0.23 0.43 0.42 0.41 0.42
60°C 0.23 0.22 0.21 0.22 0.42 0.42 0.41 0.41
70°C 0.22 0.21 0.20 0.21 0.41 0.40 0.39 0.40
80°C 0.21 0.20 0.19 0.20 0.40 0.39 0.38 0.39
Mean 0.25 0.21 0.20   0.41 0.40 0.39  
Result S S S   S S S  
S. Ed. (±) 0.006 0.005 0.005   0.007 0.008 0.004  
C.D. at 5% 0.013 0.011 0.010   0.015 0.017 0.008  

Table 4: Effect of temperature on ash content of dehydrated onion slices during storage period.

Effect of drying temperature on weight loss of fresh carrot and onion slices

The weight loss in the sample upon drying is due to loss in moisture content. As moisture forms an important component of fresh vegetables, so upon drying moisture content is reduce thereby reducing the weight. The weight loss was calculated from initial weight of the blanched carrot slices and samples which were dried at 50°C, 60°C, 70°C and 80°C (Table 5). The weight loss was calculated for 0 min up to 5 hours for every one hour. Similarly, the weight loss was calculated from initial weight of the blanched onion slices during drying at 50°C, 60°C, 70°C and 80°C, 0 mins up to 5 hours in every one-hour weight of sample [13].

Weight Loss
  Carrot(g) Onion(g)
Time(min) at 50°C at 60°C at 70°C at 80°C at 50°C at 60°C at 70°C at 80°C
0 100 100 100 100 100 100 100 100
60 40.5 38.46 36.31 34.28 38.45 36.46 33.85 31.32
120 24.4 23.68 21.50 20.45 22.45 21.05 19.15 18.32
180 19.85 19.79 19.75 19.71 17.65 17.54 17.42 17.31
240 14.93 14.81 14.76 14.49 12.23 12.18 12.15 12.13
300 14.69 14.67 14.48 14.32 11.75 11.69 11.62 11.58
  Result S. Ed. (±) C.D. at 5%   Result S. Ed. (±) C.D. at 5%  
Due to temp NS 0.816 1.730   NS 0.927 1.966  
Due to Time S 0.666 1.412   S 0.757 1.605  

Table 5: Effect of drying temperature on weight loss of fresh carrot and onion slices.

Effect of drying temperature on dehydration ratio of carrot slices

The dehydration ratio calculated from initial weight of carrot during cabinet type tray drying at 50°C, 60°C, 70°C and 80°C (blanching and KMS) is shown in Table 6, The results showed that dehydration ratio decreased with the increase in temperature as there occurs more evaporation of the moisture at higher temperature [13].

Dehydration Ratio of Carrot
Temperature Weight of the sample before drying (g) B Weight of the sample after drying (g) A Dehydration ratio(B/A)
Control Sample 50ºC 950 103 0.108
Treated Sample 50ºC 900 105 0.116
Control Sample 60ºC 1200 116 0.096
Treated Sample 60ºC 1100 115 0.104
Control Sample 70ºC 900 81 0.090
Treated Sample 70ºC 1000 98 0.098
Control Sample 80ºC 850 68 0.080
Treated Sample 80ºC 800 71 0.088

Table 6: Effect of drying temperature on dehydration ratio of carrot slices.

Effect of drying temperature on dehydration ratio of onion slices

The dehydration ratio calculated from initial weight of onion during cabinet type tray drying at 50°C, 60°C, 70°C and 80°C (blanching and KMS) is shown in Table 7. The results showed that dehydration ratio decreased with the increase in temperature as there occurs more evaporation of the moisture at higher temperature.

Dehydration Ratio of Onion
Temperature Weight of the sample before drying (g) B Weight of the sample after drying (g) A Dehydration ratio (B/A)
Control Sample 50ºC 1050 104 0.099
Treated Sample 50ºC 1100 115 0.104
Control Sample 60ºC 1100 105 0.095
Treated Sample 60ºC 1200 118 0.098
Control Sample 70ºC 1150 100 0.086
Treated Sample 70ºC 1200 107 0.089
Control Sample 80ºC 900 72 0.080
Treated Sample 80ºC 1000 84 0.084

Table 7: Effect of drying temperature on dehydration ratio of onion slices.

Effect of drying temperature on rehydration ratio of carrot slices

The rehydration was carried out by immersing dried carrot slices in boiling water, maintained at four temperatures i.e., 50°C, 60°C, 70°C, and 80°C. Approximately 5 g of sample was added to 200 ml of water, agitated and then allowed to rehydrate for 30 and 60 min time intervals and the contents were then filtered through filter paper. The weight of sample and the rehydration ratio is shown in Table 8. After the 30 min, the rehydration ratios of dehydrated carrots were found to be 6.23, 6.29, 6.35 and 6.42 respectively. After the 60 min, the rehydration ratio was found to be slight increased i.e., 6.27, 6.33, 6.39, and 6.46 respectively. The increase in the rehydration ratio was due to the absorption of water by the dried carrot slices. The rehydration ratio was seen less on 70°C and 80°C because of the high temperature due to which surface water was dried quickly and bound water was not dried properly [14,15].

Rehydration Ratio of Carrot
Temperature Control Sample Treated Sample
After 30 min After 60 min Mean After 30 min After 60 min Mean
50°C 5.95 5.98 5.96 6.23 6.27 6.25
60°C 6.01 6.05 6.03 6.29 6.33 6.31
70°C 6.07 6.11 6.09 6.35 6.39 6.37
80°C 6.12 6.16 6.14 6.42 6.46 6.44
Mean 6.03 6.07   6.32 6.36  
Result S S   S S  
S. Ed. (±) 0.041 0.008   0.011 0.014  
C.D. at 5% 0.086 0.018   0.023 0.031  

Table 8: Effect of drying temperature on rehydration ratio of carrot slices.

Effect of drying temperature on rehydration ratio of onion slices

The rehydration was carried out by immersing dried onion slices in boiling water, maintained at four temperatures i.e., 50°C, 60°C, 70°C, and 80°C. Approximately 5 g of sample was added to 200 ml of water, agitated and then allowed to rehydrate for 30 and 60 min time intervals and the contents were then filtered through filter paper. The weight of sample and the rehydration ratio is shown in Table 9. After the 30 min, the rehydration ratios of dehydrated onion were found to be 6.62, 6.67, 6.71 and 6.76 respectively. After the 60 min, the rehydration ratio was found to be slight increased i.e., 6.65, 6.68, 6.73, and 6.78 respectively. The increase in the rehydration ratio was due to the absorption of water by the dried onion slices. The rehydration ratio was seen less on 70°C and 80°C because of the high temperature due to which surface water was dried quickly and bound water was not dried properly.

Rehydration Ratio of Onion
Temperature Control Sample Treated Sample
After 30 min After 60 min Mean After 30 min After 60 min Mean
50°C 6.34 6.37 6.35 6.62 6.65 6.63
60°C 6.39 6.42 6.40 6.67 6.68 6.67
70°C 6.45 6.49 6.47 6.71 6.73 6.72
80°C 6.49 6.52 6.50 6.76 6.78 6.77
Mean 6.41 6.45   6.69 6.71  
Result S S   S S  
S. Ed. (±) 0.025 0.009   0.031 0.014  
C.D. at 5% 0.054 0.19   0.066 0.031  

Table 9: Effect of drying temperature on rehydration ratio of onion slices.

Effect of temperature on carotenoid content of dehydrated carrot slices during storage period (μg/100 g)

The effect of different temperature time combination in β-carotene content on 50°C, 60°C, 70°C, 80°C at 15days interval during storage is shown in (Table 10). At 0th day, β-carotene content of carrots dehydrated at 50°C, 60°C, 70°C, 80°C was found to be 55075.7, 50061.7, 45061.7 and 40087.3μg respectively. After 15 days of storage, β-carotene value was found to be 55073.6, 50060.6, 45060.6 and 40085.2 μg respectively. On critical evaluation of the result during storage it was found that β-carotene content decreased with increase in storage and temperature. Finally, after 30 days of storage, the values of β-carotene were 55072.5, 50058.6, 45059.6 and 40084.1 μg respectively. Carotenoids are the pigments which are sensitive to heat. Due to treatment, at different temperature thermal degradation occur there by reducing the carotenoids content [9].

Carotenoid Content
Treated Sample Control sample
Temperature 0 Day 15 Days 30 Days 0 Day 15 Days 30 Days
50°C 55075.7 55073.6 55072.5 50075.5 50074.6 50073.5
60°C 50061.7 50060.6 50058.6 45073.4 45072.6 45071.6
70°C 45061.7 45060.6 45059.6 40074.5 40073.6 40072.6
80°C 40087.3 40085.2 40084.1 35072.6 35071.2 35070.1
Mean 47571.60 47570.10 47568.70 42574 42573 42571.95
Result S S S S S S
S. Ed. (±) 5.321 6.033 6.369 4.260 3.558 3.894
C.D. at 5% 11.280 12.790 13.502 9.032 7.543 8.255

Table 10: Effect of temperature on carotenoid content of dehydrated carrot slices during storage period (µg/100 g).

Effect of different temperatures on Vitamin A content of dehydrated carrot slices during storage period (μg/100 g)

The effect of different temperatures and storage period on vitamin A content of dehydrated carrot slices at 50°C, 60°C, 70°C, 80°C, at regular interval of 15 days during storage is shown in Table 11. 0th day readings of vitamin A content of samples treated at 50°C, 60°C, 70°C, and 80°C were found to be 550.757, 500.617, 450.617 and 400.873 g respectively. On 15th day of storage, Vitamin A value was found to be 550.736, 500.606, 450.606, and 400.852 μg respectively. From the obtained results, it was found that the Vitamin A content decreased with increase in temperature as well as during storage period. On the 30th day of storage study, the values of Vitamin A were 550.725, 500.586, 450.596 and 400.841 μg respectively. Due to the thermal treatment (at different temperature) the Vitamin A content of dehydrated carrot slices decreases due to thermal degradation [16].

Vitamin A Content 
Treated Sample Control Sample 
Temperature 0 Day 15 Days 30 Days 0 Day 15 Days 30 Days
50°C 550.757 550.736 550.725 500.755 500.746 500.735
60°C 500.617 500.606 500.586 450.734 450.726 450.716
70°C 450.617 450.606 450.596 400.745 400.736 400.726
80°C 400.873 400.852 400.841 350.726 350.712 350.701
Mean 475.716 475.70 475.687 425.74 425.73 425.71
Result S S S S S S
S. Ed. (±) 5.310 6.119 5.296 4.103 4.619 2.833
C.D. at 5% 11.258 12.973 11.227 8.698 9.792 6.007

Table 11: Effect of different temperatures on Vitamin A content of dehydrated carrot slices during storage period (µg/100 g).

Microbial analysis

Dehydrated carrot and onion slices: Dehydrated products have such a restricted that there is little difficulty in preventing the growth of micro-organisms as long as they are kept dry. There moisture content is too low to support even the growth of moulds. If, however these products become moistened above the minimum of microbial growth, growth will follow. A little moistening will permit only the growth of moulds. Moulds are thus most common and most important cause of spoilage. So, the mould count at room temperature was studied for samples of dehydrated carrot and onion slices to study the accuracy in the microbial quality and also to determine the frequency of distribution within standard limits with interval of 0 days up to 30 days. But, there was no mould count seen for 30 days when pre-treated with blanching and KMS. Therefore, minimum shelf life is 30 days (Table 12).

Physico-Chemical Properties Carrot Onion
Moisture Content 85.5% 88.6%
Ash Content 0.30% 0.26%
ß-Carotene Content 75075.2 µg/100 g -
Vitamin A Content 750.752 µg/100 g -

Table 12: Physico-chemical properties of fresh carrot and onion 100 g.

Conclusion

From the results of this study it is concluded that the quality evaluation at different drying temperatures for carrot and onion slices showed similar trend or nature towards the storage conditions that were provided after packing in the LDPE for 30 days to observe the shelf life of dried carrot and onion slices. The temperatures were the most pronounced factors affecting moisture content, rehydration ratio, carotenoid content, vitamin A content of carrot and onion slices during tray drying. Results obtained showed that the effect of application of pre-treatment was significant on the initial moisture content of the carrot and onion slices and were found to be best as base material for the preparation of carrot and onion powder for the off-season. The dehydrated products will be of great use particularly in off season of carrot and dehydrated onion powder is primarily used for preparation of ready to make foods. No mould growth was observed during storage period. The Physico-chemical properties of carrot and onion slices were preserved in KMS treatment because KMS had some leaching effect on products due to the release of SO2 in water during treatment. On the basis of quality attributes, and sensory attributes especially colour and appearance the products were acceptable. However, there was difference in the overall acceptability of the product. Suggestions for future work.

References

Citation: Gupta N, Shukla RN (2017) Preparation and Quality Evaluation of Dehydrated Carrot and Onion Slices. J Food Process Technol 8: 692. Doi: 10.4172/2157-7110.1000692

Copyright: © 2017 Gupta N, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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