Yogurt drink spoilage profiles: Characterization of physico-chemical properties and coliform potability analysis

• Main Authors: Saiful Irwan Zubairi, Nursyazwanie Ishak, Norrakiah Abdullah Sani, Zalifah Mohd Kasim, Zainun Nurzahim
• Format: Article
• Language: English
• Published: Elsevier 2021-09-01
• Series: Arabian Journal of Chemistry
• Subjects: Yogurt drink; PLLA; Physico-chemical; Coliform colony; Spoilage indicator
• Online Access: http://www.sciencedirect.com/science/article/pii/S1878535221003555

This study aims to determine the yogurt drink spoilage profiles and its physico-chemical properties correlation as to investigate the coliform potability level upon exposure to an open air (unsealed condition). The commercially available three induced contamination of fruit (berry) flavoured yogurt drinks (labelled as A0 (original-flavoured Farm Fresh™), A1 (Farm Fresh™), A2 (Marigold™) and A3 (Nestle®)) were created to pre-run a spoilage indicator model system with regards to the colony formation unit (cfu) and its physico-chemical properties. Physio-chemical analysis (e.g., Brix, pH, colour and contact angle) and microbiological analysis were performed at 30 min intermittently for up to 4.5 h as soon as the food sample was unsealed (room environment condition: 27 ± 2 °C; relative humidity (RH): 73 ± 1%). The results showed the presence of yeast and fungus in yogurt drinks after all samples were opened and exposed to the environment. The total formation of yeast colonies and fungi of all three-yogurt berry drink brands on DRBC agar were inevitably high during the treatment (p < 0.05). The amount of cfu/ml of yeast and fungus was higher than the total coliform colony (Escherichia coli) formed throughout the sampling period. The pH analysis showed a significant decrease throughout the treatment due to the accumulation of lactic acid which resulted in high acidity (p < 0.05). The colour profiles of A1 brand showed a significant improvement as compared to A2 brand due to the increasing redundancy degree (p < 0.05). However, the A3 brand has a significant low reduction value, which is the degree of yellowness due to the microorganism’s contamination. Finally, the contact angle analysis at 0:00–3:00 h, the range of contact angle of A1 (exclusively selected due to highly pathogenic spoilage) was 45.34–42.80° while at 3:30–4:30 h was 58.66–61.12° with diameter 0.9 and 0.7 cm respectively. In conclusion, the presence of yeast and mould was first detected in the samples as early as 0:30 h (1.4 × 104 cfu/ml) and become unsatisfactory after being exposed to environment for 4 h and 30 min. The contact angle spoilage indicator exceeds from 45.34° (control) to 58.66° as to tangibly indicate the unsatisfactory values in terms of microbiological quality and potentially harmful to the consumers.