Determination of biochemical properties of foam‐mat dried mango powder

Investigations were carried out to see the impact of drying air temperature (65, 75 and 85 °C) and milk as foaming agent in different concentration levels (0%, 10%, 15%, 20% and 25%) on the chemical properties of foam‐mat dried mango juice powder. Chemical properties such as total sugars, ascorbic acid, total carotenes, minerals, total acid, pH, total soluble solids (TSS) and microbial load (fungal and bacterial) of foam‐mat dried mango powder were determined. Data were analysed as per two‐way anova , Duncan’s multiple range test and l.s.d. of Ag Res Software statistical package. Almost all chemical properties show decreasing trend with increase in drying air temperature. Microbial load was not detected in foam‐mat dried mango powder. It was found that addition of 10% milk as foaming agent and drying at 65 °C temperature gave better results.     

Physicochemical and microbial quality evaluation of foam‐mat‐dried pineapple powder

Present experiments were carried to study the physicochemical and microbial quality of foam‐mat‐dried pineapple powder. Pineapple pulp was foamed using two foaming agents, tricalcium phosphate (TCP) (0%, 0.25%, 0.50%, 0.75%, and 1.0%) and egg white (EW) (0%, 0.50%, 1.0%, 1.50%, and 2.0%). Carboxy methyl cellulose (0.25%) was used as foam stabiliser, and drying was carried out at 65, 75, and 85 °C in tray drier followed by pulverising the dried foam mats in to fine powder. Powdered samples were analysed for various physicochemical quality parameters viz. total sugars, reducing sugars, ascorbic acid, total acid, pH, iron, phosphorus and calcium content, and bacterial and fungal load. Statistical analysis using LSD revealed that sample dried using 1% TCP at 65 °C was the best with 4.60% total sugars, 2.71% reducing sugars, 4.05 mg per 100 g ascorbic acid, 0.35% total acid, 0.29 mg per 100 g Iron, 2.24 mg per 100 g phosphorous, and 6.58 g per 100 g calcium and zero bacterial and fungal growth.     

啤酒泡沫中发泡蛋白的研究进展

大量研究表明,啤酒泡沫产生的关键因素是啤酒中所含的发泡蛋白,发泡蛋白的性质和数量很大程度上决定着啤酒泡沫的质量。通过对发泡蛋白定义、特性和与泡沫质量的关系,以及泡沫质量测定方法、改进措施等方面的介绍,说明了发泡蛋白对啤酒泡沫质量的决定性作用及研究发泡蛋白的现实意义。     

Modelling of moisture diffusion in pores of banana foam mat using a 2-D stochastic pore network: Determination of moisture diffusion coefficient during adsorption process

The purpose of this research was to determine the diffusion coefficient of moisture in the pores of banana foam mat using stochastic pore network. A 2-D pore network was used to represent the pore voids inside the banana foam sample and the moisture movement inside the individual pore segments was described by Fick’s law. To determine the moisture diffusion coefficient, the adsorption experiments were carried out with standard static method using saturated salt solutions. Two banana foam densities of 0.21 and 0.26 g/cm³ were used to adsorb the water vapour. The interactions between moisture and pore structure were illustrated using a 3-D pictorial representation of network concentration gradients in spaces with colour representing the moisture content. The network model described the experimental results relatively well. The diffusion coefficient of moisture in pores was in order of 10^-9${10}^{-9}$ m²/s which was nine times higher than the effective diffusion coefficient calculated from the continuum model. The value of moisture diffusion coefficient was dependent on the temperature and independent of the foam densities and the relative humidity, except for the diffusivity determined from the condition at higher relative humidity of 70%.     

Drying kinetics,physico‐chemical properties,antioxidant activity and phenolic composition of foam‐mat dried germinated rice bean (Vigna umbellata) hydrolysate

This research was aimed to study physico‐chemical properties and antioxidant activities of foam‐mat dried germinated rice bean (Vigna umbellata) hydrolysate. Germination led to an increase in released phenolic content and antioxidant activity (DPPH radical scavenging activity and FRAP) of rice bean hydrolysate. The hydrolysate obtained from germinated rice bean (GRB) and non‐germinated rice beans (NGRBs) was foam‐mat dried at 60 and 70 °C. Semi‐theoretical and empirical model could suitably describe the drying characteristic of foamed bean hydrolysate. Total phenolic content and antioxidant activities of foam‐mat dried samples decreased with increasing air‐drying temperature (P ≤ 0.05). Gallic acid, catechol and epicatechin were major phenolic compounds in foam‐mat dried samples prepared from both GRB and NGRB. The higher phenolic content and antioxidant activities were found in foam‐mat dried hydrolysate of GRB. Electron spin resonance spectrometry revealed that foam‐mat dried rice bean hydrolysate showed a strong ability to scavenge free radicals, especially carbon‐centred radicals.     

脱墨剂的起泡性能及其泡沫稳定性

对表面活性剂的起泡性能和泡沫稳定性进行了研究,研究结果表明,单一表面活性剂中起泡效果最好的是LCS;而2种表面活性剂复配后起泡效果最好的是m(LWE-7)∶m(LCS)=1∶2以及m(WNL-9)∶m(LCS)=1∶2。     

Study of cooking quality of spaghetti dried through microwaves and comparison with hot air dried pasta

The aim of this work is to evaluate and compare the effects of microwave and conventional drying (hot air) on the quality characteristics of cooked pasta. Experiments were carried out on pasta type spaghetti.A huge difference was noticed between times necessary to dry samples by hot air and by microwaves, in fact in the first case, the drying time was on the average 204.5 min vs. 61.7 s of microwave treatment (average). The gelatinization degree of samples dried by hot air was faster than that of those dried by microwaves: the medium values of kinetic constant of gelatinization of samples dried by hot air and microwaves were 7.5 and 5.2, respectively. Similar total organic matter values suggest that the cooking quality of samples differently dried was comparable. Moreover, samples dried by microwaves were thicker than pasta dried by hot air (37.8 vs. 27.4).     

Drying and quality characteristics of fresh and sugar-infused blueberries dried with infrared radiation heating

We evaluated the finished product quality and infrared (IR) drying characteristics of fresh and sugar-infused blueberries dried with a catalytic infrared (CIR) dryer. IR drying tests were conducted at four product temperatures (60, 70, 80, and 90 °C) to evaluate the drying rate and the color and texture of the finished product. Fresh blueberries dried with convective hot air drying at 60 °C were used as control for comparison. The experimental data of moisture changes during IR drying were modeled with eight different models, including Page, modified Page, Thompson, Newton, Wang and Singh, and Henderson and Pabis, and two models developed in this study. The Thompson model showed the best fit to all experimental data. The CIR drying produced firmer-texture products with much reduced drying time compared with hot air drying. For fresh blueberries, CIR drying conserved drying time by 44% at 60 °C. The effective moisture diffusivity ranged from 2.24 × 10⁻¹⁰ to 16.4 × 10⁻¹⁰ m²/s and from 0.61 × 10⁻¹⁰ to 3.84 × 10⁻¹⁰ m²/s for fresh and sugar-infused blueberries, respectively.     

Moisture sorption characteristics and glass transition temperature of apple puree powder

The aim of this study was to characterise the influence of different foam‐mat‐drying methods on the moisture sorption characteristics and glass transition temperatures of apple puree powder. Apple puree was foamed with the addition of 2.5% egg albumin and 0.5% methylcellulose. Convective air‐drying and microwave‐drying techniques were used. Also foamed puree with and without maltodextrin (6% or 15% w/w) was freeze‐dried. Moisture equilibrium data of powders were determined by using a static desiccator method in a water activity range of 0.0–0.903. Modulated differential scanning calorimetry (MDSC) was used to obtain the glass transition temperature. No effect of drying method on sorption properties and glass transition temperatures of apple puree powders was observed. The addition of maltodextrin to the apple puree caused an increase in T_g by 10–30 °C depending on the amount of incorporated additive. Addition of maltodextrin significantly reduced the hygroscopicity of apple puree powders.     

Quality of dried coriander leaves as affected by pretreatments and method of drying

Coriander (coriandrum sativum), an annual herb/spice crop is widely used for culinary purpose In India, fresh coriander is abundantly available during winters from December to March but has very short shelf life even under refrigerated conditions. This leads to a marked scarcity in availability and a sharp rise in price in the lean period. During peak period, most of the crop is lost/wasted due to lack of proper post harvest processing techniques. The fresh green coriander (soft stems and leaves) if properly dried, packaged and stored may help in increasing its availability during lean periods at a lower price. Different pretreatments and methods were studied and evaluated on the basis of quality and rehydration characteristics. The best pretreatment was found to be dipping for 15 min in solution of 0.1% Magnesium chloride, 0.1% Sodium bicarbonate and 2.0% KMS in water at room temperature and the best method was drying in mini multi rack solar dryer.     

Quality control charts for storage of raisins and dried figs

 Shewhart control charts are constructed by using the Hunter Lab color scale parameters to assure maintenance of the color of raisins and dried figs during storage in modified atmosphere packages, vacuum packages, or nylon bags. These control charts may be used to maintain the quality within acceptable limits and make it possible to readjust storage conditions if the acceptable limits should be violated. Received: 11 March 1996     

Purification of yeast proteinase A from fresh beer and its specificity on foam proteins

Yeast proteinase A from fresh beer was first purified with Sephadex G‐100 column chromatography and the active fractions reached to 5.3‐fold purification with 7% of yield. After purification with DEAE Sephadex A50, proteinase A activity increased to be 10.1 times of the initial with 1% of yield. When identifying the sample from chromatography by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis (SDS‐PAGE), only one protein band with 42 kDa was observed, this indicated that the enzyme was purified. The pattern of electrophoresis of hydrolysed beer by crude proteinase A did not show lipid transfer protein (LTP) on the gel. The result of SDS‐PAGE of interaction mixture of purified proteinase A and beer also indicated that LTP was decomposed.     

The air drying behaviour of fresh and osmotically dehydrated banana slices

Ripe banana, cut to 10mm thick slabs were osmotically treated in sugar solutions of 35, 50 and 65° Brix for 36h. The initial moisture content fell from a value of 3.13kg H₂O DM to 2.19, 1.63 and 1.16kg H₂O kg⁻¹ for treatment in the three solutions, respectively. These slabs, with Total Soluble Solids (TSS) contents of 26, 34 and 39° Brix, respectively, as well as freshly cut but untreated slabs (15° Brix) were air dried in a cabinet type tray drier to near equilibrium conditions at fixed temperatures from 40 to 80°C and at a constant air speed of 0.62m s⁻¹. Drying was found to occur in the falling rate period only for both banana types and two drying constants K₁ and K₂ were established for a first and second falling rate period of drying. Increasing the drying air temperature significantly enhanced the drying rate and the K-values, except at 80°C when the rates fell, possibly because of case hardening of the slabs. Reducing the slab thickness also improved the drying rate, but increasing the air speed to 1.03m s⁻¹ did not have any profound effect. As the sugar content of the banana slabs increased through the osmotic treatment, drying rates fell. Calculated apparent moisture diffusivities at 60°C ranged from 34.8× 10⁻¹⁰ m² s⁻¹ (fresh slab) to 8.8×10⁻¹⁰ m² s⁻¹ for dried (39° Brix) slabs. The moisture diffusivity was significantly lowered as the moisture content dropped in drying and with increased levels of sugar. Previously osmosed and then air dried banana slabs showed appealing colour and texture compared to the fresh banana.     

Proximate composition and fatty acid profile of three different fresh and dried commercial sea cucumbers from Turkey

Proximate composition and fatty acid (FA) profile of three commercial sea cucumbers; Holothuria tubulosa, Holothuria polii and Holothuria mammata caught from Aegean Sea of Turkey were analysed. The effects of regional variation and drying process on FA composition were also investigated. Moisture, protein, fat and ash contents of the species ranged between 81.24% and 85.24%, 7.88% and 8.82%, 0.09% and 0.18%, and 5.13% and 7.85%, respectively, with a significant changes among species (P < 0.05) with some exceptions. Although FA values varied significantly (P < 0.05) among species and regions, the changes for most FA types representing the same region for different species were not significantly different. Total polyunsaturated fatty acids (PUFA) were found to be higher than total saturated (SFA) and monosaturated FAs (MUFA) accounting for 53.0–62.12% for ∑PUFA, 13.28–16.41% for ∑MUFA and 13.99–19.21% for ∑SFA. While some individual SFAs and PUFAs decreased after drying process, various individual FAs of MUFA increased in their amounts (P < 0.05). Among PUFAs, the highest mean value of eicosapentaenoic acid and docosahexaenoic acid for all regions were determined for H. polii as 7.25% and H. tubulosa as 12.37% in fresh samples, respectively. This study represents new information relating to FA contents and drying effect on FA profile for these species.     

Changes in aromatic profile of fresh and dried fig – the role of pre‐treatments in drying process

The aromatic profile of volatiles in fresh figs (FF), fresh figs frozen in liquid nitrogen (NF) and dried figs (DF) (dark variety Petrova?a Crna) was characterised by HS–SPME followed by GC–MS. Figs were dried in a pilot plant cabinet dryer using different pre‐treatments to preserve the dried fruit: sulphuring and immersion in a solution of citric acid and ascorbic acid (separately). The adaptability of thin‐layer drying models to whole figs was investigated. Fresh figs and fresh figs frozen in liquid nitrogen differed mainly in the amount of aldehydes. The highest abundance of volatile compounds in dried figs was found in figs pre‐treated with sulphur dioxide and the control, compared to samples immersed in the acid solutions. Preservation was the most successful for the group of terpenes and terpenic compounds, quite good for some esters and ketones, whereas aldehydes were not affected by the used pre‐treatment.     

Microwave drying characteristics of potato and the effect of different microwave powers on the dried quality of potato

Little detailed information is available on the microwave drying characteristics of potato and the use of different microwave powers to dry food products. Experiments were conducted to study the microwave drying characteristics and the dried quality of potato. The study focuses on describing the microwave drying characteristics of potato and discussing the effect of sample thickness, drying power and mass. The results show that if the power level increases, the mass load decreases and the thickness of the sample decreases, the dehydration rate increases and the drying energy consumption decreases. There are two falling rate periods during microwave drying of potato: the first falling rate period is for a moisture content of more then 1.1 (dry basis, DB); the second falling rate period is for a moisture content of less than 1.1 (DB). The same water loss will consume more energy when the moisture content is less than 1.1 (DB). A two-stage drying process was employed during microwave drying of potato. The microwave power of the first drying stage differed form that of the second drying stage. The moisture content of the breakpoint for the conversion of the first drying stage into the second drying stage is a moisture content of 1.1 (DB). A quadratic orthogonal regression experiment was conducted, and the effects of slice thickness, the first drying load power and the second drying load power on sensory quality, the rehydration ratio and the energy consumption rate were established. The slice thickness, the first drying load power and the second drying load power linearly affected the three indices. The effect of the product of the second drying load power and the potato slice thickness on the rehydration ratio and the energy consumption rate is significant. The optimum drying parameter combination for the three indices was obtained. The rehydration ratio of the dried products decreased with an increase of the second drying load power and the slice thickness. The concave curves of the sensory quality versus the three factors were shown.     

Effect of drying temperature on the quality of dried bananas cv. prata and d’água

The effect of drying temperature (60 and 70 °C) on the chemical characterization, sensorial evaluation and microbiological quality of dried bananas obtained in a forced-air drying chamber under constant air flow rate (30 m³/h) was studied. The results showed that drying did not affect the chemical composition and the products were in good sanitary conditions. The sensorial analysis showed that lower drying temperatures produced better-accepted products and that under these conditions products obtained using the banana cv. d’água showed a superior texture to that of the standard.     

采后UV-C照射对芦柑抗病性和品质的影响

研究不同剂量UV-C照射处理对采后芦柑在15℃贮藏期间腐烂率及主要品质指标的影响。结果表明,1.5kJ/m2或3kJ/m2UV-C照射能有效减轻果实贮藏期间腐烂,推迟腐烂6d或12d,显著降低腐烂率。贮藏后期,1.5kJ/m2或3kJ/m2处理降低了失重率,提高了果实的可溶性固形物含量、糖酸比和VC含量,且促进了果肉中类黄酮和总酚的次生代谢合成,从而较好地保持了果实的感官品质和营养品质。1.5kJ/m2或3kJ/m2处理也有助于提高果皮中类黄酮和总酚含量。UV-C照射处理作为采后芦柑的非化学贮藏保鲜手段,具有潜在的应用前景。