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- Điều hướng trang này:
- RESULTS AND DISCUSSION
- Physicochemical properties of freeze-concentrated coconut water
| Statistical analysis
All measurements were performed using triplicate samples. Analysis of variance (ANOVA) and Tukey’s test for multiple comparisons were used for analysing the data. SPSS version 20 (IBM, Armonk, USA) was used to complete the statistical analysis. RESULTS AND DISCUSSION Three batches of coconut water obtained from green (GC) and mature coconuts (MC), and freeze-concentrated coconut water prepared from GC (FGC) and MC water (FMC) were analysed for its physicochemical properties, composition and sensory properties. The yield of freeze-concentrated coconut water was estimated by comparing the weight of coconut water used and the amount of water obtained after the freeze-concentration process. Approximately 2 L of fresh coconut water produced approximately 1 L of freeze-concentrated coconut water. The exact yield of the freeze-concentrated coconut water could not be established since the TSS of freeze- concentrated coconut water was controlled at 2-times the initial TSS. After the freeze-concentrated coconut water was obtained, the unthawed ice remaining was discarded. The TSS of the unthawed ice from GC and MC water was approximately 0.8 and 0.5 °Brix, respectively. Despite differing in TSS value, the freeze-concentrated coconut water was visually similar to the fresh coconut water. Physicochemical properties of freeze-concentrated coconut water Table 1 shows that physicochemical properties of fresh coconut water were influenced by maturity and freeze- concentration process. Total soluble solid (TSS) indicates the sweetness of coconut water. The TSS of coconut water obtained from GC was significantly higher (P<0.05) than that of MC water. This result is in agreement with the findings from Jackson et al. (2004) and Tan et al. (2014), who reported that TSS of coconut water decreases after maturity of coconut fruit exceeded 9–10 months old. It can be seen clearly that the simplified freeze-concentration process used in this study was able to double the initial TSS value of the GC and MC, from 6.0 to 12.1 °Brix and from 3.9 to 7.9 °Brix, respectively (Table 1). The water content trapped in the unthawed ice contributes to the increased in the TSS of the coconut water. Similar observation in TSS for freeze-concentrated sugar cane juice was reported by Lo et al. (2007). Other concentration approaches were shown to be able to increase the TSS of the fruit juice; such as blood orange juice using integrated membrane process (Galaverna et al., 2008) and pineapple juice using osmotic evaporation (Hongvaleerat et al., 2008). Changes in pH were noticeable due to maturity as well as after the freeze-concentration process (Table 1). The pH of coconut water was found to increase with maturity. This trend compared favourably with those reported by Santoso et al. (1996), Jackson et al. (2004), Terdwongworakul et al. (2009), and Tan et al. (2014). During the ripening process of the coconut fruit, organic acid content (predominantly malic acid) of the coconut water was degraded and this accompanied by a steady increase in pH value from young to mature coconut water. After the freeze-concentration, freeze-concentrated coconut water was significantly lower (P<0.05) in pH. Thus, the decrease in pH shows that the acidity of the coconut water is increasing as the organic acids content increases in concentration. The decrease in pH after freeze-concentration process is supported by the finding from Lo et al. (2007), where pH of sugar-cane juice decreased after the freeze-concentration. This might be due to the concentrating process, where part of the organic acids stays trapped in the concentrate (Galić et al., 2009). tải về 221.3 Kb. Chia sẻ với bạn bè của bạn:
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