**1. Introduction**

Bread is a part of the foodstuffs that are the basis of many people's diets due to its nutritional value and the low price that is reflected from the flour from which it is obtained, the auxiliary materials used, and the technology applied. Food experts define bread as a staple food at the top of the food pyramid due to its rich content in carbohydrates, fiber, protein, B vitamins and mineral salts [1]. In most European countries bread is the most important sources of salt, its contribution to salt intake ranging between 19.1% in Spain to 28% in France [2].

According to the World Health Organization, processed foods such as bakery products are the main daily source of sodium in consumers' diet for developed countries, with an average of about 75–85% of the total sodium intake, while 5–10% are naturally provided from foods consumption that are part of the daily diet and the remaining part of 10–15% of sodium are provided from sodium chloride addition during cooking or eating [3]. However, in developing countries, salt addition during meal preparation presents a much more important role [4]. Globally, the sodium intake from processed foods is much higher than the intake of unprocessed, naturally consumed foods [5].

Although sodium is a normal constituent of the human body, distributed in the extracellular compartments, performing many functions with beneficial effects on the body, excessive sodium intake is associated with cardiovascular diseases caused by increased hypertension [6].

Epidemiological studies on hypertension have shown that many people from countries where salt consumption is high also presented high hypertension values [7]. Often, the salt consumption covers 35–50 times the renal needs and it can be concluded that one of the fundamental characteristics of contemporary diet is an excessive salt intake. It is considered

**Citation:** Codin ˘a, G.G.; Voinea, A.; Dabija, A. Strategies for Reducing Sodium Intake in Bakery Products, a Review. *Appl. Sci.* **2021**, *11*, 3093. https://doi.org/10.3390/app11073093

Academic Editor: Monica Gallo

Received: 1 March 2021 Accepted: 27 March 2021 Published: 31 March 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

that two main factors have contributed to this situation: a behavioral factor in humans salt intake which is not dependent on real needs but on the taste for salt artificially created and which is part of a hedonic behavior that develops since childhood; the second factor is the urbanization that has led to a consumption of industrialized foods in which sodium chloride is used as a flavor additive and preservative. As a result, increased consumption of salt is a relatively recent food habit, which greatly demands the body's ability to adapt [8].

Nowadays, consumers' concerns about excessive sodium intake and its associated effects have increased, and that is why some food companies have changed their product portfolios to reduce sodium intake and to promote healthier diets. An example of this is Nestle, which eliminated almost 7500 tons of sodium from their products starting 2005 [5].

Although consumers are now becoming aware of the negative effects of salt excess consumption on their health, they do not have much information on the salt connections with sodium consumption. In developed countries, consumer awareness of proper nutrition and nutritionally healthy behavior is increasing nowadays especially through education [9,10]. Unfortunately, in underdeveloped countries the level of education regarding proper nutrition behavior is very low and therefore the population awareness on the negative effect of excessive sodium consumption on health is not very high [10].

From the consumer behavior point of view, sodium chloride increases the acceptability of many foods by intensifying the salty taste and flavor and by trans-modal interactions which increase the taste of other aromatic compounds and decrease or eliminate the bitter taste [3]. It seems that the sensitivity to salt varies in the same individual from one moment of life to another: depending on age, blood pressure level, obesity, pregnancy, various diseases, drugs consumed, and even race etc. risk [11].

Sodium chloride is one of the raw materials in the bakery industry, which is used to make all bakery products except salt-free dietary products. It has an important role on the sensory characteristics of bakery products but also on the technological characteristics of bread making such as dough rheological properties, enzymatic and microbiological dough activity, and bread quality [11]. Nowadays, bread is considered one of the most important sources of salt in the diet, contributing 25% of the amount of salt consumed by the population. Therefore, for a reduction in salt intake it is necessary a reduction of salt in the bakery products. In general salt is used as a food ingredient, as a preservative, to improve moisture retention and to increase food sensory characteristics. Although in some cases it is impossible to reduce the salt content from foods, in many others it is possible to obtain processed foods with lower sodium content. This is also the case for bakery products which are the largest contributor to dietary sodium intake in Great Britain and the USA [12].

Nowadays, almost every EU country has different strategies which includes recommendation for salt reduction via food reformulation to reduce the salt content from food products including bakery ones. For example, different programs are developed in EU such as "STOP SALT!" in Hungary, "Gaining health: making healthy choices easier" in Italy which encourages in especially salt reduction in bread, in Bulgaria the National Food and Nutrition Action Plan 2012–2017 promotes salt reduction, etc. The bakery products reformulation strategies for salt reduction are continuing in EU countries, some examples in this regard being the following: in Austria the salt reduction has been established of 15% up to 2015 by the Federal Ministry for Health, in Italy of 10% up to 2012 by the Ministry of Health, in Spain of 20% up to 2014 by the Ministry of Health and Social Policy, in Hungary, the Hungarian Bakery Association recommended reducing salt in bread to reach, after December 2018, a maximum level of 2.35%, etc. [13].

Numerous strategies have been proposed to reduce sodium chloride in foodstuffs including bakery products, in order to improve the health of the population. The challenge of these strategies is to solve the technological and sensory problems caused by sodium chloride removal from bakery products recipe. From the technological point of view, a salt reduction up to 0.6% may conduct to bakery products without a significant negative effect on dough rheological properties. However, its effect on the sensory properties of bakery

products may be a problem due to the fact that the salty taste is difficult to be achieved [1]. There are a number of combinations of substances proposed as salt substitutes, which will be discussed in a more detailed way in point 4 of this review, but they still may offer to the bakery products an unpleasant taste. Different combinations based on flavor enhancers, other type of salts, only partial substitution of sodium chloride from bakery recipe may offer some solutions for sodium chloride reduction. More, to reduce the negative effects of lack of salt on technological properties of bakery products it is recommended the use of another type of salt with similar effects on dough rheology as the one produced by sodium chloride. The proposed strategies for salt reduction are shown in Figure 1, methods that as we mentioned may be combined in order to increase bakery products flavor and salty taste.

**Figure 1.** Strategies of salt reduction in bakery products.

All these strategies along with sodium chloride effect on bread making, its physiological role on the human body and legislative norms regarding the international recommendation of daily sodium intake will be discussed further.

#### **2. The Physiological Role of Sodium Chloride and Legislative Recommendations on Its Consumption**

Sodium is among the top six elements in the earth's crust, comprising 2.83% sodium in all its forms. The most important sodium salts found in nature are sodium chloride, sodium carbonate, sodium borate, sodium nitrate and sodium sulfate [14]. To obtain sodium chloride, the weight of sodium must be multiplied by 2.54. Regulating the levels of sodium and chloride in the human body is an important biological process, maintained by multiple mechanisms that work to control them. In the human body, sodium and

chloride are the major constituents of the extracellular fluid, participating in maintaining the electrochemical gradient between the extracellular space and the cytoplasm. In the absence of this gradient, life is not possible. Their presence in the human body maintains the membrane potential that is absolutely necessary in the transmission of nerve impulses, muscle contraction and therefore cardiac function. Absorption of sodium in the small intestine promotes the assimilation of amino acids, glucose and water [1].

Sodium is a colorless crystalline compound found naturally in many foodstuffs and its most widely used form is sodium chloride, also named table salt. Salt has an important role in the human history. The ancient populations used salt to preserve food, salt being for them so precious that it could be exchanged for gold. Until the end of antiquity, salt was, along with amber and tin, one of the main currencies. In American history, salt has been a vital element for survival and during the Civil War it was used not only for foodstuffs but also for tanning the skin, dyeing clothes and preserving rations [15]. The need for permanent salt intake is one of the physiological needs to which man is exposed. Blood sodium concentration is an important homeostatic parameter that controls extracellular fluid volume and blood tonicity [11].

Nowadays salt is used as a spice and preservative in processed foods, being used in various forms such as sodium nitrite, sodium benzoate, monosodium glutamate and baking soda. It is present in processed foods such as soy sauce, canned meat and vegetables, soups, processed meat and almost any food with a long shelf life [15].

#### *2.1. Aspects Regarding the Effect of Sodium Chloride Consumption on the Human Body*

Sodium (Na+) is the dominant cation in the extracellular fluid of the human body. The functions of sodium consist in its participation in the control of the volume and systemic distribution of the total water in the body allowing cellular absorption of dissolved substances and generating, by interactions with potassium, of the trans membrane electrochemical potential [16]. Sodium ions are involved in transmitting electrochemical impulses along cell membranes to maintain normal nerve and muscle susceptibility. They contribute to the swelling of colloids in the tissues and thus cause the retention of bound water in the body. At the same time, sodium takes an active part in neutralizing the acids that form in the body. It is an element present in all organs, tissues and biological fluids, which plays an important role in intercellular processes and interstitial metabolism [17].

In the body of an adult with a weight of about 70 kg, sodium is found in the body in an amount of 92 g and is distributed differently from person to person but in identical concentrations in all people, regardless of sex, age and physical or intellectual effort [18].

Sodium has multiple roles in the human body, including:


Sodium is essential for cellular homeostasis and physiological function. Claude Bernard was the first to highlight the "internal environment". Walter Cannon defined homeostasis more clearly when he referred to the "fluid matrix" of the body and emphasized the role of sodium [20]. In the last few decades, there has been an increasing amount of work exploring sodium and dietary health. The amount of sodium needed to maintain homeostasis in adults is extremely low (<500 mg) compared to the average intake of most Americans (>3200 mg) [21].

Dietary sodium deficiency is rare in healthy European populations. Sodium chloride and other sodium salts are daily used in the diet and there are adaptive physiological mechanisms that reduce the loss of sodium from urine, feces and sweat to a low sodium intake. Sodium chloride addition during industrial food processing or food preservation is the main source of dietary sodium in Western diets. Other sources of sodium include inherent native sources and sodium-containing food additives, in which sodium may be associated with anions other than chloride.

In healthy people, almost all dietary sodium is absorbed, even at a high sodium intake. After absorption, sodium ions are distributed through portal and systemic circulations, where their concentrations are maintained in a limited range. Up to 95% of the body's sodium content is in the extracellular fluid, including a large amount in bone, skin and muscle. Sodium excretion and retention (homeostasis) is performed by an integrated neurohormonal control from the centers located in the hypothalamus. The kidney is the main organ that mediates the excretion and retention of sodium. It effectively excretes sodium in response to high sodium intakes from food and stores sodium when dietary intake is deficient. In contrast, the excretion of sodium in the feces is relatively stable and usually limited to a few mmol/day. The amount of sodium excreted through perspiration can vary greatly, depending on environmental conditions or levels of physical activity [16].

Excess sodium in the diet has been linked to high blood pressure. The sensitivity of blood pressure to salt varies greatly, but certain subgroups tend to be more sensitive to salt. The mechanisms underlying sodium-induced increases in blood pressure are not fully understood, but may involve changes in renal function, fluid volume, fluid-regulating hormones, vasculature, cardiac function, and autonomic nervous system. It was established that in hypertension cases excess salt is not only an aggravating factor, but can also be one of the triggers. It appears that there is a functional abnormality of red blood cell membranes in hypertensive population, which it is reported to the ratio between the net flows of Na+ leaving and the net flow of K<sup>+</sup> entering. This abnormality is genetically transmitted and allows sodium to enter into the cells in excess. Many arguments support the role of salt as a factor in promoting atherosclerosis. Recent preclinical and clinical data suggest that, even in the absence of an increase in blood pressure, excess dietary sodium can adversely affect target organs, including blood vessels, heart, kidneys, and brain [22]. In normal individuals, the increase in excess salt has no short-term effects. In the long term, if the kidney does not have the ability to regulate the concentration of sodium, as a result of excess of NaCl consumption, there is an increase in blood pressure in the peripheral vessels. To compensate the excess of Na+ and to prevent high blood pressure, a higher amount of natriuretic hormone is secreted. As a result, the sodium pump is injected from the erythrocytes and the smooth muscles of the vessels, which causes the membrane depolarization and the internal accumulation of calcium. Gradually, hypertonia is reached [8].
