Ice cream is a well-known dessert and snack among all ages in many countries [1]. Reported that ice cream is one of the major products in dairy industry and remains to dominate attention of large segment of the population. Its mixture is made of dairy products (e.g. whole milk, condensed milk, milk powder, cream) sweeteners (sugar, glucose) emulsifiers, stabilizers and colourings. Ice cream can also serve as a topping, add-on or mix-in for other desserts. In the Philippines, tropical climate has contributed to the popularity of ice cream as a "summer treat". It is in line with other Filipino cold desserts as reported by Gimena [2] like fruit shakes, ice scramble and halo-halo (mixed sweetened fruits, beans, tapioca pearls, agar, added with crushed ice and evaporated milk) [2].

Street vended homemade ice cream in the Philippines is also called “sorbetes”. Its usual and popular flavours are “keso” (cheddar cheese flavoured ice cream with cheese bits) “tsokolate” (brown coloured chocolate flavoured ice cream) and ube (violet/purple coloured, taro flavoured ice cream and has some small bits of real taro). The peddler of the said street vended ice cream popularly called as “sorbetero” markets the street-vended ice cream. The ice cream carts can keep the ice cream from melting especially under the hot tropical sun because it is stuffed with shaved ice and salt. Salt is added to decrease the temperature of the melting ice. The brine is cooler than the ice alone; therefore, it has the capacity to facilitate removal of heat from the sides of ice cream containers [3].

According to Gimena [2], local ice cream is being considered as “dirty ice cream” due to its native flavours and less aseptic production procedures. In the study of Orallo et al. [4] regarding microbial analysis of ice cream produced in big and small scale manufacturers in Metro Manila, ice cream from small scale manufacturers were proven to be positive with faecal coliforms which indicates the presence of faecal contamination in the said food item. The Total Coliform Count was beyond what was set by Bureau of Food and Drugs (BFAD). Despite the microbial contamination of street-vended ice cream, some Filipinos would still continue to patronize it because it is cheaper as said by Gimena [2].

The critical part is majority of ice cream consumers are young children including those of vulnerable age [5]. Food contamination may lead to different illnesses of the gut like loose bowel movement or diarrhea. Further, diarrhea may result to death because it causes dehydration [6].

Ice cream, in general, is vended both in packed containers (e.g. cups, cones, cylindrical metal and plastic containers with cover) and in exposed containers at some retail stores or ice cream parlours which is served by hand in scoops, cones or sundae cups across counter. Thus the microbiological characteristic of the ice cream during retail marketing can also be determined by the post-manufacture management of the item as well as efficiency and sanitary environment during frozen storage [1]. The Filipino sorbetes or street-vended ice cream is placed in an exposed container and served in scoops.

According to Soukoulis et al. [7], the quality of ice cream is influenced by several sensory attributes which are flavor, texture, melting quality, package, and appearance. These attributes also affect the consumer preference for different variants of ice cream. In this study, researchers have focused on the effects of flavour, texture and appearance on the overall preference of street vended ice cream. Also, the study will investigate on the microbiological quality of common variants of street-vended ice cream.

Three different variants of street-vended ice cream were given to consumers’ for sensory assessment, a 15 g portion of ice cream samples in a 60 ml plastic cup were served; each consumer is provided with water for palate cleansing. Panellists are 100 Thomasian students, who were untrained. Respondents were asked to evaluate the sample without any break, and ice cream samples were examined for the Degree of Liking (DOL) using a seven point Hedonic scale with the following definition: 1=dislike a lot, 3=neither like nor dislike, 5=like a lot.

Ice cream samples for microbial identification were collected from a local vendor situated in the area of University of Santo Tomas. Three samples are subjected for microbial growth identification. Chocolate, cheese and taro (purple yam) were the chosen flavours for sampling since these were the available flavours produced on the day of collection. Also, these are the common variants consumed by buyers. Samples were collected between 3 pm to 6 pm. All batches of the tub where each representative samples were taken were freshly produced the very same day. Representative amount of each flavours were placed in individual sterile containers and immediately transported in the laboratory for analysis.

Statistical analysis used to interpret data is Backer’s table for appearance, texture and flavour preference. For the overall liking, analysis of variance was used to determine the significant difference among the different ice cream variants. All statistical analyses used p<0.05 as level of significance.

Sensory Evaluation

Of the choices offered, 94% of the panellists liked cheese-flavoured street vended ice cream based on appearance. This can be accounted to the use of cheddar cheese by local manufacturers for cheese-flavoured ice cream. Cheddar cheese, according to USDA [8] has a color of medium yellow-orange with a uniform bright color, and an attractive sheen. This visual characteristic of cheese affects food perception and drives consumer preferences.

For the other two ice cream samples, 85% of consumers liked the brown color of chocolate variant and 83% of them preferred the purple color of taro variant (Figure 1).

Figure 1: Appearance Preference of Consumers on Street-Vended Ice Cream.

Preference of chocolate-flavoured ice cream can be accounted to color-flavor associations. Singh [9] mentioned that initial perception of foods happens within the first 90 seconds of observation. Color is commonly used as a basis for the initial judgment of foods. Further, consumer judgment is approximately 60 to 90% based on appearance [9]. Recent study by Wadhwani and Mcmahon [10] noted that consumer buying decisions can be influenced on the basis of color. This can also affect the cooking and eating decisions of the consumers.

According to Kemp et al. [11], texture perception is complex. Food texture can be characterized into two components, character notes and rheology [12]. Character notes are the perceptible texture attributes of food, which are of three types: mechanical and geometric [13]. This is observed among the panellists, wherein 89% of them extremely liked the cheese flavoured street vended ice cream in terms of texture (Figure 2). This type of ice cream is usually sold with cheddar cheese bits. The presence of cheese bits gives the mechanical texture of the sample. Mechanical properties, such as chewiness and hardness, which are the reactions of food in terms of stress [12].

Figure 2: Texture Preference of Consumers on Street-Vended Ice Cream.

Compared to the cheese-flavoured street vended ice cream, the less preferred street vended ice cream variants are taro at 81% and chocolate at 78% (Figure 2). Both of these variants have similar rheological properties. The use of taro as a flavouring for street-vended ice cream gives it a starchy and homogenous texture [14]. The starchy texture contributes to the viscosity in the street-vended ice cream, which is a rheological property of food. In addition, the texture of chocolate-flavoured street vended ice cream is due to the presence of cocoa butter. This ingredient influences the creaminess and richness of chocolate-flavoured ice cream, through the fat content [15].

When it comes to flavour, cheese-flavoured street-vended ice cream had the most number of respondents, at 87%, who liked it (Figure 3). Chocolate-flavoured street-vended ice cream had 87% of the respondents who liked the variant (Figure 3). On the other hand, 4% of the respondents disliked the chocolate-flavoured street-vended ice cream (Figure 3). Contrariwise, taro-flavoured street-vended ice cream had the least number of respondents, with 80%, who liked its flavour. Also, 11% of the panellists for taro variant were uncertain in terms of flavour preference (Figure 3).

Figure 3: Flavour Preference of Consumers on Street-Vended Ice Cream.

The preference for cheese-flavoured and chocolate-flavoured street-vended ice cream is due to its high-fat content. Cheddar cheese has approximately 33 grams of fat content and cocoa butter contributes to the fat content of chocolate-flavoured street-vended ice cream [8]. Cocoa butter in chocolate is composed of three fatty acids. In quantity, 30-37% of fatty acids are mono saturated oleic acid. The other fatty acids are 32-37% of saturated stearic acid and 23-30% of saturated palmitic acid [15]. According to Montmayeur and le Coutre [16], energy-dense foods that are rich in fat are more palatable than are low-energy-density food such as root crops. High-fat foods, which contain sugar or salt, have higher sensory appeal [16].

The overall preference of street-vended ice cream in Figure 4 showed that the cheese-flavoured street-vended ice cream is the most preferred variant by 30% of the panellists. In the conducted sensory evaluation, 16% of respondents liked a lot cheese-flavoured street vended ice cream while 15% of them disliked slightly the cheese variant. Meanwhile, 21% of panellists extremely liked the chocolate-flavoured street vended ice cream (Figure 4). About 18% of the panellists disliked a lot the chocolate ice cream variant. For the taro-flavoured street-vended ice cream, 10% of respondents liked the ice cream with taro flavour while 20% of them disliked slightly the taro variant (Figure 4).

Figure 4: Consumers' Overall Preference of Street Vended Ice Cream.

The preferences of panellists in terms of different sensory attributes, which are appearance, texture and taste, contribute to the overall liking of variants of street-vended ice cream. Based from Moskowitz et al. [17], overall liking is the integration of different sensory inputs based from food product properties. In the study, it was observed that cheese had the highest mean rankings among the three variants of street-vended ice cream (Table 1). In terms of the three sensory attributes tested, cheese variant of street-vended ice cream was mostly preferred by the respondents.

Table 1: Means scores on Consumers' Overall Preference of Street Vended Ice Cream at level of p<0.05; Dissimilarity of letters indicates significant difference.

Microbiological Evaluation

The three samples were labelled AA for chocolate flavor, BB for ube (purple yam) flavor and CC for cheese flavor. From the samples, 50 microliter was inoculated in 500 microliter of Brain heart infusion broth for bacterial cultivation and increases the growth of microorganisms (Figure 5). Broth samples were incubated at 35°C for 24 hours [18]. Broth solution of AA, BB and CC where plated using the four steak pattern on Tryptic Soy Agar supplemented by 5% sheep’s blood to support the growth of gram positive, gram negative and yeast cells and to visualize the presence of haemolysis for easy differentiation [18]. The streaked plates were incubated at 35°C for 24 hours.

Figure 5: Inoculation of Street-Vended Ice Cream (Left to Right: Cheese, Chocolate and Taro-Flavoured).

Presence of bacterial growth is monitored daily. All A (Figure 6), BB (Figure 7) and CC (Figure 8) yielded heavy growth of mixed microorganisms after 24 hours of incubation. Colonies from each plate are identified based on their morphological characteristics, such as color, shape, haemolytic effect and consistency. Individual organisms are then further identified by gram staining them to assess if they are gram positive bacilli/cocci or gram negative bacilli/cocci.

Figure 6: Bacterial growth present in Cheese-flavoured Streetvended Ice Cream.

Figure 7: Bacterial growth present in Taro-flavoured Street-vended Ice Cream

Figure 8: Bacterial growth present in Cheese-flavoured Streetvended Ice Cream.

All street-vended ice-cream samples, yielded three different growths in Table 2. Upon morphological identification, organisms are purified by isolating them and re-streaking colonies in selective and enrichment media. Gram Positive cocci and bacilli are isolated on Tryptic Soy Agar (TSA) and gram negative bacilli are isolated in MacConkey Agar. Plates were further incubated at 35°C for 24 hours. Bacterial isolate plates were checked for purity prior to species identification.

Table 2: Bacterial Growth Characteristics of Different Street-Vended Ice Cream Variants

Once bacterial purity is attained, broth solution is created by mixing colonies with sterile 9% Normal Saline Solution (NSS) and equilibrated to 1.0 McFarland solution for gram negative bacilli. Broth solutions are then processed using the Vitek 2 machine by Biomeriux.

Based on observations, Enterobacter gergoviae is present in all of the ice cream samples. Also, Enterobacter cloacae is found on taro-flavored street-vended ice cream. Although it is a normal gut flora it can also cause diseases such as Urinary Tract Infection (UTI) and respiratory infections.

It is also considered as biosafety level 1 organisms both in the United States and Canada. Bacillus species isolated from chocolate and cheese samples are contaminants usually found in the soil. Only 2 species of Bacillus are considered pathogenic to huma, namely B. anthracis that causes anthrax and B. cereus that leads to gastrointestinal disease. According to Mathews et al. [19], Enterobacter species are usually ubiquitous in the environment. Contamination of ice cream can be sources such as dust, soil, equipment and hands of handling personnel either during storage of ice cream samples in the machine and selling (Table 3).

Table 3: Species identification on Different Street-Vended Ice Cream Variants.

In the chocolate-flavoured street-vended ice cream sample, Acinetobacter baumanii is identified. This presence can be accounted to the habitat of A. baumannii. This organism is commonly recovered from soil, water, animals, and humans [19]. The water used in preparation of the ice cream sample maybe contaminated. Also, this could indicate the need for proper handling of raw materials during manufacturing of ice cream to avoid contamination. Acinetobacter species are usually found on human skin and are frequently isolated from the throat and respiratory tract of hospitalized patients [19]. A baumannii is a gram-negative bacteria that can cause bacteraemia, pneumonia, meningitis, urinary tract infection, and wound infection [20].

Klebsiella pneumoniae is found in cheese –flavoured street-vended ice cream. This is also a gram-negative bacteria that can lead to pneumonia, bloodstream infections, wound infections, and meningitis [19]. It can be pathogenic once aspirated in the lungs especially for people with weakened immune systems and those suffering from debilitating disease. Growth of microorganisms of the ice cream sample can be due to the mode of transmission of K. pneumonia which is through direct contact. According to Goff and Hartel [21], the different groups of organisms isolated in the street-vended ice cream variants also suggests that soil, water, personnel, and air might be the sources of contamination for open ice cream.

Significant difference in sensory properties was found in the three flavoured street-vended ice cream in terms of the overall acceptability, appearance, texture and flavour. The consumer results indicated that cheese flavoured street-vended ice cream was preferred more than taro and chocolate flavours. The inclusion of cheddar cheese bits in cheese flavoured ice cream had a positive impact on the acceptance by consumer.

It is noted that majority of the microorganisms that grew on each samples were predominantly gram negative bacilli and a few of gram positive bacilli which are known common contaminants found on the soil. On all three samples, Enterobacter gergoviae is isolated. Isolation of these organisms in food consumed by people can pose shows the need for compliance of proper handling techniques during preparation and selling of street-vended ice cream especially to students. Also, there must be a safety monitoring and risk assessment for the street-vended products, such as ice cream, to prevent contamination.