Introduction

The increasing global population, rapid economic development, and developments in technology coupled with excessive consumption have accelerated the negative impacts on the environment. Chen and Chai (2010) reported that 30 to 40% of environmental degradation is the result of an unsustainable human consumption. According to Grunert and Juhl (1995), consumer household purchases caused 40% of ecological damage. However, while many consumers (67%) were positive about buying green food products, only a small number of consumers (4%) purchased these products (Hughner et al. 2007).

Over the last few decades, green consumerism has emerged as a result of more and more consumers being aware of these environmental problems. Henion and Kinnear (1976) description of ‘green consumerism’ includes an ‘environmentally concerned consumption’. Scheffer (1991) describes ‘green consumerism’ as ‘a specific type of socially responsible consumer behaviour that involves an environmentalist perspective’. Robert (1996) on the other hand makes the more detailed definition as ‘Recycling, purchasing and using environmentally friendly products that have minimal damage to the environment’.

As seen in the above definitions, green consumption means buying and using environmentally friendly products that minimise environmental damage. Being green includes choosing less energy-consuming electronic devices, buying cars emitting less carbon dioxide, using solar and wind energy to generate electricity, and buying locally grown and produced food products, vegetables, and fruits.

Existing research related to ‘green consumerism’ has concentrated on green customer, green products, characteristics of green buyers and products, and the impact on price and income (Asif et al. 2018; Biswas 2016; Chen et al. 2018; Li et al. 2016; Rahnama and Rajabpour 2017; Schuitema and De Groot 2015; Sharma and Foropon 2019).

A ‘green consumer’ concerns about the environment, prefers environmentally friendly and no threat to human health products, and therefore purchases green products over the standard alternatives (Handayani and Prayogo 2017). Green consumers are often the end users aimed at an individual or household consumption.

A ‘green product’ is designed and produced by using renewable/toxic-free/biodegradables resources and can be recycled or conserved. It improves environmental impact or reduces environmental damage throughout its entire life cycle (Chen and Chai 2010; Durif et al. 2010). Based on the explanations made, food products produced and consumed locally by using natural products in the homes without using additives and products produced in factories with traditional methods can be considered as green products.

Tarhana as a green food product

Typical Turkish diet is derived mainly from grains, mostly wheat (Akbay et al. 2007). Tarhana, a traditional, fermented wheat-yoghurt mixture, is made from cereal (wheat, flour, etc.), yoghurt, and vegetables (onions, tomato puree, etc.) (Loker et al. 2013). All these ingredients have an indispensable part in many people’s diets.

Tarhana is mostly consumed in the form of a soup. It is particularly essential for children and the elderly. It is also served as a remedy for patients for its rich and nutritious content (Wen-Yen et al. 2016).

Fermented foods are essential parts of diets in all parts of the world (Hesseltine and Wang 1980). It is also an inexpensive process involving the use of microorganisms to carry out enzyme-catalysed transformations of a wide range of agricultural materials (Tanguler 2014). Fermented foods represent a distinct category that shelf life and final sensory characters depend on the correct metabolism of components, mainly carbohydrates, by a specific microorganism (D'Antuono 2013). Storing tarhana for a long period is possible. It is possible to keep Tarhana for 2 to 3 years because of its moisture content and low pH (potential of hydrogen) (Kivanc and Funda 2017).

Nowadays, tarhana is produced mainly in homes. However, because of its roots in traditional cuisine and its acquired taste, it is also produced industrially as a tarhana grain and in a ready-to-make soup form (Cagindi et al. 2016; Tanguler 2014). Over 50 types of tarhana are known throughout the country. It is made in different regions, distinguished from each other in terms of ingredients and preparation methods.

The fact that the Tarhana is mostly produced in households using natural ingredients without using additives, not containing the elements that threaten human health and nature plus its healthiness, puts it in the green product category. Also, tarhana is produced and consumed locally and mainly sold locally and the industrial production being small in size does not threaten the environment.

The growing expansion of green consumerism also brings criticisms against it. The most effective way to reduce pressure and damage to nature is to reduce consumption. However, governments do not desire the decline in consumption rates, especially in stagnant economies. Therefore, green consumerism is accused of being marketing oriented. It is argued that green consumerism is suggested by the marketer to transform consumption into a different dimension in order not to undermine the economies already stagnant by reducing consumption, and at the same time to prevent the most apparent damage on nature (Akenji 2014). In light of these criticisms, it is crucial to investigate the importance of traditional food products such as tarhana that are mostly household products in terms of green consumption behaviour.

Tarhana and its health benefits

Tarhana is a good source of B vitamins, minerals (Ca, Mg, K, Zn, Mn, Fe, Cu, and Na) with favourable bioavailabilities, organic acids, and free amino acids. Therefore, it is healthy for children, the elderly, and patients with its contents (Ozdemir et al. 2007). One of the food-derived flavonoids, quercetin, was the major flavonoid found in tarhana (Ozdemir et al. 2007). As reported in the literature, flavonoids are considered to be significant anticarcinogens and antioxidants with their various biochemical and anti-allergic properties (Gocmen et al. 2003; Ibanoglu and Ainsworth 2004).

Dietary antioxidants have significant health benefits more than essential nutrition in the human body. Antioxidants, including phenolic compounds, have various beneficial bioactivities, such as anti-allergic, antiviral, anti-inflammatory, and anti-mutagenic features. Their protective effects take part by avoiding oxidation processes and preventing from the chronic diseases related to oxidative stress on essential biomolecules such as lipids, proteins, and DNA under pathological conditions (Hollman 2001; Slavin and Lloyd 2012).

According to the physicochemical and physiological mechanism, interaction of food and the human body is a complex process, depending on composition and structure of food, the characteristics of an individual, and various other factors (McClements et al. 2008). This interaction between antioxidants and human is defined by two basic concepts: bioavailability and bioaccessibility. Bioavailability is ‘the proportion of given nutrient in a given food or diet that the body can use’. Bioaccessibility is ‘the fraction of a compound that is released from its matrix in the gastrointestinal tract and thus becomes available for intestinal absorption’ (Benito and Miller 1998). Bioaccessibility is expressed as in vitro mimic gastrointestinal modelling by digestive enzyme systems. While antioxidant properties of foods and benefits for the human body are revealed, their bioavailability should be evaluated alongside their capacities.

The vast majority of studies argue those consumers’ values on the environment do not translate into green consumer behaviour. There is a gap between their values and actions (Kollmuss and Agyeman 2002). This gap is described as Attitude Behaviour Gap by Aizen (2001). As Suki (2013) argues, the environmental concern of consumers depends on the green product features, the accuracy and credibility of the information provided about the products, and the benefits that product offers to the consumer. This gap suggests that consumers do not solely value green product itself; they focus on other product attributes. Undoubtedly, health, taste, and price concern are often accounted more critical for the choice of especially food products than environmental concerns (Hirose and Ohtomo 2007; Hughner et al. 2007). Robinson and Smith (2002) added that lack of availability, perceived time barriers, inconvenience, habits, and trust increase this gap. There are also cultural factors closely related to personal attitudes and green product chose.

Research on Tarhana has substantially increased in recent years. However, vast majority of research focused on chemical composition of tarhana (Anil et al. 2016; Bayrakcı and Bilgicli 2015; Cagindi et al. 2016; Kilci and Gocmen 2014; Tanguler 2014; Yorukoglu and Dayısoylu 2016), antioxidant capacities (Ergonul and Ergonul 2016; Icli 2018), microbiological characteristics (Arslan-Tontul et al. 2018; Bozoudi et al. 2017; Gezginc 2016), effects of different ingredients such as carob flour (Herken and Aydin 2015), cherry laurel (Temiz and Tarakcı 2007), kefir (Erinc and Ciftci 2018; Sukru et al. 2018), chestnut (Koca et al. 2018), whey concentrate (Ertas et al. 2015), baker’s yeast (Ertas 2018), whole wheat flour (Demir 2018), darak dalı and basil (Icli 2018), and other raw materials (Gadallah and Hassan 2019), impact of drying techniques (Degirmencioglu et al. 2005), and nutritional properties (Ertop et al. 2019; Georgala 2013; Kumral 2015; Kaur and Das 2015; O'Callaghan et al. 2009). In addition to the above studies, two studies have been conducted on the importance of gastronomic and geographical indication due to its significance in the traditional kitchen (Cekal and Aslan 2017; Gok et al. 2017).

Nonetheless, although research investigated the nutritional value and content of tarhana exhaustively, there is hardly any research about tarhana production, consumption, and purchasing behaviour.

Only a few articles have mentioned tarhana when talking about food preparation and storage habits of women at home. However, these studies remain very local (Cicek et al. 2005; Kaya et al. 2015).

Only three studies have been conducted to measure consumer habits regarding tarhana. One of them was made to determine the consumption patterns of 435 Kahramanmaras Vocational High School students (Kaya et al. 2015; Sekkeli et al. 2015) The other study was similarly conducted in the city centre of Kahramanmaras province with 384 participants to assess the consumption behaviour of consumers. Both studies have addressed a small sample of local scale (Tumer et al. 2017).

There are also numerous studies on green consumerism. Some of these studies examined the cultural values affect environmentalist attitude and green consumption behaviour (Velnampy and Achchuthan 2016; Samarasinghe 2012), the influence of consumer attitude of green products towards purchase intention (Handayani and Prayogo 2017), and the influence of product attributes and values on purchasing intentions (Sharma and Foropon 2019; Schuitema and De Groot 2015).

Considerable amount of research focused on green food purchase intentions (Chen et al. 2018; Li et al. 2016; Pastiu 2013; Weber et al. 2015; Zhao et al. 2014; Zhu et al. 2013), the gap between positive consumer attitude and lack of purchasing behaviour of green products (Rahab et al. 2016; Sachdeva et al. 2015), and consumers’ willingness to pay for green products (Biswas 2016; Leszczyńska 2014). Factors affecting green purchase behaviour (Asif et al. 2018; Joshi and Rahman 2015) and green product price effects on green consumption (Sharaf and Perumal 2018; Weisstein et al. 2014) were another commonly researched matters.

No research found on tarhana that considered the tarhana as a green product and examined its importance and consumption characteristics from the consumers’ perspective.

In studies on green consumption and green products, consumer approaches have been examined widely within the common product groups and the framework of consumer behaviour and price. There is no research undertaken on the single specific green product especially green food product.

This research is thought to bring a new perspective to the study of green consumerism of a green product that is mostly produced and consumed in homes. Tarhana producers are not only the consumer, but they are also both the producers and consumers. Although the cost of production is essential in its consumption, its healthiness, quality, and traditional values are equally important. Therefore, we believe that analysing tarhana can bring a new perspective to the debate on green consumerism.

In the scope of green consumerism and with the latest nutritional trends in the world, this research aims to address the place of tarhana in this socio-economic structure in the context of Turkey. Therefore, the hypotheses of this study are as follows:

  • As a green product, tarhana consumption varies between urban and rural areas in terms of economic value.

  • Tarhana production patterns differ between urban and rural.

  • Tarhana consumption varies between urban and rural in terms of differences in consumption times.

  • As a green product, homemade tarhana offers a greener and healthier alternative than the commercially produced tarhana.

Materials and methods

Data collection

This research consists of two parts. The first part is intended for the consumers of tarhana. The second part consists of a laboratory analysis containing content analyses of tarhana samples.

Part 1: Survey preparation and data handling

A structured questionnaire as a primary data collection tool was used for the first part of the study. Turkey is divided into seven regions. The questionnaire forms were distributed to the urban and rural areas of the provinces and districts by taking into account the population ratios of each region. The data were obtained by using the face-to-face survey questionnaire during September–December 2015.

The sample size was determined by estimating a proportion using a formula (Thompson 2012). To obtain an estimator ˆp having a probability at least 1 − α of being no farther than d from the population proportion, the sample size formula based on the reasonable approximation gives.

$$ n= Np\left(1-p\right)/\left(N\hbox{--} 1\right)\left(d2/z2\right)+p\left(1\hbox{--} p\right) $$
(1)

where z is the upper α/2 point of the normal distribution. When the finite-population correction can be ignored, the formula reduces to

$$ n=z2p\left(1-p\right)/d2 $$
(2)

Using the formula,

$$ n=z2p\left(1-p\right)/d2=(1.96)\ 20.50(0.50)/(0.05)2=384 $$

Hence, the minimum sample size is 384. Four hundred participants were interviewed to reach 384 sample sizes, and all recorded responses were included in the research data. Interviewees were selected randomly.

In the survey forms, in addition to the demographic information, 15 closed-ended statements were presented, and the 5-point Likert scale was used to structure the statements. SPSS software version 23 was used to assess the results. A t test, one-way analysis of variance (ANOVA), and Duncan’s multiple range tests were used as statistical comparison methods.

The Cronbach Alpha was α = 0.782. The result of 0.80 > α ≥ 0.70 is acceptable; therefore, the scale used was quite reliable (Cronbach 1951).

Part 2: Antioxidant capacity and total phenolic content of tarhana samples and their bioaccessibility

Tarhana samples were obtained from Bursa Uludag University Agricultural Faculty Pilot Plant (control sample) and rural regions (experiment samples) that survey carried out. The control sample was the plain tarhana that is produced in Bursa Uludag University Agricultural Faculty Pilot Plant and sold within Bursa Uludag University kiosks. The control sample included wheat flour (48%), yoghurt (34%), tomato paste (6%), pepper paste (7%), salt (2.5%), dry yeast (1.5%), and dried onion (1%). Ingredients were mixed and fermented for 12 h at 30 °C then dried and ground. This sample was treated as commercial tarhana sample. In the test group, there were four tarhana varieties, which are widely produced by households in the regions. Different preparation techniques are used for each sample. These are as follows: fermented plain tarhana sample (TA), fermented and chickpea supplemented tarhana sample (TB), and fermented and cranberry supplemented tarhana sample (TC) are the commonly consumed tarhana products in Turkey.

Antioxidant capacity and total phenolic content analysis evaluated as extractable, hydrolysable, and bioaccessible phenolics. Extraction procedures of extractable, hydrolysable phenolic were followed according to the method of Vitali et al. (2009) with slight adaptations. For the bioaccessible phenolics, an artificial in vitro enzymatic digestion system was built by the method of Bouayed et al. (2012). Tarhana samples were subjected to gastric digestion by pepsin enzyme (40 mg/mL in 0.1 M HCl) digestion then intestinal digestion with porcine pancreatin enzyme (2 mg/mL) and porcine bile mixture (12 mg/mL).

The antioxidant capacity of the prepared extracts was determined according to three different methods as ABTS (2.20-azinobis-(3-ethyl benzothiazoline-6-sulfonic acid) diammonium salt) method, FRAP (ferric reducing ability of plasma), and CUPRAC (cupric reducing antioxidant capacity). The analytical procedures in the methods were performed as presented by Apak et al. (2008), Boskou et al. (2006), and Benzie and Strain (1996). The results were calculated as μmol Trolox equivalent (TE) per g weight sample and presented as mean ± SD for triplicates.

Total phenol content (TPC) was determined according to the Folin-Ciocalteu method proposed by Apak et al. (2008). The results were calculated as mg gallic acid equivalents (GAE) per 100-g weighted sample and presented as the mean ± SD for triplicates analyses of each sample extract. The bioaccessibility (%) of antioxidant and total phenolic contents were calculated according to Anson et al. (2009) and given as a percentage.

Results and discussion

Demographic variables

A demographic profile such as education, income level, number of people in the family, and occupation plays an essential role in the dietary habits of individuals. Therefore, the research included the demographic characteristics of individuals along with their opinions on tarhana consumption.

Of the 400 surveys, 200 were from rural and 200 from urban areas. Eighty-five percent of those surveyed were female, and 15% were male. All rural respondents were female. Whereas 70% of the urban respondents were female and 30% were male.

As expected, the income levels of urban participants were higher than those who are in rural. Sixty percent of the rural participants earn below the minimum age level [$187–$374], 40% earn just above [$375–$750]. On the other hand, 45% of urban participants’ income was in the $751–$1500 bracket, and 17% were above $1500. According to Turkish Statistical Institute (Turkstat 2015), the average household income was $659 per month throughout the country; the average monthly income was $392 in the rural and $934 in the urban. Rural participants in this research were observed to have much lower income the national average.

There was a significant difference between the levels of education of urban and rural participants. While 81% of rural only have a primary education, 66% of urban have higher degrees.

Tarhana consumption between urban and rural in terms of its economic value

As pointed out in many previous studies, environmental concern is not the only reason for customers to buy a green product. Consumers do not agree to give up on the product features, though they are interested in the environment. Therefore, green products should show characteristics based on other essential features such as quality, price, health, and durability (Diamantopoulos et al. 2003).

Green product prices are generally higher while consumers are usually sensitive about the price; they are keen to buy green products, but not at high prices. In this respect, tarhana offers a valuable opportunity for consumers to use green products as it is both green and economical. Joshi and Rahman (2015) examined the factor affecting green purchase behaviour. They reviewed 53 empirical articles on green purchase behaviour from 2000 to 2014. They noted that in 10 studies, higher prices have outweighed environmental concerns and adversely affected the attitudes of consumers in purchasing green products.

An independent t test revealed that there is a statistically significant difference in the consumption (p < 0.001) of tarhana between the rural (M = 4.14, SD = 0.92) and urban (M = 2.30, SD = 1.16) by its economic value.

The research compared the monthly income groups and found that a vast majority of those who agree were in the low-income groups. Although 79.5% of the participants in the lowest income group stated that they consumed the tarhana because they found it economical, on the other hand, only 11.8% of the people with the highest income group consumed the tarhana because it is inexpensive (Table 1). The income level and tarhana consumption by economic value have an inverse relationship. As the income increases, the proportion of those who consume tarhana for its economic value decreases.

Table 1 5-point Likert scale analysis based on monthly income
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Many studies also show that income influences green consumption (Laroche et al. 2001; Diamantopoulos et al. 2003). Most studies show that income has positively correlated the willingness and ability to purchase green products, which emphasise the outcome of our study (Rahimah et al. 2018; Rawat 2015; Zhao et al. 2014) that underlines the result of our research. Samarasinghe (2012) on the other hand found that income did not make a significant difference in consumers’ green product purchase behaviour. Certain studies have found to have an adverse relationship (Tejpal 2016).

Households that live in cities are more likely to purchase green food products than those in rural areas. Families residing in urban are more likely to find green food products in urban areas than in rural areas. Also, urban households tend to have higher income levels than rural. Income generally correlates positively with purchasing behaviour. Families with high income can spend more on food items. Second, people living in rural areas may lead to a more traditional lifestyle and have more opportunities to produce food for their consumption, thus reducing the likelihood of acquiring commercial green food products.

Although tarhana is not an expensive green product, households tend to consume more in line with the increase in income level and the variety of opportunities to obtain the tarhana from outside the home.

Homemade tarhana production pattern between urban and rural

The food culture of the particular country and the level of interest of the culture in the environmental issues hold a significant place in green food consumption.

Tarhana, a green food product, is one of the most widely home-produced traditional foods both in rural and urban along with jam and tomato paste. Ozdemir et al. (2017) examined the conventional food production models in rural areas of Trakya region and reported that 91.6% of women knew how to make tarhana. Also, 35.9% of rural women prepared less than 10 kg of tarhana annually for their consumption, and 42.30% of rural women prepared more than 10 kg tarhana annually both to consume and to sell the surplus.

In another study, which examined the food preparation habits of women who work and do not work in Samsun, 26.4% of the working women and 51.3% of the women who do not work are preparing the tarhana themselves (Kaya et al. 2015).

In this research, t test compared those who made their tarhana in terms of living in rural and urban areas and monthly income. A statistically significant difference observed between rural and urban (p < 0.001) and monthly income levels (p < 0.001).

Nationwide, 57.5% of the participants, being 35.5% in rural and 20.5% in urban areas, said that they produce their tarhana (Table 2). Considering this research also included male participants, we can say that the findings support the above analysis.

Table 2 Comparative analysis of the participant who produced tarhana themselves and their monthly income distribution
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Comparison of monthly family income and rates of making tarhana at home results revealed that those households with a low income tend to produce tarhana at home. The number of households producing tarhana at home decreases both in rural and urban as the income improves.

In a study investigating food preparation, cooking, and storage methods of women living in various socio-economic regions in Ankara province, it has been found that 67.6% of housewives belonging to high socio-economic level, 77.5% of those from middle socio-economic level, and 91.5% of those belonging to low socio-economic level prepared their tarhana (Ates et al. 1986). A similar study on the storage practices of women in Kayseri Province revealed a statistically significant difference between the socio-economic levels of the women who prepared their tarhana (p < 0.05). In the low-income group, 39.6% of those, in the middle-income group, 30.7% of them, and the high-income group, 21.5% of participants, stated that they prepared their tarhana (Cicek et al. 2005). The results of the above studies support the result of the current research.

Tarhana was produced mostly at homes in the past. Over time, owing to factors such as lack of space and equipment, an increase in urban population, and participation of women in working life, tarhana has become challenging to produce in homes. Consequently, families either started buying industrially produced tarhana from markets or went on to supply the tarhana made at by housewives at homes by order and sell to support their families. Even though the production techniques are the same, consumers believe that there are differences between the industrially made tarhana and homemade tarhana. These perceived differences are directly influential in the choice of consumers to obtain tarhana.

When the group who participated in the research but stated that they did not make their tarhana investigated, it is observed that 18% of them obtained tarhana from markets and 17% from family and friends, but 7.5% of them purchased from homemade product sellers (Table 3).

Table 3 Origin of the tarhana purchased by participants who do not produce tarhana
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When the research considered the rural and urban distinctions, there is a significant increase in the number of users of the industrial tarhana taken from the market; however, industrial consumption lags behind the homemade tarhana.

In the study conducted to determine the way Kahramanmaraş vocational school students supply tarhana, it was observed that most of the participants did not prefer industrial tarhana (n = 191, N = 450) but preferred homemade (n = 127, N = 450) and home-order tarhana (n = 185, N = 450). When the reasons for choosing homemade and order-made tarhana are explained in detail, first becomes being better quality (71.20%) followed by being more hygienic (68%). Those who prefer industrial tarhana (40.50%) favour it because they think it is more reliable (Sekkeli et al. 2015).

Tarhana consumption between urban and rural in terms of differences in consumption times

Concerns over consuming green and healthy products can affect production purchasing and consumption patterns. Changes in lifestyle may affect not only the production and purchasing habits but also consumption habits.

Table 4 indicates tarhana consumption patterns in meals. The result shows that almost all respondents (93%) consumed tarhana at dinner. It is important to note that the equal distribution of rural and urban of those consuming tarhana at dinner (46.5% and 47.0%) shows that the positive attitude towards tarhana (healthy, nutritious, and satisfying) has not eroded in urban culture; it still preserves its place in the food tradition given the results of t test.

Table 4 Tarhana consumption according to meals
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Even though consumption decreases in those who consume tarhana at lunch, it should be taken into consideration that the people living in the urban do not prepare their lunches mostly and they eat outside.

In the urban, the consumption rate of tarhana for breakfast and lunch found higher than in the rural. The critical point to be emphasised here is that tarhana is consumed as a side dish in the urban while people consume it as a main dish in the rural. The working people widely consume tarhana at lunch because of its nutritious properties. Besides, people who do not have the habit of having breakfast in the urban try to make up for breakfast they missed by consuming the tarhana as an instant take away and a cup of soup forms.

We suggested that a future study examining tarhana consumption related to consumption patterns will be useful in terms of clarifying these findings.

Health benefits of homemade tarhana versus commercially made tarhana

The health benefits, superior quality, and good taste of a product are essential aspects affecting the demand and consumption of green food products (Aertsens et al. 2011).

When choosing a product, individual values such as health and safety concerns and the enjoyment that a person will obtain from the use of the product determine the consumer choice. Therefore, the consumers’ desire for their own and their families’ well-being are defined as the main drivers of green purchasing.

A research examining the attitudes of consumers living in Sivas towards purchasing green products revealed that the main reason for them using green products was the fact that green products were healthy (52.8%), the second was environmental concern (44.8%), and the third was green products (29.6%) were considered to have a better quality (Karaca 2013).

Bryla (2016) and Asif et al. (2018) investigated the determinant factors that influence organic food purchase and found that health consciousness is a better predictor of organic food purchase intention. Both researchers confirmed that health consciousness among consumers positively affects their motive to purchase organic foods.

Various researchers came up with the same conclusion that health consciousness was a more significant predictor of consumer behaviour towards organic food than their environment concern (Asif et al. 2018; Yadav and Pathak 2016).

In the second part of the study, we have investigated the health benefits and nutritional values of tarhana because of the importance of green products in terms of health.

Three different extractions (extractable, hydrolysable, and bioaccessible) of three more widely produced homemade tarhana samples and their percentage bioaccesibilites compared with and commercially sold tarhana sample.

Cereal grains, besides being good sources of vitamins, minerals, and fibre, are also rich sources of potentially bioactive compounds, some of which are phenolic compounds (Denny and Buttriss 2007). Tarhana samples were evaluated in terms of antioxidant capacity and total phenolic compounds by extractable and hydrolysable phenolics; results are given in Table 5. Total phenolic contents of tarhana were significantly (p < 0.01) higher than the commercial control sample. Extractable phenolics of tarhana samples ranged from 90.39 mg/100 g GAE (control) to 97.65 ± 0.18 (TC sample). Similar results with control samples of previous studies were obtained (Kilci and Gocmen 2014; Degirmencioglu et al. 2005) when evaluating the extractable and hydrolysable phenolics.

Table 5 Total phenolic content and antioxidant capacity of tarhana samples
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The synthesis or enzymatic transformation of various bioactive compounds may occur during fermentation processes (Priefert et al. 2001; Katina et al. 2007) during the tarhana preparation. And supplementation of tarhana with vegetables and herbs increases the phenolic compound content. Fermentation in tarhana improves the phenolic content that might be the hydrolytic enzyme hydrolysis of different wheat polymers, leading to a more severe structural breakdown of bran cell walls (Wang et al. 2014).

Bioaccessibility of phenolic compounds and antioxidant capacity of tarhana samples are given in Table 6 with their percentage bioaccessibility values. In the determination of the food bioaccessibility and its effects on the human body, it is essential to evaluate the individuals’ diet and health interactions (Manach et al. 2004, 2005). The changes in antioxidant capacities and total phenolic contents of the tarhana sample extracts may be related to their higher phenolic compound content with regard to fermentation, supplementation, and producing methods. Cranberry-supplemented TC sample has higher values than other samples in terms of bioaccessibility parameters (TEACABTS, 6.49 ± 0.25 μmole trolox/g; TEACCUPRAC, 7.18 ± 0.05 μmole trolox/g for bioaccessible phenolics). Cranberries (Vaccinium macrocarpon) are a rich source of phenolic compounds, particularly phenolic acids and flavonoids also responsible for health benefits (Howell et al. 2010; McKay et al. 2015). According to TEACABTS results, when comparing TB sample (3.53 ± 0.05 μmole trolox/g) with the control (1.92 ± 0.03 μmole trolox/g), chickpea supplementation has improved the bioaccessible phenolic content but not as much as cranberry supplementation as in TC sample (6.49 ± 0.25 μmole trolox/g).

Table 6 Bioaccessibility of phenolic compounds and antioxidant capacity of tarhana samples
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Different from the commercial production, in traditional production, after the fermentation process by yeasts and LAB, tarhana is left for sun drying. Bioaccessibility parameters have shown that with enzymatic processes of digestion, more bioactive components could release from the product, and they are more usable by the human system compared to the control sample. Also, low moisture content of the product helps for maintaining its nutritional content.

Since the samples were not produced by controlled recipes, produced with different processes by local producers, and diverse mechanism of determination methods, there is no linear or eurhythmic changes observed between tarhana samples. The aim of the analysis of these samples was putting forth the in vitro health effects of continuously produced and consumed tarhana samples by their bioaccessibilities. Homemade samples have higher antioxidant parameters in other respects; supplementation enriches the nutritional content of tarhana.

Conclusions

Tarhana is a ‘green food product’ that can keep up with a healthy modern lifestyle and consumed in many countries around the world. Our research examined the production and consumption patterns of the tarhana as a green food product and its content in terms of health value in the socio-economic framework. The comparison of urban and rural areas was essential to see how the tarhana was perceived and evolved as a green product in urban life.

Tarhana is more economical due to its inexpensive ingredients and natural production processes, and it is consumed more intensively by families with low income.

Rural families have limited economic opportunities. It is therefore apparent that they consume homemade green products at higher rates without the price concern. Other studies in the field support this finding.

Secondly, we have examined whether the production patterns of tarhana changed between urban and rural. We have seen that more than half of the participants prepared the tarhana in their homes. This rate was twice as much in the rural compared to the urban. Those who did not make their tarhana but supplied it externally either bought it from the markets or obtained from family or friends. Tarhana has mostly consumed as a main meal in rural and as a snack for lunch and breakfast in the urban. This finding is valuable in terms of showing that the tarhana as a cheap green product has not lost its traditional importance in the transition from rural to urban life.

The second part of the research is three more widely produced homemade tarhana samples were compared with commercially sold tarhana sample in terms of antioxidant properties (by TPC; ABTS, FRAP, and CUPRAC essays) as extractable, hydrolysable, and bioaccessible phenolics. In vitro, bioaccessible phenolic contents of homemade tarhana samples were higher than the control sample. Furthermore, analysis results have revealed that tarhana is a nutritious food product and enrichment with fruits and other plants improves the potential of tarhana on health.

Even though we aimed at covering all geographical regions equally and making the rural and urban allocation equivalent, repeating the research with a larger sample will be useful in terms of underpinning the findings. Furthermore, the survey found that urban households’ incomes are above the Turkey average, and rural families’ incomes are far below the Turkey average. Comparison of the results with the income groups that are close to the country averages will be useful.

This research is significant in terms of showing that the consumption rates of tarhana in the urban have not decreased. Research findings indicate that urban people embraced tarhana as a green product. It is striking to find that tarhana is consumed more often in the urban for lunch and breakfast while it is consumed evenly between the rural and the rural for dinner. The underlying reasoning for these patterns needs further investigation.