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How does the preparation of rye porridge affect molecular weight distribution of extractable dietary fibers?

Rakha A, Aman P, Andersson R - Int J Mol Sci (2011)

Bottom Line: However, incubation of the rye flour slurries at increased temperature resulted in a significant decrease in extractable AX molecular weight.The molecular weight of extractable β-glucan decreased greatly during a rest time before cooking, most likely by the action of endogenous enzymes.The amount of salt and flour used in the recipe had small but significant effects on the molecular weight of β-glucan.

View Article: PubMed Central - PubMed

Affiliation: Department of Food Science, Swedish University of Agricultural Sciences, Box, 7051, S-75007 Uppsala, Sweden; E-Mails: Per.Aman@slu.se (P.A.); Roger.Andersson@slu.se (R.A.).

ABSTRACT
Extractable dietary fiber (DF) plays an important role in nutrition. This study on porridge making with whole grain rye investigated the effect of rest time of flour slurries at room temperature before cooking and amount of flour and salt in the recipe on the content of DF components and molecular weight distribution of extractable fructan, mixed linkage (1→3)(1→4)-β-d-glucan (β-glucan) and arabinoxylan (AX) in the porridge. The content of total DF was increased (from about 20% to 23% of dry matter) during porridge making due to formation of insoluble resistant starch. A small but significant increase in the extractability of β-glucan (P = 0.016) and AX (P = 0.002) due to rest time was also noted. The molecular weight of extractable fructan and AX remained stable during porridge making. However, incubation of the rye flour slurries at increased temperature resulted in a significant decrease in extractable AX molecular weight. The molecular weight of extractable β-glucan decreased greatly during a rest time before cooking, most likely by the action of endogenous enzymes. The amount of salt and flour used in the recipe had small but significant effects on the molecular weight of β-glucan. These results show that whole grain rye porridge made without a rest time before cooking contains extractable DF components maintaining high molecular weights. High molecular weight is most likely of nutritional importance.

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Related in: MedlinePlus

Molecular weight distribution of arabinoxylan in flour (——) and in porridges rested for 0 min (_ _ _ _) and 60 min (-------) before cooking.
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f4-ijms-12-03381: Molecular weight distribution of arabinoxylan in flour (——) and in porridges rested for 0 min (_ _ _ _) and 60 min (-------) before cooking.

Mentions: Weight average molecular weight (Mw) and number average molecular weight (Mn) of extractable arabinoxylan were not significantly influenced by the amount of salt and flour in the recipe or the rest time during porridge making. This indicates the stability of arabinoxylan molecules during resting at 20 °C for 1 h and cooking of wholegrain rye porridge, as revealed by the molecular weight distribution profiles (Figure 4). The Mw of AX in flour extract (12 × 105 g mol−1) was slightly lower than in extracts of porridges (on average 14 × 105 g mol−1) probably due to an increased extractability of high molecular weight fractions in porridge. Sub-optimal temperature (20 °C) and pH (6.2) during incubation were assumed to be responsible for non-existent activity of endogenous xylanases during the rest time. To test these hypotheses, rye flour slurries were incubated in an oven for 1 h at variable temperatures (20, 35, 45, 55 °C) and pH values (4.5 or 6.2) as described in experiment 2 of experimental section. The results from this investigation showed a significant decrease (P = 0.012) in AX Mw as a result of increasing temperature, confirming our assumption about sub-optimal temperature during incubation being one possible reason for AX molecular weight stability (Figure 5). The optimum temperature for major rye AX-degrading enzymes, i.e., endo-(1→4)-β-d-xylanase (EC 3.2.1.8), α-l-arabinosidase (EC 3.2.1.55), and β-d-xylosidase (EC 3.2.1.37), has been reported to be 40 °C, 60 °C and 70 °C, respectively, and the optimum pH around 4.5 [18]. However, the effect of pH on AX Mw was non-significant (P > 0.05, Figure 5).


How does the preparation of rye porridge affect molecular weight distribution of extractable dietary fibers?

Rakha A, Aman P, Andersson R - Int J Mol Sci (2011)

Molecular weight distribution of arabinoxylan in flour (——) and in porridges rested for 0 min (_ _ _ _) and 60 min (-------) before cooking.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3116197&req=5

f4-ijms-12-03381: Molecular weight distribution of arabinoxylan in flour (——) and in porridges rested for 0 min (_ _ _ _) and 60 min (-------) before cooking.
Mentions: Weight average molecular weight (Mw) and number average molecular weight (Mn) of extractable arabinoxylan were not significantly influenced by the amount of salt and flour in the recipe or the rest time during porridge making. This indicates the stability of arabinoxylan molecules during resting at 20 °C for 1 h and cooking of wholegrain rye porridge, as revealed by the molecular weight distribution profiles (Figure 4). The Mw of AX in flour extract (12 × 105 g mol−1) was slightly lower than in extracts of porridges (on average 14 × 105 g mol−1) probably due to an increased extractability of high molecular weight fractions in porridge. Sub-optimal temperature (20 °C) and pH (6.2) during incubation were assumed to be responsible for non-existent activity of endogenous xylanases during the rest time. To test these hypotheses, rye flour slurries were incubated in an oven for 1 h at variable temperatures (20, 35, 45, 55 °C) and pH values (4.5 or 6.2) as described in experiment 2 of experimental section. The results from this investigation showed a significant decrease (P = 0.012) in AX Mw as a result of increasing temperature, confirming our assumption about sub-optimal temperature during incubation being one possible reason for AX molecular weight stability (Figure 5). The optimum temperature for major rye AX-degrading enzymes, i.e., endo-(1→4)-β-d-xylanase (EC 3.2.1.8), α-l-arabinosidase (EC 3.2.1.55), and β-d-xylosidase (EC 3.2.1.37), has been reported to be 40 °C, 60 °C and 70 °C, respectively, and the optimum pH around 4.5 [18]. However, the effect of pH on AX Mw was non-significant (P > 0.05, Figure 5).

Bottom Line: However, incubation of the rye flour slurries at increased temperature resulted in a significant decrease in extractable AX molecular weight.The molecular weight of extractable β-glucan decreased greatly during a rest time before cooking, most likely by the action of endogenous enzymes.The amount of salt and flour used in the recipe had small but significant effects on the molecular weight of β-glucan.

View Article: PubMed Central - PubMed

Affiliation: Department of Food Science, Swedish University of Agricultural Sciences, Box, 7051, S-75007 Uppsala, Sweden; E-Mails: Per.Aman@slu.se (P.A.); Roger.Andersson@slu.se (R.A.).

ABSTRACT
Extractable dietary fiber (DF) plays an important role in nutrition. This study on porridge making with whole grain rye investigated the effect of rest time of flour slurries at room temperature before cooking and amount of flour and salt in the recipe on the content of DF components and molecular weight distribution of extractable fructan, mixed linkage (1→3)(1→4)-β-d-glucan (β-glucan) and arabinoxylan (AX) in the porridge. The content of total DF was increased (from about 20% to 23% of dry matter) during porridge making due to formation of insoluble resistant starch. A small but significant increase in the extractability of β-glucan (P = 0.016) and AX (P = 0.002) due to rest time was also noted. The molecular weight of extractable fructan and AX remained stable during porridge making. However, incubation of the rye flour slurries at increased temperature resulted in a significant decrease in extractable AX molecular weight. The molecular weight of extractable β-glucan decreased greatly during a rest time before cooking, most likely by the action of endogenous enzymes. The amount of salt and flour used in the recipe had small but significant effects on the molecular weight of β-glucan. These results show that whole grain rye porridge made without a rest time before cooking contains extractable DF components maintaining high molecular weights. High molecular weight is most likely of nutritional importance.

Show MeSH
Related in: MedlinePlus