Freeze-dried Material Research Articles

Studies on Proximate Composition, Mineral and Total Phenolic Content of Yogurt Bites Enriched with Different Plant Raw Material

Yogurt products are consumed by millions of people every day. Consumers’ priority for ready-to-eat yogurt snacks enriched with various plant raw materials have increased each year. Therefore, the aim of this study was to prepare freeze-dried yoghurt bites with the addition of powders of beetroot, mulberry leaves, nettle leaves and rosehip fruit and to investigate these raw materials’ influence on the proximate composition, mineral and total phenolic content. The moisture, protein, fat, carbohydrate and sugar content of the yogurt bites were established using standard methods: mineral composition—using an inductively coupled plasma mass spectrometer (ICP-MS); total phenolic content—by the spectrophotometric method. The results demonstrated that the addition of different raw material powders to the formulation of yogurt bites had no significant influence on carbohydrate, protein and total fat amounts. However, the incorporation of powders of beetroot, mulberry leaves, nettle leaves and rosehip fruit in yogurt bites allowed a significant increase of the amounts of all investigated minerals and total phenolic content of the manufactured bites. Among all investigated yogurt bites, the highest amounts of K, P, Mg, Fe and Zn were determined for yogurt bites enriched with nettle leaves. In conclusion, the enrichment of yogurt bites with freeze-dried plant raw material powders can increase amounts of selected minerals and total phenolic content.

Attenuation of Microcystins Using Electron Beams and Gamma Radiation: A Study with Environment-Bound Conditions

Microcystins (MCs) are toxins profusely synthesized by cyanobacteria, causing livestock poisonings and endangering human health. We design and execute an experiment to investigate the attenuation (degradation) of microcystins by exposing them to gamma radiation and electron beams at doses of 0 (control), 3, 5, 10 and 15 kGy. The experimental conditions simulate microcystin contamination of aquatic environments; we thus consider (1) microcystins inside whole cells and extracellular dissolved in water, simulated by non-sonicated and sonicated cells, respectively, and (2) two acute microcystin concentrations within water. Toxicity tests of Microcystis aeruginosa detected immobilization (i.e., paralysis) of Ceriodaphniasilvestrii exposed to aqueous crude extracts of irradiated and non-irradiated M. aeruginosa (NPLJ-4 strain) at concentrations of 45 and 90 mg.L-1 (mg dry weight of freeze-dried material), and the results were analyzed using the Trimmed Spearman-Karber statistical program to obtain 48-h EC50, the average effective concentration causing immobility in 50% of organisms after 48 hours. We conclude that electron beams are effective physical agents for toxin attenuation (degradation) and reach 100% effectiveness at 5 kGy and above; their efficiency is two orders of magnitude greater than that of gamma radiation. This new body of information contributes to (1) remediating environmental water sources; (2) designing water/wastewater treatment facilities; (3) combatting chronic microcystin environmental contamination; and (4) inspiring further studies to promote the use of biomonitors (e.g., Cladocerans) to detect and evaluate microalgae contamination.

The relatively higher concentrations of trace elements to arsenic may have influenced on methylation process of inorg- As in humans

The relatively higher concentrations of trace elements to arsenic may have influenced on methylation process of inorg- As in humans

Evaluation of yield formation and nutritive value of forage legumes and herbs with potential for diverse grasslands due to their concentration in plant specialized metabolites

The use of forage legumes and herbs in temporary grassland swards is a promising strategy to enhance productivity, protein supply, herbage quality and species diversity in forage-based low input dairy production. Species containing plant specialized metabolites (PSM; e.g. tannins or polyphenol oxidase) are associated with positive effects on ruminants’ health, performance and nitrogen use efficiency. However, plant growth characteristics and the occurrence of PSMs with potential for improved nutritive value vary greatly depending on species and environment and to date, few species have been exploited agronomically. Thus, the current study aims to screen a range of forage species that are abundant in low input and semi-natural grasslands, in terms of productivity and forage quality for dairy cows under limited nitrogen availability in a ley system. Pure stands of eight legumes, six herbs and perennial ryegrass as reference, were established in a field experiment and sampled over two years (2010 and 2013) in their first full production year. Freeze-dried plant material was analysed for crude protein (CP), enzyme soluble organic matter (ESOM), fibre parameters (ADF, NDF), total phenolics (TP) and condensed tannins (CT). The species variation was significant for each parameter (P < 0.001). In comparison to high yielding legumes, herbage production of investigated alternative species was generally low, but for Cichorium intybus and Plantago lanceolata comparable or even higher than for Lolium perenne. Differences existed in yield development throughout the year, thus exhibiting temporal asynchrony for improved performance if grown in mixtures. Apart from Onobrychis viciifolia, the CP concentration in legume species was highest while ESOM was outstandingly high in herbs (except Plantago lanceolata). TP concentration was generally higher in herbs but in Onobrychis viciifolia and Lotus corniculatus the concentration of condensed tannins exceeded 10 g kg−1 DM. The results indicate that alternative forage species exist with high forage quality and potentially promising PSM concentrations, thus making them interesting additions for temperate grasslands.

Development of the certified reference material of cadmium in human urine (freeze-dried)

Objective: To develop the certified reference material of cadmium in human urine (freeze-dried) . Methods: Urine were collected from normal human, and then the urine samples were prepared by adding standard, mixing, packing and freeze-drying. After homogeneity test and stability test, the urine samples were determined by two methods in seven independent laboratories, the uncertainty of the certified reference material was evaluated. Results: Take at least 0.20 ml solution of the certified reference material per use, and the homogeneity is good. The freeze-dried materials can be kept stable for 12 months at ≤4 °C, and the re-dissolved reference materials can be stabilized for 7 days at 4 °C. The standard values and uncertainty of the two levels were (5.34±0.34) μg/L and (15.47±0.72) μg/L, respectively. Conclusion: The standards met the requirements of national standards, and can be used to verify the methods of detecting cadmium in human urine and to detect the samples.

A mussel tissue certified reference material for multiple phycotoxins. Part 5: profiling by liquid chromatography-high-resolution mass spectrometry.

A freeze-dried mussel tissue-certified reference material (CRM-FDMT1) was prepared containing the marine algal toxin classes azaspiracids, okadaic acid and dinophysistoxins, yessotoxins, pectenotoxins, cyclic imines, and domoic acid. Thus far, only a limited number of analogues in CRM-FDMT1 have been assigned certified values; however, the complete toxin profile is significantly more complex. Liquid chromatography-high-resolution mass spectrometry was used to profile CRM-FDMT1. Full-scan data was searched against a list of previously reported toxin analogues, and characteristic product ions extracted from all-ion-fragmentation data were used to guide the extent of toxin profiling. A series of targeted and untargeted acquisition MS/MS experiments were then used to collect spectra for analogues. A number of toxins previously reported in the literature but not readily available as standards were tentatively identified including dihydroxy and carboxyhydroxyyessotoxin, azaspiracids-33 and -39, sulfonated pectenotoxin analogues, spirolide variants, and fatty acid acyl esters of okadaic acid and pectenotoxins. Previously unreported toxins were also observed including compounds from the pectenotoxin, azaspiracid, yessotoxin, and spirolide classes. More than one hundred toxin analogues present in CRM-FDMT1 are summarized along with a demonstration of the major acyl ester conjugates of several toxins. Retention index values were assigned for all confirmed or tentatively identified analogues to help with qualitative identification of the broad range of lipophilic toxins present in the material.

Zinc(ii) and cadmium(ii) amorphous metal-organic frameworks (aMOFs): study of activation process and high-pressure adsorption of greenhouse gases.

Two novel amorphous metal–organic frameworks (aMOFs) with chemical composition {[Zn2(MTA)]·4H2O·3DMF}n (UPJS-13) and {[Cd2(MTA)]·5H2O·4DMF}n (UPJS-14) built from Zn(ii) and Cd(ii) ions and extended tetrahedral tetraazo-tetracarboxylic acid (H4MTA) as a linker were prepared and characterised. Nitrogen adsorption measurements were performed on as-synthesized (AS), ethanol exchanged (EX) and freeze-dried (FD) materials at different activation temperatures of 60, 80, 100, 120, 150 and 200 °C to obtain the best textural properties. The largest surface areas of 830 m2 g−1 for UPJS-13 (FD) and 1057 m2 g−1 for UPJS-14 (FD) were calculated from the nitrogen adsorption isotherms for freeze-dried materials activated at mild activation temperature (80 °C). Subsequently, the prepared compounds were tested as adsorbents of greenhouse gases, carbon dioxide and methane, measured at high pressures. The maximal adsorption capacities were 30.01 wt% CO2 and 4.84 wt% CH4 for UPJS-13 (FD) and 24.56 wt% CO2 and 6.38 wt% CH4 for UPJS-14 (FD) at 20 bar and 30 °C.

Recent Trends in Pretreatment of Food before Freeze-Drying

Drying is among the most important processes and the most energy-consuming techniques in the food industry. Dried food has many applications and extended shelf life. Unlike the majority of conventional drying methods, lyophilization, also known as freeze-drying (FD), involves freezing the food, usually under low pressure, and removing water by ice sublimation. Freeze-dried materials are especially recommended for the production of spices, coffee, dried snacks from fruits and vegetables and food for military or space shuttles, as well as for the preparation of food powders and microencapsulation of food ingredients. Although the FD process allows obtaining dried products of the highest quality, it is very energy- and time consuming. Thus, different methods of pretreatment are used for not only accelerating the drying process but also retaining the physical properties and bioactive compounds in the lyophilized food. This article reviews the influence of various pretreatment methods such as size reduction, blanching, osmotic dehydration and application of pulsed electric field, high hydrostatic pressure or ultrasound on the physicochemical properties of freeze-dried food and drying rate.

The Freeze-Drying of Foods-The Characteristic of the Process Course and the Effect of Its Parameters on the Physical Properties of Food Materials.

Freeze-drying, also known as lyophilization, is a process in which water in the form of ice under low pressure is removed from a material by sublimation. This process has found many applications for the production of high quality food and pharmaceuticals. The main steps of the freeze-drying process, such as the freezing of the product and primary and secondary drying, are described in this paper. The problems and mechanisms of each step of the freeze-drying process are also analyzed. The methods necessary for the selection of the primary and secondary end processes are characterized. The review contains a description of the effects of process conditions and the selected physical properties of freeze-dried materials, such as structural properties (shrinkage and density porosity), color, and texture. The study shows that little attention is given to the mechanical properties and texture of freeze-dried materials obtained from different conditions of the lyophilization process.

Pulsed electric field pre-treatment improves microstructure and crunchiness of freeze-dried plant materials: Case of strawberry

In this study the effect of PEF pre-treatment on the microstructure of freeze-dried strawberry dices was investigated. The PEF treatment has been performed at an electric field intensity of 1.07 kV/cm and a specific energy input of 1 kJ/kg. The samples were freeze-dried at a temperature of 45 °C and a pressure of 1 mbar. The microstructure of dried material was evaluated by different physical and optical methods, such as SEM, μ-CT and thermogravimetry. Moreover, mechanical and acoustic properties as well as the colour of processed material have been analyzed. PEF pre-treated strawberry dices showed a more uniform shape, a better retention of volume and a visual better quality compared to untreated ones. Moreover, PEF pre-treatment led to a more homogeneous distribution and a greater thickness of pores. In accordance, analysis of textural properties evidenced that PEF treated freeze-dried strawberry dices were crispier than untreated ones. Measurement of L*a*b*-values showed that PEF treated material was characterized by a more preserved colour after freeze-drying than untreated ones.

The Principles of Freeze-Drying and Application of Analytical Technologies.

Freeze-drying is a complex process despite the relatively small number of steps involved, since the freezing, sublimation, desorption, and reconstitution processes all play a part in determining the success or otherwise of the final product qualities, and each stage can impose different stresses on a product. This is particularly the case with many fragile biological samples, which require great care in the selection of formulation additives such as protective agents and other stabilizers. Despite this, the process is widely used, not least because once any such processing stresses can be overcome, the result is typically a significantly more stable product than was the case with the starting material. Indeed, lyophilization may be considered a gentler method than conventional air-drying methods, which tend to apply heat to the product rather than starting by removing heat as is the case here. Additionally, due to the high surface area to volume ratio, freeze-dried materials tend to be drier than their conventionally dried counterparts and also rehydrate more rapidly. This chapter provides an overview of freeze-drying (lyophilization) of biological specimens with particular reference to the importance of formulation development, characterization, and cycle development factors necessary for the commercial exploitation of freeze-dried products, and reviews the recent developments in analytical methods which have come to underpin modern freeze-drying practice.

Effect of steam sterilisation on lipophilic nutrient stability in a chloroplast-rich fraction (CRF) recovered from postharvest, pea vine field residue (haulm)

Postharvest, pea vine field residue (haulm) was steam-sterilised and then juiced; a chloroplast-rich fraction (CRF) was recovered from the juice by centrifugation. The stability of selected nutrients (β-carotene, lutein, and α-tocopherol) in the freeze-dried CRF material was measured over 84 days; the impact of temperature (-20 °C, 4 °C, 25 °C and 40 °C), light and air on nutrient stability was established. All three nutrients were stable at −20 °C and 4 °C in the presence or absence of air; this stability was lost at higher temperatures in the presence of air. The extent and rate of nutrient breakdown significantly increased when the CRF samples were exposed to light. β-Carotene appeared to be more susceptible to degradation than lutein and α-tocopherol at 40 °C in the presence of air, but when CRF was exposed to light all three nutrients measured were significantly broken down during storage at 25 °C or 40 °C, whether exposed to air or not.

Fresh, freeze-dried or cell wall samples: Which is the most appropriate to determine chemical, structural and rheological variations during apple processing using ATR-FTIR spectroscopy?

Attenuated total reflectance Fourier transform spectroscopy (ATR-FTIR) was applied on fresh (NF), freeze-dried (FD) and cell wall materials (AIS) of raw and processed apples. These samples prepared from 36 apple sets and the corresponding 72 purees, issued from different varieties, agricultural practices, storage periods and processing conditions, were used to build models including exploratory analysis, supervised classification and multivariate calibration. Fresh and freeze-dried samples presented similar fingerprint spectral variations due to processing. ATR-FTIR directly on fresh purees satisfactorily predicted textural properties such as particle average size and volume (RPD>3.0), while freeze-drying improved assessment of chemical (RPD>3.2) and rheological (RPD>3.1) parameters using partial least-squares regression. The assessment of texture and macrocomponents of purees can be obtained with a limited sample preparation. For research applications because of a need of sample preparation, changes of cell wall composition during fruit processing could be assessed in relationship with pectin degradation.

Entrapped Psychrotolerant Yeast Cells within Pine Sawdust for Low Temperature Wine Making: Impact on Wine Quality.

An alternative methodology is proposed for low temperature winemaking using freeze-dried raw materials. Pine sawdust was delignified and the received porous cellulosic material was applied as immobilization carrier of the psychrotolerant yeast strain Saccharomyces cerevisiae AXAZ-1. The immobilization of yeast cells was examined and verified by scanning electron microscopy (SEM). The immobilized biocatalyst and high-gravity grape must were separately freeze-dried without cryoprotectants and stored at room temperature (20–22 °C) for 3 months. The effect of storage on the fermentation efficiency of the immobilized biocatalyst at low temperatures (1–10 °C), as well as on the aromatic characteristics of the produced wines was evaluated. Storage time had no significant effect on the fermentation efficiency of the biocatalyst resulting in most cases in high ethanol production 13.8–14.8% v/v. The volatile fraction of the produced wines was examined using headspace solid-phase microextraction (HS-SPME) followed by gas chromatography mass spectrometry (GC/MS). GC-MS/SPME analysis along with the organoleptic evaluation revealed in all produced wines a plethora of fresh and fruit aromatic notes. To conclude, fermentation kinetics and aromatic profile evaluation encourages the production of high-quality sweet wines at low temperatures using pine sawdust (Pinus halepensis) entrapped yeast cells as a promoter.

Polyphenols composition, antioxidant and antimicrobial properties of Pinus sylvestris L. shoots extracts depending on different drying methods

Scots pine (Pinus sylvestris L.) shoots have been increasingly commonly used as functional food or its component, the shoots contain various active components, unknown from other raw materials. The objective of the study was to assess the influence of the drying method on the content of bioactive compounds and antioxidative and antimicrobial activity of pine shoots. It was demonstrated that freeze drying (PSL), vacuum drying (PSP) and natural drying (PSN) have significant impact on the physicochemical properties, content of bioactive compounds and antioxidative activity of the prepared ethanol-water extracts. The content of the studied compounds varied significantly in the tested shoots. In spectrophotometric testing the highest total flavonoid content was demonstrated in the PSP sample, at 5.51 mg quercetin/g dw. On the other hand, the reducing capacity was as follows: PSN&gt;PSP&gt;PSL in the range from 13.4 to 5.73 mg gallic acid/g dw. However in assay conducted using HPLC methods the highest content of polyphenols characterized extract from freeze-dried raw material (9151.15 µg/g), followed by vacuum-dried (8264.57 µg/g), and the lowest content of phenolic compounds was found in convection-dried shoots (7621.76 µg/g). The studied extracts demonstrated antioxidative properties, both in ferric reducing antioxidant power assay (FRAP) as well as in free radical quenching measurement (DPPH). All of the studied extracts demonstrated antimicrobial and fungicidal properties, and they were particularly efficient in the case of gram-negative bacteria.

The acute toxicity of water hemlock (Cicuta douglasii) in a goat model

Water hemlock (Cicuta douglasii) is one of the most toxic plants to livestock and humans. Little is known regarding the amount of plant required to cause death. The objective of this study was to determine a lethal dose of water hemlock in a goat model. Plants were dosed to goats via oral gavage of freeze-dried ground plant material. The results from this study suggest that 1–2 fresh tubers would be lethal to goats.

Microstructure and reconstitution of freeze-dried gum Arabic at a range of concentrations and primary drying temperatures

Freeze-drying is an energy intensive unit operation used for the production of dehydrated foods, such as instant coffee and dried fruits, and results in high sensorial, nutritional and reconstitution properties of the final products. Understanding the relationships between operating conditions and product quality is essential to design processes that are energy efficient, whilst producing high quality dried foods.In this work, the properties (microstructure and reconstitution) of freeze-dried gum arabic samples (with initial concentrations ranging between 20 and 60% solids by weight) were evaluated. The materials were dried at three different primary drying shelf temperatures, Ts (−20, −30 and −40 °C).Sample temperatures recorded throughout freeze-drying were close to the pre-set Ts, with the exception of the 60% initial concentration system, where the sample was hotter than the shelf by 10–15 °C, in particular on increasing Ts. This was attributed to a combination of local temperature and pressure conditions that may have resulted in partial melting of the material. For the 20–50% systems, the properties of the freeze-dried materials were mainly affected by the initial concentration of the system, with increasing initial concentration generally resulting in lower porosities (ranging between 20 and 40%) and higher reconstitution times (ranging between 0.5 and 10min for 95% reconstitution). Pores were generally needle-shaped and <200 μm. Large (200–1800 μm), circular pores were observed in high initial concentration systems, and they were dominant in the microstructure of the freeze-dried 60% sample. The presence of these large bubbles was linked to the partial melting of the material, which enabled its expansion and puffing. For the 60% system, primary drying temperature had a profound effect on the properties of the freeze-dried solid, with samples dried at higher temperature showing higher porosity (e.g. 60–70% for Ts=−20°C) and faster reconstitution rates (e.g. 3min for 95% reconstitution at Ts=−20°C).Overall, this study demonstrates the significance of formulation and shelf temperature on the porous structure of freeze-dried samples, which directly influences product performance.

Gas Production, Digestibility and Efficacy of Stored or Fresh Plant Extracts to Reduce Methane Production on Different Substrates.

Simple SummaryMedicinal plants possess the ability to mitigate methane production from ruminants. Long-term stability of these plant extracts are essential qualities to be able to replace other rumen modifiers. After one year of storage, plant secondary metabolites used in this study reduced methane production from low-quality forages, without adverse effects on feed digestibility in vitro.Natural compounds such as plant secondary metabolites (PSM) can be used to replace antibiotic growth promoters as rumen modifiers. In this study, the effectiveness of stored and freshly extracted Aloe vera (AV), Azadirachta indica (AZ), Moringa oleifera (MO), Jatropha curcas (JA), Tithonia diversifolia (TD) and Carica papaya (CP) crude extract and monensin on in vitro gas and methane production, organic matter digestibility (IVOMD) and volatile fatty acids (VFA) were evaluated using a total mixed ration (TMR), lucerne or Eragrostis curvula substrates. Fresh extracts were processed from the same batch of frozen (−20 °C) plant material a few days before the trial while the stored extracts were extracted and stored at 4 °C for 12 months prior to the study. Extraction was done by solubilising 50 g freeze-dried plant material in 500 mL 100% methanol. Four mL of reconstituted 50 mg crude extract per 1000 mL distilled water was added per incubation vial, which already contained 400 mg substrate and in vitro fermentation, and gas production and IVOMD evaluation were carried out using standard procedures. Results showed that storing plant extracts for 12 months did not affect the activity or stability of metabolites present in the crude extracts, as shown by the lack of differences in total gas production (TGP) and methane produced between fresh or stored extracts across the substrates. In the TMR substrate, plant extracts increased IVOMD but did not affect TGP and methane production, whereas monensin did not have any effect. Plant extracts increased IVOMD of Eragrostis substrate and supressed methane production to a greater extent than monensin (p < 0.05). It can be concluded that storing plant extracts for up to 12 months did not compromise their efficacy. In addition, the use of 50 mg/kg of AV, AZ, MO, JA, TD and CP extract to a forage-based diet will reduce methane production while improving feed digestibility.

Antioxidant and Anti-Inflammatory Potential of Shiitake Culinary-Medicinal Mushroom, Lentinus edodes (Agaricomycetes), Sporophores from Various Culture Conditions.

Lentinus edodes (= Lentinula edodes) is an edible mushroom grown and marketed for centuries due to its nutritional and medicinal properties. L. edodes has multiple pharmacological activities as an antioxidant and anti-inflammatory. Few studies were performed taking into account the influence of culture conditions to optimize the biological properties of L. edodes on human health. Our work focused on the comparison of antioxidant capacity and anti-inflammatory activity of L. edodes fruit bodies cultivated by three mushroom producers in the French Occitanie region using the same strain in various growing conditions (organic and nonorganic). Sequential extraction was performed on freeze-dried fungal materials. All extracts have a quantifiable but moderate antioxidant activity measured via DPPH and ORAC tests. The anti-inflammatory activity of the ethanol and aqueous extracts was evaluated on a model of inflammatory macrophages. The ethanol extracts inhibit NO production in a dose-dependent manner when the cells are pretreated for 4 h with a 24 h stimulation time.

Effect of pulsed electric field pretreatment on shrinkage, rehydration capacity and texture of freeze-dried plant materials

For this study, strawberries and red bell peppers were pre-treated with pulsed electric fields (PEF) to reduce the negative effects on physical properties of the products after freeze-drying. PEF treatment was carried out at constant electric field strength of E = 1.0 kV/cm and specific energy input was varied between 0.3 and 6.0 kJ/kg (treatment time 2.0–28.6 ms). Additionally, the impact of different pre-freezing temperatures (−4 and −40 °C) on the final product quality was described. Investigations showed that due to PEF treatment a significant reduction of the shrinkage phenomena for both bell peppers and strawberries was detected compared to untreated samples with 30% and 50% lower volume losses, respectively. The rehydration capacity of PEF pre-treated freeze-dried samples increased for both matrices up to 50%. Furthermore, the mechanical properties of the final product were improved for both matrices with a significant firmness reduction up to 60%. The results of this study suggest that PEF can be an effective pretreatment with low energy requirements to improve the quality of freeze-dried fruits and vegetables.