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|Title: ||Production of fish powder by acid hydrolysis.|
|Authors: ||Ssali, William M.|
|Issue Date: ||1984|
|Publisher: ||© W.M. Ssali|
|Abstract: ||HapLochromis spp. is an underutilized fish stock abundant in L.
Victoria and occurring in many African lakes. Its small size and
boniness make it unpopular as human food.
A process for producing fish powder for human consumption from whole
HapLochromis by partial acid hydrolysis was developed. Whole fish
was minced and mixed with hydrochloric acid in the ratio. 30:100 v/wo
The mixture was continuously stirred for 30 minutes, neutralised with
NaOH to the original pH of the mince, homogenized and drum dried or
spray dried. The effect of varying temperature, acid concentration
and using cooked or uncooked fish as raw material on hydrolysis were
investigated by determining changes in TCA-soluble N of the hydrolysate
over the 30 minute period. Seven temperatures between 25 and 84cC
and four acid concentrations (2.5M, 5M, 7.5M and 1l.3M) were investigated.
The overall extent of hydro lysis for each run was determined by
calculating the nett increase in TCA-soluble N expressed as % of total
N, and it ranged between 0.8% and 10.4% and 6.7% and 34.1% for cooked
and uncooked fish respectively. The extent of hydrolysis was greater
in uncooked than cooked fish due to the synergistic effect of the
endogenous proteolytic enzymes in uncooked fish and its absence in
cooked fish. Cooking had destroyed the enzymes.
Eight different products were produced. Data for crude protein, true
protein, amino acid profiles, total lipid, ash, NaCl, aw, in vitro
digestibility, colour, particle size distribution and sensory evaluation
of the products were obtained. The data indicated the products
had a high nutritional value and would be micrcbiologically stable for
several months but susceptible to oxidative rancidity unless antioxidant
were added. Using the data a process in which uncooked fish would
be partially hydrolysed with 2.5M HCl at 48oC (approximately) for
30 minutes and the hydrolysate spray dried was proposed|
|Description: ||A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Chemical Engineering)|
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