The physico-chemical properties of spray-dried pitaya peel powders kept at accelerated (45 ± 2°C) and room temperature (28 ± 2°C) for 14 weeks and 6 months, respectively were evaluated. Changes in physico-chemical properties of the peel powder were used as indicators of stability, while changes of the betacyanin pigment retention was used to calculate the shelf-life of the powder. Storage temperatures significantly (p < 0.05) affected all the studied parameters and Hunter a value had the most significant change. The pigment retention of peel powder was approximately 87% at 45°C and 89% at room temperature storage. Degradation of betacyanin pigment in the powder followed the first order reaction kinetics with the half-life (t1/2) of approximately 76 weeks at 45°C and 38 months at 28°C. The spray-dried pitaya peel powder had a solubility of 87 to 92% and low in powder hygroscopicity. The final Aw of the powder did not exceed 0.6 for both storage temperatures.
This study examined the physicochemical properties of rice flours with five different particle sizes (≤63, 80, 100, 125, and 140 μm) prepared by dry milling and their effects on textural properties of laksa noodles. Rice flour with the smallest particle size had the highest water absorption index, peak viscosity, hot paste viscosity, breakdown, final or cold paste viscosity and gel hardness, but the lowest gelatinization temperature. Reduction of rice flour particle size improved textural properties of laksa noodle. Laksa noodle produced from rice flour with the smallest particle size had the best textural properties.
This study investigated the effect of citric, nitric and sulfuric acid on the yield and
physicochemical properties of pectin extracted from jackfruit and chempedak fruit rinds. Yield
and physicochemical properties such as uronic acid content, degree of esterification, degree of
acetylation and colour of pectin solution were determined and compared. Yield of pectin from
jackfruit and chempedak fruit rinds with nitric acid as extractant were 14.81 ± 1.02% and 17.62
± 0.69%, respectively, which were the lowest. The uronic acid content of all extracted pectin
was more than 65%. All jackfruit and chempedak fruit rind pectins in this study were high
methoxyl pectin with degree of esterification ranging from 72-75% for jackfruit rind pectin and
66-69% for chempedak rind pectin. The degree of acetylation of all extracted pectin was lower
than 1%. For both jackfruit and chempedak fruit rind pectins, the citric acid-extracted pectin
produced darker, more reddish and yellowish solution and thus is least preferable. Among
the acids studied, sulfuric acid was the best extractant due to the high yield of pectin and the
solution of this pectin was brighter, less reddish and yellowish.
Pitaya peel (Hylocereus polyrhizus), which consists approximately 22% of the whole fruit weight, is discarded during processing. Physico-chemical properties of the discarded pitaya peel were determined in
order to evaluate its potential for recovery of any value-added materials. The moisture content of the peel was approximately 92.7% and it was low in total soluble solids, protein, ash and fat content. Betacyanin pigment (150.46 ± 2.19 mg/100 g) and pectin (10.8%) were high in the peel. Glucose, maltose and fructose were detected in the peel but not sucrose and galactose. The peel also had very high insoluble and soluble dietary fibre which had exhibited a good ratio of insoluble dietary fibre to soluble dietary fibre (3.8: 1.0).
The nutritive value of spontaneously fermented brown rice flour medida, a Sudanese cereal thin porridge, is low. This study was carried out to improve the nutritional quality of medida. The flour was soaked and malted at 30◦C to optimise the protein content. Flour malted for two days had the highest protein content. Skim milk was added to the malted brown rice flour medida and fermented using Bifidobacterium longum BB 536. Maximum count of B. longum BB 536 up to 9 log CFU/ ml was attained at 4.6 final fermentation pH. The resultant viscosity was similar to that of the spontaneously fermented brown rice flour medida. There was significant (P< 0.01) increase in both the energy density and the protein content, having increased 12 folds and 24 folds, respectively. The essential amino acids including lysine and methionine were highly augmented. The resultant medida have stable flowing characteristics and meet the whole protein and energy requirements for infants and children aged 1 - 10 years old.