Farina di konjac (glucomannano)

Descrizione

• Polvere alimentare ottenuta dal tubero di Amorphophallus konjac, ricca di glucomannano (polisaccaride solubile).

• Profilo sensoriale: sapore neutro, colore bianco–panna, odore lieve. In acqua forma soluzioni molto viscose e, in presenza di alcali/ioni calcio, gel elastici (base di konnyaku/shirataki).

• Posizionamento: addensante/gelificante clean-label, senza glutine, idonea a formulazioni plant-based e low-calorie.

Valore calorico (per 100 g di polvere)

• ~160–220 kcal (prevalenza fibra solubile). Carboidrati totali ~80–90 g (quasi tutti fibra), proteine <1 g, grassi <1 g, sodio basso. L’uso tipico è a dosi molto inferiori (0,2–2%).

Principali sostanze contenute

• Glucomannano (copolimero β-1,4 di glucosio e mannosio; spesso ≥70–85% s.s.), con acetilazioni parziali che influenzano gelificazione.

• Umidità contenuta (spec. ≤10–12%), ceneri basse; proteine/lipidi traccia.

• Micronutrienti trascurabili; FODMAP bassi.

Processo di produzione

• Materie prime: tuberi di A. konjac pelati, affettati, essiccati.

• Macinazione & setacciatura: produzione di farina; per il “gomma di konjac” si esegue estrazione/raffinazione del glucomannano (acqua → precipitazione alcolica → essiccazione).

• Controlli: metalli pesanti, carica microbica, viscosità in soluzione (p.es. 1%), granulometria.

• Per gel alimentari: deacetilazione/reticolazione in ricetta tramite Ca(OH)₂ o Na₂CO₃ durante la cottura.

Proprietà sensoriali e tecnologiche

• Idratazione/viscosità: altissima capacità d’idratazione (decine di volte il proprio peso) e viscosità già a 0,5–1,0%.

• Gelificazione: con alcali/ioni Ca²⁺ forma gel termostabili ed elastici (konnyaku); sinergie con κ-carragenina/xanthan.

• Stabilità di processo: buona a pH ~4–10; a pH acido e alte T può idro-lizzarsi (perdita di viscosità).

• Congelamento/scongelamento: gel generalmente stabili se ben deacetilati; le soluzioni possono sinere → gestire con zuccheri/sali o blend.

Impieghi alimentari

• Noodles/konnyaku/shirataki: struttura ed elasticità tipiche (konnyaku: farina + Ca(OH)₂).

• Salse, zuppe, bevande: addensante a basso dosaggio; buona stabilità in shear moderato.

• Bakery & gluten-free: migliora ritenzione d’acqua, morbidezza e freschezza; in pasta supporta tenuta in cottura.

• Carni/analoghi vegetali: legante e stabilizzante acqua/grassi; in gel d’emulsione aumenta sliceability.

• Sostituto dei grassi/fibre funzionali: crea corpo a basso apporto calorico.

• Confetteria/gelatine: gel opachi e mordenti, anche in sinergia con carragenina.

Nutrizione e salute

• Fibra solubile con alta viscosità → può aumentare sazietà e modulare risposta glicemica a livello di ricetta.

• In UE sono previsti claim per controllo ponderale (con 3 g/die in dieta ipocalorica, in dosi frazionate con acqua) e per la colesterolemia (con 4 g/die), se rispettate le condizioni d’uso/etichetta.

• Possibili disturbi GI (gonfiore) a dosi elevate: introdurre gradualmente e idratare adeguatamente.

Profilo dei grassi

• Grassi trascurabili: **PUFA**, **MUFA**, **SFA** irrilevanti; **TFA** e **MCT** non presenti in quantità significative.

Qualità e specifiche (temi tipici)

• Identità/purezza: glucomannano ≥70–85% s.s., umidità ≤10–12%, ceneri ≤3%, metalli (Pb, As, Cd, Hg) nei limiti.

• Funzionalità: viscosità (p.es. soluzione 1% a 25 °C), indice di gelificazione con Ca(OH)₂, granulometria (mesh), colore L*.

• Microbiologia: patogeni assenti/25 g, TAMC/lieviti/muffe bassi; Salmonella negativa.

• Conformità additivo: come E425 (E425(i) gomma di konjac / glucomannano), ove applicabile alla categoria d’uso.

Conservazione e shelf-life

• Conservare al fresco, asciutto, al buio, in pack barriera all’umidità e ermetico (evitare odori).

• Shelf-life tipica 24 mesi chiuso; dopo apertura richiudere e usare entro poche settimane.

Allergeni e sicurezza

• Non è un allergene maggiore; senza glutine per natura.

• Rischio soffocamento se assunta a secco o in gel durevoli poco masticabili (es. mini-gelatine): usare sempre con acqua sufficiente e forme idonee; in alcune giurisdizioni le mini-cup gel di konjac sono vietate.

• Etichettare eventuali claim salutistici secondo normativa; gestire GMO/IP se richiesto.

Funzioni INCI in cosmesi (ove applicabile)

• INCI: Amorphophallus Konjac Root Powder, Glucomannan, Hydrolyzed Konjac Mannan.

• Ruoli: filmogeno, addensante, texturizzante e assorbente in gel/lozioni; spugne di konjac per detersione delicata.

Troubleshooting

• Grumi all’idratazione: premiscelare con zucchero/olio o usare gradi agglomerati; versare a pioggia sotto alto shear.

• Perdita di viscosità in acido/calore: ridurre tempo/T, tamponare pH, usare blend (es. xanthan).

• Gel troppo rigido / gommoso: ridurre Ca(OH)₂, diminuire dose, tagliare deacetilazione o miscelare con idrossi-/carragenine.

• Sinèresi in gel: aumentare solidi/zuccheri, ottimizzare pH/ioni, valutare sinergie con κ-carragenina.

Sostenibilità e filiera

• Coltivato in Asia orientale/sud-est (Cina, Giappone, Indonesia); basso input di campo e resa tuberi elevata.

• In impianto: recupero acqua/alcool nei cicli di estrazione, gestione reflui verso **BOD/COD**, energia ottimizzata; pack riciclabili, **GMP/HACCP** e tracciabilità robuste.

Etichettatura

• Denominazioni: “farina di konjac”, “glucomannano”, o “gomma di konjac (E425)” secondo uso/categoria.

• Indicare funzione tecnologica (addensante/gelificante/fibra), origine, lotto; per claim (peso/colesterolo) specificare dose, modalità d’assunzione e avvertenze richieste (es. assumere con molta acqua).

Conclusione

La farina di konjac è una fibra solubile ad altissima funzionalità: permette viscosità elevatissime e gel elastici a basso tenore calorico, risultando versatile in noodles/konnyaku, salse, bakery gluten-free e analoghi vegetali. Scelta del grado, gestione di pH/ioni/temperatura e corretta idratazione sono chiave per ottenere texture e stabilità ottimali in sicurezza.

Mini-glossario

• Glucomannano: polisaccaride di glucosio+mannosio responsabile di viscosità e gel della farina di konjac.

• Deacetilazione: rimozione di gruppi acetile che abilita reticolazione con Ca²⁺ → gel elastici (konnyaku).

• **PUFA** — grassi polinsaturi: in questo ingrediente sono irrilevanti (grassi traccia).

• **MUFA** — grassi monoinsaturi: irrilevanti; presente solo traccia lipidica.

• **SFA** — grassi saturi: trascurabili nella farina di konjac.

• **TFA** — acidi grassi trans: assenti in pratica.

• **MCT** — trigliceridi a media catena: non presenti in misura significativa.

• **GMP/HACCP** — good manufacturing practice / hazard analysis and critical control points: sistemi igienico-preventivi con CCP definiti.

• **BOD/COD** — domanda biochimica/chimica di ossigeno: indicatori per la gestione dei reflui di processo.

Bibliografia__________________________________________________________________________

Laignier F, Akutsu RCA, Lima BR, Zandonadi RP, Raposo A, Saraiva A, Botelho RBA. Amorphophallus konjac: Sensory Profile of This Novel Alternative Flour on Gluten-Free Bread. Foods. 2022 May 10;11(10):1379. doi: 10.3390/foods11101379. 

Abstract. This study aimed to evaluate the sensory profile of gluten-free bread with Amorphophallus konjac (AK) flour in different concentrations. This experimental study is divided into three steps: preparation of the gluten-free bread formulations, sensory analysis, and statistical analysis. The addition of Konjac flour in a gluten-free bread formulation was tested in different proportions, 12.5%, 25%, 37.5%, and 50% of the flour content. The checking all-that-apply (CATA) was conducted with 110 panelists; among these, 43 were consumers of gluten-free bread. Sensory analysis was conducted using a 9-point hedonic scale for color, aroma, texture, flavor, appearance, and overall acceptability. The AK flour influenced the sensory characteristics of gluten-free bread. Bread with characteristics closer to those found in bread with gluten was the one with 12.5% of konjac flour for both the acceptability analysis as the attributes raised through a detailed CATA map. The control sample is located next to features like dry appearance, dry texture and grainy, dark color, and salty. Therefore, 12.5% AK gluten-free bread is closer to the characteristics of the control sample, such as light crust color, light crumb color, soft and moist texture, cohesion, and brightness. The bread with the highest percentage of overall consumer acceptance was 12.5% konjac with 93% and 96% acceptance among consumers and non-consumers of gluten-free bread, respectively.

Drugs and Lactation Database (LactMed®) [Internet]. Bethesda (MD): National Institute of Child Health and Human Development; 2006–. Glucomannan. 2024 Dec 15. 

Abstract. Glucomannan is a soluble, highly viscous fiber commonly derived from Amorphophallus konjac root. Glucomannan has no specific lactation-related uses. It is most often used to lower cholesterol, to treat constipation and diabetes, and is contained in products to promote weight loss. No data exist on the safety and efficacy of glucomannan in nursing mothers or infants. However, because glucomannan is not absorbable, it will not reach the breastmilk and is very unlikely to affect the nursing infant. Dietary supplements do not require extensive pre-marketing approval from the U.S. Food and Drug Administration. Manufacturers are responsible to ensure the safety, but do not need to prove the safety and effectiveness of dietary supplements before they are marketed. Dietary supplements may contain multiple ingredients, and differences are often found between labeled and actual ingredients or their amounts. A manufacturer may contract with an independent organization to verify the quality of a product or its ingredients, but that does not certify the safety or effectiveness of a product. Because of the above issues, clinical testing results on one product may not be applicable to other products. More detailed information about dietary supplements is available elsewhere on the LactMed Web site.

Laignier F, Akutsu RCCA, Maldonade IR, Bertoldo Pacheco MT, Silva VSN, Mendonça MA, Zandonadi RP, Raposo A, Botelho RBA. Amorphophallus konjac: A Novel Alternative Flour on Gluten-Free Bread. Foods. 2021 May 27;10(6):1206. doi: 10.3390/foods10061206.

Abstract. The demand for gluten-free products is rising, but their production with similar quality as their gluten counterparts is challenging. This study aimed to develop gluten-free bread samples using different concentrations of Amorphophallus konjac flour (0%, 12.5%, 25%, 37.5%, and 50% of the total flour content) and to evaluate their nutritional and physicochemical properties. Proteins, lipids, carbohydrates, moisture, ash content, fibers, resistant starch, firmness, specific volume, and color were evaluated using official methods. Protein varied from 2.95% to 4.94%, the energy value from 347.93 to 133.55 kcal/100 g, dietary fiber from 8.19 to 17.90%, and resistant starch from 0.67% to 0.75% on wet basis. The addition of konjac flour positively influenced the specific volume. Higher concentrations of konjac flour in the formulations led to lower calories of the bread due to the significant addition of water to the dough. The bread samples with konjac showed high fiber content due to the composition of the flour. They had lower levels of carbohydrates, which can positively influence the glycemic index. Konjac flour provided dough mold, growth, and better texture for gluten-free bread. The best formulations were prepared in concentrations up to 37.5% konjac. The 50% konjac bread showed slightly reduced specific volume and pale color.

Islam F, Labib RK, Zehravi M, Lami MS, Das R, Singh LP, Mandhadi JR, Balan P, Khan J, Khan SL, Nainu F, Nafady MH, Rab SO, Emran TB, Wilairatana P. Genus Amorphophallus: A Comprehensive Overview on Phytochemistry, Ethnomedicinal Uses, and Pharmacological Activities. Plants (Basel). 2023 Nov 23;12(23):3945. doi: 10.3390/plants12233945. 

Abstract. The genus Amorphophallus belongs to the family Araceae. Plants belonging to this genus are available worldwide and have been used in traditional medicines since ancient times, mainly in Ayurveda and Unani medical practices. Amorphophallus species are an abundant source of polyphenolic compounds; these are accountable for their pharmacological properties, such as their analgesic, neuroprotective, hepatoprotective, anti-inflammatory, anticonvulsant, antibacterial, antioxidant, anticancer, antiobesity, and immunomodulatory effects, as well as their ability to prevent gastrointestinal disturbance and reduce blood glucose. Moreover, Amorphophallus species contain numerous other classes of chemical compounds, such as alkaloids, steroids, fats and fixed oils, tannins, proteins, and carbohydrates, each of which contributes to the pharmacological effects for the treatment of acute rheumatism, tumors, lung swelling, asthma, vomiting, abdominal pain, and so on. Additionally, Amorphophallus species have been employed in numerous herbal formulations and pharmaceutical applications. There has been no extensive review conducted on the Amorphophallus genus as of yet, despite the fact that several experimental studies are being published regularly discussing these plants' pharmacological properties. So, this review discusses in detail the pharmacological properties of Amorphophallus species. We also discuss phytochemical constituents in the Amorphophallus species and their ethnomedicinal uses and toxicological profiles.

Jiang M, Li H, Shi JS, Xu ZH. Depolymerized konjac glucomannan: preparation and application in health care. J Zhejiang Univ Sci B. 2018 Jul;19(7):505-514. doi: 10.1631/jzus.B1700310. 

Abstract. Konjac glucomannan (KGM) is a water-soluble polysaccharide obtained from the roots and tubers of konjac plants. Recently, a degraded product of KGM, depolymerized KGM (DKGM), has attracted attention because of its low viscosity, improved hydrophily, and favorable physiological functions. In this review, we describe the preparation of DKGM and its prebiotic effects. Other health benefits of DKGM, covering antioxidant and immune activity, are also discussed, as well as its safety. DKGM could be a candidate for use as a tool for the treatment of various diseases, including intestinal flora imbalance, and oxidative- and immune-related disorders.