Diatoms are rich sources of high-value bioactive compounds such as polysaccharides (chrysolaminarin, chitin), protein and bioactive peptides, and pigments (chlorophylls, carotenoids, marennine). These bioactive compounds have demonstrated diverse biological activities with potential applications in the food, nutraceuticals, pharmaceuticals, feed, and aquaculture sectors. This chapter provides information on the various bioactive compounds that have been discovered from diatoms including their chemical characteristics, functionality, and potential applications. The challenges and future recommendations related to the exploitation of bioactive compounds from diatoms are also discussed.

Truffles usually contain a high microbial load and establishing a decontamination strategy without affecting the organoleptic features of fresh truffles before any postharvest processing is an imperative. In this study, the im-pacts of decontamination treatments including ozonated water (3 mg/L and 6 mg/L) and citric acid (5% and 10%) on the microbiological populations (total aerobic, total anaerobic, and Pseudomonas spp. counts) and organoleptic characteristics (firmness and colour) of fresh truffles were investigated. Furthermore, the effect of time of exposure (5, 10, 15, and 20 min) to each treatment was assessed. Treatment that demonstrated the most effective microbial reduction without compromising the colour and firmness of truffles was deemed preferred and its impact on the key volatile profile of truffles was assessed. Truffles treated with different concentrations and exposure times of ozonated water showed no significant changes in microbial counts, firmness, or colour compared to the control. A significant microbial reduction without compromising the colour and firmness of truffles was observed with citric acid treatments. In particular, the antimicrobial effect of citric acid against Pseudomonas spp. was improved significantly with increasing concentration and exposure time. Truffles treated with 10% citric acid treatment for 15 min promoted about 1.0 log CFU/g of reduction for the total aerobic and anaerobic microbes and the Pseudomonas spp. count was reduced from 6.18 +/- 0.19 log CFU/g (control) to < 3.48 log CFU/g. The key volatile profile of the selected treatment was not significantly different from the control. The overall finding shows that a single-step washing with citric acid could be a promising decontamination treatment for fresh truffles before any postharvest processing.

This study aimed to develop a novel technique to retain and stabilize compounds contributing to truffle aroma by encapsulation using β-cyclodextrin. Two experiments were conducted. In the first experiment, the key volatile profile and microbial population of products resulting from three different encapsulation methods, namely direct mixing method (M1), direct mixing followed by ethanol addition method (M2), and paste method (M3), were compared with untreated truffles (positive control) over a 90-day period. The M2-derived product was the least optimal for retaining key volatile compounds despite showing the lowest microbial population. There was no significant difference in the volatile profile of products derived from M1 and M3 on day 0. However, it was observed that the M3-derived product could retain its volatile profile better than the M1-derived product by day 90. M3 was compared with freeze-drying in the second experiment. Freeze-dried truffles showed an overall higher relative percentage of volatiles than the M3-derived product on day 0. However, by day 90, some volatile changes occurred in the freeze-dried truffles but not in the M3-derived product. The findings indicate that while freeze-drying could adequately conserve truffle volatiles, the encapsulation of volatile compounds in β-cyclodextrin could improve the volatile stability of truffle products and allow for longer storage times. Microbes were found in all encapsulated truffle products and freeze-dried truffles on days 0 and 90, suggesting the need to explore the possibility of incorporating a decontamination step in the process prior to either encapsulation or freeze-drying. PRACTICAL APPLICATION: A technique to capture and stabilize compounds responsible for truffle aroma by encapsulation using β-cyclodextrin was developed and compared with freeze-drying in this study. The overall finding suggests that while freeze-drying of truffle could sufficiently preserve volatiles, encapsulating truffle volatiles with β-cyclodextrin may improve its stability, extending its shelf life, which can be applied in the development of a natural truffle ingredient that can be applied in food product development.

The cover image is based on the Original Article Methods used for extraction of plant volatiles have potential to preserve truffle aroma: A review by Ranil Coorey et al., https://doi.org/10.1111/1541-4337.12927.

Truffles are considered one of the world's most highly prized foods mainly due to their desirable organoleptic properties and rarity. However, truffles are seasonal (harvested mostly in winter from June to August in the Southern Hemisphere and from December to February in the Northern Hemisphere) and extremely perishable. Truffles deteriorate rapidly showing undesirable changes within 10 days from harvest in aroma and visual appearance after harvest. The very short postharvest shelf life (about 7-10 days) limits the potential for export and domestic consumption all year round. Several preservation methods have been studied to prolong their shelf life without the loss of aroma. However, all traditional preservation techniques have their own shortcomings and remain challenging. The extraction of natural truffle aroma volatiles for food applications could be a potential alternative to replace the existing synthetic flavoring used for processed truffle products. Four commonly used extraction methods for recovering volatile compounds from plants, namely, supercritical carbon dioxide extraction, Soxhlet extraction, distillation, and cold pressing, are critically analyzed. Up to date, existing research about the extraction of aroma volatiles from truffles is limited in the literature but based on the volatility of the key truffle volatile compounds, supercritical carbon dioxide extraction may offer the best possibility so that a natural truffle-based product that can be used in food applications throughout the year can be made available.

Black truffle ( Tuber melanosporum ) is usually available in a form of a whole, offcut pieces (sliced to remove defects or broken from larger truffles) or freeze-dried (one of the preservation methods), but there is insufficient knowledge about microbial spoilage of these products. The changes in the microbiology of whole, sliced, and freeze-dried black truffles ( Tuber melanosporum ) were determined in this study. All truffle samples were vacuum-packaged and stored at 4°C for 30 days and evaluated on day 0, 4, 8, 15, and 30. The total plate count, Pseudomonas spp. count, yeast, and mold count, as well as the presence of Listeria spp., Salmonella spp., and Bacillus spp., were examined. The main finding of this study was that the total microbial count, Pseudomonas spp. count, and yeasts count associated with the freeze-dried truffles were generally lower than that of the whole and sliced truffles. While mold, Listeria spp., and Salmonella spp. were not detected (<2.00 log CFU/g), Bacillus spp. were detected at a very low count in all sample types (<3.48 log CFU/g). Overall, the results suggest the need to establish an effective decontamination treatment before packaging and storage to delay microbial spoilage.

Fresh truffles which include black truffle (Tuber melanosporum Vittadini) deteriorate and lose aroma rapidly after harvest; therefore, postharvest processing via freeze-drying or encapsulation is an option to preserve truffle aroma for extended supply. However, the aroma profile that directly affects the truffle quality and consumer acceptance is influenced by processing and producers require processing options that balance processing feasibility with retention of a suitable aroma profile. This study aimed to determine the impact of freeze-drying and encapsulation on the profile of key volatiles, consumer discrimination, and overall sensory impression (aroma intensity, liking, and acceptability) of processed truffle products compared to the starting material (positive control). The study combined experimental-scale processing with GC-MS analysis and consumer sensory evaluation to compare and optimize postharvest processing options. Based on the results, some volatile changes were detected in the processed truffle products compared to the positive control which were aligned with the consumer discrimination (triangle test) and the aroma intensity score (consumer sensory test). Despite some chemical and sensory differences detected, the consumer panel did not have any preference for processed truffle products compared to the positive control. The overall finding indicates the potential value of processing truffles into a natural flavoring ingredient for food application via freeze-drying or encapsulation, which should be of great interest for the truffle and food industry. According to the correlation analysis, the consumer acceptance of a truffle product may be increased by retaining 1-octen-3-ol and methional, while reducing the amount of p-cresol in the product. Practical Application The postharvest process of turning truffles into a food flavoring ingredient may cause undesirable volatile changes that would directly impact the aroma quality and consumer acceptance of the processed truffle products. Hence, the impacts of freeze-drying and encapsulation on the chemical and sensory profile of truffles were evaluated in this study. Overall, the results of the concurrent instrument and sensory analysis demonstrated that both freeze-drying and encapsulation are potential options for processing.

Persiscaria tenulla, commonly known as Polygonum, is a plant belonging to the family Polygonaceae, which originated from and is widely found in Southeast Asia countries, such as Indonesia, Malaysia, Thailand, and Vietnam. The leaf of the plant is believed to have active ingredients that are responsible for therapeutic effects. In order to take full advantage of a natural medicinal plant for the application in the pharmaceutical and food industries, extraction and separation techniques are essential. In this study, an emerging and rapid extraction approach known as liquid biphasic flotation (LBF) is proposed for the extraction of protein from Persiscaria tenulla leaves. The scope of this study is to establish an efficient, environmentally friendly, and cost-effective technology for the extraction of protein from therapeutic leaves. Based on the ideal conditions of the small LBF system, a 98.36% protein recovery yield and a 79.12% separation efficiency were achieved. The upscaling study of this system exhibited the reliability of this technology for large-scale applications with a protein recovery yield of 99.44% and a separation efficiency of 93.28%. This technology demonstrated a simple approach with an effective protein recovery yield and separation that can be applied for the extraction of bioactive compounds from various medicinal-value plants.

Aqueous two-phase system (ATPS) has been suggested as a promising separation tool in the biotechnological industry. This liquid-liquid extraction technique represents an interesting advance in downstream processing due to several advantages such as simplicity, rapid separation, efficiency, economy, flexibility and biocompatibility. Up to date, a range of biotechnological products have been successfully recovered from different sources with high yield using ATPS-based strategy. In view of the important potential contribution of the ATPS in downstream processing, this review article aims to provide latest information about the application of ATPS in the recovery of various biotechnological products in the past 7 years (2010-2017). Apart from that, the challenges as well as the possible future work and outlook of the ATPS-based recovery method have also been presented in this review article. (C) 2018, The Society for Biotechnology, Japan. All rights reserved.

One of the critical challenges in releasing protein from microalgae is to effectively disrupt their rigid thick cell walls. This study could provide some guidance on the implementation of a simple, cost-effective and scalable cell disruption in a downstream processing of microalgal industry for the recovery of protein from microalgae. The effects of solvent types, alkalis, and ultrasonication in disrupting microalgal cell wall and protein solubility were studied. It was found that alkaline treatment played a key role in cell disruption and protein solubilisation. From the industrial perspective, water is an excellent choice of extractive solvent due to low-cost, safety, and scalability. Among all the tested methods, the combination of both alkaline and ultrasonication treatment demonstrated the greatest cell disruption efficiency and was thus suggested to be use at large scale. (C) 2018 Published by Elsevier B.V.

Microalgae emerge as the most promising protein sources for aquaculture industry. However, the commercial proteins production at low cost remains a challenge. The process of harnessing microalgal proteins involves several steps such as cell disruption, isolation and extraction. The discrete processes are generally complicated, time-consuming and costly. To date, the notion of integrating microalgal cell disruption and proteins recovery process into one step is yet to explore. Hence, this study aimed to investigate the feasibility of applying methanol/potassium ATPS in the integrated process for proteins recovery from Chlorella sorokiniana. Parameters such as salt types, salt concentrations, methanol concentrations, NaCl addition were optimized. The possibility of upscaling and the effectiveness of recycling the phase components were also studied. The results showed that ATPS formed by 30% (w/w) K3PO4 and 20% (w/w) methanol with 3% (w/w) NaCl addition was optimum for proteins recovery. In this system, the partition coefficient and yield were 7.28 and 84.23%, respectively. There were no significant differences in the partition coefficient and yield when the integrated process was upscaled to 100-fold. The recovered phase components can still be recycled effectively at fifth cycle. In conclusions, this method is simple, rapid, environmental friendly and could be implemented at large scale.

In this work, the extraction of microalgal protein from wet Chlorella sorokiniana species using alcohol/salt liquid biphasic flotation (LBF) with the aid of ultrasonication for cell rupturing was proposed. The effect of varying crude feedstock concentration, flotation time, salt type, salt concentration, alcohol type, alcohol concentration, initial volumes of salt and alcohol were investigated. After the optimization process, the highest proportion of protein recovered in the top phase was achieved with 250g/L ammonium sulphate, 60% (v/v) 2-propanol, 1.0VR,initial, 20g/L crude biomass load, 4mm3/min air flowrate and 10min of flotation time. The recycling of phase components was introduced to minimize the use of alcohol and salt in the corresponding LBF. It was demonstrated that top phase (alcohol) recycling can achieve increasing performance for three consecutive recycling runs. Under optimized process conditions, the proportion of protein recovered in the top phase was 88.86% for the third recycle run.

Bio-functional proteins from microalgae have numerous biological properties with health-promoting effects. However, efficient harnessing of bio-functional proteins from microalgae is still in its infancy. One of the major obstacles that hinder the mass production of bio-functional proteins is the presence of resistant cell wall that diminishes the liberation of cell contents. As the bio-functional proteins are very sensitive to denaturation, selecting a mild disruption method to rupture the cell wall, while preserving their bioactivity and functionality, is of vital importance in downstream processing. To ensure the future development of efficient mild disruption methods for maximum recovery of bio-functional proteins from microalgae, this review provides useful information on various mild disruption approaches, current status, potential technologies that are still under development, as well as their advantages and constraints. In particular, those potential technologies that require further attention in the future (namely, explosive decompression, microfluidization, pulsed arc technology and cationic polymer coated membranes) are also discussed in this review.

Microalgae emerge as the most promising protein source for aquaculture industry. However, the commercial production of microalgal protein at low cost remains challenging. The release of protein from microalgae is restricted by the presence of rigid thick cell wall. Another technical hurdle is that the whole protein recovery process involves several steps such as cell disruption, isolation and extraction; which is generally complicated, time-consuming and costly. To solve the technical hurdles, two experiments were designed in this study. The first experiment focused on the evaluation of a simple, economic, practical and scalable cell disruption technique for the protein recovery from microalgae. The effects of solvent types, alkali, and ultrasonication in cell disruption and protein solubility of microalgae (Chorella sorokiniana, Chorella vulgaris, Chlamydomonas sp. Tai-03 and Scenedesmus sp. Esp-07) were studied. To date, the notion of integrating microalgal cell disruption and protein recovery process into one step is yet to explore. Therefore, the feasibility of applying methanol/potassium ATPS in the extractive disruption integrated process for protein recovery was investigated in the second experiment. Parameters such as salt types, salt concentrations, methanol concentrations, NaCl addition were optimized. The possibility of upscaling and the effectiveness of using the recycled phase components at each recycling step were also studied. Based on the findings from the first experiment, it was found that alkaline treatment played a key role in cell disruption and protein solubilisation. From the industrial perspective, water is an excellent choice of solvent for simultaneous cell disruption and protein solubilisation due to low cost, ubiquitous availability and scalability. The combination of both alkaline and ultrasonication treatment showed the highest percentage of protein release and was thus proposed to be suitable for industrial application. The protein concentrations obtained from all the four microalgal strains after treated with the combination treatment were about 15-30% higher than alkaline treatment and about 27-261% higher than ultrasonication treatment when using water as the solvent. Protein-rich strain of C. sorokiniana was selected for further study in the second experiment. The disruption method used in the second experiment was the combination of alkaline and ultrasonication treatment. Based on the results obtained from the integrated process, it was found that ATPS formed by 30% (w/w) K3PO4 and 20% (w/w) methanol with 3% (w/w) NaCl addition was optimum for protein recovery. In this system, the partition coefficient and yield were 7.28 and 84.23%, respectively. There were no significant differences in the partition coefficient and yield when the integrated process was scaled up to 100-fold. The recycled phase components can still be performed effectively at the 5th cycle. In conclusion, the findings suggested that the integrated process is simple, environmental friendly and could be implemented at large scale.

The commercial production of microalgal proteins at low cost remains challenging. The release of proteins from microalgae is restricted by the presence of rigid thick cell wall that could hinder the extraction process and affect the proteins recovery yield. In view of this, this study aimed to provide some guidance on the selection of the efficient solvent in facilitating the proteins release during the cell disruption process. The effects of different solvent types such as methanol, ethanol, 1-propanol and water in facilitating the process of proteins release from microalgal cell wall were studied in the present study. Based on the results, it was found that water able to release the highest concentration of proteins from microalgae compared to the other solvents.