Fortification of yogurt with flaxseed powder and evaluation of its fatty acid profile, physicochemical, antioxidant, and sensory properties

Highlights

• Yogurts enriched with flaxseed powder were produced to achieve potential health benefits.

• Flaxseed significantly enhanced pH, water holding capacity, and viscosity of yogurts.

• Enriched yogurts had a higher antioxidant activity compared to the control.

• The organoleptic characteristics of enriched yogurts were acceptable.

Abstract

Flaxseed is a natural ingredient with health benefits because of its rich contents of omega-3 fatty acids, phenolic compounds, and fiber. In this study, yogurt samples enriched with flaxseed powder were produced to achieve the potential health benefits of flaxseed. The results showed that the addition of flaxseed powder significantly increased pH, acidity, water holding capacity, and viscosity of yogurts. This enrichment led to a significant decrease (P < 0.05) in saturated fatty acids (SFAs), the ratio of omega-6 to omega-3 fatty acids, and atherogenic indices of yogurts and an increase in the polyunsaturated fatty acids (PUFAs). In addition, the enriched yogurts had a higher antioxidant activity compared to the controls. The color tests revealed that there was a statistically significant difference in color attributes (except a* values) between the samples (P < 0.05). Finally, the organoleptic characteristics of enriched yogurts were acceptable.

Introduction

Flaxseed or linseed (Linum usitatissimum) is a fiber and food crop that is cultivated in cold areas of the world [1]. This plant contains a number of essential fatty acids (FAs), including linoleic acid (ω6), α-linolenic acid (ω3-ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) [2,3]. All of these fatty acids are known to significantly reduce cardiovascular problems in patients with cardiovascular disease. Moreover, beneficial effects of ALA in the brain development in infants, an increase in muscle mass, management of clinical sign of knee osteoarthritis, anticarcinogenic, hypoglycemic, and hypolipidemic activity have been reported in this regard [4,5]. Flaxseed contains other biologically active substances such as bioactive peptides, soluble fiber, lignan, vitamins (predominantly γ-tocopherol), and minerals (in particular, magnesium, calcium, and phosphorus) [6,7]. Lignan is a very complex class of bioactive polyphenolic phytochemicals, with flaxseeds being a major source of its precursors [8]. The flaxseed lignans secoisolariciresinol (SECO) and its diglucoside secoisolariciresinol diglucoside (SDG) are known as potent antioxidants and phytoestrogens [6]. These compounds and herbacetin, as natural flavonoid compounds in flaxseed, possess cardioprotective, hypochlosteromic, and antidiabetic effects, retard hormone-related cancers (such as breast cancer) and improve renal function in lupus nephritis patients [2,9]. Low-density cholesterol-reducing effect and energy balance due to increasing fat exertion have resulted in some double-blind crossover studies [6].

Among the dairy products, yogurt has been especially considered because of being a probiotic carrier, which could positively modify intestinal flora, and having beneficial effects on consumers such as reducing the levels of β-glucuronidase and other carcinogens, protection of urogenital tract and bowl against inflammatory disease, modulating the immune response, and preventing the allergies [10,11]. Accordingly, in addition to recommending increased consumption, its use as a vehicle for supplementing objectives and producing a healthier yogurt is an attractive research field [12,13]. Considering the mentioned nutritional parameters of yogurt, it is fascinating to develop functional foods based on flaxseed. In this regard, production of functional bakery products through replacing wheat flour with flaxseed powder has been surveyed in several studies [6,[14], [15], [16]]. However, there is no study on using flaxseed powder in dairy products yet, and the previous reports about production of functional yogurt has focused on addition of walnut and flaxseed oil [2], herbal extracts [[17], [18], [19]], fruit or fruit pomace [20,21], skin of hazelnut [22], encapsulated fish oil [23], and olive leaf extract [24].

The purpose of the present study is to investigate the effects of adding flaxseed powder on total phenolic content (TPC) and antioxidant activity, fatty acids composition and the related health lipid indices such as atherogenic (AI) and thrombogenic (TI) indices, and physicochemical and sensory parameters of enriched yogurt samples during 21 days of refrigerated storage compared with the control sample.