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Journal of Food Science and Technology logoLink to Journal of Food Science and Technology
. 2021 Aug 18;59(6):2220–2230. doi: 10.1007/s13197-021-05235-w

Low carbohydrate high fat flour: its rheology, bread making, physico-sensory and staling characteristics

Smruthi Rao 1,2, K Ashwath Kumar 1,✉, D Indrani 1
PMCID: PMC9114241  PMID: 35602456

Abstract

A low carbohydrate and high fat (LCHF) flour was developed by combining almond flour, desiccated coconut flour, defatted soya flour, dry gluten powder, psyllium husk and skimmed milk powder. Determination of rheological, bread making, nutritional, and staling characteristics of LCHF flour in comparison with wheat flour (WF) was studied. The results showed that LCHF flour had lower amylograph pasting temperature (31.6 °C), peak viscosity (200 BU), farinograph dough stability (0.8 min), and bread volume (315 ml) compared to WF (61.0 °C; 782 BU; 8.7 min; and 525 ml) respectively. The use of additive mixes such as fungal alpha-amylase, sodium stearoyl-2-lactylate and xanthan gum, improved the volume and texture of the LCHF bread. Scanning electron microscope images showed little or no presence of starch granules in LCHF dough and bread. Differential scanning calorimetry studies indicated that, during storage (1–5 days), the enthalpy for gelatinization of endotherm starch increased (0.71–3.40 j/g) in WF bread, however, in LCHF bread this increase was lesser (0.53 to 2.2 j/g) indicating slower staling rate in LCHF bread. The LCHF bread showed lower carbohydrate (13.7%), in-vitro starch digestibility (17.3%) and staling rate, higher protein (22.51%), fat (11.01%), and medium-chain fatty acids than WF bread (51.9%; 38.2%; 12.57%; 3.78%) respectively. The results showed that the developed product would be beneficial for people suffering from diabetics and obesity.

Keywords: Low carbohydrate high fat (LCHF) flour, Coconut flour, Rheology, Bread, Storage study, Differential scanning calorimetry (DSC)

Introduction

The bread and other bakery products are generally prepared using refined wheat flour (WF) as a basic raw material, which is high in carbohydrate, low in fat, protein and dietary fibre. Consuming refined carbohydrates along with changing lifestyle habits, has been associated with increased occurrence of lifestyle diseases such as diabetes, obesity, irritable bowel syndrome etc. (Rahaie et al. 2014). This has motivated the researchers to explore low carbohydrate, high fat, protein or fibre ingredients to formulate processed foods with superior shelf life, satisfying taste. Hence, recently speciality products such as low GI, low carbohydrate, paleo and ketogenic bread are being manufactured commercially.

Diet can be stated as a specific variety of foods, usually prescribed for treatment of a disease or to increase/lose weight. In the recent years, the following diets have been highly popular: (a) Atkins diet: It is a diet that focuses on controlling insulin level in our body by consuming low carbohydrates, high protein and fat. (b) Zone diet: The main goal of the zone is to achieve a dietary balance of 40% carbohydrates, 30% fat and 30% protein in each mealtime. (c) Ketogenic diet: It includes the reduction of carbohydrate intake to less than 10% and increase the intake of healthy fats. This diet permits the body to burn fat as a fuel, rather than carbohydrates (Noakes et al. 2017). (d) Vegan diet: It is a diet in which a person does not consume any animals or animal-based products such as dairy and honey. (e) Mediterranean diet: It is Southern European diet that mainly emphases on plant foods, a moderate amount of poultry and fish, small amounts of red meat and wine. Among different diets, the low carbohydrate, high fat diet is gaining a lot of importance. The Low Carbohydrate, High Fat (LCHF) diet is defined as the diet which limits the carbohydrate consumption to 130 g/day. Studies have shown that LCHF diet help in the reduction of body fat up to 1.3% as compared to LFHC diet (Low Fat, High Carbohydrate) (Noakes et al. 2017). As per reports by Westman et al. (2008) the LCHF diet helped in increasing the HDL levels in blood and patients suffering from type 2 diabetes were able to reduce or terminate their diabetic medicine.

The almond (Prunus dulcis) flour is known for its excellent nutritional value, with the majority being unsaturated fatty acids, essential amino acids viz. lysine, methionine and threonine (Li et al. 2016). Coconut flour contains 29.30% fat, 5.77% protein and 19.82% fibre (Dat et al. 2018) and it helps in prevention of colon cancer due to presence of high fibre in addition to lowering blood sugar and cholesterol levels (Gunathilake et al. 2009). Defatted soy flour is a processed product that contains only 1% of fat and iso-flavones, which reduces the risk of cardiovascular diseases and hyperlipidaemia (Nishinari et al. 2014). It contains 38–40% protein, thereby making it a good substitute for wheat flour (Sabanis and Tzia 2009). Psyllium husk contains 6.5% protein and 74.5% dietary fibre. Due to the higher percentage of dietary fibre, it is often used as an emulsifier (Ray et al. 2018). Skim milk powder contains 37.02% protein, 0.73% fat and 52.9% lactose (Nunes et al. 2009).

Mohamed et al. (2006) formulated low carbohydrate bread in combination with hard red spring wheat flour, soya protein and gluten powder. Soya protein and gluten powder were added to the wheat flour (control) to decrease the final starch by 52%. The final product contained protein content of 56%, which is higher than that stated in the literature. Dhinda et al. (2012) used wheat flour, oat bran, soya protein isolate and chickpea flour along with a combination of additives to develop low carbohydrate bread which is rich in protein and fibre. The bread prepared had 19% protein, 11% dietary fibre and 0.8% β glucan. In the study conducted by Folashade et al. (2019) moringa seed powder was utilized to enrich the bread at different quantities that are from 0 to 20% considerably increased the protein (8.55–13.46%), fibre content (0.08–0.62%) and fat (7.31–15.75%) of the bread samples, whereas the carbohydrate content (57.68–46.73%) of the bread decreased.

With this background, work was undertaken to develop LCHF bread by replacing WF with a mixture of almond flour, desiccated coconut flour, defatted soy flour, dry gluten powder, psyllium husk and skimmed milk powder (ACSGPM). Determination of rheological, dough microstructural characteristics; physical, chemical, sensory, nutritional and storage properties of LCHF flour bread with an additive mix consisting of fungal alpha amylase, sodium stearoyl-2-lactylate and xanthan gum in comparison with wheat flour bread was carried out. The fatty acid profile and in-vitro starch digestibility were determined.

Materials and methods

Materials

The commercial wheat flour (WF) (Triticum aestivum), Almonds (Prunus dulcis), defatted soya flour (Glycine max), compressed yeast, coconut oil (Cocos Nucifera), salt and sugar, desiccated coconut (Cocos nucifera) (Bakers desiccated coconut powder, Coimbatore), skimmed milk powder (Karnataka Cooperative Milk Producers Federation, Mysuru) and psyllium husk (Plantago Psyllium) (The Sidhpur Sat Isabgol Factory, Sidhpur) were purchased from the local super market, Mysore, Karnataka, (India). Almonds were ground using a flaker mill (Laboratory mill 3100, Perten Instruments (Perkin Elmer), Australia) to a particle size of 250–300 μm. Desiccated coconut and psyllium husk were also made into a fine powder (250–300 μm) and both the flours were stored separately in an airtight container. Dry gluten powder, fungal alpha-amylase (FAA) from Aspergillus Oryzae, sodium stearoyl-2-lactylate (SSL) and xanthan gum (XAN) were acquired from M/S PD Navkar Bio-chemical Pvt Ltd., Bangalore, India.

Preparation of LCHF flour and additives mix (AM)

In order to produce bread with low carbohydrate, high fat, protein and dietary fibre contents, LCHF flour was prepared by replacing 100% WF with a mixture of ACSGPM [almond flour (30%), desiccated coconut flour (30%), defatted soy flour (10%), dry gluten powder (10%), psyllium husk (10%) and skimmed milk powder (10%)]. The ingredients selection and levels of addition were finalized based on the initial preliminary studies on acceptability of bread. Similarly, an additive mix (AM) containing 0.005% FAA + 0.5% xanthan + 0.5% SSL was prepared based on preliminary sensory acceptability.

Flour characteristics

The WF and LCHF flour were analyzed for moisture (44–15 method), dry gluten (38–10 method), total ash (08–01 method), fat (30–10 method), protein (46–10 method), sedimentation value (Zeleny’s) (56–61 method) and Hagberg falling number (56-81B method) using standard AACC (2010). The water activity (aw) and pH of bread samples were determined using water activity meter (Aqualab, Pawkit, Washington) and pH meter (pH 510, Eutech instruments, Singapore) respectively.

Rheological characteristics

The rheological properties were determined as per the methods described by AACC (2010) using farinograph (Model No. E-380, Brabender GmbH & Co. KG, Duisburg, Germany) (54–22 Method) and amylograph (Model No. 803201, Brabender GmbH & Co. KG, Duisburg, Germany) (22–10 method).

Bread-making characteristics

The LCHF bread was made using the following formulation: LCHF flour: 100 g; compressed yeast: 5 g; baking powder: 2 g; sugar: 5 g; coconut oil: 5 g; salt: 1.5 g and water. Bread was prepared in quadruplicate by mixing all the ingredients in a Hobart mixer (Model N-50, Hobart, Germany) with a flat blade for 2 min at 58 rpm, 2 min at 112 rpm and 3 min at 173 rpm. Immediately moulded the dough and transferred to proofing chamber (30 °C and 85% RH) for 45 min and finally, baked for 25 min at 220 °C, cooled to room temperature before packing in polypropylene pouches until further analysis. The LCHF + AM bread was also prepared in the same method with AM (0.005% FAA, 0.5% xanthan and 0.5% SSL). However, the WF bread was prepared as per Indrani et al. (2010).

Scanning electron microscopy (SEM) characteristics

The micro-structural characteristics were determined using a scanning electron microscope 435 VP model (Leo electronic systems, United Kingdom) as per the method followed by Dhinda et al. (2012).

Physical and sensory characteristics

The weight of bread was noted, and the volume of the bread loaf was measured using rapeseed displacement method (10–05 method) as per AACC (2010). The hardness, cohesiveness, springiness and gumminess was analysed using a texture analyser (LR 5 K, Lloyd Instruments Ltd., United Kingdom) using cylinder probe of 80 mm diameter as per the methods of Indrani et al. (2010). The Hunter Lab colour meter (Lab scan XE system, USA) was used to measure the colour of bread in terms of L (lightness (L = 100), darkness (L = 0) dimensions), a (± : red/green) and b (± : yellow/blue).

The sensory evaluation was carried out by twenty five panellists of age from 25 to 59 years, including ten female and fifteen males, who have earlier experience in sensory evaluation of bread. The sensory panel was further trained in four sessions of two hours each. Samples were evaluated under room temperature and day light as per the method explained by Dhinda et al. (2012).

Chemical properties of bread

The LCHF and WF bread were analyzed for moisture, total ash, fat, protein and dietary fibre as described earlier. The in-vitro starch digestibility (IVSD) was determined as per the method provided by Goni et al. (1997), and carbohydrate content was determined by difference.

Fatty acid composition

The fat from WF, LCHF flour, WF bread and LCHF bread were extracted and converted this fat into fatty acid methyl esters as per AOAC (2003) method and were analysed in a gas chromatography-mass spectroscopy (PerkinElmer (Turbomass Gold), Waltham, Massachusetts). The percentage of single fatty acid was reported.

Storage characteristics

Since preliminary storage studies showed maximum shelf life of 5 days for LCHF bread with permitted preservatives, the 5 days storage period was fixed for both the bread. The LCHF bread and WF bread were prepared in quadruplicates, cooled, packed individually and heat sealed in low-density poly-propylene pouches. The breads were stored at room temperature for five days. During storage period, the breads were evaluated for moisture, colour, texture, water activity, pH and sensory analysis on 1st, 3rd and 5th day as per the method described earlier. The samples were freeze-dried in Heto freeze-dryer (Model DW3, Allerod, Denmark), powdered and further analysed for Differential Scanning Calorimetry (DSC 8000, Perkin Elmer) as per method mentioned by Liu et al. (2019).

Statistical analysis

All the experiments were carried out in duplicate, and the results were presented as mean and standard deviation. The obtained data were subjected to statistical analysis using Statistical software (Statistica, 7.0 of Stat Soft Incorporation, Tulsa, USA) and the means, compared by Duncan’s New Multiple Range test (p ≤ 0.05) (Kumar et al. 2016).

Results and discussions

Physico-chemical characteristics of flours

The results of the chemical characteristics of flours showed that LCHF flour had 11.54% gluten, 23.75% protein, 34.53% fat, 3.42% ash, 29 ml sedimentation value, 245 s falling number. The WF had 10.8% gluten, 11.09% protein, 2.23% fat, 0.53% ash, 21.60 ml sedimentation value, 505.7 s falling number. The difference in the results of two flours could be attributed to the ingredients presence in LCHF flour, which are rich in protein, fat, dietary fibre, minerals and alpha-amylase activity.

Rheological characteristics of flours

Farinograph characteristics

The quantity of water added to WF to attain 500 BU consistency was 61%, whereas 70% of water was required for achieving the highest consistency of 441 BU for LCHF flour (Table 1). The WF water absorbing capacity is mainly related to the high hydration property of starch and gluten proteins. The higher water absorption capacity of LCHF flour is attributed to the presence of higher protein and fibre (Pejcz et al. 2015). Earlier, Kamaljit et al. (2011) also reported increase in water absorption with the increasing level of incorporation of psyllium fibre and attributed to the gelling and water absorbing capacities of this biopolymer. The LCHF flour had weaker mixing profile when compared to WF as shown by the lower dough development time or peak time, stability value, and higher mixing tolerance index. It can be concluded that LCHF flour having weaker mixing profile is due to the presence of higher amount of non-wheat protein, fat, and dietary fibre. This weakening of dough could be due to (a) the presence of sulphydryl groups of fiber in soya, psyllium husk, which causes softening of dough, (b) an effective decrease in gluten content, and (c) increased competition for water hydration between proteins of non-wheat and WF (Kumar and Sudha 2021). Effect of addition of additives mix (AM) increased water absorption from 70 to 72%, stability (0.8–3.4 min) and decreased mixing tolerance index (289–210 BU) indicating an improvement in the strength of the LCHF dough (Kumar and Sharma 2017). The overall increase in the water absorption and dough strength by the addition of AM is due to the presence of xanthan and sodium stearoyl-2-lactylate (Tebben and Li. 2018).

Table 1.

Rheological characteristic of wheat flour and LCHF flour

Parameters WF LCHF LCHF + AM
Farinograph
Water absorption (%) 61.0 ± 0.1a 70.0 ± 0.1b 72.0 ± 0.1b
Dough development time (min) 6.2 ± 0.2c 4.2 ± 0.1a 5.5 ± 0.1b
Stability (min) 8.7 ± 0.2c 0.8 ± 0.1a 3.4 ± 0.1b
Mixing Tolerance Index (BU) 35.0 ± 0.1a 289.0 ± 2.5c 210.0 ± 3.5b
Amylograph
Pasting temperature(C0) 61.0 ± 0.2b 31.6 ± 0.1a 30.7 ± 0.1a
Peak viscosity (BU) 782.0 ± 4.5c 200.0 ± 2.5a 412.0 ± 2.0b
Hot paste viscosity (BU) 555.0 ± 5.0c 117.0 ± 1.5a 324.0 ± 2.5b
Cold paste viscosity (BU) 1069.0 ± 5.5c 364.0 ± 4.5a 455.0 ± 2.5b
Breakdown (BU) 227.0 ± 1.5c 83.0 ± 0.5a 186.0 ± 2.5b
Setback (BU) 514.0 ± 2.5c 247.0 ± 3.5b 229.0 ± 3.0a
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Values are expressed as mean ± SD (n = 3); Mean values in the same row followed by different superscripts (a, b, c) differ significantly (P ≤ 0.05). LCHF Low carbohydrate and high fat; AM Additives mix (0.005% Fungal Alpha Amylase, FAA + 0.5% xanthan (XAN) + 0.5% SSL)

Amylograph characteristics

The LCHF flour had lower pasting temperature, peak, hot paste and cold paste viscosities. These results indicate that the viscosity of the LCHF flour paste containing low carbohydrate (Table 1) has revealed the early onset of initial viscosity, reduced viscosity during heating, cooking and cooling. LCHF flour showed lower value for break down and set back viscosities. Morris et al. (1997) observed that the utilization of chickpea flour decreased the peak, cold paste and set back viscosities due to their lower carbohydrate content. The Increasing level of fibre incorporation also decreases the gelatinization of the cooked starch (Olubunmi et al. 2015). With the use of AM, amylograph pasting temperature and setback decreased, while other viscosity parameters improved, indicating the action of additives on the LCHF flour starch.

Microstructure of dough and bread

In the SEM micrograph of WF dough, small, medium, large starch granules and protein matrix embedded with cluster of cells can be seen (Fig. 1a). The matrix appears smooth, continuous, enveloping starch granules. In the micrograph of LCHF bread dough (Fig. 1b), irregular structures, few clumped protein bodies may be from defatted soya flour and few pits can be seen. Also, few covered areas may be representing protein deposits are seen. It is reported that the micrograph of protein rich soya bean displays aggregates of proteins along with more number of elongated cells (Indrani et al. 2010). The LCHF bread dough has disrupted matrix due to lack of well-defined protein—starch—lipids network due to reduction in the starch, increased amount of non-wheat proteins and fat as observed from the results of farinograph and amylograph analysis.

Fig. 1.

Fig. 1

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Scanning electron micrograph of WF, LCHF dough and breads (2000 x). a Surface structure of WF bread dough, b LCHF bread dough c WF bread and d LCHF bread respectively. LSG: large starch granule; MSG: Medium starch granule; SSG: small starch granule; PM: protein matrix; PB: protein bodies; IS: Irregular structures; DPM: disrupted protein matrix; GS: gelatinized starch granule. See Table 1 for abbreviations

Figure 1c is the micrograph of WF bread. Many starch granules have lost their shape due to gelatinisation. The micrograph also shows some partial outline of starch granules and starch granules seems too shrivelled owing to gelatinisation process and are embedded in the protein matrix (Hug-Iten et al. 1999). In the micrograph of LCHF bread (Fig. 1d), irregularly shaped thin creep like sheets may be representing protein, irregular fibre structures; few cells with the hollow core can be seen. The micrograph of bread with concentrated plant proteins showed thin and thick cover areas representing protein depositing over the starch granules (Flemming and Sosulski 1978). It appears that irregular structures are dispersed in a non-continuous loose protein matrix. There are no visible starch granules, which seemed to be wrapped by xanthan.

Physico-sensory characteristics

Bread making characteristics of LCHF and WF showed that the volume of LCHF bread was significantly lower (315 ml) than WF bread (525 ml) may be due to weak network formed by the high amount of non-wheat proteins. Mohamed et al. (2006) observed that low carbohydrate bread with higher protein from non-gluten ingredients lost their volume immediately after being removed from the oven and decrease in the loaf volume which could be due to the lack of sufficient starch because gelatinized starch forms a gel during cooling. However, volume formed is due to structure forming ability of the wheat protein; complex formation of highly branched soluble arabinoxylan with proteins (Sudha et al. 2007).

The texture of bread depends mainly on the gluten, which contributes to the formation of the cellular crumb structure of the bread. Typical bread made with 100% WF will have a soft texture, easily disintegrates without any residue in the mouth during chewing. The LCHF bread had higher hardness, gumminess, lower cohesiveness and springiness indicating that the LCHF bread offered higher resistance to the first bite; higher energy was required to disintegrate; lower ratio of the work was needed to compress the bread for a second time to that of the first and showed lower ability to recover its original after first deforming force is removed (Pamisetty et al. 2020).

The L value of LCHF bread was 45.65 when compared to 68.14 of wheat bread. The a and b value were higher for LCHF bread than WF bread. The above results indicate that LCHF bread had dull-white crumb colour, the red and yellow colour intensity was more when compared to WF bread. The almond, defatted soya flour must have contributed these colours to the LCHF bread.

The results of the sensory analysis are consistent with the volume and texture characteristics of bread (Table 2). The WF bread had golden-brown colour crust (sensory score:14); normal crust shape (13.5); creamish white colour crumb (8.5); uniform, fine crumb grain with thin cell walls (17); soft in texture (18) and clean mouthfeel, with typical taste and no residue formation (18). The overall quality score, indicating the combined score of crust and crumb characteristics of bread, was 88 out of 100. The LCHF bread showed brown colour crust (8); normal crust shape (8); dull white colour crumb (6); non-uniform, medium-coarse crumb grain with thick cell walls (8); firm texture (8); slightly gummy mouthfeel with residue formation (15), perceptible almond, coconut taste and with an overall quality score of 53. The bread making potential (specific volume) of LCHF bread decreased significantly due to decreased ability of the gluten network to enfold the carbon dioxide gas produced during fermentation. The crust and crumb texture of LCHF bread become harder and is the evidence of thickened cells due to the lower gluten (Sabanis and Tzia 2009). These results indicate that the overall quality score of LCHF bread is very low and therefore, AM was added to improve the LCHF bread quality. With the addition of AM, volume increased from 315 to 450 ml; decreased the hardness and gumminess; increased cohesiveness and springiness, thereby indicating an improvement in the texture and volume of LCHF bread. Addition of gluten is required in protein and fibre rich breads to get normal loaf volume as it provides visco-elastic properties to the dough. The fungal a-amylase helps to increase the gas production capacity during fermentations and increase bread volume through its ability to lower starch gelatinization viscosity which helps in better oven spring (Cauvain and Chamberlain 1988). The crust shape, improved to normal shape from slightly flat showing an improvement in the strength and gas holding property of the dough. The coarse crumb grain was changed to medium fine. The texture changed from firm to soft. There was no gummy feeling or residue formation, and however, there was not much change in taste. These improvements were reflected in the increase in the overall quality score from 53 to 74, which was due to the presence of FAA, xanthan and SSL. The photographs of bread are presented in Fig. 2.

Table 2.

Physico-sensory analysis of WF bread and LCHF bread with addition of additives

Parameters WF LCHF LCHF + AM
Volume (ml) 525.0 ± 5.5c 315.0 ± 2.5b 450.0 ± 4.5a
Texture
Hardness (N) 17.30 ± 0.2a 107.01 ± 0.1c 57.02 ± 0.3b
Cohesiveness 0.39 ± 0.0c 0.26 ± 0.0a 0.29 ± 0.0ab
Springiness (mm) 10.88 ± 0.4c 9.40 ± 0.2a 9.85 ± 0.2ab
Gumminess (N) 169.74 ± 0.2a 849.72 ± 0.2c 451.76 ± 0.2b
Colour
L* 68.14 ± 0.2c 45.65 ± 0.2a 48.62 ± 0.2b
a* − 1.01 ± 0.2a 1.63 ± 0.2b 0.71 ± 0.2c
b* 10.66 ± 0.2a 11.65 ± 0.2c 11.05 ± 0.2b
Overall quality score (100) 88.00 ± 0.5c 53.00 ± 1.1a 74.00 ± 0.8b
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Values are expressed as mean ± SD (n = 3); Mean values in the same row followed by different superscripts (a, b, c) differ significantly (P ≤ 0.05)

L*- Lightness, a*-greenness, b*- blueness. Please refer Table 1 for abbreviations

Fig. 2.

Fig. 2

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Images of the breads. a WF bread; b LCHF bread; c LCHF bread + AM. Please refer Table 1 for abbreviations

Nutritional characteristics of bread

The WF bread and LCHF bread had 30.93 and 53.42% moisture, total ash (0.94 and 3.28%), fat (3.78 and 11.01%), total protein (12.57 and 22.51%), and carbohydrate (51.90 and 13.71%) respectively. The results showed that LCHF bread had higher ash, protein, fat and dietary fibre content and lower carbohydrate than control bread. The LCHF bread has a low value of IVSD (17.3%) as compared to WF bread (38.2%). This can be attributed to low carbohydrate content in the LCHF bread and also due to protein-starch interactions which affect the amylolysis of starch, thereby reducing the digestibility (Gopalakrishnan et al. 2011). LCHF bread provides glucose (from sugars and starch, including maltodextrins) at a rapid rate for absorption in the human small intestine and found correlation with glycemic response (Englyst et al. 1999). Namsirilert et al. (2015) observed that 20 and 30% coconut flour exerted a significant reduction in term of glucose release throughout the 120 min starch digestion process. Thus it can be concluded that the carbohydrate content of LCHF bread decreased by 3.8 times, fat, protein, ash, and dietary fibre contents increased by 2.9, 1.8, 3.5 and 1.8 times respectively.

Fatty acid profile

The main fatty acids present in the fat content of WF are lauric acid (23.51%), followed in decreasing order by palmitic acid (15.09%) and myristic acid (6.07%). In LCHF flour, high amount of lauric acid (42.97%) was present when compared to WF (19.55%) (Fig. 3). The other fatty acids such as myristic acid, linoleic acid, palmitic acid, capric acid and caprylic acid were present in the range of 1.14 to 13.06%. These results indicate that LCHF flour is rich in lauric acid, which is contributed by the coconut flour present in LCHF and coconut oil used in bread formulation. De Roos et al. (2001) reported that fat present in coconut is a rich source of lauric acid. Also lauric acid is a 12 carbon atom chain falling under medium-chain fatty acids group known to increase high-density lipoprotein (HDL) or good cholesterol. The LCHF flour is also found to contain linolenic acid, an essential fatty acid. The major fatty acid present in the fat content of bread with WF flour was palmitic acid whereas lauric acid was the major fatty acid present in the fat content of LCHF bread. The other fatty acids such as myristic acid (18.12%), palmitic acid (7.98%), linolenic acid (6.57%), capric acid (6.09%) and caprylic acid (2.18%). It is reported that the major fatty acids present in coconut oil are lauric acid (47.7%) and myristic acid (19.9%) (Orsavova et al. 2015). It can be concluded that among WF and LCHF breads, the bread with LCHF was found to be rich in medium-chain fatty acids that are believed to increase good cholesterol (high-density lipoprotein); bread with WF was found to be rich in palmitic acid, a saturated fatty acid raising bad cholesterol (low-density lipoprotein) (Denke and Grundy 1992).

Fig. 3.

Fig. 3

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Fatty acid profile of flour and breads. WF: Wheat flour; LCHF: Low carbohydrate and high fat bread

Storage characteristics

With an increase in storage (1 to 5 days), there was not much variation in the moisture content, water activity and pH of breads during storage (Table 3). The hardness value of WF bread was 70.5 N and LCHF bread (102.74 N). The higher hardness value indicates that the LCHF bread is firmer than WF bread. During storage period from 1 to 5 days, hardness value increased from 70.5 N to 91.94 N; the cohesiveness, springiness and gumminess values decreased from 0.33 to 0.24; 11.04 to 10.940 mm and 30.55 to 22.45 N respectively. For LCHF bread, hardness cohesiveness and springiness values increased from 102.74 to 126.51 N, 0.23 to 0.34 and 6.43 to 11.04 N respectively and while gumminess value decreased. These results showed that the increase in hardness and decrease in gumminess values during storage for both the breads were similar. However, the cohesiveness and springiness increased for LCHF bread whereas it decreased for WF bread may be due to less staling in LCHF bread than WF bread.

Table 3.

Storage characteristics of wheat flour bread (control) and LCHF bread

Parameters Breads
WF LCHF
Storage (days)
1 3 5 1 3 5
Moisture (%) 28.06 ± 0.2a 28.07 ± 0.2a 28.43 ± 0.2a 43.15 ± 0.2b 44.45 ± 0.2b 42.94 ± 0.2b
Water activity (aw) 0.991 ± 0.2a 0.993 ± 0.2a 0.995 ± 0.2a 0.994 ± 0.2b 0.995 ± 0.2b 1.001 ± 0.2b
pH 5.43 ± 0.2b 5.35 ± 0.2b 5.3 ± 0.2b 4.57 ± 0.2a 4.50 ± 0.2a 4.49 ± 0.2a
Texture
 Hardness (N) 70.5 ± 0.2a 80.1 ± 0.2b 91.94 ± 0.2c 102.74 ± 0.2a 116.29 ± 0.2b 126.51 ± 0.2c
 Cohesiveness 0.33 ± 0.2d 0.26 ± 0.2b 0.24 ± 0.2a 0.23 ± 0.2a 0.29 ± 0.2c 0.34 ± 0.2d
 Springiness (mm) 11.04 ± 0.2d 10.98 ± 0.2c 10.94 ± 0.2c 6.43 ± 0.2a 8.71 ± 0.2b 11.04 ± 0.2d
 Gumminess (N) 30.55 ± 0.2f 28.55 ± 0.2e 22.45 ± 0.2c 24.14 ± 0.2d 20.97 ± 0.2b 16.33 ± 0.2a
 Overall quality score (100) 88.0 ± 0.2e 85.0 ± 0.2d 82.0 ± 0.2c 74.0 ± 0.2ab 72.0 ± 0.2a 70.0 ± 0.2a
DSC characteristics
 Onset temperature (T0) (in C°) 54.48 ± 0.2c 53.19 ± 0.2b 50.77 ± 0.2a 101.47 ± 0.2e 99.68 ± 0.2d 99.19 ± 0.2d
 Peaktemperature (Tp) (in C°) 59.99 ± 0.2c 58.37 ± 0.2b 57.32 ± 0.2a 105.23 ± 0.2e 104.50 ± 0.2d 103.85 ± 0.2d
 End temperature (Te) (in C°) 69.55 ± 0.2c 68.68 ± 0.2b 66.33 ± 0.2a 114.49 ± 0.2d 114.40 ± 0.2d 114.31 ± 0.2d
 Enthalpy (∆H) (in J/g) 0.71 ± 0.2b 1.34 ± 0.2b 3.40 ± 0.2e 0.53 ± 0.2a 1.65 ± 0.2c 2.20 ± 0.2d
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Values are expressed as mean ± SD (n = 3); Mean values in the same row followed by different superscripts (a, b, c, d, e, f) differ significantly (P ≤ 0.05). Please refer Table 1 for abbreviations

Organoleptic evaluation of LCHF bread and WF bread indicated that there was not considerably change in the crust colour, shape, crumb colour and grain with time. During storage period from 1 to 5 days, the texture of WF bread became firm; there was a progressive increase in the crumbliness, it was maximum at 5th day of storage as a result of the onset of staleness. The overall quality score decreased from 88 to 82.

The LCHF bread showed a slight firm texture on the 1st day, and the firmness increased with increase in storage period from 1 to 5th day. There was no crumbliness, as seen in the WF bread. On storage of LCHF bread, there was no adverse effect on the mouthfeel. The overall quality decreased from 74 to 70. From these results, it can be concluded that LCHF bread indicated better storage stability than the WF bread, which attributed to the presence of less starch, more fat and protein.

Differential scanning calorimeter (DSC) characteristics

Staling is a multifaceted process, which includes moisture migration, interaction between gluten and starch, and retrogradation of starch, mainly of amylopectin (Goesaert et al. 2005). DSC has been used for measuring thermos-physical properties of foods (Liu et al. 2010). The gelatinization of retrograded WF bread samples occurred between 53.19 and 69.55 °C. During increase in storage period from 1 to 5 days, the To, Tp and Te decreased for both LCHF and WF breads. Several authors have also reported an increase in the temperature of gelatinization endotherms with the incorporation of additives. Dissanayake et al. (2013) studied the thermal behaviour of additives, namely xanthan gums using DSC and reported an increase in the onset (To) and peak (Tp) with the addition of xanthan and also whey protein concentrate. Szczodrak and Pomeranz (1992) reported the DSC results for control bread and chia mucilage bread. There were two peaks corresponding to the gelatinization process and the amylose–lipid complex and concluded that the endotherm between 95 and 130 °C is corresponds to the amylose–lipid complex. In our studies, the higher thermal transition temperatures may be attributed to the melting of amylose–lipid complex and ingredients of LCHF flour and xanthan.

In WF bread, the values of enthalpy for the gelatinization endotherm of the starch increased from 0.71 to 3.40 J/g with an increase in storage time from 1 to 5 days showing the increase in staling rate. The increase in the values of the enthalpy for the gelatinization endotherm of the LCHF bread from 0.53 to 2.2 J/g is lesser when compared to WF bread. These results confirm that the staling rate in LCHF bread is less when compared to WF bread. Mohamed et al. (2006) also observed that low carbohydrate bread showed lower staling, as shown by lower firmness after storage of five days. It is also reported that the psyllium husk and xanthan gum lowers DSC enthalpy values (Czuchajowska et al. 1992).

Conclusion

This study shows that bread with low carbohydrate, high fat, and protein can be prepared by replacing 100% WF with LCHF flour made up of almond flour, desiccated coconut flour, defatted soy flour, dry gluten powder, psyllium husk and skimmed milk powder (ACSGPM). In general, LCHF flour had higher water absorption, lower dough stability and overall quality score of bread when compared to WF. The use of AM increased dough stability and overall quality score of LCHF bread further. LCHF bread had higher moisture, ash, fat, protein and dietary fibre contents than control bread in addition to nutritionally superior fatty acids. The staling rate of LCHF bread was lower owing to a lower amount of carbohydrate present in it. These results are important for the production of low carbohydrate, high-fat bread to cater to the needs of people suffering from obesity.

Abbreviations

LCHF

Low carbohydrate high fat

WF

Wheat flour

ACSGPM

Almond flour, desiccated coconut flour, defatted soya flour, dry gluten powder, psyllium husk and skimmed milk powder

AM

Additive mix

FAA

Fungal alpha-amylase

SSL

Sodium stearoyl-2-lactylate

XAN

Xanthan gum

rpm

Rounds per minute

BU

Brabender unit

IVSD

In-vitro starch digestibility

DSC

Differential scanning calorimetry

T0

Onset temperature

Tp

Peak temperature

Te

End temperature

∆H

Enthalpy

Authors contribution

SR: Formal Analysis, Investigation; Tabulation, Writing Original Draft; AKK: Investigation, Methodology, Data curation, Validation, Supervision, Statistical analysis; Writing: Review & editing; ID: Conceptualization, Methodology, Supervision, Writing: Review & editing.

Availability of data/material

The data is available upon a reasonable request from corresponding author.

Declarations

Conflict of interest

The authors have declared no conflict of interest for this article.

Consent for publication

All the authors have given their consent for publication.

Footnotes

D. Indrani: Deceased

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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