Frozen desserts are defined in the food product standard and specification of the Ministry of Food and Drug Safety as the frozen products of raw milk, processed milk, and drinking water to which other foods or food additives are added, including ice creams, ice cream mix products, ice cakes, and edible ice. The types of frozen desserts; ice creams, ice cream mix products, ice cakes, and edible ice, are subcategorized further. Particularly, ice creams are divided into ice cream, low-fat ice cream, ice milk, sherbet, and non-fat ice cream [1]. The regulations in South Korea require commercial frozen desserts to have their type marked on the packaging. In addition, as frozen desserts are stored in a frozen state that prevents changes in quality or microbial growth; hence only the date of manufacture should be marked without shelf life or best before date [2].

The frozen dessert market size in South Korea has shown a trend of decrease from 2.02 trillion KRW in 2015 to 1.43 trillion KRW in 2019 [3]. This may be due to the reduced sales caused by a fall in the population of children, the main consumers of frozen desserts. However, the sales in the first half of 2020 showed a slight increase compared to the same time in 2019. In addition, the trend of social media buzz volume of ice cream increased from January to April 2020, compared to the same period in 2018 and 2019. This has been attributed to the increased home purchase of desserts including ice creams under the influence of abnormal temperatures and the COVID-19 pandemic that began in 2020 [4].

In 2018, the percentage of children aged 5 years with the experience of childhood caries was 68.5% showing a steadily increasing trend from 61.5% in 2010, while the caries prevalence in primary dentition also increased from 2.99 in 2010 to 3.43 in 2018. The percentage of children aged 12 years with caries of permanent tooth was 56.4% in 2018 exhibiting a decrease compared to 60.5% in 2010, while the caries prevalence in permanent dentition also slightly decreased from 2.08 in 2010 to 1.84 in 2018 [5]. However, the experience of caries in primary dentition is rising and that in permanent dentition is falling.

Dental caries is caused by the complex action of a diversity of factors including bacteria, host, diet, and time [6]. As dental caries is an irreversible condition, an emphasis is placed on its prevention in growing children to maintain oral health. Notably, oral health is influenced by the nutritional contents and food intake; thus, dietary control is an essential part of the prevention of dental caries in early childhood. In a study investigating the correlation between dental caries and intake of desserts in elementary school children, the prevalence of dental caries was shown to be correlated with the frequency of dessert intake after lunch and the number of tooth brushing after lunch [7] to suggest the need for the management of the dental plaque and the dietary control to restrict the time and frequency of dessert intake.

Frozen desserts are foods with high sugar contents that may influence the incidence of dental caries in children as the main consumers. As they are readily available in various forms at ice cream shops and discount shops whose numbers have recently increased, and considering the increased consumption of ice creams at homes related to the COVID-19 pandemic [8], care should be taken by the general public in the management of oral health.

While numerous studies have analyzed the influence of energy drinks on dental erosion [9] and enamel surface [10,11], and the characteristics of beverages in relation to dental caries such as carbonated drinks and their effects on enamel erosion [12], no study has yet examined the characteristics of frozen desserts by type regarding the causal factors of dental caries. This study thus aimed to determine the effects of the different types of frozen desserts on dental caries in children by analyzing the sugar content, acidity, and viscosity of each type of frozen dessert.

With the changes in population structure due to low birth rate and aging, the commercial frozen dessert market size in South Korea has steadily decreased until 2019 from the peak of 2 trillion KRW in 2015. In 2020, however, the frozen dessert sales suddenly increased with the prolonged time of stay at home since the winter of 2019 due to abnormal temperatures and the COVID-19 pandemic [8]. In other words, as the number of people enjoying home meals and desserts increased, the sales of frozen desserts increased.

On the part of the consumers, frozen desserts are advantageous in allowing relatively low cost to enjoy a variety of tastes and types, while simultaneous concerns on the high calorie and sugar content that could negatively affect the health may be raised [4]. The intake of frozen desserts may also affect oral health as the sugars and other factors such as viscosity could cause dental caries or periodontal diseases.

In this study, the risk of dental caries was determined for frozen desserts by comparing the risk factors including acidity, specific viscosity, and sugar content among the different groups of commercial frozen desserts, in line with the increased consumption of frozen desserts at homes.

Sixty frozen dessert products were divided into three groups and analyzed, and the results showed that the ice cake group had the lowest mean acidity (3.67) among the characteristics related to dental caries. In a study investigating beverages for children, the mean pH of commercial beverages was 3.41, while that of beverages sold by cooperative associations was 3.67, indicating similar pH levels between beverages and ice cakes [15]. Ice cakes are produced by mixing drinking water with food or food additives to be frozen, and they do not belong to ice creams or ice cream mix products [1]. Ice creams are produced by adding food or food additive to the basic ingredient of raw or processed milk to be frozen or hardened [1] so that naturally, the contents of raw or processed milk of ice cakes are lower than ice creams. In addition, most ice cakes are characterized by unique fruit taste or flavor, which may reduce the acidity compared to other frozen dessert products. The correlation of food acidity with dental health has been identified across numerous studies, and energy drinks and carbonated drinks with low acidity are a known cause of dental caries [10,16]. Kim et al.[16] reported that the mean acidity of seven beverage types including juice, ion drinks, and carbonated drinks, was 3.01, which was similar to the acidity of ice cakes. These commercial beverages were also reported to induce the risk of dental caries by reducing the enamel surface hardness. Thus, it is recommended that a straw be used in drinking beverages with low acidity to minimize contact with the tooth surface and that the mouth be rinsed with water after drinking [10,17]. Most ice cakes are ingested after they melt in the mouth so that the retention time in the oral cavity is longer than beverages. Thus, the mouth must be rinsed with water immediately after the intake of an ice cake product to minimize the retention time in the oral cavity.

The Brix value and viscosity were higher for milk-fat and non-milk-fat ice creams than ice cakes. The milk-fat and non-milk-fat ice creams belong to the category of ice creams among frozen desserts [1], and in this study, the milk-fat group included ice cream and ice milk products whereas the non-milk-fat group included sherbet and non-milk-fat ice cream products. Ice creams are produced from the basic ingredient of raw or processed milk; therefore, they all contain (milk) fat. Thus, compared to ice cakes produced based on drinking water [1], the viscosity and sugar content appear to be comparatively high. The high viscosity indicates the longer time of retention in the oral cavity such as on the tooth surface upon intake due to low flow ability. The increase in retention time of foods with high sugar contents, in turn, increases the dental caries activity. The mean acidity of milk-fat and non-milk-fat ice creams was 6.37 and 6.29, respectively, a level similar to water. Thus, for these products, the dental caries activity increases with an increase in viscosity or sugar content rather than acidity.

In a study conducted on children, the generally preferred dessert type was soft ice creams (51.1%), followed by crispy snacks (30.0%) and semi-solid yoghurts (14.5%) [7]. In another study regarding food preference of pre-school children, the most preferred food was ice creams for both boys and girls [18]. As such, frozen desserts exhibit high preference by children, with easy availability based on accessibility at close markets and relatively low cost for children. Thus, it is necessary to increase the direct awareness in children regarding the potential impact of frozen dessert intake on oral health, while continuous education should be given regarding the appropriate oral health management after frozen dessert intake and control of the frequency of intake. In addition, as home meals and desserts have increased with the COVID-19 pandemic, the parents and guardians should also be guided to assist their children with proper oral health management after the intake of frozen desserts at home.

Not every commercial frozen dessert product could be analyzed in this study, while only the viscosity, acidity, and sugar content among the dental caries risk factors were examined. This prevents the results in this study from generalization to the association between frozen desserts and dental caries or oral health. In addition, although all products were equally kept at room temperature for 4 hours prior to measurement, all products could not be analyzed at the same temperature condition, which poses a limitation. However, considering the general lack of studies regarding the correlation of the characteristics of frozen desserts with oral health as well as the current increase in the intake of frozen desserts, this study is significant in having analyzed the association between frozen desserts and oral health. Further studies should examine more variables such as the CFU of acid-forming bacteria and salivary buffering capacity in analyzing the correlation of the intake of frozen desserts with oral health.

This study investigated the nutritional contents as well as sugar content, acidity, and viscosity of sixty frozen dessert products produced and marketed in South Korea, after random selection and categorization in accordance with the classification criteria into ice cake, milk-fat ice cream, and non-milk-fat ice cream. The findings in this study are as follows:

1. Analyzing the nutritional contents showed that the sodium content was the highest (59.94 mg) in non-milk-fat ice creams and significantly low (15.94 mg) in ice cakes. The fat content was the highest (7.07 g) in milk-fat ice creams.

2. The lowest acidity was 2.70 for ice cakes, 4.83 for milk-fat ice creams, and 5.16 for non-milk-fat ice creams. The highest Brix value as measured using the digital Brix meter was 32.53 for ice cakes, 42.3 for milk-fat ice creams, and 43.3 for non-milk-fat ice creams. The viscosity increased from 19.75 for ice cakes to 71.67 for milk-fat ice creams to 119.70 for non-milk-fat ice creams.

3. Analyzing the characteristics related to dental caries activity per product type showed that the pH was the lowest (3.67) for ice cakes, while the sugar content was significantly higher for milk-fat ice creams (33.22) and non-milk-fat ice creams (32.89) than ice cakes (p<0.05). The specific viscosity was also the highest for milk-fat ice creams (32.62) and significantly low for ice cakes (9.42) (p<0.05).

The intake of frozen desserts at homes has shown a trend of increase with abnormal temperatures and the COVID-19 pandemic. To prevent childhood caries at home, education for the children and their parents and guardians should be provided regarding appropriate oral health management methods such as reducing the frequency of frozen dessert intake and rinsing the mouth with water immediately after intake.