Page 50 - New additives and ingredients in the formulation of aquafeeds

(Pereira and Oliva-Teles, 2003). In turbot, however, the inclusion of corn
gluten meal causes a decreased of the total protein digestibility as well as
somne amino acids as leucine, decreasing from 94% to 68% when the fish
meal is totally replaced by corn gluten meal (Regost, 1999). It is important
to know that most of these experiments have been carried out in stages
with fish juveniles which have an efficient and fully developed digestive
system in contrast to the larval stage which does not present a functional
stomach and hence the protein digestion may vary according to the source
from which comes the protein and the process that the ingredients have
suffered during the manufacture of the food (Garcia, 2000). In this way, the
protein isolates could present a major disadvantage as the low digestibility
since they are composed by intact proteins with high molecular weights
and aggregations in some cases. That is why these protein isolates are the
ideal substrate for the production of plant protein hydrolysates which have
a higher digestibility than the intact starting proteins.
Table 1. Chemical characterization of meals, protein isolates and hydrolysates from chickpea and
lupin
Chickpea
Meal
Chickpea
Isolate
Chickpea
Hydrolysate Lupin Meal Lupin
Isolate
Lupin
Hydrolysate
Protein 26.2 ± 3.1 74.98 ± 0.12 62.65 ± 0.83 33.8 ± 6.9 85.17 ± 0.75 68.94 ± 0.05
Ash 2.8 ± 0.3 2.71 ± 0.04 8.21 ± 0.05 2.1 ± 0.1 2.39 ± 0.07 8.78 ± 0.05
Moisture 8.9 ± 1.6 1.54 ± 0.19 3.82 ± 0.06 7.9 ± 0.6 0.54 ± 0.20 4.00 ± 0 05
Fat 4.7 ± 1.1 14.94 ± 0.04 14.28 ± 0.20 13.6 ± 2.0 11.04 ± 0.18 8.62 ± 0.23
FIber 10.7 ± 2.0 1.65 ± 0.25 2.40 ± 0.54 39.9 ± 6.1 0.25 ± 0.20 2.59 ± 0.33
Soluble Sugars 1.9 ± 0.6 0.49 ± 0.01 0.28 ± 0.01 2.7 ± 0.1 1.42 ± 0.10 0.14 ± 0.01
Polyphenols 0.1 ± 0.0 0.03 ± 0.01 0.20 ± 0.01 0.1 ± 0.0 0.27 ± 0.01 0.04 ± 0.01
D.H. ------- ------- 44.26 ± 0.32 ------ ------ 40.42 ± 0.79
FAA <0.01 <0.01 14.65±0.21 <0.01 0.09±0.01 14.31±0.52
Results are expressed in percentage as mean ± standard deviation of three different determinations
D.H.: Degree of hydrolysis
FAA: Free amino acids
Based on the characterization of different plant protein products (meal,
isolates and hydrolysates), protein enrichment and the decreased in non-
protein components of protein isolates and hydrolysates are the biggest
differences comparing with the starting meal (Table 1). The fat content is
also higher than the starting raw materials. Firstly, this is because there is
no a process of extraction of the oil phase of the meal trying not to increase
the global operational costs by adding a defatting process, especially
when the percentages of fat given in the chickpea and lupin meal are not
a factor too limiting to solubilize and purify the protein fraction. Secondly,
a significant proportion of fat, during the alkaline solubilization and
subsequent precipitation of proteins at their isoelectric point for obtaining
48 Plant protein isolates and hydrolysates as alternative to the animal protein in aquaculture diets