Document Type : Original Article
Author
Department of Food Technology & Dairying, National Research Centre, Dokki, Cairo, Egypt.
Abstract
Sheep milk was used in making of yoghurt by a traditional method in five treatments. Yoghurt was manufactured without ferrous salts (control), the other four treatments of yoghurt were fortified by adding 10 and 20 mg. Ferrous chloride (T1,T2) and 10,20 mg. Ferrous gluconate (T3,T4) / litre of sheep milk. The resultant yoghurt was kept in refrigerator for 7 days and analysed when fresh and after 3,5 and 7 days for T.S% fat%; T.P. %; pH; lactose content; Thiobarbituric acid (T.B.A).; Total volatile fatty acids(T.V.F.A).; acetaldehyde and diacetyl contents. All yoghurt samples were evaluated organoleptically for flavour; consistency and appearance. The obtained results showed that fortification of yoghurt with ferrous (chloride and gluconate) increased T.V.F.A; T.B.A; and diacetyl contents. While decreased pH; lactose % and acetaldehyde content during storage period, on the other hand, ferrous gluconate took the same trend but with more pronounced effect on these properties whether by increasing or decreasing except the T.B.A. content which increased more with adding ferrous chloride. Also, results revealed that, no prounced differences (not significant., P>0.05) were noticed for T.S%; fat % and T.P.% in control and fortified samples either fresh or during storage period. However, clear difference (highly significant P<0.01) for pH; lactose content; T.V.F.A; T.B.A; acetaldehyde and diacetyl contentswere noticed. Sensory evaluation indicated that fortification of yoghurt with iron salt (chloride or gluconate) and storage had no effect on the appearance (not significant P > 0.05) whereas a clear effect was founed in flavour and consisitency (highly significant P<0.01) of the resultant product. Sensory evaluation indicated that adding ferrous gluconate was considered as the most suitable source of iorn supplement with its two ratios. It produced gyoghurt having favourable flavour, acceptable consistency, good appearance and no wheying – off.
Sheep milk was used in making of yoghurt by a traditional method in five treatments. Yoghurt was manufactured without ferrous salts (control), the other four treatments of yoghurt were fortified by adding 10 and 20 mg. Ferrous chloride (T1,T2) and 10,20 mg. Ferrous gluconate (T3,T4) / litre of sheep milk. The resultant yoghurt was kept in refrigerator for 7 days and analysed when fresh and after 3,5 and 7 days for T.S% fat%; T.P. %; pH; lactose content; Thiobarbituric acid (T.B.A).; Total volatile fatty acids(T.V.F.A).; acetaldehyde and diacetyl contents. All yoghurt samples were evaluated organoleptically for flavour; consistency and appearance. The obtained results showed that fortification of yoghurt with ferrous (chloride and gluconate) increased T.V.F.A; T.B.A; and diacetyl contents. While decreased pH; lactose % and acetaldehyde content during storage period, on the other hand, ferrous gluconate took the same trend but with more pronounced effect on these properties whether by increasing or decreasing except the T.B.A. content which increased more with adding ferrous chloride. Also, results revealed that, no prounced differences (not significant., P>0.05) were noticed for T.S%; fat % and T.P.% in control and fortified samples either fresh or during storage period. However, clear difference (highly significant P<0.01) for pH; lactose content; T.V.F.A; T.B.A; acetaldehyde and diacetyl contentswere noticed. Sensory evaluation indicated that fortification of yoghurt with iron salt (chloride or gluconate) and storage had no effect on the appearance (not significant P > 0.05) whereas a clear effect was founed in flavour and consisitency (highly significant P<0.01) of the resultant product. Sensory evaluation indicated that adding ferrous gluconate was considered as the most suitable source of iorn supplement with its two ratios. It produced gyoghurt having favourable flavour, acceptable consistency, good appearance and no wheying – off.
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