Algae-derived hydrocolloids in foods: applications and health-related issues

Figures & data

Figure 1. The simple classification of algae. Adapted from 110 and 111

Figure 2. Chemical structures of algae-derived hydrocolloids. (A] Three main types of carrageenan, (b) Agar – agarose and agaropectin, and (c) Alginate-β-D-mannuronate (M and -L-guluronate [G). Adapted from 112,113 114, and 77

Table 1. Properties of the three main types of carrageenan. Adapted from 38

Carrageenan type	Kappa	Iota	Lambda
Degree of sulfation	One sulfate per disaccharide	Two sulfates per disaccharide	Three sulfates per disaccharide
Solubility
Hot (80°C] water	Soluble	Soluble	Soluble
Cold (20°C) water	Sodium salt soluble	Sodium salt soluble	All salt soluble
Hot (80°C) milk	Soluble	Soluble	Soluble
Cold (20°C) milk	Insoluble	Insoluble	Thickens
Cold milk (TSPP added)	Thickens or gels	Thickens or gels	Increased thickening or gelling
50% sugar solutions	Soluble hot	Insoluble	Soluble
10% salt solutions	Insoluble	Soluble hot	Soluble hot
Gelation
Effect of cations	Strongest gels with potassium	Strongest gels with calcium	Non-gelling
Gel texture	Firm, brittle	Soft, elastic	Non-gelling
Syneresis	Yes	No	Non-gelling
Hysteresis	10–20°C	5–10°C	Non-gelling
Freeze-thaw stability	No	Yes	Yes
Synergy with locust bean gum	Yes	No	No
Synergy with konjac glucomannan	Yes	No	No
Synergy with starch	No	Yes	No
Shear reversibility	No	Yes	Yes
Acid stability	Hydrolysis in solution, accelerated by heat; gels are stable	Hydrolysis in solution, accelerated by heat; gels are stable	Hydrolysis
Protein reactivity	Specific reaction with kappa-casein	Strong protein interaction in acid	Strong protein interaction in acid

Table 2. Different viewpoints in ‘the Carrageenan Controversy’

The carrageenan controversy [45]
1. Carrageenan is approved for food use by all major food regulatory agencies worldwide.
2. Carrageenan is approved for use in liquid infant formula.
3. The negative attitude toward carrageenan is evolved from the research using an in-vitro model.
4. Bloggers made the issue go viral.
5. 106,found that carrageenan did not cross intestinal epithelial cell wall, was not cytotoxic, did not increase oxidative stress, and did not induce pro-inflammatory gene expression.
Reply to comments regarding ‘the Carrageenan controversy’ [107]
1. Carrageenan has been used in labs for decades to induce inflammation.
2. Carrageenan has been used in an ever-increasing list of foods, and one may consume several grams per day, day after day for years.
3. The potential contribution of carrageenan to chronic human diseases is unknown.
4. Carrageenan is unarguably inflammatory, and its usage is a serious public issue.
5. More than 10,000 publications on PubMed website are about carrageenan, and carrageenan exposure predictably and reproducibly provokes inflammation.
6. Inflammation leads to human diseases, including atherosclerosis, cancer, arthritis, colitis, diabetes, and other diseases.
7. Carrageenan exposure may lead to relapses of ulcerative colitis and diabetes.
8. Exposure to a low dose of undegraded lambda-carrageenan may change the gene expression profiles of a human colonic epithelial cell line.
9. Food-grade carrageenan contains some low-molecular weight carrageenan.
Revisiting the carrageenan controversy: do we really understand the digestive fate and safety of carrageenan in our foods? [47]
1. There are gaps in our understanding of carrageenan: (1) Current levels of public exposure are unknown; (2) The link between carrageenan physicochemical properties and the impact on digestive proteolysis, microbiome, and inflammation are not yet resolved; (3) The digestive fate of carrageenan and the predisposed populations need to be determined.
2. Carrageenan is approved for food use by all major food regulatory agencies worldwide, but the supportive evidence may either based on animal studies or studies that are ethically challenged.
3. Carrageenan toxicology and possible health impacts have been reported in extensive in vivo and in-vitro studies since the 1970s.
4. Carrageenan may cause neoplasms, tumors, and ulcers in the small intestine and colon.
5. Carrageenan can play a role in the onset of glucose intolerance in mice.
6. Carrageenan may lead to an earlier relapse in ulcerative colitis in humans.
7. Low doses of undegraded carrageenan can activate inflammatory pathways in-vitro.
8. The low-MW (degraded) carrageenan can undisputedly provoke epithelial ulcerations and induce secretion of inflammatory cytokines.
9. Low-MW carrageenan diffuses through the mucus layer and to the intestinal epithelium faster.
10. The risk from the hypothesized physiologically digested carrageenan needs to be confirmed.
Comment on ‘Revisiting the carrageenan controversy: do we really understand the digestive fate and safety of carrageenan in our foods?’ [108]
1. Poligeenan or degraded carrageenan used for testing are generated under very harsh conditions and are not the same as commercial carrageenan.
2. High-MW carrageenan is a food additive and is never intentionally injected into humans to induce significant inflammatory responses.
3. If food-grade carrageenan is stable in the gut, it cannot induce inflammatory responses.
4. No allergy or anaphylaxis caused by carrageenan is reported in humans.
5. Well-designed studies with good laboratory practices showed no harmful effects of dietary carrageenan.
6. The carcinogenic effect of carrageenan needs to be confirmed with long-term animal studies.
7. No adverse effects of carrageenan were observed in recent clinical trials.
8. The in-vitro adverse effects of carrageenan cannot be reproduced.
9. There is no controversy, only confusion.
10. Carrageenan does not cause inflammatory or gastrointestinal effects in animals using standard protocols for safety evaluation.
11. Degraded carrageenan (Poligeenan) is not permitted to be used as a food additive.
12. Carrageenan injection is not relevant to the usage as a food additive.
Reply to the Comment on ‘Revisiting the carrageenan controversy: do we really understand the digestive fate and safety of carrageenan in our foods?’ [109]
1. There is little information on (1) the physicochemical properties of commercial carrageenan, (2) carrageenan exposure levels in human diets, (3) the role of carrageenan in gut microbiome dysbiosis and inflammation, and [4) the effects of carrageenan on susceptible populations.
2. Food-grade carrageenan has possible adverse effects on digestive proteolysis, epithelial integrity, and human health in double-blind, placebo-controlled independent trials.
3. Carrageenan is a complicated mixture of natural biopolymers, thus posing significant challenges for analyzing its physicochemical characteristics.
4. The molecular-weight distributions of carrageenan are not disclosed.
5. There is no confusion over carrageenan terminology.
6. Studies for enhancing our understanding of carrageenan’s broad-spectrum, polydisperse nature, and possible bio-transformations during human digestion are warranted.
7. The challenge of experimental reproducibility of carrageenan will be overcome by independent trials.
8. Possible impacts of long-term carrageenan exposure on the gut ecosystem and low-grade inflammation should be determined.

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