Assessment of the Erosive Potential of the Commonly Consumed Fruit-Based Beverages Among Children

Introduction

The evolution of mankind has brought about drastic changes in the dietary patterns. The diet has become more refined and is associated with a substantial increase in the consumption of carbonated beverages and fruit drinks.¹ As the awareness on the deleterious effect of carbonated beverages on the teeth is increasing the preference for more natural and healthy products such as fresh fruit juices have increased. Fruit juices are popular among all age groups, especially children, as they are perceived to be tasty and healthy, leading to an upsurge in the consumption of fruit juices. Also, commercially, packed fruit juices are being marketed aggressively and promoted as “Health Drink”. However, claims of safety of fruit juices for teeth are unsubstantiated.²

Dental erosion is an irreversible loss of dental hard tissue by a chemical process without the involvement of microorganisms and is due to either intrinsic or extrinsic sources.^3-5 The dietary factors represent the most important external risk factor for dental erosion in children due to the general high consumption of acidic foods and drinks. Many commonly consumed beverages have pH sufficiently low to erode and soften the enamel surface. Acidic beverages are thus likely to be a major factor in the etiology of dental erosion, which is common among children and adolescents.

The most important parameter of beverages effecting dental erosion is their pH, titratable acidity and their ability to cause dissolution of tooth structure. The pH is a good predictor of the erosive potential of drinks for the first few minutes of erosive challenge, while the titratable acidity characterizes the erosive potential during longer exposure times.

As there is an increase in the consumption of fruit juices, which are considered to be healthy, the present study was undertaken to evaluate the erosive potential of commonly consumed fruit-based beverages among children.

Material & Methods

The present in vitro study was conducted in the Department of Pediatric and Preventive Dentistry, Sri Rajiv Gandhi College of Dental Sciences and Hospital, Bengaluru in collaboration with Analytical Research & Metallurgical Laboratories, KSSIDC complex, Electronic city, Bengaluru following clearance from Institutional Review Board, Sri Rajiv Gandhi College of Dental Sciences and Hospital, Bengaluru.

Three commonly consumed flavours (Orange, Apple, Mixed fruit,) of the fruit-based beverages (fresh fruit juice, packed fruit juice and packed fruit drink) were selected and divided into three groups as follows:

Group I: Fresh fruit juice (freshly extracted)

Group II: Packed fruit juice (commercially available)

Group III: Packed fruit drink (commercially available)

The fruit-based beverages were analyzed for pH and titratable acidity. The composition of the fruit juices is as described below.

I. Fresh Fruit Juices: 100% juice (Orange, Apple, Mixed fruit) was freshly extracted without added sugar or water.

II. Packed Fruit Juice (commercially available)

III. Packed Fruit Drinks (commercially available)

Assessment of pH and titratable acidity

The initial pH was determined using a digital pH meter (Hanna, USA). The digital pH meter, with an accuracy of 0.1 was first calibrated according to the manufacturer’s instructions employing buffer standards (pH 4 & 7) at room temperature. The titratable acidity was then measured by adding 1M sodium hydroxide (NaOH) in increments of 0.2 ml to 100 ml of the freshly prepared/ opened fruit-based beverages until the pH reached 5.5 and 7. The pH reading was measured after each increment (0.2 ml) of NaOH, until a stable pH was achieved. All the measurements were repeated in triplicates. The collected data was tabulated and comparisons were made amongst the three study groups.

Results

pH assessment

The intra group comparison of the pH of the three study groups is represented in Table 1.

In Group 1 (freshly extracted fruit juice), orange juice exhibited the lowest pH (3.46) followed by mixed fruit (3.88) and apple (4.43). In Group 2 (packed fruit juice), the apple juice (3.72) exhibited lower pH compared to orange juice (3.76) and mixed fruit juice (3.84); while in Group 3 (packed fruit drink), apple juice (3.24) demonstrated lower pH in comparison to mixed fruit juice (3.28), orange juice (3.48).

Titratable acidity

Intra group comparison of the titratable acidity

The intra group comparison of the titratable acidity (ml NaOH) of the three study groups at pH 5.5 and 7 is depicted in Table 2.

In Group 1: Orange juice exhibited the highest titratable acidity of 6.4 and 10.2 at a pH of 5.5 and 7 respectively. The mixed fruit juice demonstrated a titratable acidity of 4.8 and 7.0 at pH of 5.5 and 7 respectively, while the apple juice demonstrated a titratable acidity of 1.4 and 3.4 at pH 5.5 and 7 respectively.

In Group 2: Orange juice exhibited the highest titratable acidity of 8.8 and 15.6 at pH of 5.5 and 7 respectively, followed by apple juice 7.8 and 9.0 at pH of 5.5 and 7 respectively and mixed fruit juice 5.6 and 9.0 at pH of 5.5 and 7 respectively.

In Group 3: Mixed fruit demonstrated the highest titratable acidity of 9.8 and 12.8 at pH of 5.5 and 7 respectively, followed by orange juice 8.2 and 12.2, and apple juice 7.4 and 8.4 at pH of 5.5 and 7 respectively.

Inter group comparison of the titratable acidity

The inter group comparison of the titratable acidity of the three study groups at pH 5.5 and 7 is depicted in Table 3. On intergroup comparison of different flavours, the mixed fruit juice exhibited the highest titratable acidity in Group 3 (9.8 and 12.8) followed by Group 2 (5.6 and 9.0) and Group1 (4.8 and 7.0) at pH 5.5 and 7 respectively.

Orange juice exhibited the highest titratable acidity in Group 2 (8.8 and 15.6) followed by Group 3 (8.2 and 12.2) and Group 1 (6.4 and 10.2) at pH 5.5 and 7 respectively.

Apple juice exhibited the highest titratable acidity in Group 2 (7.8 and 9.0) followed by Group 3 (7.4 and 8.4) and Group1 (1.4and 3.4) at pH 5.5 and 7 respectively.

Discussion

The diet has been the most extensively studied etiologic factor in dental erosion. The mineral loss from teeth and its association with dietary factors may be due to the constantly changing life styles and dietary patterns, which involves increased sugar and acidic exposures in the form of fruit juices or carbonated soft drinks as part of a refined diet. The awareness among parents of the harmful effects of carbonated beverages on the teeth has led to an increased preference for more natural and healthier fresh fruit juices, which are also regarded as a good source of vitamin C. However, as fruits and fruit juices contain a variety of acids that can have a detrimental effect on the teeth, the present in vitro study was conducted to evaluate the erosive potential of commonly consumed fruit based beverages among children.

Two ways to quantify the acid content or the erosive potential of foods and beverages include pH and titratable acidity (neutralizable acidity). The pH or actual acidity is the negative logarithm of the hydrogen ion concentration (actual hydrogen ion concentration) and is measured on a scale of 0 to 10, with a reading below 7 indicating an acid content or environment. The neutralizable acidity is regarded a more realistic and accurate method of measuring the potential acidity in a given beverage.⁶ The pH corresponds to the equilibrium measure of hydrogen ion concentration, but it does not indicate the overall acidic content of the drink or food, whereas, titratable acidity gives a measure of all free hydrogen ions available to cause erosion.⁷

In the present study, the pH and titratable acidity of three commonly consumed flavours (orange, apple, mixed fruit) of freshly extracted fruit juice and commercially available packed fruit juice and packed fruit drink selected on the basis of a simple market survey was determined. The pH of all drinks investigated in the present study ranged between 3.29 to 4.43, which was well below the critical pH of 5.5 at which enamel dissolution occurs. Also, in the present study packed fruit drink (Group 3) exhibited highest titratable acidity followed by packed fruit juices (Group 2) and fresh fruit juices (Group 1).

Jensdottir et al., (2005)⁸ observed that fruit juices, especially pure fruit juices had a high titratable acidity and accordingly a high buffer capacity compared to the carbonated soft drinks coca cola. Saeed S et al., (2010)⁹ on comparison of the erosive potential of fresh orange juices, cola and milk, found that the orange juice showed highest titratable acidity of 41.33 (ml 0.1N NaOH) compared to cola (4.8 ml 0.1N NaOH) and milk (2.02 ml 0.1N NaOH). Similarly, in the present study, orange juice in Group 1 (freshly extracted juices) and Group 2 (packed fruit juice) showed highest titratable acidity of 10.2 (ml 0.1N NaOH) and 15.6 (ml 0.1N NaOH) respectively.

Saha S et al., (2011)¹⁰ on evaluation of the acidogenic potential of commonly consumed freshly prepared fruit juices (pomegranate, lime) and commonly consumed commercially available fruit juices (guava and apple) at room temperature on pH of saliva at various time intervals, observed that all the fruit juices were acidic and reduced the salivary pH of saliva at various time intervals, with the commercially available fruit juices being more acidogenic than the fresh fruit juices. The group consuming commercially available packed fruit juices showed maximum drop in salivary pH, dropping to critical pH level (5.5+3) at 1 minute interval, followed by gradual recovery within 30 minutes of study. This greater drop was attributed to the relatively lower intrinsic pH of commercially available fruit juices.

Bamise et al., (2007)¹¹ on determination of the erosive potential of commonly consumed soft drinks in Nigeria, which included cola drinks, non cola drinks and fruit juices, observed that cola drinks despite having the lowest pH on opening were easy to neutralize than the fruit juices and non cola drinks. Banan LK et al., (2005)¹ on evaluation of plaque and salivary pH changes following consumption of fresh fruit juices (grapes, orange and pine apple) observed that the fruit juices demonstrated a low pH ranging between 2.97- 4.11, and brought about a maximum percentage reduction in plaque and salivary pH within 5 minutes of consumption. Birkhed DC et al., (1984)¹² observed that fruit juices had the highest titratable acidity, approximately 2-3 times higher than the carbonated beverages and sports drinks. In the present study, it was observed that all the test beverages demonstrated erosive potential. It was further observed that the inherent pH of the fruit beverages gave no indication of the underlying titratable acidity and therefore, the erosive potential of the drink. Generally the more the titration required, the higher the buffering capacity, with a corresponding increase of erosion potential on dental enamel.

Conclusion

All the fruit beverages in the present study exhibited an erosive potential. Due to the potential detrimental effect of fruit-based beverages on the teeth, especially of very young children, the emphasis should be on increasing the public awareness of the modern society, mainly the parents about the harmful effects of these beverages. The importance of consumption of whole fruits rather than fruit juices should be accentuated.

Conflict of Interest

None.