Celling properties of cactus pear mucilage-hydrocolloid combinations in a sugar-based confectionery

English: Mucilage from the cladodes of O. ficus-indica is under investigation for application in several foodstuffs. The first objective was to replace gelatin in marshmallows with different concentrations of fluid mucilage, combined with different concentrations of powdered hydrocolloids. Nine different formulations were prepared: control (100% gelatin); 75% mucilage + 25% xanthan (MX); 75% mucilage + 25% agar (MA); 75% mucilage + 25% guar (MG); 80% mucilage + 20% xanthan (8M2X); 80% mucilage + 20% agar (8M2A); 80% mucilage + 20% guar (8M2G); 75% mucilage + 12.5% xanthan + 12.5% agar (MXA); 75% mucilage + 12.5% xanthan + 12.5% guar (MXG); and 75% mucilage + 12.5% agar + 12.5% guar (MAG). Consistency, texture, tenderness of gel and shear measurements were determined, along with colour (L* values, as well as C* and Hº values) and aw. There were significant (p<0.05) differences between the different samples for all measurements. The best formulation for gelatin replacement was found to be the MXA combination, as it only differed significantly (p<0.05) from the control sample in regard to shear. It was significantly (p<0.05) less tender and resembled the shear of commercially available marshmallows in South Africa. All samples had a light, greyish yellow colour. The second aim was to compare consumer liking of flavoured and unflavoured marshmallows made with liquid mucilage, to that of a flavoured and unflavoured control sample (with 100 % gelatin), as well as a flavoured and unflavoured commercial brand. Ninety-two consumers tasted the following six samples: white commercial (Manhattan); white control (100 % gelatin); white MXA; pink commercial (Manhattan); pink control (100% gelatin); and pink MXA. The white MXA marshmallows had the lowest ranking for taste, aftertaste, texture and overall acceptability, and differed significantly (p<0.05) from all the other samples. The pink MXA marshmallow did not differ from the pink Manhattan (which had the highest rankings for taste, aftertaste, texture, and overall acceptability) and pink control marshmallows. The differences between the white and pink MXA marshmallows ranged between 2.75 and 2.89 on the nine point hedonic scale. Flavouring successfully masked the distinctive aroma of the mucilage in the marshmallows, thereby also increasing scores for texture and overall acceptability. Rapid visco analyser, differential scanning calorimetry and scanning electron microscopy studies were done on gelatin, mucilage (dry), xanthan, agar and MXA marshmallow samples, as well as individual hydrocolloid samples. Rapid visco analyser profiles showed very high viscosities for xanthan (< 15 000 cP) and mucilage (> 20 000 cP) samples, in contrast to gelatin (± 5 000 cP) and MXA (< 5 000 cP) samples. The addition of ingredients, such as sugar and egg whites, resulted in lowering of the general RVA viscosity, from ± 20 000 cP for mucilage-containing to 730 cP for MXA-containing marshmallows. Xanthan- and MXA-containing marshmallows had final viscosities of 237 cP and 727 cP, respectively, while almost no viscosity was measured for mucilage-containing marshmallows. A 100% mucilage sample showed no thermal events during DSC, indicating that no significant gelation occurred and no gel was formed. The four other samples showed very weak exothermal events, indicating that some phase change took place; in some cases gels were even formed before samples were placed in the DSC. For the hydrocolloid samples, gelatin and agar showed characteristic scaffolding on SEM micrographs, while xanthan appeared flaky. Mucilage had irregular pores, with thick walls and branching. Images showed sugar crystals suspended in the continuous phase for agar-, xanthan-, mucilage- and MXA-containing marshmallow samples; the crystals were the biggest for the mucilage-containing sample, while the MXA–containing sample also had clear zones like the gelatin-containing sample.