草莓红色素稳定性的研究

研究了草莓红色素的稳定性。结果表明 :pH值对草莓红色素的影响明显 ,在酸性条件下 ,该色素较稳定 ;金属离子Na+、Ca2 +、Zn2 +、Cu2 +对色素有增色作用 ,Al3+对草莓红色素的影响不大 ,而Fe3+则有明显的不良影响 ;食品中常用的葡萄糖、蔗糖对草莓红色素有一定的降解作用 ,而Vc、H2 O2 、Na2 SO3则有严重的破坏作用 ;低浓度的 ( <1 % )防腐剂苯甲酸钠对草莓红色素有增色作用 ,高浓度 ( >1 % )的则有明显的降解作用。     

草莓复合涂膜保鲜效果的研究

以草莓为实验原料,采用魔芋精粉、丁香提取物和氯化钙复合涂膜方法对草莓进行涂膜保鲜实验。选择失重率和Vc含量为指标,以单因素实验和正交实验优化保鲜膜配方,结果表明,常温下,魔芋精粉浓度0.5%、丁香提取物浓度2.0%、氯化钙浓度1.2%的复合涂膜剂对草莓的保鲜效果最好,有效地延长了保质期。该最佳配比的复合涂膜剂在低温下对草莓的保鲜效果比在室温下更显著,相关指标明显优于室温下的涂膜组。     

Effect of γ-Irradiation on Phenolic Acids in Strawberries

ABSTRACT: The content of phenolic acids in strawberries was determined before and after gamma-irradiation in the dose range 1 to 10 kGy. Fresh whole strawberries were irradiated, acid-base-hydrolyzed, and purified on polyamide columns. The compounds were analyzed by reversed-phase chromatography and detected with a diode-array detector. Dose/concentration relationships were obtained for gallic acid, 4-hydroxybenzoic acid, cinnamic acid, p-coumaric acid, and caffeic acid. Whereas radiolysis of the individual acids in aqueous solutions led to their efficient degradation and to a notable hydroxylation, in the complex matrix of food no hydroxylation products were formed and only the amount of 4-hydroxybenzoic acid was affected by irradiation (build up: 0.68 ± 0.04 mg kg⁻¹kGy⁻¹).     

An evaluation of the retention of quality characteristics in fresh and freeze-dried alpine strawberries

Alpine strawberries (Fragaria vesca) are used in fruit juice, marmalade, or jam production and as a result have economical importance in food sector. The fresh alpine strawberries have a tendency to lose their quality in a few days as a result of high water loss and spoilage. In this paper, the results of a study on the effects of freeze drying process on the characteristics of the alpine strawberries, such as firmness, sugar content, pH, colour, weight loss, dissolved solids, anthocyanin and vitamin C content with reference to the fresh, are reported. Freeze‐drying indicated no difference in the characteristics of the alpine strawberries when compared with the fresh. It is found that a slight acid or base addition onto the rehydrated alpine strawberry juice preserved the stability of pigments and the colour. In addition, the rehydrated alpine strawberry juice exhibited an antimicrobial activity towards an important foodborne pathogen, Enterobacter faecium ATCC 6057.     

Effect of Edible Coating Process and Irradiation Treatment of Strawberry fragaria spp. on Storage-keeping Quality

ABSTRACT: Gamma-irradiation and various edible coatings were tested on fresh strawberries ( Fragaria spp. ) for keeping fruit quality and extending shelf life. Four coatings based on milk protein were evaluated. In 1 experiment, coating formulation based on caseinate and/or strawberries were irradiated using a ⁶⁰Co source. Both gamma-irradiation treatment and edible coating process significantly delayed (p ≤ 0.05) molds growth. Edible coating based on irradiated caseinate was more effective than that of unirradiated caseinate. In a 2nd experiment, 3 irradiated coatings based on calcium caseinate and whey proteins were evaluated. The coating formulation based on 1:1 caseinate-whey was found to be more effective than those based on calcium caseinate. Addition of calcium chloride or a mixture of pectin and agar increased the effectiveness of the coating by delaying molds' apparition.     

Vacuum Infiltration of Polyamines Increases Firmness of Strawberry Slices Under Various Storage Conditions

Strawberry slices were vacuum infiltrated with polyamines and changes in firmness during storage were determined. Spermine and spermidine at 10 mM or 100 mM significantly increased firmness, whereas pu-trescine was not as effective at increasing firmness of slices stored at 1°C. The firming effect of the polyamines was similar to that of calcium chloride, and may have been due to their ability to bind to cell walls and membranes. In ripe receptacles of various cultivars which differed in firmness, putrescine (12–38 nmol/g fresh weight) and spermidine (19–33 nmoI/g fresh weight) were the predominant polyamines, while only low levels of spermine (<10 nmol/g fresh weight) were present. There was no discernible relationship between endogenous polyamine levels and fresh fruit firmness for the cultivars studied.     

Simultaneous HPLC Determination of 2,5-Dimethyl-4-hydroxy-3 (2H)-Furanone and Related Flavor Compounds in Strawberries

A rapid methodology (less than 90 min) is described for the qualitative and quantitative analysis of 2,5-dimethyl-4-hydroxy-3 (W)-furanone (furaneol), furaneol-β-glucoside, and 2,5-dimethyl-4-methoxy-3 (2H)-furanone (mesifurane) in strawberries. These compounds were resolved by HPLC with a RP C18 column, using acetate buffer and methanol as binary mobile phase and detection at 280 nm, and confirmed by GC-MS. The aqueous extraction procedure gave an average recovery of these compounds from strawberries > 90%, with detection limits: 0.14 furaneol, 0.05 furaneol-β-glucoside, and 0.36 μg/rnL mesifurane.     

Influence of Storage Temperature on the Kinetics of the Changes in Anthocyanins, Vitamin C, and Antioxidant Capacity in Fresh-Cut Strawberries Stored under High-Oxygen Atmospheres

ABSTRACT:  Changes in the main antioxidant properties of fresh-cut strawberries stored under high-oxygen atmospheres (80 kPa O₂) were studied at selected temperatures (5 to 20 °C). The suitability of zero- and 1st-order kinetics as well as a model based on Weibull distribution function to describe changes in experimental data is discussed. A non-Arrhenius approach was used to determine the temperature dependence of the estimated rate constants. A Weibull kinetic model most accurately  ( R ²_adj≥ 0.800)  estimated changes in anthocyanins and antioxidant capacity of fresh-cut strawberries throughout the storage period, whereas a 1st-order model adequately fitted  ( R ²_adj≥ 0.982)  the variation of vitamin C. The temperature dependency of the kinetic rate constants for each antioxidant property was successfully modeled through the non-Arrhenius approach  ( R ²_adj≥ 0.709)  . The T_c obtained for anthocyanins, vitamin C, and antioxidant capacity degradation were 290, 284, and 289 K, respectively, indicating the temperature at which a marked acceleration of the losses in the antioxidant potential of strawberry wedges occurs. These findings will help to describe the variation of the antioxidant potential of fresh-cut strawberries upon storage time and temperature.     

Strawberry Texture and Pectin Content as Affected by Electron Beam Irradiation

Fresh Tristar' strawberries were irradiated with electron beam irradiation at 0, 1, and 2 kGy. Fruit firmness decreased as irradiation dose increased. Water-soluble pectin increased and oxalate-soluble pectin decreased at 0 and 1 day after 1 and 2 kGy irradiation. Fruit firmness correlated with oxalate-soluble pectin content. Total pectin and nonextractable pectin were not affected by irradiation. The oxalate-soluble pectin content and firmness of irradiated strawberries increased slightly at the beginning of 2°C storage and then decreased as storage time increased. No changes occurred in water-soluble pectin, nonextractable pectin, or total pectin during storage.     

Effect of Pectinmethylesterase Infusion Methods and Processing Techniques on Strawberry Firmness

Strawberry halves were pretreated with fungal pectinmethylesterase (PME) and calcium chloride using, respectively, passive osmotic infusion, vacuum‐assisted infusion, and pressure‐assisted infusion with the aim to improve the firmness. The vacuum‐assisted procedure was observed to be the only method able to accomplish an uptake of infusion solution and hence capable of improving the firmness of the strawberries. Significantly less firmness increase was realized when tomato PME was vacuum‐infused instead of fungal PME. Strawberry halves were pretreated by vacuum‐assisted infusion with fungal PME and calcium chloride and were subsequently subjected to thermal treatments at 60 °C and 80 °C and pressure treatments at about 400 MPa and 550 MPa. For all treatments studied, the pretreated sample was significantly firmer compared with the reference sample. For the thermal processes, the residual firmness relative to the initial value before treatment was depending on the temperature of the treatment and not on the pretreatment. However, vacuum‐assisted infusion of PME and calcium could limit the portion of firmness loss due to pressure treatment to 30% compared with 80% for non‐pretreated fruits.