This study investigated the effects of konjac proportion in 1% konjac/κ-carrageenan blend (25:75-50:50) and sweetener concentration (sucrose and xylitol at 2-20% and erythritol-sucralose at 0.25-2.5%) on gel strength of konjac gels using Response Surface Methodology (RSM). The statistical analysis revealed that all models of konjac gels with sweeteners were effective and adequate fitted. The most variable affecting gel strength was konjac/κcarrageenan n blend. Quadratic effect of konjac/κ-carrageenan blend was more profound (p<0.001) on konjac gels with each sweetener. The variation of xylitol and sucrose had a linear effect (p<0.001) and a quadratic effect (p<0.05) on gel strength, respectively, while an increase in erythritol-sucralose had no significant effect. Also, the interaction between the two variables had no significant effect on gel strength. The optimal conditions for the highest gel strength were 1% konjac/κ-carrageenan (39.56:60.44) with 9.58% sucrose, 1% konjac/κ-carrageenan (39.87:60.13) with 2% xylitol and 1% konjac/κ-carrageenan (38.18:61.82) with 0.94% erythritol-sucralose. Orange konjac jellies made with three optimal conditions showed no significant differences in appearance and color. Most panelists preferred sweet and texture of the jelly with erythritol-sucralose than that with xylitol. Nevertheless, the jelly with sucrose significantly received the most scores of sweet and overall acceptance. The appropriate level of texture and sweet was evident on the jelly with sucrose, followed by that with erythritol-sucralose and xylitol, respectively.

The understanding of textural characteristics of gels, which replace for sugar with sugar substitute, is essential for designing gel-based healthy food products. This research aimed to investigate the changes in textural characteristics as well as to optimize the gel condition of sugar-free konjac gel using the response surface methodology. A central composite rotatable design was implemented to determine the texture profile analysis, including the hardness, cohesiveness and springiness. Two independent variables, comprising different levels of konjac flour-to-xanthan ratio (25:75 to 50:50 w/w) and erythritol-sucralose (ES) concentration (0.2-2.5% w/v), were studied. Konjac gels showed an increase in all textural characteristics when increasing the konjac content, while a slight change was induced by ES. The optimized konjac gel condition was tested for its characteristics and acceptability as pineapple jam, during the storage for 30 days at refrigerated temperature (10-12°C). The low-sugar jam made with ES was acceptable and showed its overall acceptability score in a moderate preference. Both sucrose and ES jams were firmer and brighter during storage. After refrigeration for 30 days, both products showed lowered liking scores for some sensory attributes; however, they were microbiologically safe.

This research aimed to investigate the quality of fruit bars prepared with different ratios of sapodilla-wild almond seed (80:20 and 70:30 w/w) and sugar substitution with stevia (0, 1/3, and 2/3 as equivalent sweetness basis). Physical properties (moisture and water activity), sensory acceptability, and preference mapping of the fruit bars were investigated. The samples formulated with a higher proportion of sapodilla pulp had higher moisture and water activity than those with less sapodilla pulp. Increasing the sugar substitution with stevia tended to decrease the moisture and water activity of the fruit bars. The stevia incorporation had effects on sensorial attributes, especially the flavor depending on how much sapodilla pulp proportion used in fruit bar preparation. The fruit bars formulated with 80:20 of the sapodilla-wild almond seed and 2/3 sugar substitution and that with 70:30 and full-sugar perceived the highest overall acceptability. The preference mapping revealed the importance of product attributes, and the texture was an important attribute on sensorial acceptance. In conclusion, the fruit bar prepared with 80/20 of sapodilla-wild almond seed and 2/3 sugar substitution with stevia was the most preferred formulation.

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