FUNCTIONAL PROPERTIES OF GOAT AND
BUFFALO
د. محمود ابرهيم باحث بمعهد بحوث تكنولوجيا الاغذية
ملخص رسالة الماجستير ( جامعة الاسكندرية )
SUMMARY AND CONCLUSIONS
The physicochemical properties of food proteins
affect their functional properties of the food as texture, colour, flavour,
water binding and stability. Probably the most important physicochemical
properties are solubility, hydration, rheology, surface activity and gelation. Milk proteins, either caseins or whey
proteins, due to their heterogeneity, range of physical properties and
amphipolar characteristics, were used in food processing for multiple functions.
Most of research was focused on bovine milk
proteins due to the dominance of such type of milk all over the world. However,
little attentions were directed to evaluate the functional properties of
non-bovine milk proteins.Therefore, this study was conducted to study different
functional properties of both goat and buffalo milk proteins in order to gain
some knowledge to evaluate these proteins for further application in food industry.
To achieve such goals, various caseins (HCl, lactic, rennet) and casein-
coprecipitate preparations were prepared by different methods. Meanwhile, the
effect of some factors as concentration of protein, pH of the medium, trypsin
treatment on functional properties of prepared proteins was studied. The
obtained results revealed the following:
- Goat
milk proteins have higher significant (P≤ 0.05) degree of
solubility than those of buffalo milk.
- The
solubility of both goat and buffalo milk proteins was protein concentration
and pH dependent, i.e. the higher the concentration and pH value, the
higher the solubility.
- Goat
and buffalo HCl-casein showed the highest solubility at pH 8 followed by
lactic casein then rennet casein. But casein co-precipitate was
characterization by very low solubility at all pH values comparing to the
other caseins.
- The
emulsifying capacity (EC) of goat and buffalo caseins was concentration
and pH dependent, i.e, the higher the concentration and pH value, the
higher the EC.
- Goat
HCl-casein showed the highest EC at pH 8 and there was no significant (p≤
0.05) change between lactic casein and rennet casein. But casein
co-precipitate was characterization by very low EC at all pH values
comparing to the other caseins.
- Buffalo
lactic -casein showed the highest EC at pH 8 followed by HCl-casein, and
then casein co-precipitate. But rennet casein was characterization by very
low EC at all pH values comparing to the other caseins.
- Goat
milk proteins (HCl- , lactic -, rennet casein and casein co-precipitate ) have higher significant (P ≤
0.05) degree of EC than those of buffalo milk at all concentrations and pH
values.
- The
viscosity of different goat and buffalo milk casein preparations as
affected by concentrations. The viscosity of all casein preparations was
significantly increased by
concentration increase. Meanwhile the two types of goat and buffalo milk
casein preparations were not affected by the increase of pH from 7 to 8.
- Goat milk casein coprecipitate is the
proper preparation for the food application in order to obtain high
viscous mixture followed by lactic casein. The viscosity of all
goat milk casein preparations except rennet casein was pH independent.
- At
all pH values, the ascending order of
viscosity of goat and buffalo proteins was HCl-casein, rennet casein, lactic
casein and casein coprecipitate.
- Over
all results revealed that goat milk rennet casein and casein coprecipitate
have significantly (p≤0.05) higher viscosity values than those of
buffalo milk caseins but there were no significant differences between
lactic casein and HCl-casein of both types of milk. Both types of casein
preparations are similar in that HCl-casein had the lowest viscosity,
while casein co-precipitate had the highest viscosity value.
- The
foaming capacity FC and foam expanded FE of goat and buffalo HCl-casein
increased with the concentration increase. Meanwhile the FC and FE of
buffalo HCl-casein were higher significant than that of goat HCl-casein at
all concentrations and pH value.
- The highest foam volume of buffalo
HCl-casein was obtained at pH 7.0 for all casein concentrations. On the
other side the highest FC of goat HCl-casein was obtained at pH 7.5.
- The foam volume stability FVS of buffalo
HCl-casein was higher than that of goat casein. The higher FVS was found at buffalo HCl-casein,
concentration 1.00% and pH 8.0.
- The FC and FE of goat and buffalo lactic
casein were increased with the concentration increase at all pH value. The
FC, FE and FVS of buffalo lactic-casein were higher than that of goat
casein. The higher FVS was found at
buffalo lactic casein, at pH 7.0 and concentration 1.00%.
- The FC and FE of goat and buffalo rennet
casein were increase with the concentration increase at all pH values. The
FC, FE and FVS of buffalo casein were higher than that of goat casein.
- The behaviour of buffalo rennet casein
is different than that of goat rennet casein because the best foam
stability of the former casein can be obtained at higher pH value and
concentration than the latter casein.
- The behaviour of goat and buffalo casein
co-precipitate CCP is similar, the foam capacity of buffalo CCP is better
than that of goat milk at higher concentrations and pH values.
- The
obtained results revealed that the
FVS of goat casein co-precipitate is higher than that of buffalo at both pH 7.5 and 8.0.
- The
solubility of both goat and buffalo milk HCl-casein was significantly (p
≤ 0.05) increased then decreased by trypsin treatment for 5and 15 min,
respectively.
- The
solubility of native and trypsin treated goat milk HCl-casein, lactic
casein and casein co-precipitate was significantly higher than these of
buffalo milk.
- Trypsin hydrolysis at pH 7.0 for 5 min
enhances the EC of goat HCl-casein and lactic casein as well as buffalo
lactic casein and no HCl-casein. But the EC of casein co-precipitate of
goat and buffalo milk is retarded by the same treatment under the same
conditions.
- The
behaviour of HCl-casein of buffalo milk is different than any other casein
preparations whether buffalo or goat milk. Meanwhile, the tryptic products
of most of casein preparations in both goat and buffalo milk have lower
viscosity than native proteins.
- Trypsin treatment for 5 min of both
types of casein resulted a significant increase in foam volume; followed
by another significant increase after 15 min. the FC of buffalo HCl- and
lactic casein hydrolysate was higher than that of goat casein.
- The behaviour of foam stability of goat
milk HCl-casein is completely different than that of buffalo milk, since
the tryptic treatment enhanced the foam stability of the former but
reduced that of the latter.
- Trypsin treatment for 5 min of both
types of casein resulted a significant increase in foam volume, followed
by another significant increase after 15 min. The rate of foam volume increase
was significantly higher in case of buffalo lactic casein than
that of goat milk.
- The
behaviour of foam stability of goat milk lactic casein is completely
different than that of buffalo milk, since the tryptic treatment enhanced
the foam stability of the former but reduced that of the latter.
- After trypsin treatment for 5 min of
both types of casein co-precipitate have a significant increase in foam
volume, followed by another significant increase after 15 min in case of
goat but there was no significant change in case of buffalo milk casein
co-precipitate.
- The
trypsin treatment had no effect on FVS of goat and buffalo casein co-precipitate.
- Results showed also that goat and
buffalo milk casein preparations were completely different in their
electrophoretic behaviors due to the differences in charges and molecular
weights. B) The behaviour of goat and buffalo milk casein preparations
towards trypsin hydrolysis was entirely different. Since, buffalo lactic
casein and casein coprecipitate were higher in proteolysis by trypsin than
those of goat proteins, while goat HCl-casein has the opposite behaviour.
Conclusions
- Goat and buffalo milk protein preparations
are highly different in their functional properties.
- All goat milk protein preparations are
characterized by their higher solubility, emulsifying capacity than
buffalo milk proteins, therefore they can be used in food application as
beverages, baking, candy, soups, sausage and ice cream making.
- To improve the functional properties of
either goat and buffalo milk protein preparations, trypsin treatment for 5
min is recommended.
