Cross-Processing Fish Co-Products with Plant Food Side Streams or Seaweeds Using the pH-Shift Method - a new sustainable route to functional food protein ingredients stable towards lipid oxidation
Doktorsavhandling, 2023
The seafood value chain is highly inefficient as 50-60% of the fish weight end up as co-products in the filleting operation. Despite their abundance in high-quality proteins, fish co-products mainly go to low value products such as fodder. The pH-shift process, i.e., acid/alkaline solubilization followed by isoelectric precipitation, is an opportunity to instead recover these proteins in a food grade manner while maintaining their functionality. A challenge when subjecting hemoglobin-rich fish raw materials to pH-shift processing is however oxidation of polyunsaturated fatty acids (PUFAs).
This thesis investigated, for the first time, cross-processing of fish co-products with antioxidant-containing support materials (''helpers'') to protect the fish protein isolates from lipid oxidation in a clean label and sustainable manner. The helpers, including locally sourced plant food side streams (press cakes from lingonberry (LPC) and apple, barley spent grain, oat fiber residues), shrimp shells, and seaweeds, were also expected to introduce new characteristics to the protein isolates.
All helpers, except shrimp shells, reduced lipid oxidation in herring/salmon co-products when added at 30% (dw/dw) at start of the pH-shift process. LPC was the most effective, and even at 2.5% addition it prevented volatile aldehyde formation during production of herring protein isolates while at 10% addition, the isolates were also stable towards oxidation for ≥8 days on ice. When the 10% LPC instead was added during protein precipitation, the oxidation lag phase was extended to 21 days. The oxidative stability of protein isolates correlated with their total phenolic content, and the very high antioxidant ability of LPC's was mainly attributed to anthocyanins, e.g., ideain and procyanidin A1.
LPC also improved the water solubility, emulsifying activity, and gel-forming capabilities of herring protein isolates, expanding their potential applications in food products. The water solubility and emulsifying activity were also boosted by adding shrimp shells and Ulva, while the gel-forming ability was also enhanced by apple press cake. LPC-derived anthocyanins resulted in red isolates under acidic conditions and dark-colored isolates under neutral/alkaline conditions. Ulva resulted in green isolates due to the presence of chlorophyll. The color of protein isolates was also affected by oxidation of fish-derived pigments like Hb and astaxanthin. The addition of helpers also influenced the composition of protein isolates. LPC added at the start of the process reduced lipid content, while shrimp shells and LPC added during precipitation increased it. Seaweeds raised ash content by introducing minerals.
Additionally, the organic acids of LPC saved the use of HCl in acid-aided protein solubilization and in isoelectric precipitation of alkali-solubilized proteins. During the latter, adding 30% LPC decreased HCl usage by as much as 61%. Opposite, alkaline protein solubilization in presence of LPC required more NaOH than the control, but this issue was naturally less pronounced at low LPC additions. Another challenge of introducing helpers was that they reduced total protein yield in the pH-shift process. This was however successfully mitigated by optimizing solubilization/precipitation pH, increasing water addition, and employing more powerful high shear homogenization and ultrasound techniques.
In summary, this thesis introduced a completely new concept of cross-processing fish co-products with antioxidant-containing food materials, significantly reducing lipid oxidation and enhancing protein isolate techno-functionalities. Herring co-products paired with 10% LPC was particularly promising. Beyond its technical advantages, cross-processing can add economic value to side streams of both fish and other food industries, while stimulating circularity and industrial symbiosis. Altogether, these features reduce food chain losses and promote a more sustainable food system.
This thesis investigated, for the first time, cross-processing of fish co-products with antioxidant-containing support materials (''helpers'') to protect the fish protein isolates from lipid oxidation in a clean label and sustainable manner. The helpers, including locally sourced plant food side streams (press cakes from lingonberry (LPC) and apple, barley spent grain, oat fiber residues), shrimp shells, and seaweeds, were also expected to introduce new characteristics to the protein isolates.
All helpers, except shrimp shells, reduced lipid oxidation in herring/salmon co-products when added at 30% (dw/dw) at start of the pH-shift process. LPC was the most effective, and even at 2.5% addition it prevented volatile aldehyde formation during production of herring protein isolates while at 10% addition, the isolates were also stable towards oxidation for ≥8 days on ice. When the 10% LPC instead was added during protein precipitation, the oxidation lag phase was extended to 21 days. The oxidative stability of protein isolates correlated with their total phenolic content, and the very high antioxidant ability of LPC's was mainly attributed to anthocyanins, e.g., ideain and procyanidin A1.
LPC also improved the water solubility, emulsifying activity, and gel-forming capabilities of herring protein isolates, expanding their potential applications in food products. The water solubility and emulsifying activity were also boosted by adding shrimp shells and Ulva, while the gel-forming ability was also enhanced by apple press cake. LPC-derived anthocyanins resulted in red isolates under acidic conditions and dark-colored isolates under neutral/alkaline conditions. Ulva resulted in green isolates due to the presence of chlorophyll. The color of protein isolates was also affected by oxidation of fish-derived pigments like Hb and astaxanthin. The addition of helpers also influenced the composition of protein isolates. LPC added at the start of the process reduced lipid content, while shrimp shells and LPC added during precipitation increased it. Seaweeds raised ash content by introducing minerals.
Additionally, the organic acids of LPC saved the use of HCl in acid-aided protein solubilization and in isoelectric precipitation of alkali-solubilized proteins. During the latter, adding 30% LPC decreased HCl usage by as much as 61%. Opposite, alkaline protein solubilization in presence of LPC required more NaOH than the control, but this issue was naturally less pronounced at low LPC additions. Another challenge of introducing helpers was that they reduced total protein yield in the pH-shift process. This was however successfully mitigated by optimizing solubilization/precipitation pH, increasing water addition, and employing more powerful high shear homogenization and ultrasound techniques.
In summary, this thesis introduced a completely new concept of cross-processing fish co-products with antioxidant-containing food materials, significantly reducing lipid oxidation and enhancing protein isolate techno-functionalities. Herring co-products paired with 10% LPC was particularly promising. Beyond its technical advantages, cross-processing can add economic value to side streams of both fish and other food industries, while stimulating circularity and industrial symbiosis. Altogether, these features reduce food chain losses and promote a more sustainable food system.
valorization
pomaces
protein techno-functionality
press cakes
by-products
fish protein
fruit
natural antioxidants
lipid oxidation
berry
protein gels
Författare
Jingnan Zhang
Chalmers, Life sciences, Livsmedelsvetenskap
Minimizing lipid oxidation during pH-shift processing of fish by-products by cross-processing with lingonberry press cake, shrimp shells or brown seaweed
Food Chemistry,;Vol. 327(2020)
Artikel i vetenskaplig tidskrift
Radial discharge high shear homogenization and ultrasonication assisted pH-shift processing of herring co-products with antioxidant-rich materials for maximum protein yield and functionality
Food Chemistry,;Vol. 400(2023)
Artikel i vetenskaplig tidskrift
Cross-processing herring and salmon co-products with agricultural and marine side-streams or seaweeds produces protein isolates more stable towards lipid oxidation
Food Chemistry,;Vol. 382(2022)
Artikel i vetenskaplig tidskrift
Zhang, J., Hong, B., Abdollahi, M., Wu, H., and Undeland, I. Towards circular food production: Investigating the effects of lingonberry press cake on oxidative stability and yield in herring co-product protein isolation.
Lingonberry (Vaccinium vitis-idaea) press-cake as a new processing aid during isolation of protein from herring (Clupea harengus) co-products
Food Chemistry: X,;Vol. 17(2023)
Artikel i vetenskaplig tidskrift
Seafood is very rich in omega-3 fatty acids, high-quality proteins, vitamins, and minerals and is therefore a vital component of our diets and health. Globally, fish consumption is rising, which is a challenge to accomplish given that >35% of the wild fish stocks are overfished and 57.3% are maximally used; facts that also hamper the growth of aquaculture. At the same time, there is an overwhelming focus on only eating fish fillets, i.e., just 40-50% of the fish weight. Frames, heads, skin, fins and guts are hereby dedicated to fodder meal and oil instead of feeding people, despite being very high in all the mentioned nutrients. Taking Sweden as an example, as much as 85% (!) of landed fish is allocated for feed, including both "fodder fish" and fish filleting co-products. This scenario calls for a change.
A promising tool for producing food protein ingredients from fish co-products is the pH-shift method. Here, fish proteins are solubilized in water under acid or alkaline conditions, allowing them to be separated from for example bones and skin. The proteins can then be made “solid” again and recovered from the water by changing the pH. A challenge in the process which needs to be overcome is that the fish lipids easily oxidize, i.e., become rancid. Hereby, unpleasant odor, reduced nutritional value, and impaired dry mouthfeel may develop.
This thesis investigates if cross-processing of herring and salmon co-products with various natural antioxidant-rich raw materials, such as plant-food side streams, shrimp shells or seaweed, can prevent rancidity during the pH-shift process. Results showed that some of the antioxidant raw materials, such as lingonberry juice press cakes (LPC), effectively limited rancidity during both the production and ice storage of fish protein ingredients. In fact, protein isolates made with LPC were stable for up to 21 days. Our research points to that molecules called “anthocyanins” are the secret behind this strong antioxidant effect.
In addition to their antioxidant ability, raw materials such as LPC, shrimp shells, and sea lettuce also made the protein ingredients more water-soluble and easier to emulsify with oil. These properties are crucial in food applications. LPC and apple press cake also helped the protein ingredients to form a “gel” which is important for example in burgers and fish balls. Moreover, the addition of antioxidant-rich material gave new colors to the protein ingredients which could be unusual to the consumer, but also open up new product possibilities. Lingonberry anthocyanins are for example red at low pH but bluish/purple at neutral/alkaline pH. Sea lettuce on the other hand produced green protein ingredients due to chlorophyll.
In conclusion, the cross-processing concept developed in this thesis is highly promising for the production of new food protein ingredients from fish filleting co-products, taking advantage of antioxidant-rich seaweeds and side streams from other food industries. Beyond its technical advantages, this breakthrough can stimulate symbiosis between food companies and a more circular food chain with lower losses and higher sustainability. Thus, the sea can now serve more dishes of food without increasing the fish catches, and at the same time, losses from land-based food production can be minimized.
A promising tool for producing food protein ingredients from fish co-products is the pH-shift method. Here, fish proteins are solubilized in water under acid or alkaline conditions, allowing them to be separated from for example bones and skin. The proteins can then be made “solid” again and recovered from the water by changing the pH. A challenge in the process which needs to be overcome is that the fish lipids easily oxidize, i.e., become rancid. Hereby, unpleasant odor, reduced nutritional value, and impaired dry mouthfeel may develop.
This thesis investigates if cross-processing of herring and salmon co-products with various natural antioxidant-rich raw materials, such as plant-food side streams, shrimp shells or seaweed, can prevent rancidity during the pH-shift process. Results showed that some of the antioxidant raw materials, such as lingonberry juice press cakes (LPC), effectively limited rancidity during both the production and ice storage of fish protein ingredients. In fact, protein isolates made with LPC were stable for up to 21 days. Our research points to that molecules called “anthocyanins” are the secret behind this strong antioxidant effect.
In addition to their antioxidant ability, raw materials such as LPC, shrimp shells, and sea lettuce also made the protein ingredients more water-soluble and easier to emulsify with oil. These properties are crucial in food applications. LPC and apple press cake also helped the protein ingredients to form a “gel” which is important for example in burgers and fish balls. Moreover, the addition of antioxidant-rich material gave new colors to the protein ingredients which could be unusual to the consumer, but also open up new product possibilities. Lingonberry anthocyanins are for example red at low pH but bluish/purple at neutral/alkaline pH. Sea lettuce on the other hand produced green protein ingredients due to chlorophyll.
In conclusion, the cross-processing concept developed in this thesis is highly promising for the production of new food protein ingredients from fish filleting co-products, taking advantage of antioxidant-rich seaweeds and side streams from other food industries. Beyond its technical advantages, this breakthrough can stimulate symbiosis between food companies and a more circular food chain with lower losses and higher sustainability. Thus, the sea can now serve more dishes of food without increasing the fish catches, and at the same time, losses from land-based food production can be minimized.
Mot en ny generation hållbara sjömatsprodukter - en cross-process-approach (CROSS)
Formas (2016-00246), 2016-01-01 -- 2021-12-31.
Drivkrafter
Hållbar utveckling
Innovation och entreprenörskap
Infrastruktur
Chalmers infrastruktur för masspektrometri
Ämneskategorier
Livsmedelsvetenskap
Livsmedelsteknik
Kemiska processer
Styrkeområden
Hälsa och teknik
ISBN
978-91-7905-822-7
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5288
Utgivare
Chalmers