Computed tomographic evaluation of gas hole formation and structural quality in Gouda‐type cheese

Computed tomography (CT) was performed on Gouda‐type cheese during ripening to evaluate gas hole formation and structural quality. The cheese was exposed to different ripening conditions, including variations in ripening temperature and concentration of butyric acid bacteria. Computed tomography images were obtained every 2 weeks for 16 weeks to assess the volume, shape and location of gas holes. The results demonstrate that CT makes the nondestructive monitoring of cheese gas hole formation and evaluation of the structural features of cheese possible throughout the ripening period.     

Identification of polyphenolic compounds in red and white grape varieties grown in R. Macedonia and changes of their content during ripening

The composition of polyphenols in the skin, seed and pulp extracts of the grapes of Vranec and Smederevka varieties, and Merlot and Chardonnay as well, was analyzed by liquid chromatography-diode array detection-mass spectrometry (HPLC-DAD-MS) and MS/MS techniques. Thirty-one phenolic compounds, including anthocyanins, flavonols and flavan-3-ols, as well as phenolic acids derivatives, have been identified in the extracts prepared from the grapes at physiological maturity, by mass spectrometry applying electrospray ionization operated in alternating ion mode and by performing tandem MS experiments in the ion trap mass analyzer. Grapes were analyzed at three different phases: (i) veraison, (ii) physiological ripeness and (iii) late harvest, in order to follow the evolution of polyphenolic content during berry development, applying spectrophotometric methods. Vranec had a higher polyphenolic content compared to Merlot due to the higher levels of total phenolics and flavonoids in the skins and seeds as well as a higher content of flavan-3-ols and anthocyanins in the skins, allowing discriminating the varieties. HPLC-DAD-MS analysis presented significantly higher relative amounts of anthocyanin monoglucosides and p-coumaroylglucosides in Vranec grapes. Smederevka seeds had a higher amount of flavan-3-ols than Chardonnay, while a higher content of total phenolics and flavonoids was found in the skins of the Chardonnay variety. Anthocyanin content in both red varieties increased during the berry ripening, while flavan-3-ols in seeds were mainly accumulated in the veraison phase followed by decrease of the content with ripening.     

Changes in the texture,physicochemical properties and volatile compound profiles of fresh Kashar cheese (<90 days) during ripening

In this study, four different fresh Kashar cheese samples were ripened for 90 days. The physicochemical properties, texture attributes, fatty acid composition and volatile compound profiles of the samples were measured every 30 days of ripening. The texture properties of the cheese samples were significantly affected by the duration of the ripening period. The results of this study highlighted that texture parameters as a function of ripening period should be considered for both fresh and aged Kashar cheeses to determine the ripening period as they are very important for consumer acceptability and consumption of the end product.     

Carbohydrate changes in ripening Capsicum annuum in relation to textural degradation

 Within 8 days of harvest, fruits of Capsium annum showed striking changes in texture when ripened at room temperature. Physiologically, they showed a significant weight loss and organoleptically, a change in textural firmness which was evident microscopically, as extensive cellular damage. The associated biochemical changes during ripening were: (1) an increase in free-sugar levels, (2) an increase in in situ hydrolysis of some hemicellulose fractions (Hem a, b and c) and (3) a general increase in the activity of cellulase, α-mannosidase, laminarinase, polygalacturanase, galactanase, mannanase, β-galactosidase and hemicellulase (HCe) activity on Hem b and c. In contrast the activity of xylanase, pectin methyl esterase and HCe on Hem a decreased during ripening. Cold storage (8°C) held textural changes in check, resulting in a longer shelf-life for cold-stored fruits compared to fruits stored at room temperature. Received: 14 May 1997     

多聚半乳糖醛酸酶(PG)反义基因对加工番茄果实成熟的影响

采用农杆茵(agrobacterium tumefaciens)介导法将多聚半乳糖醛酸酶(PG)反义基因导入新疆加工番茄(lycopersicon esculentum,品种代号98-75)。通过卡那霉素抗性筛选获得10株转化植株,PCR和Southern blot分析表明,其中4株为阳性植株,反义PG基因已整合到这4株加工番茄基因组中。转基因加工番茄的硬度和可溶性固形物含量高于同期对照果实;果实饱满有光泽;此4株转基因番茄果实的PG活性分别为对照番茄果实的83％、88％、63％和46％;脂氧合酶(LOX)活性下降;可溶性果胶含量在同期低于对照。Northem blot分析表明,转基因番茄果实的PG、LOX和LeEXPl基因表达水平下降。研究结果表明,转反义PG基因加工番茄果实成熟软化进程被延缓,果实品质有一定改善。     

Effect of soy protein supplementation on the quality of ripening Cheddar-type cheese

The impact of soy protein isolate on the proteolysis and organoleptic properties of Cheddar-type cheese during ripening was studied. Cheese was prepared from cow's milk (control) and cow's milk plus soy protein isolate by using a starter culture of Streptococcus thermophilus and Lactobacillus delbrueckii subsp . bulgaricus, and then ripened at 12  ±  1°C for 3 and 5 months. The molecular weight range and peptide fraction in the cheeses were determined by high-performance liquid chromatography (HPLC), and the microstructure was observed by scanning electron microscopy (SEM). Sensory evaluation was used to compare the flavour, body, texture and appearance of the cheeses. The results show that the molecular weight range (9924–9966  Da) in the control cheese was larger than that (6954–6957   Da) in the soy protein-treated cheese and the microstructure in the latter was less compact than in the control cheese. In the sensory evaluation, higher scores were given for some experimental cheese than the control cheese. After 5 months of ripening, the organoleptic properties of the cheese had markedly improved and no bitter off-flavour was detected in the treated cheeses. It was concluded that soy protein could be used to improve the quality of cheese and the addition of 5% soy protein isolate could be recommended for improving the flavour and texture of Cheddar-type soy supplemented cheese.     

Spatial and temporal changes in the volatile profile of Alphonso mango upon exogenous ethylene treatment

Alphonso is a highly favoured and exported mango cultivar among the vast mango germplasm of India. Being a climacteric fruit, ethylene plays an important role in ripening of mango. For deeper understanding of effect of pre-climacteric ethylene treatment on volatile profiles of Alphonso mango, 26 volatiles were tracked through six ripening stages of pulp and skin of ethylene-treated and control Alphonso fruits. The study revealed accelerated ripening in terms of early appearance of ripening-specific compounds, lactones and mesifuran, upon ethylene treatment. While the level of lactones remained unaffected, the mesifuran level vastly increased upon ethylene treatment. Skin showed high terpene content while pulp had higher amount of lactones compared to skin. This work points towards involvement of ethylene as a natural hormone in the biosynthesis of lactones and furanones in naturally ripened fruits; whereas, an increase in the terpene level during ripening appears to be independent of ethylene.     

Changes in free amino acids and biogenic amines of Egyptian salted-fermented fish (Feseekh) during ripening and storage

The aim of this study was to investigate changes in the formation of amino acids and biogenic amines in Egyptian salted-fermented fish (Feseekh) during ripening (20 days) and storage (40–60 days). The total concentration of free amino acids increased from 8 (dry weight; DW) to 72 g/kg (DW) after 60 days of storage. The predominant free amino acids were leucine, glutamic acid, lysine, alanine, valine, aspartic acid, isoleucine and citrulline. Their concentrations accounted for 68% of the total concentration of amino acids after 60 days. The total contents of biogenic amines ranged from 84 to 1633 mg/kg (DW) during the investigated period. Cadaverine was the major amine detected in Feseekh at all sampling stages and its concentration varied between 21 and 997 mg/kg (DW). The histamine content (211 mg/kg DW) only exceeded the maximum tolerance level (200 mg/kg) after 60 days. It could be concluded that Feseekh can be consumed without any health risks between 20 and 40 days but it can be hazardous after 60 days due to the biogenic amine content.     

Prediction of the rheology parameters of ripened semi-hard cheeses using fluorescence spectra in the UV and visible ranges recorded at a young stage

Storage modulus (G′), loss modulus (G″), strain, tan (δ) and complex viscosity (η*) of 20 semi-hard cheeses were measured by dynamic oscillatory analysis after 2, 30 and 60 days of ripening. On the same cheeses and at the same ages, tryptophan and riboflavin fluorescence spectra were recorded. The aim was to predict the rheology parameters of ripened cheeses from spectra recorded on these cheeses at a young stage. Using partial least square, tryptophan fluorescence spectra recorded at 20 °C on 2-days-old cheeses predicted G′, G″, strain, tan (δ) and η* measured at 80 °C on the 60-days-old cheeses with correlation coefficients (R) of 0.98, 0.97, 0.98, 0.98 and 0.97, respectively. Riboflavin fluorescence spectra gave slightly lower correlation coefficients of 0.88, 0.88, 0.92, 0.87 and 0.88, respectively. Dependent only on visible light, the riboflavin fluorescence spectra potentially provide viable and economic prediction of the rheology of ripe cheese.     

Changes in sugar,organic acid,flavonol and carotenoid composition during ripening of berries of three seabuckthorn (<Emphasis Type="Italic">Hippophae rhamnoides</Emphasis> L.) cultivars

Soluble solid, sugar, organic acid, flavonol and carotenoid content were determined in seabuckthorn berries of the three German cultivars Askola, Hergo and Leikora, collected at different harvesting times, to provide a more thorough knowledge of quality changes occurring during ripening of the berries. The main organic acids were malic (1940–4660 mg/100 g), quinic (810–2820 mg/100 g), ascorbic (180–370 mg/100 g) and citric acid (90–160 mg/100 g). In all three cultivars a marked decline in total organic acid concentration was observed during ripening. The pattern of variation of sugars, glucose (0.26–2.10 g/100 g) and fructose (0.14–0.54 g/100 g), was somewhat different among the three cultivars. In all three cultivars ascorbic acid concentration decreased during ripening. The main flavonols were isorhamnetin (350–660 mg/kg), quercetin (30–100 mg/kg) and kaempferol (2–5 mg/kg). The trends of flavonol content during ripening were quite different among the three cultivars. The main carotenoids were zeaxanthin (30–150 mg/kg), -carotene (3–50 mg/kg) and -criptoxanthin (5–19 mg/kg). The genotype seemed to affect both the extent of carotenoid accumulation and the carotenoid profile but in all three cultivars ripening was accompanied by an increase in total carotenoid concentration. The various classes of antioxidants showed quite different patterns of variation during ripening, achieving their maximum level at different harvesting dates.