**1. Introduction**

Bakery and pastry products are consumed worldwide in large quantities on a daily basis and play an important role in human nutrition. Among bakery products, biscuits are the most popular amongst consumers as a rich source of carbohydrates and fats, but low in proteins and dietary fibers along with quite a good shelf life [1]. Generally, biscuits are made with refined wheat flour which is deficient in some essential amino acids (lysine, tryptophan, threonine, methionine and histidine) and other nutrients (fiber, minerals and vitamins) [2–4]. Nowadays there is a high demand for high nutritional value foods. In the current Western society's diet, the intake of ω-6 fatty acids is generally higher compared to the intake of ω-3 fatty acids and this leads to unfavorable nutritional consequences. Therefore, there is a need on the market for innovative products that meet the nutritional requirements of consumers. Some authors suggest that diet supplementation with flaxseed (*Linum usitatissimum*) offers potential health benefits in cases like cardiovascular risk, severe hyperlipidemia, certain types of cancers and other metabolic disorders [5–9]. Flaxseed contain protein (20 g/100 g), dietary fiber (28 g/100 g), fat (41 g/100 g), moisture (6.5 g/100 g), minerals (2.4 g/100 g) and carbohydrates (28.9%), being recognized as an important oilseed and fiber crop [10–12]. It ought to be emphasized that the linseed chemical composition

P ˘aucean, A.; Chi¸s, M.S.; Mure¸san, V.; Socaci, S.A.; Pop, A.; Muste, S. Nutritional, Sensory, Texture Properties and Volatile Compounds Profile of Biscuits with Roasted Flaxseed Flour Partially Substituting for Wheat Flour. *Appl. Sci.* **2021**, *11*, 4791. https://doi.org/10.3390/ app11114791

**Citation:** Man, S.M.; Stan, L.;

Academic Editor: Silvia Mironeasa

Received: 27 April 2021 Accepted: 21 May 2021 Published: 23 May 2021

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may vary depending on the genetic characteristics, growing conditions and crop management practices. Furthermore, flaxseed has a unique fatty acid profile. It is high in polyunsaturated fatty acids (73 g/100 g of total fatty acids), moderate in monounsaturated fatty acids (18 g/100 g), and low in saturated fatty acids (9 g/100 g). The content of linoleic acid is about 16 g/100 g of total fatty acids while α-linolenic acid (ALA) reaches about 57 g/100 g [13]. Tocopherols (20–70 mg/100 g) and carotenoids (~5.7 mg/100 g) are also found in flaxseed oil, therefore flaxseed is considered an important ancient medicine and functional food ingredient [14].

Flaxseed is one of the most important oilseed crops for industrial as well as for food and feed purposes, being part of the human diet for thousands of years, and more recently it has been used as a source of nutraceuticals [10,11,15]. The bioactive components in flaxseed that provide health benefits include α-linolenic acid, lignans and dietary fiber [16,17], proteins and soluble mucilage [8,11,16,18–21]. The flaxseed mucilage may be considered a food hydrocolloid due to its composition, which consists of a mixture of neutral arabinoxylans and acidic rhamnose-containing polysaccharides [22]. Evenmore, antioxidant activity of the lignans and the presence of different types of phenolic compounds such as phenolic acids, flavonoids, phenylpropanoids and tannins [23] may reduce the risk of cardiovascular diseases and contribute to the anticancer activity [12,24–26], particularly hormone-dependent cancers such as prostate and breast [27].

The behavior of proteins in a food system is affected by their techno-functional properties which are mainly dependent on the following factors: the structure of the protein, their hydration mechanisms for solubility and water or oil retention capacity, rheological characteristics for viscosity and gelation, and their interfacial properties for emulsions and foams [28]. Flaxseed proteins have real potential to be used as techno-functional food ingredient in several food products particularly in breads, meat emulsions, and sauces [26]. Thus, flaxseed can be incorporated into diet as ground flaxseed or flaxseed oil. Flaxseed was previously incorporated in various bakery products such as cookies and biscuits [26,29–33] bread [13,22,34,35] and cakes [15,36]. The results of these studies showed that a substitution levels up to 20% led to good product acceptability [29].

Consumers' trend to seek nutritional foods with remarkable value in the diet is highly directed toward the use of flaxseed as a potential ingredient in foods. The nutrient profile of flaxseed biscuits is a valued option, especially for consumers interested in healthy snack diversification.

The aim of this study was to examine the effects of partial replacement of wheat flour with roasted flaxseed flour on the quality attributes of biscuits, with special attention on their nutritional proprieties and volatile profile. Wheat flour substitution with flaxseed flour in biscuits formulation proposed in this study can be an example of successful collaboration between research and food industry and are in agreement with the confectionery products trends.

#### **2. Materials and Methods**

#### *2.1. Materials*

All the ingredients used in the biscuit formulations were bought from the local market in Cluj-Napoca, România. The wheat flour (WF) sample was produced by a local mill (Boromir, Deva, Romania) and sold as type 000 according to its ash content following the Romanian classification [37] (0.48% ash content and 29.57% wet gluten). Flaxseeds originating from Ukraine were used to prepare the flaxseed flour as described further. Initially, flaxseeds were roasted at 180 ◦C for 15 min, then cooled and ground on a GM200 laboratory mill (Grindomix, Retsch GmbH, Haan, Germany) at 10,000 rotations/min for 50 s. To ensure the uniformity of particles, the roasted flaxseed flour (RFSF) was sieved through a 0.8 mm sieve. Four blends of various ratios of both flours were used to prepare the biscuits, as presented in Section 2.2.2.

*2.2. Methods*

2.2.1. Proximate Composition Analysis

The chemical characteristics were determined using the AACC (2000) methods [38]. Wheat flour (WF), roasted flaxseed flour (RFSF), control biscuits and RFSF incorporated biscuits were analysed for moisture (AACC 44-15.02, 2000), ash (AACC 08-01.01, 2000), fat (AACC 30-25.01, 2000), crude fiber (AACC 32-07.01, 2000). The proteins were measured using the Kjeldahl method (AACC 46-11.02, 2000) using the nitrogen to protein conversion factor of 5.7. Total carbohydrate (%) content was calculated according to Equation (1) according to methods reported by Man et al. [39]:

*Total carbohydrates*(%) = 100 − [*moisture*(%) + *ash*(%) + *proteins*(%) + *lipids*(%) + *crude fiber*(%)] (1)

All determinations were made in triplicate.
