1. Introduction
Dietary habits and lifestyle affect quality of life and the sustainability of health systems. Unhealthy food choices and a lack of physical activity contribute significantly to the burden of chronic non-communicable diseases (NCDs) and to the costs of health care funds [
1]. Among NCDs, cardiovascular diseases (CVDs) are considered the number one cause of death (over 30% of all global deaths) and many of these deaths are preventable, inter alia with suitable modifications to unhealthy diets [
2]. High sodium intake is considered as the most important dietary factor related to the global burden of CVDs [
3,
4]; globally, over half of diet-related deaths and about two-thirds of diet-related disability-adjusted life-years (DALYs) are due to high sodium intake [
2]. A direct relationship has long been established between hypertension and sodium intake [
2,
3,
5,
6] and a notable proportion of deaths due to CVDs can be attributed to high blood pressure. Since even a very small reduction in blood pressure can have large positive effects on systolic blood pressure [
7,
8,
9], a significant decrease in mortality rate can be achieved with a reduction of dietary salt intake, making this an important public health intervention in the CVDs domain. The World Health Organisation (WHO) has set the population target for salt intake at an equivalent of 5 g of salt daily and a 30% reduction in mean population salt intake by 2025 [
3,
10], and a number of activities have been implemented by healthcare authorities to reach them. However, in many countries, salt intake is still well above this target, commonly even double the recommended value [
11,
12,
13,
14].
In addition to improving the scientific understanding of the negative consequences of excessive salt consumption and appropriate consumer information and awareness, the modification of food products, either stimulated by consumer demand for healthier products or supported by government incentives, has been identified as the key pillar of salt intake reduction [
15]. This approach is particularly promising in populations where the majority of dietary salt is consumed via food products such as bread, meat products, cheese, savoury snacks, sauces and condiments, and ready meals, which are recognized as the major contributors to salt intake [
11]. The great majority of dietary salt consumed in developed countries originates from processed food, while only 15% is added during cooking or at the table, and 5% is naturally present in foods [
16]. Therefore, a focus on reducing the amount of salt added by food producers is well-justified. Some governments already work with industry to reduce the salt content of foods and some progress has been made [
17,
18], but there remains a pressing need for further improvement.
Focusing on a specific food product group, reducing the level of salt in breads and bakery products would have a major impact on global public health due to both the quantity consumed and their salt content [
11,
19,
20]. Indeed, salt in bread is a critical ingredient from the perspective of production processes and technology (e.g., yeast activity, gluten network formation, bread volume, dough handling, shelf life, etc.) as well as a sensory characteristic [
21,
22,
23]. Therefore, the bakery industry and other food manufacturers are often reluctant to reduce the salt just because of public health targets since they face various challenges when reformulating food products. The reformulated products have to achieve satisfactory sensory quality while maintaining safety, shelf life, and commercial viability [
24]. In order to preserve the basic properties of the food and prevent negative consequences on product acceptability and a drop in sales, food product reformulation must be undertaken in a consumer-driven manner [
15].
Studies show that a considerable proportion of the population is neither aware of salt intake recommendations nor interested in salt reduction [
25], and this limits the consumer demand-side stimulation for food product reformulation. Furthermore, some studies have shown that the use of “low salt” nutrition claims alone (without sensory evaluation) can have a negative impact on purchasing decisions [
26]. A special challenge for the food industry is therefore to successfully apply the “stealth reformulation approach” [
15], where the consumer will not receive any information on salt reduction, nor perceive the difference in taste, while preserving the food’s acceptability and technological properties [
22,
27]. Based on reported studies, gradual silent reformulation that reduces salt in bread by 20–30% without the use of substitutes may be advisable [
28,
29,
30,
31,
32]. Further, several studies report that stealthy salt reduction in breads had no sales impacts [
27,
33,
34]. When using (for example) sourdough as a taste enhancer, further reductions of up to 50% may be achievable [
35,
36].
Slovenia is an example of a country with a very high daily salt intake (about 12 g daily, with over 5 g derived from purchased food [
37]), with bread and bakery products being the key contributors [
38]. Average yearly per capita in-home consumption of bread was almost 27 kg in 2018 [
39], while mean salt content in plain bread has remained unchanged for a decade at around 1.3 g/100 g [
40,
41]. This is despite the efforts envisaged in the national action plan [
42] which anticipated a very ambitious reduction of the salt content in bread to 1.0 g per 100 g by 2020.
The barriers to achieving the objectives of the national salt reduction plan are fears regarding consumer acceptance of reformulated breads and a consequential loss of sales. Readiness to reformulate was high with the largest national bakeries, but the smaller bakeries were not interested. As the former feared the “first mover risk” and loss of consumers to the producers of non-reformulated breads, the notion failed to get traction. The largest producers also claimed they already produced low salt breads, but that their market shares remained marginal [
43].
In 2019, the National Association of Millers and Bakers established a salt-reduction taskforce of their own initiative, which committed to preparing a factual basis for reducing salt levels in their products that also included the provision of relevant guidelines on the underlying technology and consumer response.
Considering the abovementioned challenges, the objective of this study was to explore individual differences between consumer reactions to reductions in the salt content of the leading breads in the Slovenian market. Also, the importance of the bread matrix was investigated since the best-selling white and multigrain breads were considered for reformulation. The results provide valuable insights that can support national bread reformulation activities and the managerial decisions of individual bakeries in this regard.
4. Discussion
In contemporary, highly competitive markets, bakers and other food manufacturers perceive salt reduction as highly risky activity due to concerns that the reformulated foods will not meet the expected sensory characteristics enjoyed by the consumers, which would result in a loss of sales. This is despite the fact that several academic studies showed the opposite—that consumers are rather insensitive to small salt reductions [
32,
33,
57,
58,
59]. The present study is therefore conceptualized on industrial-driven interest with a relatively small (but highly relevant) level of modification in the salt content, using the market-leading bread formulations as a reference. This study confirmed a very low sensitivity to differences in the tested saltiness levels, however several interesting insights were revealed.
The first important observation is related to the impact of the bread matrix on the consumer response to modifications in salt content. As shown in our research, the tested differences in salt concentration did not have a significant influence on the consumer hedonic liking score for white breads, whereas the hedonic liking score for multigrain type breads was statistically significantly reduced in the sample with a 15% lower salt level (1.1 g/100 g). This means that for multigrain breads, the salt level reduction in line with the recommendation of the national plan on salt reduction [
42] to 1.0 g/100 g is highly likely to be noticed by the consumers, if not accompanied by other technological measures.
Although salt is a minor component in bread formulations, it has a critical and complex effect on the bread dough system [
23,
60]. Salt toughens gluten and make dough more stable. It also affects the rate of fermentation, reduces the rate of gas production, and thus significantly influences the bread making process. However, from the perspective of our study, one should not underestimate the effect of salt on other organoleptic properties, besides (salty) taste. Namely, salt has also an important impact on bread texture (mouth feel), overall flavour and colour [
21,
22,
23,
46,
61].
Therefore, food manufacturers should consider not only a gradual salt reduction approach, but also the use of salt substitutes, flavour enhancers and novel technologies as accompanying measures to salt reduction [
15,
62,
63]. Our results reinforce an important but often overlooked fact that saltiness perception depends on the food matrix in which salt is added [
61,
64]. To the best of our knowledge, not many other studies on salt reduction in bread point out this important matter. An older study by Wyatt et al. [
65] for example reported that the salt content of white or whole wheat bread could be reduced by 50% without any change in flavour and overall acceptability. Most other studies consider bread in a rather generic manner. For example, a meta-analysis of eight studies [
58] showed that a reduction in plain bread salt content of more than 40% significantly reduced acceptability. Further, studies suggest that salt content in bread could be reduced by up to 30% without affecting its liking score among consumers [
27,
29,
30,
32,
33,
34,
58]. Also, the comparison of consumer sensory and hedonic perception of salt-reduced breads in a two-bite evaluation and (classic) single-bite evaluation did not find significant differences. However, the overall liking scores obtained from the second bite evaluation better reflected differences among samples according to their actual saltiness level [
66].
Bolhuis et al. [
59] showed that with the use of different sandwich fillings, it is possible to reduce salt level in brown bread by up to 52% without the use of substitutes or sodium intake compensation by choice of filings; also, no lowering of food consumption was observed. However, the study by Rødbotten et al. [
67] working with barley bread with normal and reduced (−50%) salt content (starting at 1.3% of salt by weight of flour) reported a significant decrease in consumer liking score. It is evident from our results that approaches for salt reduction should be made on a product-specific basis even within the same food category. Therefore, for multigrain breads, salt reduction must be implemented more carefully, whereas for white breads, salt reduction of at least 15% can be done without risking a negative consumer response.
To provide further insights, our next focus was the analysis of hedonic liking vs. the perceived intensity of the saltiness level. When consumers were asked to assess the saltiness intensity of the bread samples using the JAR scale, aggregated analysis yielded no significant differences. The consumers, on average, perceived all the bread samples in our study as slightly unsalted—i.e., they scored the samples slightly below the JAR salty level. Moreover, when both the perceived saltiness intensity scores and actual salt concentration in breads are correlated, inconsistent patterns are revealed, suggesting that untrained consumers are unable to discriminate modification of the salt levels in testing breads. For example, the respondents scored the multigrain bread (MGB3) with highest salt level (1.4 g/100 g) as the least intense in saltiness, whereas for all white bread samples, the perceived intensity of saltiness is practically identical. Therefore, modification of the salt content did not evoke differences in saltiness intensity perception. However, previous researchers warn that separately considering the consumer’s hedonic liking of a product and a sensory attribute intensity perception (e.g., saltiness) can result in misleading conclusions [
68,
69]. In order to diminish this risk, our research combined hedonic liking and JAR scores using the penalty analysis, which provided further valuable information. The results show that consumers penalize hedonic liking scores if breads are perceived as non-optimally salty. The two sub-groups of consumers perceiving the bread as having either “too much salt” or “not enough salt” gave statistically significant lower liking scores in comparison to the “JAR” sub-group. Therefore, perceived saltiness intensity was a clear liking driver for hedonic liking scores, which systematically decreased due to the perceived non-optimal saltiness level. The already-described relationship between liking and saltiness intensity [
70] has been confirmed, since the results form an inverted U-shaped curve with highest hedonic liking for the breads with an optimum salt intensity (JAR salty level) and overall liking decreases above and below this point. Therefore, in order to successfully reformulate “less healthy” foods, producers should understand complex relations between sensory attributes and consumer liking [
15]. In the case of salt reduction in breads, the objective is to avoid diminishing the perceived intensity of the key liking drivers, and salt plays an important role in bread despite the fact that saltiness itself is not a dominant flavour of this product category. It is responsible for overall flavour profile, amplifying sweetness, and masking bitterness [
22,
71].
Additionally, results of the penalty analysis revealed a significant degree of heterogeneity of the consumers regarding their response towards perceived differences in saltiness intensity. This reinforces the somehow overlooked challenge for food producers that it is not necessarily appropriate to treat all consumers with a single strategy for salt reduction. The number of studies recognising the importance of considering potential differences between consumers in food product reformulation success has only recently increased [
26,
57,
72,
73,
74]. In order to contribute towards the understanding of this aspect of food reformulation, the present research provides further confirmation of previously reported differences between consumers. The segmentation is based on the perceived saltiness intensity measured with the JAR scale, since the correlation of product liking and perceived saltiness intensity level has been clearly confirmed [
75,
76,
77] but not extensively studied. Latent class clustering identified three clusters differing significantly in the saltiness perception of breads. The “salt adherent” consumers consistently perceived bread samples as having not enough salt; they tend to be more common in the lower–mid age groups of the population and are rarely retired. They also report a higher education level and are more commonly male. Vice versa, the “salt sensitive” cluster members are predominantly female, and more often either retired or students, which gives the cluster a bipolar age distribution. The perceived saltiness intensity of the “salt sensitive” cluster was higher for all breads. Approximately two-thirds of consumers fall into the “salt indifferent” cluster, and their perceived saltiness was in between the two abovementioned clusters. Since the hedonic liking of the non-optimal saltiness level significantly affects hedonic liking score, it is important to focus on the consumers perceiving breads as not-JAR for salt and to understand their bread purchasing behaviours and consumption-related characteristics. This is due to the reduced risk of adverse effects from bread reformulation, which is an important barrier for industrial activities in salt reduction programs.
Our results also show that the “salt sensitive” cluster systematically assign lower importance rates for the extrinsic attributes of breads compared to the other two clusters; however, the rankings of attributes are very similar. A similar pattern was also revealed for the intrinsic bread attributes, but it is noteworthy to point out two explicit differences. The “salt sensitive” group ranks the taste of bread as the most important attribute, but importance is significantly lower than for the other two clusters. Finally, the least important intrinsic attribute of bread for the “salt adherent” and “salt indifferent” clusters is the salt content, however the “salt sensitive” cluster rates this attribute as slightly more important than the high fibre content and no additives in bread attributes. This is in contrast with the conclusions of other researchers who underlined that the perceived individual health benefits present an essential motivation in bread choice [
78,
79]. The low importance of health-related bread attributes (e.g., low salt, high fibre and no additives) is also confirmed by the result of the PCA. When the main sources of variation were extrapolated, one can conclude that the “salt adherent” cluster is clearly associated with the sensory and rheological variables of bread (e.g., taste, not crumbling, soft core, crispy crust), whereas the “salt sensitive” cluster stepped out by an indicative negative correlation to the health-related variables, and similar trends were revealed for intrinsic attributes and the marketing-related variables. It is clear that the so called “credence quality attributes” [
80], which are not self-evident and are based on consumer trust, have relatively limited importance when purchasing bread. Consumer quality perception of bread is mainly determined by sensory and health attributes, which further influence purchasing decision making [
81]. Such complexity might be assigned to various determinants, however consumers’ perceived relevance of determinants for their own food choices are not necessarily the most important explaining factors [
82,
83]. Habits related to eating and acquiring foods explain a large number of choices, which is also of particular importance when the saltiness in food is concerned [
84], followed by food experiences by culture, age, gender and taste phenotype [
75,
77,
85]. Certainly, the process of bread reformulation should be managed by considering the related eating habits and individual differences in this respect. Our results also confirm significant variability, particularly with regard to practices and behaviours related to adding salt by consumers. Furthermore, previous research shows that people with high-sodium diets tend to prefer foods with higher sodium levels [
86,
87], whereas the opposite trend has been observed for those who follow low-sodium diets [
86,
88,
89]. Our results show that the “salt adherent” cluster members are notably heavier in habit of adding additional salt at the table, but they are also highly aware of their excessive salt use and significantly less attentive in limiting their salt consumption. Studies suggest that general changes in dietary habits are needed for an effective decrease in salt content to affect NCD risks [
90,
91,
92]. A survey by Mørk et al. [
74] showed that consumers who have already changed their dietary salt intake or intend to do so are also more willing to purchase salt-reduced food products. To change dietary habits, salt awareness and knowledge needs to be increased, since significant deficits have been detected in this respect. Sarmugam and Worsley [
93] reported that consumers recognize health risks associated with high salt intake, but knowledge of recommended daily intakes, understanding of the salt–sodium ratio, and foods that contribute the most salt to diet is poor. On the other hand, our results showed quite high and homogenous awareness of the negative health consequences from excessive salt consumption. This is comparable with the study by Newson et al. [
25] that also showed high level of consumer awareness in this respect and understanding the necessity of salt intake control. Also, Di Vita et al. [
94] showed evidence of a certain risk consciousness among the more vulnerable subjects, such as overweight individuals. Moreover, they found that body mass index (BMI) significantly influences willingness to pay (WTP) for low salt bread alternatives, highlighting that this specific sub-group of consumers shows positive intention to pay a price premium for healthier alternatives. Certainly, specific groups of consumers are increasingly oriented towards healthier diets and consequently bread producers are extending their assortment with healthier options such as organic, whole grain, ancient grain (pseudo-cereals) or sourdough breads. Health benefits are often among essential motivations for the choice of bread, but research shows that consumers are not necessarily aware of their main salt intake source [
25,
31]. When they are asked to estimate where the most salt in their diet comes from, 43% of consumers globally reported that their main salt intake source was salt added during cooking [
25]. Our results also suggest that the consumers are usually not aware of the main sources of salt intake. The largest share of the consumers in our research believe that the most appropriate approach for managing salt intake is careful use of salt during cooking (36%), followed by the limitation of the addition of salt at the table (32%). This is despite the commonly agreed fact that in developed countries, only about 15% of dietary salt originates from addition during cooking or at the table [
11,
16]. Furthermore, non-adherence to salt restriction appears to be a complex problem and studies showed that consumer behaviour change based on education and awareness-raising interventions alone are unlikely to be adequate in reducing population salt intake to the recommended levels [
95]. A significant difference was observed between the clusters in this study, where the “salt sensitive” subjects highly agree that limiting the use of salt at the table is the most appropriate approach to reduce salt consumption in the population, and the level of agreement from the “salt adherent” cluster is statistically significantly lower. Finally, the full sample and all the clusters place the selection of breads with lower salt content as the least effective approach to limit salt intake, which brings out the issue of consumer information deficit. Adequate consumer understanding and awareness related to the sources of dietary salt and adverse health consequences of excessive salt consumption is a precondition for necessary habit changes, and in combination with optimal management of other closely related processes (e.g., scientific understanding, industrial reformulation and government incentives), will lead to the nutritional optimization of processed foods [
15]. Evidence of the positive effects of food product reformulation are strong for sodium interventions [
17], which means that reducing salt in bread as one of the main salt sources in our diet may be one of the most effective strategies to reduce the risk of NCDs. The best achievements in salt reduction can be achieved with a combination of multiple population-wide regulatory policies that also include mandatory reformulation and food labelling [
96]. It should be also mentioned that sensory acceptability of low-salt foods can be also achieved with the use of herbs and other no-salt seasoning blends [
97], but is likely that such foods will be of particular interest to more health-conscious consumers, while a reduction of salt in the market-leading types of bread will affect much larger population groups.
A major strength of this study is the inclusion of two types of breads, both of which were based on market-leading bread formulations taken as a reference for the experimental samples. The consumer sensory evaluation was done on a relatively large sample, making the results particularly relevant. While non-probability sampling was used, we aimed for a balanced representation of genders and age groups. A possible limitation of the study could be that we tested samples with relatively small differences in salt levels (national average; −15%; +10%), which turned out to be challenging for consumers to detect. However, this approach was intentional and can be also considered as study strength. Namely, the tested levels of salt concentration are highly pertinent with regard to the real reformulation targets of Slovenia and many other countries, as well as currently existing levels of salt in breads on the market. While we would probably be able to detect more significant consumer responses if larger differences in salt level were applied, the results of such a study would be less relevant for meeting real-life food reformulation challenges. Bread is also rarely consumed alone, thus our study design could be upgraded by the addition of commonly eaten spreads or sandwich fillings [
59], and may as such give more relevant, real-life results. A further limitation of the study is also the focus on overall liking and saltines perception in breads, whereas reduction of salt clearly also influences other bread quality characteristics which are important for consumer acceptance. Therefore, further research is needed to analyse the effects of salt reduction on other flavour constituents, particularly for multigrain breads. Better insight is needed for clear recommendations to the baking industry on how to retain the sensory characteristics of the salt-reduced multigrain breads. Finally, another possible limitation of the study could be that we did not explicitly evaluate some relevant physiological parameters (e.g., hunger, thirst) of the consumers which could affect sensory evaluation and saltiness level perception [
98,
99]. This would certainly improve the quality of the results.