Composite Flours-Characteristics of Wheat/Hemp and Wheat/Teff Models ()
1. Introduction
Bakery cereal products represent a basic daily-eaten food, and their role lay in a satiating function. Traditionally, mainly wheat and rye flours undergo fermentation and common rolls and bread are manufactured. Composite flours containing wheat and others cereals and non grain seeds have become popular in the baking technology due to customers’ increasing interest in healthier food. In the last few decades, soy or spelt have been successfully included among common bakery raw materials. Furthermore, new non-traditional ingredients (e.g. amaranth, quinoa, lupine, chickpea, chia, hemp, teff) are receiving intense interest due to their multiple roles in enhancing the rheological properties of dough, overall bread quality and nutritional value [1-5].
Hemp (Cannabis sativa) is planted as two subspecies, namely ssp. culta a ssp. indica. The latter is called hash hemp and belongs to forbidden raw material with respect to intoxicating substances production [6]. Hemp flour composition differs according to used feedstock (dependent on variety and planting locality), means of preparation and defatting. However, protein, fat and starch rates are typically present at 30% - 33%, 7% 13% and approx. 40%, respectively. Approx. two-thirds of hemp proteins is composed by edestin, belonging to low molecular weight globulins. Hemp flour is naturally gluten-free, suitable for celiatics. Hemp also contains a significant level of beta-carotene and vitamins B1 and E. From a mineral contain perspective, benefit could be found in higher portion of iron and zinc [7].
Teff (Eragrostis tef) is classified into the cereal group of Poaceae (Gramineae) family. As was reported in [8], the main producer of teff is Ethiopia with annual production of 1 million tons (20% of local cereals yield). Flat bread injera (ingera) dominates the culinary treatments, and is manufactured from thin fermented dough with a portion of wheat flour. Because of its tiny seeds, the wholemeal flour is characterized by high rate of coating layers and sprout, resulting into higher content of insoluble polysaccharides. Teff proteins have non-gluten nature and owing to prevailing portion of prolamins belong to easily digestible ones. From a nutritional benefit viewpoint, high minerals content is cited (mainly iron, calcium, phosphorus and copper) and B1 vitamin [9].
Nowadays, testing of non-traditional plant materials is one of leading scopes in cereal chemistry, both for contemporary offer of baking product extending and for their nutritional value increasing. The work presented herein was aimed at exploration of wheat/hemp and wheat/teff flour effect on blends composition including dietary fibre content, on technological quality as Solvent Retention Capacity profile and on baking and consumer’s quality of laboratory prepared bread.
2. Materials and Methods
For cereal mixture formatting, wheat flour samples M and M1 originated from harvest 2010 were used as base, and they were blended with two pairs of commercial samples of hemp (K1, K2) and teff (R1 or R2, respectively). Flour samples K2 and R2 differ from fine K1 and R1 ones by their dark colour and composition because of their wholemeal character (a diverse flour form). Model samples were blended in ratios 90:10 or 80:20 (w/w), and samples were named by type and content, e.g. K1.10 or R2.20.
Analysis of the basic analytical composition of wheat flour and tested composites included moisture (MOI), protein amount (PRO) and quality (Zeleny’s sedimentation value, ZET) as amylase activity estimation (Falling Number, FN). For this aim, the Czech standards (ČSN 56 0512, ČSN ISO 1871 “Kjeldahl’s method”, ČSN ISO 5529 and ČSN ISO 3093) were followed. The solvent retention capacity (SRC) profiles were determined according to AACC Norm No. 56-11, including a standard 5 g flour sample and centrifugation by usage the Eppendorf 5702 apparatus (Eppendorf AG, Germany). The water, sucrose, sodium carbonate and lactic acid SRC values measured were abbreviated to WASRC, SUSRC, SCSRC and LASRC, respectively. Hemp and teff supplemented samples were assessed by insoluble, soluble and total dietary fibre contents determination (IDF, SDF and TDF, respectively) by using commercial Megazyme kit (AOAC method 985 29). Baking test was performed according to internal method of ICT Prague [10], examining wheat and composite flour water absorption and a final product characteristics (specific bread volume “SBV”, bread shape “BRS” as height-to-diameter ratio, sensorial profile “SEN” and crumb firmness as a penetration rate “PEN”). Sensorial quality was described by 9-point score, including attributes from overall appearance to crumb chewiness and flavour, with limits of 9 and 27 point for the best and unacceptable bread consumer’s quality, respectively. For the latter test, the penetrometer PNR 10 (Petrotest, Germany) was employed. Determined repeatability as variation coefficients for the SVB and PEN are 7.1% and 9.8% [11].
For statistical analysis, Statistica 7.1 software (Statsoft Inc., USA) was employed. ANOVA of flour type and addition factors was performed for hemp and teff flour model composites separately owing to both difference in wheat flour M and M1 quality (of group standards, respectively) and with respect to reversal influence of the tested non-traditional crops. Combining all gained data, a linear correlation matrix was calculated. The mentioned methods were evaluated on likelihood level 95% (p < 0.05).
3. Results and Discussion
3.1. Hemp and Teff Effect on Analytical Composition
Pure wheat samples M and M1 were characterised by good baking quality (PRO 12.4% and 13.2%; ZET 41 mL and 41 mL, respectively; Figure 1), suitable for partial replacement by non-gluten material. Furthermore, a difference between their amylase activity estimations (FN 336 s and 284 s, respectively; Tables 1(a) and (b)) was insignificant with respect to measurement accuracy.
Both hemp and teff flour lowered flour moisture content depending on the additive used (Tables 1(a) and (b)), with a maximal decrease of 0.8%. Comparing hemp and teff mixtures, MOI levels were subordinated to value determined for basic flour M or M1, and in both groups impacts of alternative flour type or addition were statistically improvable. Protein properties changed in content and quality reversely, with higher impact of alternative flour type then addition level. Figure 1 documents a softer increase of PRO in case of teff addition (about 1.1 units for R2 composites) compared to approx. four-time higher change observed for K1.20 composite. Opposite to that, teff flour protein was not as dispersed in the wheat gluten structures as ZET values decreased to 30
Figure 1. Hemp and teff influence on protein content (PRO) and quality as Zeleny value (ZET). M, M1—wheat flour (standards); K1, K2—hemp flour; R1, R2—teff flour.
vs. 32 mL and to 22 vs. 23 mL for blends with 10% and 20% of R1 and R2, respectively. For corresponding hemp composites, calculated descents were 9 vs. 16 mL and 14 vs. 27 mL, respectively, i.e. observed change was governed by tested hemp flour type. All the results correspond to plant’s botanical classification, e.g. teff be-
Table 1. Influence of non-traditional flour and addition on analytical features of wheat flour.
longs in the same family as wheat, thus partially similar protein fractions categorisation in flour from both species was indirectly confirmed. On the other hand, neither hemp nor teff flour was affected enzymatic activity as the slightly decreasing and increasing FN values, respectively, were not statistically different and practically verifiable (Tables 1(a) and (b)).
Analytical data of wheat flour and its composites with 10 and 20% of teff flour was published recently [12]. For wheat flour as control, contents of crude protein and DF were 10.5% and 4.1%, respectively. Both teff additions increased both parameters (to 10.6% and 10.9% for crude protein and to 4.2% and 4.3% for DF, respectively), but those changes were statistically insignificant.
3.2. Hemp and Teff Effect on SRC Profiles
The overall holding capacity of all network-forming flour constituents, level of damaged starch, pentosans and gliadins characteristic as well as glutenin characteristics were accounted for via SRC test [13,14]. Table 2(a) presents the results of the SRC test for M and hemp composites. In this regard, the quality of used wheat standards differed mainly in SCSRC and LASRC, i.e. in starch and glutenin physical stages, respectively. All four SRC’s were affected by the hemp type at a higher rate than by wheat flour replacement level. The water, sucrose or sodium carbonate retention profile of the standard M was not seriously affected by the hemp flour K1 polysaccharides composition (a decrease between 4% - 17%). Considering lower molecular weight fraction prevailing in hemp proteins, the LASRC descent from 182.5
Table 2. Influence of non-traditional flour and addition on solvent retention capacity profile of wheat flour.
units to 128.8 and 112.1 units (about 30% and 40%) at K1.10 and K1.20 testing is understandable. Coating particles present in model K2 blends (wholemeal hemp flour form) are constituted of cellulose and hemi-celluloses, whose influence was identified through complete SRC profile of fortified M. Determined values of WASRC and SCSRC fell verifiably to 75% and 66% of the standard values, respectively. In wholemeal K2 composites, total pentosan and gliadin rates were lower compared to the K1 samples. The SUSRC values of composites with 10 and 20% of K2 hemp flour were lower and differed in a higher rate (90.2% and 74.3%, respectively. Finally, the LASRC course of K2 mixtures was similar to K1 ones, and gluten dilution reached a higher extent. Absorption of lactic acid solution dropped to 90.8 and 77.2 units for K2.10 and K2.20, respectively, representing 50 and 40% of value determined for M.
During testing of the two teff flour variants, when solvent retention was kept at levels comparable to wheat flour M1, even a little increase of the SCSRC was found (from 3 to 8 units; Table 2(b)). Between model composites containing 10% and 20% of teff flour, a difference circa 15 units of the SUSRC was calculated for both bright R1 and dark R2 types. The small negative change is therefore a result of teff flour type and addition level interaction. Composites behaviour in presence of lactic acid was unexpectedly different compared to diminishing of ZET values ad both substitution rates. By 10% of teff flour, LASRC’s increased about 30% and 55% (to 126.7 and 151.6 units for R1 and R2 blends, respectively, against 97.6 units for M1), and consecutively fell to 115.6 and 120.9 units (for R1.20 and R2.20 samples; Table 2(b)). Summarised, teff flour type affected the SRC profiles somewhat stronger than addition level, but both factors were not identified as statistically significant.
3.3. Hemp and Teff Effect on Dietary Fibre (DF) Content
According to current research, hemp and teff seed (and similarly wholemeal flour) was characterised by crude fibre content of approx. 25% - 30% [15] and 3% - 7% [16]. In a dehulled stage and consecutively milled flour, fibre content was partially lowered, but the difference between the tested flour types was maintained. Ranges of DF content were 2.08% - 3.44%, 1.02% - 1.86% and 3.21% - 5.25% for its insoluble, soluble and total constituents, respectively. The lowest contents were assessed in M and M1 standard, i.e. addition of hemp or teff flour unequivocally meant nutritional improvement of that basic bakery raw material.
Figure 2 shows that wheat flour enhancing effect was about 33% higher for hemp composites compared to teff ones (e.g. 3.44% and 2.60% of IDF for 80/20 composites,