In vitro release kinetics of nisin as affected by Tween 20 and glycerol co-encapsulated in spray-dried zein capsules

Delivery systems with sustained release of antimicrobials have been proposed to improve long-term effectiveness of antimicrobials in foods. In this work, we studied the effect of Tween 20 and glycerol in spray-drying formulations on resultant microstructures of zein capsules and release profiles of encapsulated nisin. Tween 20 and glycerol changed capsules from a continuous matrix to shell-type structures. All samples showed complete release of nisin in 30 min at pH 2.0. Capsules with a higher amount of Tween 20 showed more complete release of nisin at pH 8.0, in contrast to no apparent impact by glycerol. Addition of 0.05% Tween 20 or glycerol in the feed both reduced the burst release of nisin at pH 6.0, but no conclusive trends were observed for the impact of their usage levels. Our work showed that an appropriate formulation is needed to obtain desirable delivery systems of antimicrobials such as nisin.     

Physicochemical stability of antilisterial proteins from P. polymyxa Kp10 as potential food biopreservative

Listeria monocytogenes has continuously become a significant threat to consumers worldwide. The use of chemical-derived preservatives that are commonly associated with safety and nutritional issues has prompted the use of natural-based preservatives as a better alternative. Many bacterial strains including Paenibacillus polymyxa Kp10 have been reported to produce various antimicrobial proteins and compounds that are considered more natural. However, their stability in various physicochemical conditions should be examined before being applied in various types of food. In this study, the stability of four previously identified antilisterial proteins in P. polymyxa Kp10 upon exposure to several physicochemical conditions was examined. More than 80% residual antilisterial activity is conserved upon heat and proteinase K treatment. But, sensitivity to 24 h trypsin digestion has been observed. P1 and P2 proteins (histone-like DNA binding proteins HU) were sensitive to alkaline pH (pH 10-12) as compared with other proteins. More than 70% and 97% residual antilisterial activity were recovered after incubation in raw beef homogenates and simulated meat gravy model, respectively. However, the antilisterial activity of most proteins was highly compromised in chicken and salmon meat homogenates, and UHT cow milk. Inoculation of these proteins into Listeria-contaminated simulated meat gravy showed that all proteins exerted a bactericidal action against L. monocytogenes. P1 and P2 shared almost similar antilisterial activity rates, while P4 was the most potent antilisterial protein. The findings in this study could provide important preliminary data for future applications of these proteins as preservative in food products especially beef-based meat products.     

Cellular injuries of spray-dried Lactobacillus spp. isolated from kefir and their impact on probiotic properties

The injuries caused by spray drying (SD) of three potential probiotic lactobacilli isolated from kefir grains and the impact on some probiotic properties, were evaluated. Results demonstrated that Lactobacillus plantarum 83114 and L. kefir 8321 showed a slight reduction of viability (0.11 and 0.29 log CFU/ml respectively) after SD process, and L. kefir 8348 was found to be more sensitive to the process with a reduction in viability of 0.70 log CFU/ml. Neither membrane damage, evaluated by increased sensitivity to NaCl, lysozyme, bile salt and penicillin G, nor changes in acidifying activity in MRS and milk by lactobacilli were detected after SD. L. plantarum 83114 and L. kefir 8321 after SD did not lose their capacity to adhere to intestinal cells. Nevertheless, L. kefir 8348 showed a significant loss of adhesion capacity after SD. In addition, rehydrated spray-dried L. kefir 8321 retained the ability to protect against Salmonella invasion of intestinal cells. This effect was observed when L. kefir is co-incubated with Salmonella before invasion assay.This work shows that the membrane integrity evaluated by indirect methods and some probiotic properties of lactobacilli isolated from kefir did not change significantly after SD, and these powders could be used in functional foods applications.     

Stability of spray-dried microencapsulated anthocyanins extracted from culinary banana bract

Culinary banana bracts are a potential source of anthocyanin, which can be widely used in the food industry because of its health beneficial effects. The aim of the present study was to study the stability of microencapsulated anthocyanin extracted from culinary banana bracts using ultrasound-assisted extraction (UAE). Central composite design (CCD) was used to optimize the process variables for the extraction of anthocyanin and the optimum condition was observed at 15:0.5 solvent to solute ratio, 53.97 ml/100 ml ethanol concentration, and 49.4°C. The optimized experimental anthocyanin content was 56.98 mg/100g and it closely agreed with the predicted value (57.29 mg/100g). High-performance liquid chromatography (HPLC) results revealed that cyanidin-3-O-glucoside and peonidin-3-O-glucoside were two constituents of anthocyanin. Encapsulated pigment powder exhibited satisfactory properties in terms of hygroscopicity, solubility, and good encapsulation efficiency with smooth spherical morphology (2–10µm) as confirmed by Scanning Electron Microscope (SEM). The storage stability of microencapsulated anthocyanin did not change noticeably up to 7 days but thereafter gradually decreased at 30°C and 75% relative humidity. During 21 days of storage, anthocyanin stability decreased by 44 %along with the decline in free radical scavenging activity.     

不同干燥温度对鹿茸菇品质及其抗氧化活性的比较分析

为探究不同热风干燥温度对鹿茸菇品质及抗氧化活性的影响,以新鲜的鹿茸菇为原料,对不同热风干燥温度获得的鹿茸菇的外观、复水率、总酚和黄酮含量进行检测,并考察了样品对DPPH、ABTS、羟自由基的清除能力。结果表明:随着干燥温度提高,鹿茸菇复水率呈现下降趋势,55~65℃干燥温度下,鹿茸菇子实体外观较好;总酚和黄酮含量分别在55℃、75℃达到最高值11.7mg/g、0.23mg/g;鹿茸菇干品中的ABTS和羟自由基清除率在60℃最高,其EC50分别为0.86mg/mL及2.20mg/mL。综合各项指标,热风干燥温度为60℃时,可以较好的保持鹿茸菇的色泽和抗氧化活性。     

不同干燥温度对鹿茸菇品质及其抗氧化活性的比较分析

为探究不同热风干燥温度对鹿茸菇品质及抗氧化活性的影响,以新鲜的鹿茸菇为原料,对不同热风干燥温度获得的鹿茸菇的外观、复水率、总酚和黄酮含量进行检测,并考察了样品对DPPH、ABTS、羟自由基的清除能力。结果表明:随着干燥温度提高,鹿茸菇复水率呈现下降趋势,55~65℃干燥温度下,鹿茸菇子实体外观较好;总酚和黄酮含量分别在55℃、75℃达到最高值11.7mg/g、0.23mg/g;鹿茸菇干品中的ABTS和羟自由基清除率在60℃最高,其EC50分别为0.86mg/mL及2.20mg/mL。综合各项指标,热风干燥温度为60℃时,可以较好的保持鹿茸菇的色泽和抗氧化活性。     

Comparative survival and evaluation of functional probiotic properties of spray-dried lactic acid bacteria

The effect of spray drying on the viability and retention of key probiotic properties like acid and bile tolerance and cholesterol assimilation of three probiotic lactic acid bacteria (LAB) ( Lactobacillus plantarum CFR 2191, Lactobacillus salivarius CFR 2158 and Pediococcus acidilactici CFR 2193) has been studied. More than 97% survival was exhibited by the three LAB (1% cell suspension) spray dried with maltodextrin and nonfat skimmed (NFSM) as carriers. LAB cultures spray dried with maltodextrin showed significantly greater ( P ≤  0.05) retention of functional properties than those with NFSM. The results highlight a cost-effective way of producing large quantities of selected probiotic cultures with functional properties for neutraceutical application.     

Microencapsulation of flax oil with zein using spray and freeze drying

Microencapsulation of flax oil was investigated using zein as the coating material. Central Composite Design - Face Centered was used to optimize the microencapsulation with respect to zein concentration (x₁) and flax oil concentration (x₂) using spray drying. Also, freeze drying was carried out at two zein:oil ratios. The quality of microcapsules was evaluated by determining encapsulation efficiency, flowing properties (Hausner ratio), and evaluating the morphology with scanning electron microscopy. The response surface model for microencapsulation efficiency showed a high coefficient of determination (R² = 0.992) and a non-significant lack of fit (p = 0.256). The maximum microencapsulation efficiencies were 93.26 ± 0.95 and 59.63 ± 0.36% for spray drying and freeze drying, respectively. However, microcapsules prepared by spray and freeze drying had very poor handling properties based on the Hausner ratio. The bulk density decreased with an increase in zein concentration at the same flax oil concentration. The morphology of the flax oil microcapsules depended on the zein:flax oil ratio and the process used for microencapsulation. Flax oil microcapsules prepared by spray drying appeared to be composed of heterogeneous spheres of various sizes at high zein:flax oil ratios. Microcapsules prepared by freeze drying resulted in agglomerated small spheres. These microcapsules might find a niche as functional food ingredients.     

Physical properties and antilisterial activity of bioactive edible films containing Lactobacillus plantarum

Bioactive polymeric films were developed from the incorporation of Lactobacillus plantarum into polysaccharide or protein edible films. Lactic acid bacteria (LAB) were added directly to the film forming solution and films were obtained by casting. Four different biopolymers were tested: sodium caseinate, pea protein, methylcellulose and hydroxypropylmethylcellulose. In order to study the impact of the incorporation of the protective culture into the biopolymer matrix, the water vapour permeability (WVP), optical and mechanical properties of the dry films were evaluated. Furthermore, survival of L. plantarum and the antimicrobial potential of bioactive films against Listeria innocua were studied. Whereas optical and mechanical properties of the films were not notably altered by the LAB incorporation, WVP values increased for all biopolymers. Viability of the strain was lower in cellulose derivative matrices than in protein films, although bacteriocin production in the newly prepared films was greater in these matrices. As a result, a significant antimicrobial activity against L. innocua was observed for polysaccharide matrices, which was not observed for protein films, where the bacteriocin production is delayed. In pea protein films the maximum bacteriocin production occurs at 15 storage days and afterwards decreases. So, the nature of the biopolymer and the knowledge of time when an adequate bacteriocin concentration is produced are key to use bioactive films in an effective way.     

Synergistic effect of nisin and garlic shoot juice against Listeria monocytogenes in milk

The aim of this research was to determine the synergistic effect of nisin and garlic shoot juice (GSJ) against Listeria monocytogenes ATCC 19118 found in whole (3.5%), low (1%) and skim (no fat content) milk. Garlic shoot juice (GSJ) at concentrations of 2.5%, 5% and 10% revealed strong and similar patterns of antilisterial effect against L. monocytogenes ATCC 19118 in all categories of milk. Nisin only at concentrations of 62.5, 125, 250 and 500 IU/ml displayed a strong antilisterial effect as compared to the control group. Also, the synergistic combinations of GSJ (2.5%, 5%) and nisin (62.5, 125, 250 and 500 IU/ml) had a remarkable antilisterial activity in all categories of whole, low and skim milk after 14 days. Results of this study indicated the synergistic effect of GSJ and nisin as a potential antilisterial agent for the food industry.     

Effect of nisin on growth boundaries of Listeria monocytogenes Scott A, at various temperatures, pH and water activities

The effect of nisin on growth boundaries of Listeria monocytogenes Scott A in Tryptone Soy Broth (TSB) under different a(w)s, pH, and temperatures was studied. Growth/no growth turbidity data was modeled using logistic regression. Combinations of various temperatures (5-35 degrees C), pH (4.05-6.70) adjusted with HCl, a(w)s (0.937-0.998) NaCl (0.5-10.5%) and nisin (0-100 IU/ml) were used to monitor the growth/no growth response of L. monocytogenes Scott A for 60 days. The concordance of the logistic regression model was 99.4%, indicating successful data fitting. The minimum pH at which growth was observed was 4.81 at the temperature range of 25-35 degrees C and at a(w) as high as 0.992. Growth was observed at a(w) as low as 0.937, at pH 6.7, at the temperature range of 25-35 degrees C. Increasing nisin concentrations above 25 IU/ml resulted in a more inhibitory environment for L. monocytogenes. Presence of 100 IU/ml resulted in a minimum pH for growth at 5.20, and a minimum a(w) at 0.967 at the temperature range of 25-35 degrees C. It was remarkable that low to medium salt concentrations (2.5-4.5 NaCl% w/v) provided a protective effect against inhibition of L. monocytogenes by nisin. The present study points out the applicability of growth/no growth modeling in order to study any interactions between various factors affecting initiation of growth of micro-organisms, in which its turn helps the understudying of microbe-food ecosystem relations and the development of safer food.     

Characteristics of soy sauce powders spray-dried using dairy whey proteins and maltodextrins as drying aids

This study investigated the effect of adding whey protein isolate (WPI) as a complementary drying aid of maltodextrin (MD) on spray drying of soy sauce powders. Soy sauce powders were prepared by spray drying soy sauce liquid adding 5%, 10% and 15% of WPI respectively together with MD as the drying aids. Tests were conducted to evaluate the powder properties relevant to the caking issue of the soy sauce powders. Results showed that addition of just 5% WPI could significantly increase the product yield for the spray drying process. At the same time, the caking strength of the spray dried soy sauce powders were significantly reduced during storage with WPI addition. XPS results indicated that WPI have preferential migration to the surface of the soy sauce powder. The over-expression of WPI on powder surface after spray drying might explain the improved stability for soy sauce powders during the caking test.     

Effect of thermal processing and storage condition on the flavour stability of spray-dried durian powder

Stability of key odour volatiles (propanethiol, ethyl propanoate, ethyl 2-methylbutanoate and diethyl disulfide) from spray-dried durian powder that was subjected to accelerated storage were analysed quantitatively using headspace solid phase microextraction coupled to fast gas chromatography-mass spectrometry. The type of drying aids incorporated significantly influenced volatiles retention in the powder product. The addition of gum Arabic resulted in higher retention of volatiles in the durian powder as compared to maltodextrin and N-Lok starches. Volatiles that remained in the powder ranged from 57% to 76% of the original concentration. Volatile composition of the powder product was altered with only two aldehydes included 2- and 3-methyl butanal and no off-flavour volatile was detected throughout the storage. The rates of volatiles release from the spray-dried powder under accelerated storage condition increased markedly at higher relative humidity.     

Effect of inlet temperature on the physicochemical properties of spray-dried seed-watermelon seed protein powder

Here, we studied the effects of inlet temperature on the physicochemical properties of the hydrolyzed protein (seed-watermelon seed hydrolyzed protein [SWSP]) powder in seed-watermelon seeds. The inlet temperature of the study was in the range of 150 to 180 °C, and the remaining experimental parameters remained constant, that is, the feed flow rate was 0.2 L/hr, the concentration of maltodextrin was 30%, and the outlet temperature was 80 °C. We studied the water activity and moisture content, bulk density, flowability (Carr index and Hausner ratio), angle of repose, solubility, color, hygroscopicity, powder morphology, particle size, crystallinity, and odor of the sample. Inlet temperature of 170 to 180 °C reduced the moisture content and increased the particle size. It was found that the value of measured water activity was less than 0.5, which helped in maintaining stability of the sample. Powders produced at the temperatures showed smoother particle surfaces, whereas higher inlet temperature showed spherical particles with some shrinkage as analyzed by scanning electron microscope. The inlet temperature affected the color of the sample, thus at high temperature, the sample had a brighter color. The sample was approximately 18% crystalline. At a preparation temperature of 160 °C, the sample showed significant antioxidant activity (P < 0.05).     

热泵温度对白萝卜干燥速率及品质的影响

分别以热泵温度50,55,60,65℃对白萝卜进行干燥,比较不同热泵温度下的白萝卜干燥速率、色泽、营养成分、复水率、微观组织结构等。结果表明:热泵温度50,55,60,65℃下,白萝卜含水量降至(8±1)%分别需12,11,10,9h;热泵温度55,60℃对白萝卜色泽保持较好;影响白萝卜干复水率的热泵温度依次为55℃>60℃>50℃>65℃,其中55,60℃下差异不显著(P>0.05);白萝卜干总糖、蛋白质和VC含量以热泵温度50℃干燥的较高,且随热泵温度的升高而降低;而热泵温度过低或过高都会对产品品质产生不利影响。综合考虑,热泵温度55℃可作为白萝卜热泵干燥的最佳干燥温度,此条件下获得的白萝卜干具有最佳的综合品质。     

不同温度对番茄红素原料和胶束中番茄红素异构体的影响

目的 分析番茄红素原料和胶束中的番茄红素在不同温度下的构型变化规律。方法 通过YMC Carotenoid C30-HPLC 高效液相色谱法对其构型变化情况进行研究。结果 各异构体降解速率常数（k）的绝对值会随着温度的升高而变大,表明其降解速率加快,结构越不稳定。通过对比显示,四种番茄红素异构体,稳定性由高到低依次为：5Z> All-E> 9Z>13Z。番茄红素原料中13Z、9Z、ALL-E和5Z的活化能分别为22.0 kJ/mol、23.4 kJ/mol、26.5 kJ/mol、27.6 kJ/mol,而番茄红素胶束中13Z、9Z、ALL-E和5Z的活化能均高于番茄红素原料,分别为25.8 kJ/mol、26.0 kJ/mol、31.5 kJ/mol、31.9 kJ/mol。结论 将番茄红素包载于聚合物胶束中,可以降低其降解速率,提高稳定性。     

Moisture diffusivity and water activity of part-baked bread at above and sub-freezing temperatures

Accurate values of the effective moisture diffusivity and water activity of foodstuffs are necessary in order to study mass transfer and the weight loss during freezing. This work focuses on the evaluation of the effective moisture diffusivity of part‐baked bread and its crumb and crust and of the water activity of the part‐baked bread crust. The effective diffusivities have been estimated by analyses of drying data on the bread and crumb samples. They were related to the temperature by the Arrhénius relationship. Water activity was experimentally determined at positive temperatures. Experimental data were modelled by the Guggenheim–Anderson–de Boer (GAB) model and a model deduced from the Clausius–Clapeyron equation. The results predicted by the Arrhénius and GAB models showed a good agreement with the experimental values. Finally, the moisture diffusivity and water activity in the subzero domain were obtained by extrapolation using an Arrhénius model and a GAB model, respectively.     

Physical and chemical properties of ultrasonically, spray-dried green banana (Musa cavendish) starch

Ultrasonic wave propagation and the spray dryer technique were applied to study their effect on the physical and chemical properties of green banana starch. The results showed high resistant starch content, which was reduced by ultrasound treatment and also by spray drying. Both techniques increased the solubility, swelling power and water absorption capacity. The gels exhibited non-Newtonian shear-thinning behavior, since flow behavior index was less than one (n < 1). Ultrasound wave propagation reduced yield stress and consistency coefficient in starch gels. Under oscillatory shear, all gels exhibited solid-like viscoelastic behavior, storage modulus was higher than loss modulus to entire frequency range (G′ > G′′), which was confirmed by the Cox-Merz experiment that showed that the complex dynamic viscosity was greater than the apparent viscosity in all samples. The gelatinization temperature was mainly influenced by drying technique and ultrasound treatment reduced the amount of energy required to gelatinize the starch.     

Fish silage prepared from different cooked and uncooked raw materials: chemical changes during storage at different temperatures

Four silage types were prepared from raw and cooked whole herring, whole mackerel, by‐products from the filleting‐line of cod and saithe, and from the viscera of cod. Each silage type was stored at 4, 20 and 50°C for 48 days. The raw materials were analysed fresh and after 2, 4, 8, 16, 32 and 48 days of storage. Dry matter, crude protein and total fat were not affected by the different storage temperatures or the length of the storage period. Neither was there any change in amino acid contents. Chemical composition in different silage types reflected the amounts in the raw materials used for silage production. Hydrolysis, on the other hand, varied with the type of raw material used for silage production as well as with the temperature under which the silages were stored. Cooked raw materials did not show any change in hydrolysis during storage. © 1999 Society of Chemical Industry