Impact of processing on n-3 LC-PUFA in model systems enriched with microalgae

Nutrient removal and biomass production of marine microalgae cultured in recirculating aquaculture systems (RAS) water with low phosphate concentration

This study was conducted to investigate the feasibility of microalgal biomass production and nutrient removal from recirculating aquaculture systems (RAS) water (RASW) with low phosphate concentration. For this purpose, Nannochloropsis oculata, Pavlova gyrans, Tetraselmis suecica, Phaeodactylum tricornutum, and their consortium were cultivated in RASW and RASW supplemented with vitamins (+V). Among them, N. oculata showed the maximum biomass production of 0.4 g/L in RASW. Vitamins supplementation significantly increased the growth of T. suecica from 0.16 g/L in RASW to 0.33 g/L in RASW + V. Additionally, T. suecica showed the highest nitrate (NO3-N) removal efficiency of 80.88 ± 2.08 % in RASW and 83.82 ± 2.08 % in RASW + V. Accordingly, T. suecica was selected for scaling up study of microalgal cultivation in RASW and RASW supplemented with nitrate (RASW + N) in 4-L airlift photobioreactors. Nitrate supplementation enhanced the growth of T. suecica up to 2.2-fold (day 15). The fatty acid nutritional indices in T. suecica cultivated in RASW and RASW + N showed optimal polyunsaturated fatty acids (PUFAs)/saturated fatty acid (SFAs), omega-6 fatty acid (n-6)/omega-3 fatty acid (n-3), indices of atherogenicity (IA), and thrombogenicity (IT)). Overall, the findings of this study revealed that despite low phosphate concentration, marine microalgae can grow in RASW and relatively reduce the concentration of nitrate. Furthermore, the microalgal biomass cultivated in RASW consisting of pigments and optimal fatty acid nutritional profile can be used as fish feed, thus contributing to a circular bioeconomy.

Conversion of Retinyl Palmitate to Retinol by Wheat Bran Endogenous Lipase Reduces Vitamin A Stability

Wheat bran can be used as a cost-effective food ingredient to stabilise vitamin A. However, wheat bran endogenous enzymes have been shown to reduce vitamin A stability. In this study, we elucidated the mechanism for this negative effect in an accelerated storage experiment with model systems consisting of native or toasted wheat bran, soy oil and retinyl palmitate (RP). Both native and toasted wheat bran substantially stabilised RP. While RP was entirely degraded after ten days of storage in the absence of wheat bran, the RP retention after ten days was 22 ± 2% and 75 ± 5% in the presence of native and toasted bran, respectively. The significantly stronger stabilising effect of toasted bran was attributed to the absence of bran endogenous enzymes. In contrast to toasted bran systems, noticeable free fatty acid production was observed for native bran systems. However, this did not result in a pronounced lipid oxidation. Next to lipid hydrolysis, wheat bran lipase was shown to hydrolyse retinyl esters to the less stable retinol and fatty acids. This reaction could explain the major part, about 66 ± 5%, of the difference in RP stabilisation between native and toasted wheat bran.

Oxidative stability differences of aqueous model systems of photoautotrophic n-3 LC-PUFA rich microalgae: The antioxidative role of endogenous carotenoids

Microalgae rich in omega-3 long-chain polyunsaturated fatty acids (n-3LC-PUFA) have already shown their potential for developing functional food rich in these healthy fatty acids. Not only could they offer a more sustainable alternative for the fish stock that is currently relied upon but is unable to keep up with the demand, enrichment with certain microalgae also leads to oxidatively stable products. Although the reason for this stability has been attributed to the presence of endogenous carotenoids, further insight into their antioxidative role is missing and would be clarifying for selecting the proper microalgae for food enrichment. In trying to further accomplish this, a storage experiment (4 weeks, 37 °C) was set up with the parallel analysis of both oxidation products (primary and secondary) and carotenoids of two aqueous model systems of different (promising) microalgae (Nannochloropsis and Phaeodactylum). The results showed a clear difference in oxidative stability despite both microalgae containing endogenous carotenoids: Nannochloropsis led to oxidatively unstable and Phaeodactylum to oxidatively stable products. This was clearly confirmed by the analysis of n-3LC-PUFA throughout storage which showed a breakdown of half of the n-3LC-PUFA for Nannochloropsis. All carotenoids (violaxanthin, zeaxanthin and β-carotene for Nannochloropsis, and fucoxanthin and β-carotene for Phaeodactylum) acted as an antioxidant as shown by their degradation throughout storage, but the difference in oxidative stability pointed out an impact of carotenoid content and (possibly) type. The presence of a sufficient amount of carotenoids seems to be an important factor for perceiving oxidative stability. Phaeodactylum has shown to be more potent for food enrichment.

Antioxidative capacity of microalgal carotenoids for stabilizing n-3LC-PUFA rich oil: Initial quantity is key

The health-beneficial long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFA) are easily affected by the undesired process of lipid oxidation in fish oil, while being stable in the lipid extracts of photoautotrophic microalgae. The current research investigates the role of carotenoids by evaluating the oxidative stability of mixtures of fish oil with total lipid extracts of two different microalgae (Phaeodactylum and Isochrysis) throughout an accelerated storage experiment of 4 weeks at 37 °C. A clear separation between oxidatively stable and oxidatively unstable mixtures was observed for which the initial amount of carotenoids relative to the amount of n-3LC-PUFA was a good indicator. The lipid class composition, clearly differing between the two algae, was probably of minor influence. The antioxidative role of fucoxanthin, and diatoxanthin and β-carotene as minor carotenoids, was illustrated by their gradual degradation throughout storage. However, when their initial contents were too low, this role could not be exerted leading to thorough lipid oxidation.

The Potential of Phaeodactylum as a Natural Source of Antioxidants for Fish Oil Stabilization

Worldwide, fish oil is an important and rich source of the health-beneficial omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA). It is, however, troubled by its high susceptibility towards lipid oxidation. This can be prevented by the addition of (preferably natural) antioxidants. The current research investigates the potential of Phaeodactylum carotenoids in this regard. The oxidative stability of fish oil and fish oil with Phaeodactylum addition is evaluated by analyzing both primary (PV) and secondary (volatiles) oxidation products in an accelerated storage experiment (37 °C). A first experimental set-up shows that the addition of 2.5% (w/w) Phaeodactylum biomass is not capable of inhibiting oxidation. Although carotenoids from the Phaeodactylum biomass are measured in the fish oil phase, their presence does not suffice. In a second, more elucidating experimental set-up, fish oil is mixed in different proportions with a Phaeodactylum total lipid extract, and oxidative stability is again evaluated. It was shown that the amount of carotenoids relative to the n-3 LC-PUFA content determined oxidative stability. Systems with a fucoxanthin/n-3 LC-PUFA ratio ≥ 0.101 shows extreme oxidative stability, while systems with a fucoxanthin/n-3 LC-PUFA ratio ≤ 0.0078 are extremely oxidatively unstable. This explains why the Phaeodactylum biomass addition did not induce oxidative stability.

Photo-Oxidative Stability of Aqueous Model Systems Enriched with Omega-3 Long-Chain Polyunsaturated Fatty Acid-Rich Microalgae as Compared to Autoxidative Stability

Several species of microalgae are promising as an alternative source of omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA). Photoautotrophic species show the greatest potential, since incorporating them into food products leads to oxidatively stable products; however, the presence of photosensitizers could reduce the shelf-life due to the appearance of photo-oxidation on exposure to light. This study investigated the oxidative impact of illumination for aqueous model suspensions enriched with Phaeodactylum (phototrophic microalgae─containing potential photosensitizers) and Schizochytrium (heterotrophic microalgae─lacking photosensitizers) during storage for 28 days at 37 °C. Primary (peroxide value) and secondary (volatiles with gas chromatography (GC)-mass spectrometry) oxidation products, n-3 LC-PUFA content (GC), and pigments (high-pressure liquid chromatography) were assessed. The results showed that photo-oxidation did not cause oxidative instability for Phaeodactylum samples compared with strong autoxidation in Schizochytrium samples. For the Phaeodactylum-enriched suspensions, only minimal photo-oxidation could be detected and the n-3 LC-PUFA content remained stable throughout storage regardless of illumination.

A novel strategy to simultaneously enhance bioaccessible lipids and antioxidants in hetero/mixotrophic Chlorella vulgaris as functional ingredient

Microalgae are a promising source of polyunsaturated fatty acids as well as bioactive antioxidant compounds such as carotenoids, phenolics and tocopherols. However, the accumulation of these biomolecules is often promoted by conflicting growth conditions. In this study, a phased bioprocessing strategy was developed to simultaneously enhance the lipid and antioxidant amounts by tailoring nitrogen content in the cultivation medium and applying light stress. This approach increased the overall contents of total fatty acids, carotenoids, phenolics, and α-tocopherol in Chlorella vulgaris by 2.2-, 2.2-, 1.5-, and 2.1-fold, respectively. Additionally, the bioaccessibility of the lipids and bioactives from the obtained biomasses improved after pulsed electric field (5 μs, 20 kV cm^-1, 31.8 kJ kg^-1_sus) treatment (up to +12%) and high-pressure homogenization (100 MPa, 5-6 passes) (+41-76%). This work represents a step towards the generation of more efficient algae biorefineries, thus expanding the alternative resources available for essential nutrients.

Research advancement and commercialization of microalgae edible oil: a review

The global food crisis has led to a great deal of attention being given to microalgal oil as a sustainable natural food source. This article provides an overview of the progress and future directions in promoting the commercialization of microalgal edible oils, including microalgal triglyceride accumulation, suitable edible oil culture strategies for high nutritional value, metabolic engineering, production, and downstream technologies. The integration of the production process, biosafety, and the economic sustainability of microalgal oil production are analyzed for their critical roles in the commercialization of microalgal edible oil to provide a theoretical and scientific basis for the comprehensive development and utilization of microalgal edible oil. © 2021 Society of Chemical Industry.

Normal-Phase HPLC-ELSD to Compare Lipid Profiles of Different Wheat Flours

Normal-phase high-performance liquid chromatography (HPLC) is widely used in combination with evaporative light scattering detection (ELSD) for separating and detecting lipids in various food samples. ELSD responses of different lipids were evaluated to elucidate the possibilities and challenges associated with quantification by means of HPLC-ELSD. Not only the number and type of polar functional groups but also the chain length and degree of unsaturation of (free or esterified) fatty acids (FAs) had a significant effect on ELSD responses. Tripalmitin and trilinolein yielded notably different ELSD responses, even if their constituting free FAs produced identical responses. How FA structure impacts ELSD responses of free FAs is thus not predictive for those of triacylglycerols and presumably other lipids containing esterified FAs. Because ELSD responses of lipids depend on the identity of the (esterified) FA(s) which they contain, fully accurate lipid quantification with HPLC-ELSD is challenging and time-consuming. Nonetheless, HPLC-ELSD is a good and fast technique to semi-quantitatively compare the levels of different lipid classes between samples of comparable FA composition. In this way, lipid profiles of different flours from near-isogenic wheat lines could be compared.

Hemiselmis andersenii and Chlorella stigmatophora As New Sources of High-value Compounds: A Lipidomic Approach

To unlock the potential of Chlorella stigmatophora (Trebouxiophyceae, Chlorophyta) and Hemiselmis andersenii (Cryptophyceae, Cryptophyta) as natural reactors for biotechnological exploitation, their lipophilic extracts were characterized using Fourier Transform Infrared spectroscopy with Attenuated Total Reflectance (FTIR-ATR) and Gas Chromatography-Mass Spectrometry (GC-MS) before and after alkaline hydrolysis. The GC-MS analysis enabled the identification of 62 metabolites-namely fatty acids (27), aliphatic alcohols (17), monoglycerides (7), sterols (4), and other compounds (7). After alkaline hydrolysis, monounsaturated fatty acids increased by as much as 87%, suggesting that the esterified compounds were mainly neutral lipids. Hemiselmis andersenii yielded the highest Σω3/Σω6 ratio (7.26), indicating that it is a good source of ω3 fatty acids, in comparison to C. stigmatophora (Σω3/Σω6 = 1.24). Both microalgae presented significant amounts of aliphatic alcohols (6.81-10.95 mg · g dw^-1 ), which are recognized by their cholesterol-lowering properties. The multivariate analysis allowed visualization of the chemical divergence among H. andersenii lipophilic extracts before and after alkaline hydrolysis, as well as species-specific differences. Chlorella stigmatophora showed to be a valuable source of essential fatty acids for nutraceuticals, whereas H. andersenii, due to its high chemical diversity, seems to be suitable for different fields of application.

Effect of Solid-State Fermented Wheat Bran Supplemented with Agrimony Extract on Growth Performance, Fatty Acid Profile, and Meat Quality of Broiler Chickens

Simple Summary

The current work evaluates the application of solid-state fermented wheat bran supplemented with agrimony extract in broiler nutrition. Broiler production parameters, blood and bone variables and meat quality were analysed. The quality of breast and thigh meat was evaluated by the use of physicochemical variables, fatty acid profile, lipid oxidation and sensory variables. The presented results showed that supplementation of the broiler diet with fermented feed positively influenced the quality of the produced breast and thigh meat. The application of fermented feed increased the nutritional value of broiler chicken meat, as shown via the positive modification of the fatty acid profile, without affecting sensory quality.

Abstract

The impact of the broiler diet modification on the following parameters was evaluated: meat quality, carcass traits, and bone and blood parameters. One hundred twenty one-day-old COBB 500 broiler chickens were assigned to three experimental groups (40 birds per group) with four replications (10 per pen) for 35 days of fattening. The control (C) was fed a basic feed mixture. The diet supplemented with 10% of fermented feed (FF10) and additionally supported by 0.2% of agrimony extract (FF10 + AE) was applied to the second and third groups, respectively. FF10 showed both a lower average daily feed intake and total feed consumption when compared to that of C (p < 0.05). Lower concentration of alkaline-phosphatase and calcium and higher total lipids and triglycerides in blood were observed in FF10 + AE. Breast and thigh meat showed a lower content of polyunsaturated fatty acid n-3 and n-6 in the FF10 + AE group (p < 0.01). The increase of gamma-linolenic acid content in breast and thigh meat samples obtained from the experimental groups was significant (p < 0.001 and p < 0.05; respectively). Lower lipid oxidation was observed in the thigh muscle of the FF10 + AE group on the first day of storage (p < 0.01). The current study indicates that FF10 + AE supplementation can be successfully applied to enhance broiler performance and meat quality.

Evaluation of Microbial Load, Formation of Odorous Metabolites and Lipid Stability during Wet Preservation of Nannochloropsis gaditana Concentrates

Wet preservation of algae allows us to bridge the time period between algae harvest and processing while avoiding the costs and nutritional losses associated with algae drying. This study aimed to identify suitable storage conditions for the wet preservation of Nannochloropsis gaditana concentrates. The impact of storage temperature, time and the way of closing the storage recipient was evaluated using a full factorial design. The effect of acetic acid addition was tested for one storage condition. Storage temperature was the main factor determining the microbial count and had a vast impact on the formation of odorous metabolites. Storage at 20 °C in closed recipients led to rapid O2 consumption, accumulation of malodorous short-chain fatty acids above their odor thresholds, and the production of H2S and methanethiol. These odorous metabolites were not formed or to a much lower extent during 4 °C and 8 °C storage in closed recipients. Acetic acid supplementation (50 mM) suppressed the formation of short-chain fatty acids during 8 °C storage in unsealed recipients and reduced the aerobic microbial count and the number of yeasts and molds by approximately one log unit after 14 days. Yet, acetic acid addition also induced lipid hydrolysis and decreased chlorophyll levels when algae were stored for more than one week. This study demonstrated that temperature control is needed and that acetic acid addition is a promising approach when N. gaditana concentrates are stored for less than one week.

Functional Foods: Product Development, Technological Trends, Efficacy Testing, and Safety

Functional foods is a very popular term in the social and scientific media; consequently, food producers have invested resources in the development of processed foods that may provide added functional benefits to consumers' well-being. Because of intrinsic regulation and end-of-use purposes in different countries, worldwide meanings and definitions of this term are still unclear. Hence, here we standardize this definition and propose a guideline to attest that some ingredients or foods truly deserve this special designation. Furthermore, focus is directed at the most recent studies and practical guidelines that can be used to develop and test the efficacy of potentially functional foods and ingredients. The most widespread functional ingredients, such as polyunsaturated fatty acids (PUFAs), probiotics/prebiotics/synbiotics, and antioxidants, and their technological means of delivery in food products are described. The review discusses the steps that food companies should take to ensure that their developed food product is truly functional.