The effect of modified atmospheres on the saw-toothed grain beetle Oryzaephilus surinamensis (L.)(Coleoptera: Silvanidae) and the quality of semi-dried dates

The saw-toothed grain beetle Oryzaephilus surinamensis plays a major role in reducing the quality and volume of dried fruits. The aim of this study was to evaluate the effect of modified atmospheres (MAs) enriched in CO₂ or N₂ at 25 °C and 35 °C on the adult and larval stages of O. surinamensis and dried date quality. The tested MAs containing 20%, 30%, 40%, and 50% CO₂ and the MAs containing 97% and 98% N₂, with different exposure periods were performed in the laboratory at 25 °C or 35 °C ± 2 °C, 65% ± 5% r.h and photoperiod of 16 Light:8 Dark. The adults and larvae were found to be more susceptible to CO₂ or N₂ at 35 °C than those at 25 °C. Both adults and larvae reached 100% mortality after 4–6 days exposure to 20%–50% CO₂ at 25 °C and 3–5 days exposure to the same concentrations at 35 °C. The mortality reached 100% after 2–3 days when adults were exposed to 97% or 98% N₂ at 35 °C, but the larvae reached the complete mortality after 5 and 4 days exposure to 97% and 98% N₂, respectively, at 35 °C. The adult stage was more susceptible than the larval stage to MAs enriched in CO₂ or N₂. Also, the results showed that an MA containing 50% CO₂ and another containing 98% N₂ led to increased total carbohydrates, protein, fat, and ash in treated dates compared to control dates. MAs at high temperatures may be recommended to control O. surinamensis populations in dried date stores due to the advantage of a short duration treatment capable of killing larvae and adult stages of this insect, with positive effects on dried fruit quality.     

Enhancing spray-drying tolerance of Lactobacillus bulgaricus via non-sporeforming dormancy induction

Employing 0.64 mg/mL of rifampin (RFP) for dormancy induction of Lactobacillus bulgaricus sp 1.1, a 2.5-fold survival rate was achieved after spray drying, while the dried bacteria displayed delayed acidifications. Under the same condition for dormancy treatment, division analysis indicated that high proportions of cells would enter into a dormant state with around 90% of non-proliferating bacteria in the original population. Cells shrank with median diameters decreasing from 3.23 to 2.98 μm. The Raman spectrum revealed a lower ATP level, varied protein expression profiles and conformations and saccharides accumulation in bacteria. Protein aggregates formed in dormancy-induced cells may contribute to increased heat resistance which showed a 2 °C rise in the denaturing temperature in the 0.64 mg/mL group. Therefore, dormancy treatments may be developed as a protective strategy for spray-dried L. bulgaricus.Industrial relevanceEnhancing the drying tolerance of bacteria is one of the crucial strategies to adapt the industrial production of spray-dried LAB. Our study proved that the non-sporeforming dormancy pre-treatment can promote the spray-dried viability of L. bulgaricus by triggering suppressed metabolism activity and protein aggregation. The non-sporeforming dormant state has potential to be exploited in industrial production of spray-dried LAB with a high viable cell density to reduce the cost of probiotics and related products.     

Compositions and antioxidant properties of protein hydrolysates from the skins of four carp species

Compositions and antioxidant properties of protein hydrolysates prepared from four carp skins: black carp, grass carp, silver carp and bighead carp, using pepsin, with a degree of hydrolysis (DH) of 6–15%, were investigated. The yield of freeze‐dried hydrolysates was in the range of 54–62 g/100 g (dry skin). The content of protein and ash in four freeze‐dried hydrolysates was 72–81% and 8–17%, respectively. All hydrolysates contained high amount of hydrophobic amino acid residues (389–480 residues/1000 residues). Meanwhile, their antioxidant properties were evaluated by in vitro assays. The results revealed that all hydrolysates possessed potent antioxidant activities and showed dose dependency as the activity increased with sample concentration, capable of scavenging 72–88% of DPPH and 61–69% of hydroxyl radicals, respectively, at the highest tested concentration. The hydrolysates exhibited high reducing power and β‐carotene–linoleic acid oxidation inhibition. Among the four hydrolysates, the hydrolysate derived from bighead carp skin was superior to others in terms of yield, DH and antioxidant activities.     

Optimization of Enzymatic Hydrolysis of Visceral Waste Proteins of Yellowfin Tuna (Thunnus albacares)

Fish protein hydrolysate was produced from the viscera of yellowfin tuna (Thunnus albacares). Hydrolysis conditions (enzyme activity, temperature, and time) were optimized using response surface methodology. A factorial design was applied to minimize enzyme utilization and modeling of degree of hydrolysis (r ² = 0.94). Lack-of-fit test revealed a non-significant value for the model, indicating that the regression equation was adequate for predicting the degree of hydrolysis under any combination of the variables (P < 0.05). The optimum conditions to reach the highest degree of hydrolysis were: 60.4 °C, 90.25 min, and a protease (Alcalase 2.4 L) activity of 70.22 AU/kg protein. The spray-dried tuna visceral protein hydrolysates had relatively high protein (72.34%) and low lipid (1.43%) content. The chemical score of the hydrolysate indicated that it fulfils adult human nutritional requirements except for methionine. Lysine and methionine were the first and the second limiting amino acids in that order. Phenylalanine was the predominant amino acid in the hydrolysates with respect to common carp requirement. In addition, the protein efficiency ratio of tuna visceral hydrolysate was 2.85–5.35.     

Cricket protein hydrolysates pre-processed with ultrasonication and microwave improved storage stability of goat meat emulsion

The study was designed to evaluate the potential of cricket protein hydrolysates as a novel food bio-preservative using goat meat emulsion as a food-model system. The efficacy of the hydrolysates was improved using microwave (T₁) and ultrasonication (T₂) as pre-treatments before hydrolysis of cricket protein using alcalase enzyme (3% w/w). Both the pre-treatments caused a significant increase in the antioxidant and antimicrobial potential of the hydrolysates. The hydrolysates were added to the emulsion at the maximum level of 2.0% and analysed for quality for two weeks storage (4 ± 1 °C) compared to the control samples. The effect of digestion simulation was also evaluated on the emulsion samples. A significant positive effect of the pre-treated hydrolysates was observed on the storage stability (antioxidant potential, lipid stability, protein oxidation, microbial stability, and sensory quality). The digestion simulation significantly increased the radical-scavenging and ion-reducing activity of the meat emulsion, improving its functional value and health-promoting properties.     

Production of High-protein Hydrolysate from Poultry Industry Residue and their Molecular Profiles

The use of mechanically deboned poultry meat (MDPM) as a source of raw protein for the enzymatic preparation of hydrolysates was investigated using commercial proteases Alcalase and Flavourzyme. Hydrolysis conditions were optimized by response surface methodology, and the influence of temperature, pH, and enzyme concentration were evaluated to determine the hydrolysis index. For Alcalase, optimal values of temperature, pH, and enzyme concentration were found to be 50°C, 7.5%, and 2.5%, respectively, while for Flavourzyme the optimized variables were at 50°C, 6.0%, and 3.5%, respectively. Compared to raw MDPM, Alcalase produced a very high recovery of 89% of the nitrogen from the hydrolysates, while for Flavourzyme recovery was around 67%. Alcalase was used to produce a spray-dried hydrolysate containing 62% of total protein with molecular weights ranging from 5,807 to 12,000 Da, and had excellent microbiological quality.     

The use of spray drying technology to reduce bitter taste of casein hydrolysate

The utilization of protein hydrolysates in food systems is frequently hindered due to their bitterness and hygroscopicity. Spray drying technology could be an alternative for reducing these problems. The aim of this work was to reduce or to mask the casein hydrolysate bitter taste using spray drying and mixtures of gelatin and soy protein isolate (SPI) as carriers. Six formulations were studied: three with 20% of hydrolysate and 80% of mixture (gelatine/SPI at proportions of 50/50, 40/60 and 60/40%) and three with 30% of hydrolysate and 70% of mixture (gelatine/SPI at proportions of 50/50, 40/60 and 60/40%). The spray-dried formulations were evaluated by SEM, hygroscopicity, thermal behavior (DSC), dissolution, and bitter taste, by a trained sensory panel using a paired-comparison test (free samples vs. spray-dried samples); all samples were presented in powder form. SEM analysis showed mostly spherically shaped particles, with many concavities and some particles with pores. All formulations were oil and water compatible and showed lower hygroscopicity values than free casein hydrolysate. At Aw 0.83, the free hydrolysate showed Tg about 25 °C lower than the formulations, indicating that the formulations may be more stable at Aw ≥ 0.65 since the glass transition should be prevented. The sensory panel found the formulations, tasted in the powder form, to be less bitter (P < 0.05) than the free casein hydrolysate. These results indicated that spray drying of casein hydrolysate with mixtures of gelatin and SPI was successful to attenuate the bitterness of casein hydrolysate. Thus, spray drying widens the possibilities of application of casein hydrolysates.     

Bioactive components and antioxidant properties of γ-aminobutyric acid (GABA) tea leaves

Various ethanolic concentrations (0–95%, v/v) and temperatures (25–95 °C) were used to extract γ-aminobutyric acid (GABA) tea leaves. Extraction yields, and contents of total phenols, various catechins, GABA, theanine, and antioxidant properties of extracts were determined. The 50% (v/v) ethanol at 50–95 °C gave higher yields (32.05–32.56 g dried extract/100 g dried tea leaves). The bioactive components and antioxidant properties of extracts were affected by the ethanolic concentrations and temperatures. Among catechins, epigallocatechin gallate was the main catechin in all extracts, followed by epigallocatechin, epicatechin, epicatechin gallate, gallocatechin and gallocatechin gallate. The 50–75% (v/v) ethanol at 75–95 °C gave higher contents of ester type (102.92–104.54 mg/g extract) and non-ester type (61.75–63.55 mg/g extract) catechins. Water at 50–75 °C gave higher GABA and theanine contents and higher chelating ability of extracts. The 75% (v/v) ethanol at 25–75 °C gave higher scavenging ability and reducing power of extracts. Based on dried tea extracts or leaves results obtained, the optimal extraction conditions to maintain the total contents of various catechins, GABA and theanine in the maximum level were 50% ethanol (v/v) and 75–95 °C.     

Original article: Thermal pretreatment and chemical modifications as a means to alter hydrolytic characteristics and prevent bitterness in hydrolysates of fishery by‐catch (Decapterus maruadsi) protein

In this study, fishery by‐catch protein (Decapterus maruadsi) was first thermal treated (60–100 °C), phosphorylated (0.5–4.0 g g^?1 protein) or succinylated (0.05–0.3 g g^?1 protein) before hydrolysis to prevent the bitterness of the resulting hydrolysate. Hydrolysis was performed at 50 °C, 10 h, pH 8.0 by Alcalase. Results showed that thermal treatment upon 80 °C, succinylation and phosphorylation resulted in significant decrease in amino acid content and increase in larger peptide content (>1450 Da). Succinylation did not reduce the bitterness as a result of higher content of small peptides (<550 Da), which was found to be correlated positively with the bitterness of hydrolysates. However, thermal treatment, especially phosphorylation, could reduce the bitterness to discernible level, indicating that phosphorylation before hydrolysis could be a potential means to prevent the evolution of bitter flavour which restricts the practical uses of the hydrolysates.     

Development of cantaloupe (Cucumis melo) juice powders using spray drying technology

Cantaloupes are a good source of carotenoids and vitamin C. Cantaloupe fruit juice powder containing vitamin C and β-carotene can be produced by spray drying. The objective of this study was to develop cantaloupe fruit juice (CJ) powder and to evaluate its nutritional and physical properties. Fresh cantaloupe fruits purchased from a local store were diced and juiced. CJ with 10% maltodextrin (MD) added was spray dried at inlet temperatures of 170, 180 and/or 190 °C. Three spray dried cantaloupe powders, including CJ dried with MD at 170 °C (CJP1), CJ dried with MD at 180 °C (CJP2), CJ dried with MD at 190 °C (CJP3) were analyzed for moisture, water activity, vitamin C, β-carotene, dissolution, and microstructure. The actual production rate of the cantaloupe juice powders was lower than the estimated production rate. CJP1 had (p < 0.05) higher moisture content and water activity than CJP2, and CJP3. Vitamin C content (mg/100 g, dry solids) was significantly (p < 0.05) higher in CJP1 (136.36 ± 5.84) than CJP2 (91.85 ± 5.23) and CJP3 (78.30 ± 1.96). The powder produced at inlet temperatures 170 °C had higher β-carotene content (μg/g) than that produced at 180 and 190 °C.     

Amino acid composition,antioxidant and functional properties of protein hydrolysates from the roe of rainbow trout (Oncorhynchus mykiss)

A fish roe protein hydrolysate from rainbow trout (Oncorhynchus mykiss) trout roe protein hydrolysates (TRH) was produced by pepsin and Alcalase. Proximate, amino acid compositions, protein digestibility and molecular mass distribution of the hydrolysates were determined. The degree of hydrolysis was found to be 44.08% and 27.62% (pepsin and Alcalase, respectively). The two hydrolysates contained a high amount of essential amino acids (33.53% Alcalase–29.39% pepsin). The results showed that TRH by different enzymes is a good source of the leucine and lysine amino acids. The pepsin produced a white powder with higher brightness (L* = 89.50). Alcalase hydrolysate was brownish yellow in colour (L* = 52.85, a* = 10.30, b* = 26.25). The hydrolysates represented excellent antioxidant activities in various concentrations. TRHs showed a good foaming and emulsification properties. The results thus revealed that protein hydrolysates from rainbow trout roe could be used as food additives possessing essential amino acids and antioxidant activity.     

Effect of heat and enzymatic treatment on the antihypertensive activity of whey protein hydrolysates

The influence of heat and enzymatic treatments on the hypotensive activity of hydrolysates derived from whey protein isolate was examined. The whey protein isolate (WPI) was previously denatured at 65 or 95 °C and hydrolyzed using the enzymes Alcalase, α-chymotrypsin or Proteomix. The hydrolysates thus obtained were characterized and studied with regard to their angiotensin converting enzyme (ACE) inhibitory activity and hypotensive activity in spontaneously hypertensive rats (SHR). The enzyme α-chymotrypsin was found to produce hydrolysates with the highest ACE inhibitory activity. The hydrolysate that most effectively reduced blood pressure in SHR was obtained from WPI previously denatured at 65 °C and treated with the enzyme Alcalase. The hydrolysate with the highest ACE inhibitory activity was able to reduce the arterial blood pressure of the animals only after intraperitoneal administration, suggesting an interference of gastrointestinal enzymes in the absorption of active peptides from this hydrolysate.     

Potentially bioaccessible phenolics,antioxidant capacities and the colour of carrot,pumpkin and apple powders – effect of drying temperature and sample structure

The study aimed to examine carrot, pumpkin and apple powders produced by hot-air-drying (50, 60, 70 °C) of samples with different levels of fragmentation (cut, grated, blended). The drying temperatures and sample structure were shown to be important determinants of the quality of the powders. The best colour stability of carrot, pumpkin and apple was found for the grated sample dried at 70 °C, the blended sample dried at 70 °C and the blended sample dried at 70 °C, respectively. The highest antiradical capacity and reducing power were found for powders obtained after drying the cut samples at 70 °C. Total phenolics and free radical quenchers were well bioaccessible in vitro. In turn, the reducing power was markedly reduced after drying at 50 °C. The analysed powders are a valuable source of concentrated bioactive ingredients, which predisposes them to serve as functional food components.     

Characterization and storage stability of spray dried soy-rapeseed lecithin/trehalose liposomes loaded with a tilapia viscera hydrolysate

Drying-induced stabilization is a challenge that delivery systems still face. This study aims to investigate the effects of adding trehalose to spray dried soy-rapeseed lecithin liposomes, and the storage stability of the dried liposomes loaded with a tilapia viscera protein hydrolysate, during 42 days at 4 °C and 23 °C, and at different relative humidity (RH). Particle size increased from 215 to 250 nm in fresh liposomes to 258–314 nm after spray drying according to trehalose concentration, all preparations showing a strong electronegative ζ Potential (−48.5 to −59.9 mV). Dried liposomes stored at 4 °C maintained lower polydispersity and higher solubility than those stored at 23 °C. Changes in water activity (A_w), FTIR and DSC revealed structural changes in samples stored at 23 °C and high RH. Spray dried hydrolysate-containing liposomes could be considered as a functional food ingredient due to the substantial antioxidant activity and angiotensin-converting enzyme (ACE) inhibitory capacity after in vitro simulated gastrointestinal digestion.Industrial relevanceThe availability of a natural liposomal preparation in dry powder form, capable to maintain its bioactive properties, is a great advantage for the functional food industry, since it favours the stability, transport and storage of the ingredient prior to use, and allows great versatility to be incorporated in solid restructured products.     

Effects of temperature and relative humidity on growth and enzyme production by Actinomucor elegans and Rhizopus oligosporus during sufu pehtze preparation

Sufu is a Chinese soybean cheese obtained after maturation of solid-state mould-fermented tofu. Ambient temperatures of 30–35 °C during the summer season prohibit the use of the usual starter Actinomucor elegans. We compared the properties of the latter with a potential alternative starter Rhizopus oligosporus that could be used at higher temperatures. The effects of temperature and relative humidity on growth rate of Actinomucor elegans and Rhizopus oligosporus were optimum at 25 °C at RH 95–97%, and 35 °C at RH 95–97%, respectively. Yields of protease (108 U/g pehtze), lipase (172 U/g) and glutaminase (176 U/g) by A. elegans were maximum after 48 h at 25 °C and RH 95–97%, and for α-amylase (279 U/g pehtze) and α-galactosidase (227 U/g) at 30 °C and RH 95–97% after 48 and 60 h of incubation. Highest protease (104 U/g pehtze), and lipase (187 U/g) activities of R. oligosporus were observed after 48 h at 35 °C and RH 95–97%, while maximum α-amylase (288 U/g pehtze) and glutaminase (187 U/g) activities were obtained after 36 h at 35 °C and RH 95–97%. Maximum α-galactosidase activity (226 U/g) by R. oligosporus was found after 36 h at 30 °C and RH 95–97%. It is concluded that R. oligosporus is a potential alternative to A. elegans as sufu pehtze starter during hot seasons.     

Optimization of trypsin-assisted extraction,physico-chemical characterization,nutritional qualities and functionalities of palm kernel cake protein

The extraction of palm kernel cake protein (PKCP) was enhanced by trypsin-assisted assay. From the Response Surface Methodology (RSM) generated model, the optimum conditions were using trypsin at concentration 1.36 g/100 g, reacted on palm kernel cake (PKC) slurry (1.1 g/100 mL) at 50 °C and pH 9.5. The trypsin extracted protein yield (61.99 ± 0.74 g/100 g) was significantly (P < 0.05) higher than the alkaline (pH 9.5) method (10.21 ± 0.24 g/100 g). Surface hydrophobicity of PKCP (159.36) was significantly (P < 0.05) higher than soy protein isolate (SPI) (51.51). PKCP had a lower denatured temperature (66.88 °C) than SPI (101.41 °C). The electrophoretograms of PKCP showed 3 bands at 2.20, 3.51 and 4.28 kDa, compared to SPI which had 22 bands with molecular weight ranging from 2.00 to 82.79 kDa. Except lysine, the essential amino acids of PKCP met the suggested requirements of FAO/WHO for 2–5 year old infants. The in-vitro digestibility, essential amino acids/total amino acids (E/T) value, biological value and computed-protein efficiency ratio (C-PER) value for PKCP were significantly (P < 0.05) higher than that of SPI. PKCP also showed better solubility (30.12–97.79 vs. 9.15–69.78 g/100 g) emulsifying activity (143.25 vs. 32.57 m²/g); but lower emulsifying stability (37.83 vs. 43.08%), foaming capacity (22.5 vs. 100.0 ml/100 ml) and foam stability (3.70 vs. 19.20 ml) than the SPI.     

Effect of drying methods on the reactivity of chitosan towards Maillard reaction

The effect of drying methods on chitosan reactivity towards Maillard reaction during storage of dried chitosan–lactose systems was investigated. Two different structural forms of chitosan, scaffold and microspheres, were prepared. Then they were dried by lyophilization or using supercritical fluid technology (SF-CO₂) and stored with lactose under controlled temperature conditions (60 °C) and water activity (a_w = 0.65). The drying method produced slight modifications on the chitosan structure especially in samples submitted to SF-CO₂ treatment. Differences were more evident in the reactivity of chitosan–lactose systems during storage. Maillard reaction development was assessed by quantification of a new compound which originated from the acid hydrolysis of Amadori compounds (NFMD) resulting from chitosan–lactose interactions, and not detected in the acid hydrolysates of freshly prepared chitosan-lactose systems. Maillard reaction was influenced by different factors such as the manner of lactose addition, structure of chitosan (microspheres and scaffolds) and drying method. Lyophilized chitosan in the form of microspheres with lactose, presented the highest values of NFMD (428.45 mg/100 g of sample). The determination of this compound could be used as an index of the progress of Maillard reaction.     

The nutritive value of porcine blood plasma concentrates prepared by ultrafiltration and spray Drying

Concentrated solutions of porcine blood plasma proteins, prepared by centrifugation and ultrafiltration⁴ were spray dried directly at air inlet temperatures of 154, 170.3, 225 and 243.2 °C. Spray dried concentrates contained ca 86–90% protein, ca 2–7% moisture and ca 5% minerals. The overall amino acid composition of the plasma proteins compared favourably with that of FAO whole egg protein.¹² Although the values of essential amino acids generally fell below the egg values, the only serious limitations were in the content of isoleucine (less than half of the egg value). The chemical score (CS) and essential amino acid index (EAAI) were 49.1 and 70.1 respectively. Rats fed on a diet containing plasma concentrate as the sole protein source showed a net weight increase. NPU carcass for plasma protein was 65.8 ± 1.9 compared with a value of 72.1 ± 0.4 for a casein control. An inverse correlation between denaturation status of plasma proteins and spray drying temperature was found. The percent denaturation as measured on pH 4.0 filtrates increased from 8.4% at an air inlet temperature of 154 °C to 48.6% at a temperature of 243.2 °C. A similar inverse relationship was found between the available lysine content of plasma proteins and spray drying temperature. A maximum decrease in percent lysine availability of 16% was found at an air inlet drying temperature of 243.4 °C.     

Thermo-mechanical properties of egg albumen–cassava starch composite films containing sunflower-oil droplets as influenced by moisture content

The effect of moisture content on the thermo-mechanical and structural properties of egg albumen–cassava starch composite films containing sunflower oil droplets was studied using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Composite films were prepared by cold gelation, dried in a moisture controlled incubator (83.5%RH) at 25 °C for 8 days and aged at different relative humidity at room temperature (21 ± 1 °C) for 7 days to obtain composite films with moisture contents of 4%, 7%, 11%, 17% and 46% (dry weight basis). In DMA thermograms the magnitude of G′ and G″ increased with increasing temperature in high-moisture samples, decreased and then again gradually increased for intermediate-moisture samples, and decreased in low moisture samples. DSC thermograms indicated two distinct peaks (at 49–53 °C and 79.8 to 132.4 °C) which were attributed to phase transitions and protein denaturation. SEM images indicated that the microstructure of the composite matrix changed with moisture content and heating temperature. Our study confirms that moisture content plays a key role in the thermo-mechanical properties and microstructure of egg albumen–cassava starch composite films containing sunflower oil.     

Influence of hot-air temperature on drying kinetics,functional properties,colour, phycobiliproteins,antioxidant capacity,texture and agar yield of alga Gracilaria chilensis

Effect of air temperature on drying kinetics, functional properties, phycobiliproteins (PE and PC), colour, antioxidant capacity, total phenolic content, texture and agar yield during drying of algae Gracilaria chilensis were studied. Drying curves were satisfactorily simulated with the Weibull model at 40, 50, 60 and 70 °C. Both, Rehydration Ratio and Water Holding Capacity decreased with increasing temperature. Low drying temperatures showed higher PE and PC concentration than higher temperatures (e.g. 60 and 70 °C). In particular, dehydration at 50 °C presented the higher values of these two pigments. The three chromatic coordinates (L1, a1 and b1) were influenced by the treatments showing the highest ?E value at 50 °C. Antioxidant activity as well as texture were notably influenced by increasing drying temperatures. At 70 °C, a maximum agar yield of 40 g/100 g was obtained. Results indicated that agar yield and quality of dried algae showed opposite behaviours leading to a compromise decision on operating conditions involved in the overall process. According to these results, optimization of the process based on economical aspects of the final dried product is required.