Stepwise analysis of factors affecting the yield of hot-air-dried carrots
Abstract
Carrots (variety - Red Cored Chantenay) were subjected
to a stepwise analysis during processing prior
to dehydration (hot-air-drying), to determine the
parameters that affect the yield of the final product
and its quality.
The raw material quality was assessed as a prime
factor affecting the overall results. Peeling with
stearn at 5 bar pressure was evaluated at 60, 65, 70
and 80 seconds peeling time. The effect of the raw
material quality on the peeling and trimming losses
was noted. Trimming was done by hand and the losses
were found to be influenced by the raw material and
the effectiveness of the peeling process.
The peeled and trimmed carrots were diced into
10 x 10 x 2 mm and 10 x 10 x 7 mm cuts; these were
then blanched in hot water at 90oC. The correct blanching
time was evaluated using peroxidase. The 10 x
10 x 2 mm cut required less blanching time than that
of 10 x 10 x 7mm. Leaching losses during blanching
were determined by analysing the dry matter content of
the carrots after each blanching time of: 0, 1, 2,
3, 4, 5 and 6 minutes.
In order to reduce leaching losses sugar was added
to the blanching liquor to give a soluble solid concentration
of 0, 5, 8, 10 and 120 Brix. The carrots were
then blanched in these liquors and a sample of each
liquor taken after blanching in order to analyse the
sugar content. The blanching liquor was recirculated
and the soluble solids concentration maintained at 100
Brix.
Carrots blanched in these liquors and air-dried
to 7% moisture content were analysed for sugar content.
The sugar increased in each sample depending on the
amount of sugar added to the blanching liquor.
The quality of the dried product was examined for
B-carotene content and hydroxymethylfurfural. The
B-carotene increased with the amount of sugar added
upto 100 Brix, after which it decreased. The carrots
blanched at 120 Brix had a deep brown colour after
drying. This was probably due to caramelization of
sugars. The decrease in B-carotene in the same sample
could be due to the fact that some intermediate compounds
of the caramelization process affected its stability.
It was noted that the yield of the final product
(given as a conversion ratio) for the same quality of
raw material and processing parameters increased with
the amount of sugar added to the blanching liquor.
The limiting factor was the quality of the final dried
product achieved.
Citation
Mbaabu, A.G(1982). Stepwise analysis of factors affecting the yield of hot-air-dried carrotsSponsorhip
University of NairobiPublisher
Department of Food Science, Nutrition and Technology, University of Nairobi
Description
Msc- Thesis