Cassava Fermentation and Associated Changes in Physicochemical and Functional Properties

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VI. Functional Properties

Functional properties of starch extracted from fermented tubers and that were subjected to fermentation are invariably modified by fermentation. Baking tests using sweet, fermented (29 to 30 d) and acid-treated starches showed that fermented sour starch provided a baked product with excellent volume, alveolar loose crumb structure, and a thin crispy crust (Table 33).^74,101 The acid treated starch did not produce such an effect. The results indicate that in addition to the modification brought about by acids, the enzymes also play a role offering certain properties that can impart typical and acceptable quality to the baked products. The effect of fermentation on the dough characteristics have been investigated.¹⁰⁷ Cereda has carried out a number of studies on the functional properties of fermented starch in Brazil.

The textural properties of starch gels from naturally fermented and inoculum provided fermented starches are compared in Table 34⁶⁷. The results showed that tha hardness, gumminess, cohesiveness, and elasticity of flour gels were reduced in fermented products. Gel hardness and gumminess have been associated both to the degree of granule swelling and net work formation by leached amylase. A reduction in cohesiveness of fermented products has been explained as due to failure of starch granules to release sufficient amylase. The improvement in textural quality has also been attributed to production of organic acids that complex with the soluble amylosse portion.⁷²

The functional properties of two samples of fermented starch from Parana and Sao Paulo in Brazil were compared,₉₅ and it was found that the fermented starch with higher biscuit volume showed the greatest variation under baking conditions. This starch sample possessed a higher fiber content, lower ash content, and higher acidity as well as lower Brabender viscosity with higher retrogradation power, less water absorption, and consequently lower biscuit yield. The only different between the biscuits made with the

Two samples were yield and volume because the biscuit had similar appearance and chemical composition. Based on the results, methods for production of salty and sweet biscuits using commercial fermented starch have been proposed.¹⁰⁰

Tests carried out in our laboratory indicated that bread prepared by 40% fermented sour flour was almost as acceptable as wheat bread.⁴³ The fermentation time influenced many products, including confectionery and bakery items that were found to be quite acceptable (Figure 14). It has already been mentioned that many of the starch granules from fermented tuber are sticking together under scanning electron microscopy.44 It is possible that the agglomeration of these granules retain the CO₂ released during fermentation and allow the dough to puff up during baking. Studies on the functional properties of sour cassava starch Polvilho Azedo revealed that the chemical composition was not significantly modified by the fermentation step, whereas the granular structure was similar to that resulting from short period of mild acid treatment.₄₀ The released CO₂ lactic acid, and propionic acid during the fermentation step of sour cassava production were assumed to have adsorbed to the granular starches, and their desorption suring cooking would be an additional driving force for the expansion of the resultant product. It was further opined that water vaporization might also perform the same role.

Table 32 : Solubility (% of Total Starch), Water-Imbibing Capacity (g ger/g Dried Sample) and Apparent Viscosity of Fermented and Nonfermented Cassava Starches

	250C		1000C		Viscosity
Sample	Imbibition	Solubility	Imbibition	Solubility	(mPa-sec)app
Sweet starch from colombia	2.23 ± 0.04	0.14 ± 0.01	28.25 ± 0.07	12 ± 2	105 ± 2
Fermented starch from (1 d)	2.41 ± 0.04	0.36 ± 0.11	36.6 ± 0.3	12 ± 2	57 ± 4
Fermented starch (5 d)	2.34 ± 0.12	0.21 ± 0.03	32.1 ± 0.9	46 ± 3	31 ± 3
Sweet starch from Brazil	2.29 ± 0.06	0.20 ± 0.02	37.7 ± 1.8	17 ± 3	154 ± 8
Fermented starch (3 d)	2.13 ± 0.03	0.36 ± 0.05	37.0 ± 1.3	14 ± 4	140 ± 4
Fermented starch (20 d)	2.33 ± 0.07	0.11 ± 0.01	36.1 ± 1.2	50 ± 2	40 ± 4

Source: Petrucelli.⁵⁹

The digestibility of starch subjected to fermentation was not found to be affected by fermentation.⁸⁰ However, during garification, the digestibility was enhanced, probably due to the effect of heat.