Characterisation of prebiotic compounds from plant sources and food industry wastes: inulin from Jerusalem artichoke and lactulose from milk concentration permeate

The development of processes for the preparation of prebiotic compounds, namely inulin from tubers of Jerusalem artichoke (JA-Helianthus tuberosus L.), and lactulose from milk concentration permeate (MCP) was examined. Inulin was extracted from the whole JA tubers using hydrothermal extraction process, followed by clarification and concentration. The concentrate was fractionated using two different procedures i.e. ethanol fractionation and cold precipitation (+4 and/or -24C) into high- and low-molecular-weight components. The most satisfactory method was cold fractionation wherein the insoluble heavier inulin fractions were found to settle to the bottom and were separated and spray-dried to obtain inulin powder. Lactose in MCP was isomerised into lactulose using carbonate-based catalysts (oyster shell and egg shell powders) followed by clarification and concentration. Th e high-performance liquid chromatography with refractive index detector (HPLC-RID) chromatograms and changes in pH and colour values confirmed the conversion of lactose into lactulose and decomposition of lactulose into by-products. The results obtained showed the suitability of oyster shell powder for lactose isomerisation in lieu of egg shell powder. For preparing lactulose-enriched MCP with acceptable lactulose yield of 22%, the optimum reaction conditions were found to be catalyst loading of 12 mg per mL of MCP and isomerisation time of 120 min at 96C. The resulting products i.e. JAI concentrate and powder and lactulose-enriched MCP syrup (40ºB) were tested for their prebiotic power in media broth and in fermented milk models. Prebiotic properties of these compounds were observed as supplementation levels increased from 0-2% to 3-4%. Based on the growth and acidification abilities of the probiotic strains tested, the combination of Lactobacillus casei LC-01 with JAI, and Lactobacillus acidophilus LA-5 with lactulose-enriched MCP syrup were found to be the best for development of synbiotic yoghurt. The prebiotic effect of JAIP was then compared with the two commercial chicory inulin products (Raftiline GR and Raftilose P95). Probiotic yoghurts supplemented with 4% inulin powders were prepared from reconstituted skim milk using mixed cultures of Lactobacillus casei LC-01, Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus (1:0.5:0.5, w/w). The survival and acidifying activity of probiotic and lactic acid cultures were investigated during the shelf life of 28 days at 4ºC. Incorporation of JAIP and chicory inulins resulted in a significant improvement in viability of LC-01 compared with non-supplemented yoghurt, maintaining more than 107 CFU g-1 throughout storage time. Additionally, the suitability of JAIP as fat replacer was determined in a set of fat-free yoghurt in comparison to three commercial chicory inulin products. Results of large deformation tests revealed that the firmness of JAIP-supplemented yoghurt was reduced to a similar level as the full-fat control yoghurt. However, small deformation results showed that the JAIP could not fully mimic milk fat to the same extent as Raftiline HP with an average DP of 23. The rheological effects of JAIP addition were comparable to those of short-chain (Raftilose P95 with an average DP of 4) and medium-chain inulins (Raftiline® GR with an average DP of 12)

Probiotic stability of yoghurts containing Jerusalem artichoke inulins during refrigerated storage

Experimentally prepared Jerusalem artichoke inulins (JAI) were compared with two commercial chicory root inulins for their prebiotic potentials in media broth model and growth-sustaining ability in non-fat yoghurts. Experimental yoghurts were made with 12% reconstituted skim milk (RSM) supplemented with 4% inulin powders, inoculated with mixed cultures of Lactobacillus casei LC-01, Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus (1:0.5:0.5 based on supplier's recommendation) and incubated overnight at 37 ºC. Non-supplemented yoghurt was prepared from 16% RSM and used as control. The survival and acidifying activity of lactic and probiotic cultures in all yoghurts were investigated on weekly intervals during the shelf life of 28 days at 4 ºC. Incorporation of JAI resulted in improved viability of LC-01, maintaining >7.0 log CFU/g during cold storage but did not affect the viability of yoghurt bacteria in comparison with the control

Prebiotic and rheological effects of Jerusalem artichoke inulin in low-fat yogurt

Inulins extracted from Jerusalem artichoke (Ja) tubers were tested for their prebiotic and fat-replacement properties and compared to commercial inulin, Beneo ST, extracted from chicory roots. Each inulin type was incorporated into skim milk at a level of 4% for the production of low-fat yogurts. Viable counts of probiotic and yogurt cultures as well as texture and rheology of the yogurts were investigated during refrigerated storage for 28 days. Overall, yogurts with added Ja-inulin showed better retention of probiotics viability (Bifidobacterium bifidum and Lactobacillus acidophilus) than yogurts made with Beneo ST. Textural and rheological studies indicated that Ja-inulin could function as a fat replacer in low-fat yogurt to mimic the properties of full-fat yogurt

Process optimisation for fractionating Jerusalem artichoke fructans with ethanol using response surface methodology

Optimal conditions for fructan precipitation from Jerusalem artichoke concentrate by adding ethanol were established by response surface methodology. The combination of the starting syrup concentration (9.9-40°B), ethanol-to-syrup (E/S) ratio (2.3:1-15.7:1) and precipitation temperature (3.1-62 °C) was varied at design points of a central composite rotatable design. Significant regression models describing the changes of average chain length, fructan precipitation yield and purity value of fructans were developed with the coefficient of determination greater than 0.8. The results suggested that higher syrup concentration resulted in an increased fructan yield, but further increase in concentration had a reverse effect on average chain length and purity values. The optimum conditions for fractionating fructan composition by ethanol were estimated to be 32 °B initial syrup concentration, E/S ratio of 13 and temperature of 42 °C