Abstract:
Background and objective: White and red guava pulp concentrates produced in this study were stored at room temperature (25+5°C) for 13.5 months. The purpose of this research was to study the effects of storage on the quality characteristics of Guava (Psidium guajava L.) fruit concentrates with respect to their physicochemical, chemical and microbiological properties in comparison with their initial values before storage. Materials and Methods: After processing of the white and red guava pulp concentrates by evaporation under normal atmospheric pressure, changes in the physicochemical, chemical and microbial characteristics of white and red guava (Psidium guajava L.) fruit concentrates during storage were investigated using standard and official methods of analysis. Results: The results showed significant differences (p≤0.05) between the two concentrates before storage with respect to their total soluble solids (TSS), ascorbic acid and sugar contents. Then, the levels of TSS in both the white and red guava concentrates were gradually and significantly (p≤0.05), increased from 17.00-21.55% in the white guava concentrate and from 19.00-22.96% in the red guava concentrate at the start and end of the storage period, respectively. In contrast, the level of hydrogen ion concentration (pH) decreased from 4.60-3.00 and from 4.53-3.02 in the white and red guava concentrates, respectively, while the acidity of the two guava pulp concentrates (as citric acid) increased with increasing storage time from 0.30% at the initial period (zero time) to 0.90% at the end of the period. While, the levels of ascorbic acid and total, reducing and non-reducing sugars in the two guava pulp concentrates significantly (p≤0.05) decreased at the end of the storage period. The optical density (OD) values of the white and red guava concentrates remained constant at 0.13 and 0.14 OD, respectively, until the fifth month of the period. Afterwards, significant (p≤0.05) colour degradation was observed in the white guava concentrate (0.054 OD), while the OD value of the red guava concentrate slightly decreased from 0.13-0.11 by the end of the storage period. In addition, the results of the microbiological analysis revealed that the two guava concentrates remained free from any microorganisms for 12 months of storage. Conclusion: During the storage of the white and red guava pulp concentrates at room temperature (25±5°C) for 13.5 months, the two guava concentrates underwent similar changes in their TSS, pH and acidity. Colour degradation was very clear in the white guava pulp concentrate, especially at the end of the storage period. In addition, both the guava concentrates found to be free from any pathogenic microorganisms and with stable physical and chemical properties during storage period of up to 12 months.