Glycoprotein Fortification of Bioyoghurt

摘要

Bioyoghurt fortification with healthy valuable milk glycoproteins (GP), whether lactoferrin (LF) or glycomacropeptide (GMP), in relation to its numerous attributes beyond its probiotic benefits was aimed to study. Yoghurt milk was supplemented with GP whether being LF or GMP at a level of nil, 0.025, 0.050 or 0.100 %. Thereafter, milk was heat treated to 85℃ for 5 min followed by temperature adjustment to 42℃. Then, milk was inoculated with 2% of freshly activated ABT-2 bioyoghurt bacterial starter culture, and incubated at 42℃ until complete coagulation (through about 3 hr.). Thereafter, products were kept at the refrigerator temperature (5±1℃). For the biological study, bioyoghurt was fed in the dried form. The obtained results indicated that, GP-fortified bioyoghurts were significantly distinguished with increased values of dry matter, protein, ash, pH, acetaldehyde, Str. thermophilus. Lb. acidophilus, Bifidobacterium sp., consistency coefficient (K), yield stress (YS), apparent viscosity (ηa), and sensory attributes versus unfortified ones. The best fortifier GP was mostly LF and the best level was 0.025%. Prolonging cold storage period of all samples for 3 weeks was associated with increasing values of titratable acidity. K, YS, ηa and panelist consistency score; and decreasing the values of other properties. Biologically, the consumption of GP-fortified bioyoghurts reduced White Blood Cells count (WBC), Hemoglobin (HB), Haematocrit (HCT), Mean corpuscular volume (MCV), Mean corpuscular Hemoglobin (MCH), Mean corpuscular hemoglobin concentration (MCHC) and platelet count (PLT) and did not affect the Red Blood Cells count (RBC). Moreover, the rats fed on LF fortified products possessed lower WBC and higher PLT, MWC, MCH and MCHC versus those fed on GMP fortified products. While, all of RBC, HB and HCT were not affected by the type of GP. The GP fortification whether of milk or bioyoghurt resulted significantly in improvement of the micronutrient bioavailabilily by heightening the levels of all parameters measured namely total protein (TP), albumin (Alb), globulin (Glb), Ca, P, Mg, Na, Fe, Cu, Mn and Zn of blood serum of rats fed thereon. LF versus GMP caused significant increment in the levels of TP, Alb, Ca, P, Mg, Fe, Mn and Zn while both of Glb and Cu levels did not significantly exhibit any significant differences. The usage of ABT-2 in fermentation of GP fortified milk led to an increase in the levels of TP, Alb, Glb, Fe and Cu; and led to decreased levels of Ca, P, Mg, Mn and Zn of blood serum of rats, thereon were fed. The counts of Str. thermophilus , Lb. delbrueckii ssp. bulgaricus, Lb.acidophilus and Bifidobacterium sp were higher in rats feces when GP and rather LF fortified products (milk and especially bioyoghurt) was fed, while the count of Escherichia coli was declined. The foregoing results led to conclude that, yoghurt beyond its ability to be probiotic food via its culturing with the gut strains, it could further carry more healthy benefits when it was fortified either with LF or GMP at any level up to 0.1%, preferring, bacteriologically, the level of fortification to be 0.025%. The biological results induce to suggest that, the carbohydratic parts bound to such glycoproteins, may act as prebiotics in the intestinal and colon.