Storage stability of pineapple slices preserved by combined methods

Storage stability during 3 months was evaluated for pineapple slices preserved by combined methods (blanching for 1 min with saturated vapour, a_w reduction by osmotic concentration in sucrose syrup, pH reduction by addition of citric acid, and the addition of 1000 parts per million (ppm) of potassium sorbate and 150 ppm of sodium bisulphite). Pineapple slices were microbiologically sound and their moisture content, °Brix, pH and a_w remained almost constant during storage with mean values of 71.8%, 26.1, 3.65 and 0.978, respectively. Total sulphite and potassium sorbate concentrations of the pineapple slices were reduced during storage at 5 and 25 °C, being final concentrations 51% and 38% and 63% and 48% of the initial concentrations, respectively. Colour, texture and sensory evaluation revealed that there were no significant (P < 0.05) changes between samples stored at 5 or 25 °C. Good overall acceptability (initial mean score 7.21) of preserved pineapple slices even after 3 months storage at 25 °C (final mean score 7.02) was observed.     

Physicochemical characteristics and sensory optimisation of pineapple leather snack as affected by glucose syrup and pectin concentrations

Effects of glucose syrup (2%, 4%, and 6%) and pectin (0.5%, 1.0%, and 1.5%) concentrations on physicochemical characteristics and sensory acceptability of machine‐formed pineapple leather snack were investigated. Changes in glucose syrup and pectin concentrations significantly affected velocity of forming and total soluble solids content of pineapple paste, but did not affect thickness of pineapple leathers. Increasing pectin concentrations generally increased redness (a*) and yellowness (b*), and hardness (tensile force and work) while decreased moisture content and a_w of pineapple leathers. Two most acceptable pineapple leathers were prepared with 6% glucose syrup and 0.5–1.0% pectin. Increasing pectin concentration from 1.0% to 1.5% negatively affected toughness acceptability, which was attributed to reduced moisture and a_w, and increased tensile force and work. The optimum formulation range consisted of 3.5–6.0% glucose syrup and 0.5–1.0% pectin, yielding products with acceptability scores of 6.7–7.3 (on a 9‐point hedonic scale) for appearance, sourness, sweetness, overall‐taste, toughness and overall‐liking.     

Search for predictors of cooking quality of marrowfat pea (Pisum sativum L) cultivars

The grain from 116 marrowfat pea breeding lines was assessed subjectively using current visual methods and then analysed objectively for L*a*b* colour, hydration capacity and cooking quality. The data show that the current method of selecting genotypes by subjective methods is not able to select marrowfat peas for specific processing uses. However, an objective measure, the ?a* value of the dry grain, was a very good predictor (p < 0.001) for the hydrated and cooked green colour. Cultivars which have a high hydration coefficient may be more suitable for canning and deep frying because they hydrate to a larger size, while cultivars with a high bulk density and a darker green grain are more suitable for use as extrusion products. © 2001 Society of Chemical Industry     

Effects of deep‐fat frying temperature on antioxidant properties of whole wheat doughnuts

The total phenolic (TP) content, phenolic acid composition and in vitro antioxidant capacity of whole wheat doughnuts fried at 120–180 °C were determined to identify the effects of frying temperature. Significant differences (P < 0.05) in TP content were observed between doughnuts fried at different temperatures. The TP content of doughnuts decreased significantly when doughnuts were deep‐fat fried. The TP content of doughnuts increased with elevation with frying temperatures. These increases in TP content of doughnuts were also detected in the determination of individual phenolic compounds using HPLC. DPPH radical and iron‐chelating capacity of deep‐fat fried doughnuts exhibited increases with elevation of frying temperature from 120 to 180 °C. Deep‐fat frying at 120 °C lowered lipid peroxidation inhibition capacity of doughnuts prepared from both refined flour and whole‐grain meals and increased consistently with increased frying temperature from 120 to 180 °C. Moderate deep‐fat frying temperature would increase the content and activity of antioxidants of doughnuts.     

Thermal stability of corn oil flavoured with Thymus capitatus under heating and deep-frying conditions

BACKGROUND: The thermal stability of corn oil flavoured with thyme flowers was determined and compared with that of the original refined corn oil (control). The oxidative stability index (OSI) was measured and samples were exposed to heating (30 min at 150, 180 and 200 °C) and deep‐frying (180 °C). Changes in peroxide value (PV), free fatty acid (FFA) content, specific absorptivity values (K₂₃₂ and K₂₇₀), colour and chlorophyll, carotenoid and total phenol contents were monitored. RESULTS: The OSI and heating results showed that thyme incorporation was effective against thermal oxidation based on the increased induction time observed for the flavoured oil (6.48 vs 4.36 h), which was characterised by lower PV, FFA content, K₂₃₂ and K₂₇₀ than the control oil after heating from 25 to 200 °C, with higher red and yellow colour intensities and chlorophyll, carotenoid and total phenol contents. The deep‐frying test showed the accelerated deterioration of both oils in the presence of French fries. CONCLUSION: Compared with the control oil, the thyme‐flavoured oil showed improved thermal stability after heating. This could be attributed to the presence of thyme pigments and antioxidant compounds allowing extended oil thermal resistance. Copyright © 2011 Society of Chemical Industry     

Effect of maltodextrin weight fraction on the amorphous state and critical storage conditions of freeze-dried juices

Diagrams relating to water activity (a_w), equilibrium moisture content (X_w) and glass transition temperature (Tg) are valuable tools for predicting amorphous fruit powders' storage procedure and stability. Thus, T_g–a_w–X_w diagrams were constructed to characterise the amorphous state and define the critical values of water content (X_wc) and water activity (a_wc) of freeze-dried juices of strawberry, pineapple, kiwi and prickly pear prepared with maltodextrin at the dry mass fraction (W_MD) of 0, 0.4 and 0.8. The T_g and sorption data were fitted with a polynomial equation and the Guggenheim–Anderson–de Boer (GAB) model respectively. A Tukey test was performed to evaluate the difference between critical values of the powders (P < 0.05). The a_wc and X_wc increase with W_MD and depend on the chemical composition of the powders. The highest critical values were found in pineapple powders, ranging from 0.174 to 0.632 and 0.029 to 0.142 dry basis (d.b.), and the lowest ones in kiwi juice powders ranging from 0.029 to 0.550 and 0.013 to 0.129 (d.b.). For W_MD of 0.8, however, regardless of juice composition, stable powders in an amorphous state were obtained up to an a_w of 0.52 at 25°C.     

A chromametric method for the rapid assessment of deep frying oil quality

A rapid chromametric method was developed for the assessment of deep frying oil quality based on the strong correlation between colour index and total polar compounds in deep frying oil. Colour indices of frying oil samples, measured by chromameter, decreased significantly during frying and were strongly correlated with frying time (r ≥ 0.95, p < 0.001). Colour indices of a set of oil samples taken from 0 to 80 h of deep frying were also significantly correlated with total polar compounds of the same samples determined using the official method of the American Oil Chemists' Society (r = 0.96, p < 0.001). The equation for conversion of the colour index (x) to the content of total polar compounds (y) in an oil sample is y = 0.0174x² ? 2.9506x + 124.34. In addition, colour indices of 10 different types of frying oils were strongly correlated with the corresponding contents of total polar compounds in the oils with samples taken from 0 to 80 h of deep frying in duplicate (r = 0.95, p < 0.001, n = 220). The results of colour index analyses agreed well with the results of chemical and sensory analyses of the frying oils tested. This chromametric method is rapid, convenient and reliable. Copyright © 2003 Society of Chemical Industry     

Influence of hot‐air treatment,superatmospheric O2 and elevated CO2 on bioactive compounds and storage properties of fresh‐cut pomegranate arils

The impact of heat treatment using hot air (HT 45 °C and 55 °C for 1 h) and two active modified atmosphere packaging (MAP) conditions of high oxygen atmosphere (HOA: 80 kPa O₂, 20 kPa N₂) and high CO₂ atmosphere (HCA: 20 kPa CO₂, 80 kPa N₂), individually or combined, on the antioxidant capacity, polyphenols, vitamin C content, total anthocyanins, polyphenoloxydase (PPO) activity and shelf life of fresh‐cut (FC) pomegranate arils stored for 14 days at 4 °C was studied. The results indicate that HT 45 °C along with HOA inhibited PPO activity and prevented loss of antioxidant capacity, vitamin C and phenolic compounds in arils, in comparison with control and HT 55 °C. All treatments reduced the accumulation of anthocyanins, but HCA‐treated arils lost more anthocyanins besides having worse a* colour parameter values. No significant differences in titrable acidity (TA) and total soluble solids (TSS) were observed between treatments. The combination of HOA and HT 45 °C enhanced the benefits of applying each treatment separately and could be useful to improve and extend postharvest life of pomegranate FC arils.     

Adsorption isotherm and heat of sorption of osmotically pretreated and air-dried pineapple slices.

Slabs (1 ×1.5 ×5 cm) of pineapple were immersed in sucrose solutions of 52°B, 60°B and 68°B (w/w) at 25 °C for 12 h. Osmosed pineapple slices were subsequently air-dried at 60 °C for 72 h. Adsorption isotherms of osmo-dried pineapple slices were determined at 20 °C and 40 °C, using the gravimetric-static method. Isotherms were modeled using Brunnauer, Emmet and Teller (BET) and Guggenheim Anderson de Boer (GAB) models. Heat of moisture adsorptions were calculated from adsorption data using the Clausius-Clapeyron equation. Adsorption isotherms of osmo-oven-dried pineapple followed the characteristic type III (J-shape) isotherms. Equilibrium moisture contents at constant water activity decreased with increasing temperature, but crossing of the isotherms occurred at a_w~ 0.86. GAB and BET monolayer moisture decreased with increased temperature. The net isosteric heat increased with decreased moisture content, and decreased with increased sucrose pretreatment concentration of pineapple slices.     

Reduction in hydroxymethylfurfural content in ‘churros’, a Spanish fried dough,by vacuum frying

This work explores the advantages of vacuum frying of ‘churros’, a Spanish dough pastry, compared to standard deep‐fat frying. Oil uptake, texture change, colour development, nonenzymatic browning and hydroxymethylfurfural (HMF) concentration were analysed at different frying conditions. The results obtained during vacuum frying at 100, 120 and 140 °C and 21 kPa were compared with those obtained at atmospheric pressure at 140 and 180 °C. For the same final water content, the vacuum fried ‘churros’ showed no significant differences in the fat uptake compared to those fried at atmospheric pressure (P > 0.05). However, the vacuum fried dough had a much crunchier texture. The evolution of the CIELab a* coordinate and the browning measurement at 280 nm show that vacuum frying is able to slow down the development of browning tones. Furthermore, products can be obtained with an HMF content <1 mg kg^?1 of dry dough.     

Growth and Enterotoxin A Production by Staphylococcus aureus in Precooked Bacon in the Intermediate Moisture Range

Different water activities were obtained in precooked bacon by varying the frying time. Water activity (a_w) correlated best to the moisture, salt and protein content. When stored aerobically at 37°C, S. aureus A100 was capable of rapid growth in precooked bacon at a a_w of 0.84 or above, whereas at 20°C a a_w of 0.88 or higher was required. Under anaerobic storage at 37°C, growth was observed at a a_w of 0.90, and at 20°C slight growth was noted at a a_w of 0.91. The increase in the minimal a_w required for aerobic growth at the lower temperature was reflected in the differences between the isotherms obtained at 37°C and 20°C. The maximum populations achieved were higher for samples stored aerobically. Enterotoxin A (19–821 ng/g) was found in all aerobically stored samples where growth occurred. Enterotoxin A (38–109 ng/g) was also found in all anaerobically incubated samples where the population of S. aureus increased more than one logarithmic cycle.     

低场核磁共振技术检测大豆煎炸油品质的研究

煎炸食品一直受到消费者的喜爱,煎炸食品的质量与煎炸油的品质息息相关。传统评价煎炸油品质的理化方法检验费时、操作繁琐、易接触有毒试剂,不能实现在线检测。低场核磁共振技术(LF-NMR)是一种快速、准确、无损的检测方法。以大豆油和添加抗氧化剂大豆油为原料、薯条为煎炸食品,对大豆煎炸油进行理化指标及低场核磁检测。通过研究LF-NMR检测参数S_(21)及t_(2w)与煎炸时间、酸价、羰基价、极性组分含量的相关性,发现S_(21)与2种大豆煎炸油的上述指标均呈正相关、t_(2w)与之均呈负相关,且相关性良好,相关系数在0.905 8~0.994之间。说明利用低场核磁共振技术检测的S_(21)和t_(2w)可以有效地反映大豆煎炸油品质的变化,且不受抗氧化剂的影响。     

CHANGES IN TEXTURAL CHARACTERISTICS OF PANEER IN READY-TO-EAT CANNED PANEER CURRY DURING STORAGE

Paneer is an Indian soft cheese obtained by coagulating hot milk using citric acid or vinegar, pressing the hot coagulum and cooling by dipping in chilled water. In this study, paneer curry with a water activity (A_w) of 0.95 and a pH of 5.0 was prepared using ingredients like tomatoes, onions, cream, milk powder, curds and different spices, then canned at an F value of 0.80 (lethality). The product was stored at 15, 30 and 45C, and change in textural characteristics during storage was studied. Cohesiveness and chewiness increased, but hardness decreased. These changes were attributed to continued changes in texture initiated by frying of paneer and canning process. These were also linked to Maillard browning which progressed during storage as measured by hydroxymethylfurfural content. These changes were found to be slower vis‐à‐vis those observed in the product, which was sterilized at conventional F value of 15.0 (control) (A_w = 0.98 and pH 5.2).     

Effect of superheated steam prefrying treatment on the quality of potato chips

Superheated steam drying (SSD) was used as a prefrying treatment prior to deep‐fat frying for potato slices. The effect of SSD at 130, 150 or 180 °C and steam velocity of 2.0 m s^?1 on the fat uptake, colour and texture of fried potato chips was evaluated; microstructure and degree of starch gelatinization were also evaluated to help explain the fat uptake results. SSD and frying yielded potato chips with the fat content from 0.263 ± 0.002 to 0.304 ± 0.002 kg kg^?1 (d.b.), while frying without SSD led to chips with the fat content as high as 0.359 ± 0.003 kg kg^?1 (d.b.). SSD did not promote starch gelatinization. Lower fat uptake was correlated to modified surface structure and lower moisture content of potato slices prior to frying. Frying with/without SSD pretreatment yielded potato chips of similar hardness, crispness and lightness. On the other hand, SSD significantly increased redness and yellowness of the fried chips.     

Effects of different pre-freezing blanching procedures on the physicochemical properties of Brassica rapa leaves (Turnip Greens, Grelos)

For optimal freeze storage, green vegetables should first be blanched. The present study compared four different procedures for the blanching of grelos (leaves of Brassica rapa L.): steaming for 2 min, immersion in boiling water for 2 min, immersion in boiling water containing 1% citric acid for 1 min, and immersion in boiling water containing 5% citric acid for 1 min. After blanching, the grelos were stored for up to 120 days at ?18 °C, with sampling at two‐weekly intervals for analysis of physicochemical properties (ash weight, vitamin C content, pH, acid value, moisture content and CIE_L*a*b* colour variables). In almost all respects steam blanching gave the best results: notably, vitamin C losses were markedly lower, while moisture content and colour remained closer to those of the fresh product.     

Effect of blanching and drying treatments on quality of bamboo shoot slices

The enzymes activity, texture, pectin, microstructure and colour change in bamboo shoots (Dendrocalamus latiflorus) were examined to evaluate the effect of blanching and drying treatments on quality of bamboo shoot slices (BSS). Peroxidase (POD), phenylalanine ammonia‐lyase and polyphenol oxidase in BSS will become completely inactive at 95 °C for 6‐, 9‐ and 12‐min blanching treatments, respectively. The hardness and protopectin (PP) content decreased after the blanching treatment. Meanwhile, the content of water‐soluble pectin increased initially and then decreased gradually during the blanching. After the blanching treatment, the L* and a* of BSS decreased, while b* increased, ΔE > 2. The hardness of rehydrated BSS decreased by 43.57% after freeze drying (FD), which, however, decreased more after hot air drying (HAD). The pectin of rehydrated BSS was also determined to explain the hardness change in BSS. The BSS acquired similar microstructure of fresh samples after FD, while microstructure of BSS was severely damaged after HAD. The colour of BSS changes significantly after drying treatment. However, FD can maintain better colour of BSS than HAD. The results may provide a reference for industrial production of BSS.     

Radical scavenging and anti‐proliferative capacity of three freeze‐dried tropical fruits

Tropical fruits are rich in antioxidant and anticancer phytochemicals, but their nutraceutical potential could be enhanced by drying technologies. Mango cv. Ataulfo, papaya cv. Maradol and pineapple cv. Esmeralda ripe pulps were freeze‐dried (?42 °C, 0.12 torr, 48 h) and their physicochemical and phytochemical profile, radical scavenging and antiproliferative capacity evaluated. The content of soluble solids, phenolic compounds and ascorbic acid was higher in mango (16.1^oBrix, 9.9 mg GAE per g and 9.6 mg g^?1) than in papaya/pineapple, but the later had more flavonoids (0.45 ± 0.05 mg QE per g). A fruit‐specific phenolic profile was detected by HPLC‐ESI‐QTOF‐MS, being shikimic (mango), chlorogenic (papaya), and protocatechuic (pineapple) acids the most abundant. Mango was the strongest radical scavenger and showed antiproliferative capacity (IC₅₀, μg mL^?1) in RAW 264.7 (100.7), HeLa (193.1) and L929 (138.5) cell lines. Papaya and pineapple extracts showed no antiproliferative activity. Freeze‐dried mango is a ready‐to‐eat functional food with better cancer preventing properties than papaya or pineapple.     

Effects of spray drying conditions on the physicochemical and antioxidant properties of the Gac (Momordica cochinchinensis) fruit aril powder

Gac fruit aril has an attractive orange red colour and very high level of carotenoids, giving it exceptional antioxidant properties. However, spray drying of this material has not been successful and malto dextrin is considered as a suitable drying aid to preserve its colour and antioxidant properties. This paper reports the effects of inlet drying air temperature (120, 140, 160, 180 and 200 °C) and maltodextrin addition (10%, 20% and 30%) on the physicochemical and antioxidant properties of the Gac aril powder. Moisture content and bulk density, colour characteristics, total carotenoid content (TCC), encapsulation efficiency and total antioxidant activity (TAA) were significantly affected by maltodextrin concentration and the inlet air temperatures. However, pH, a_w and water solubility index were not significantly influenced by the spray drying conditions. Overall, a good quality Gac powder in terms of colour, TCC and TAA can be produced by spray-drying at inlet temperature of 120 °C and adding maltodextrin concentration at 10% w/v.     

Influence of quinoa roasting on sensory and physicochemical properties of allergen‐free,gluten‐free cakes

The objectives of this study were to determine pasting properties of non‐roasted (NR) and roasted quinoa (RQ) and to investigate the effect of RQ on consumer acceptance and physicochemical properties of an allergen‐free, gluten‐free cake formulation. Quinoa seeds were roasted at 177 °C for 15 (R15), 30 (R30) and 45 min (R45), and flours were analysed for pasting properties. Five cakes including a commercial chocolate cake (CCC) and cakes made with NR and RQ flours were evaluated for preference by fifty panelists. Quality parameters included colour, water activity, moisture content, firmness, weight and height. Peak and final viscosity increased with roasting time. The NR cake had the highest sensory scores for appearance, colour and texture. On flavour and overall acceptability, CCC was the highest. Regarding quality data, CCC, NR and R15 cakes had similar L* values, while CCC had the lowest a*, b*, a_w, moisture content and firmness values.     

Effect of Treating of Squid with Sodium Chloride in Combination with Oxidising Agent on Bleaching,Physical and Chemical Changes During Frozen Storage

Pink discolouration is a problem faced in the squid processing industry, and some treatments have been implemented to tackle such a problem. The study aimed to elucidate the impact of NaCl in combination with oxidising agents on the quality changes of squid during frozen storage. The effects of treatment of pink squid using 3% (w/v) NaCl solution containing oxidising agents (0.05–0.5% (w/v) H₂O₂ or 0–10 ppm NaOCl) on colour and chemical and physical changes of squid during frozen storage were investigated. The lowest decreases in a*, b* values, ∆E* and ∆C* of squid were obtained with the treatment using 3% NaCl solution containing 0.5% H₂O₂. Nevertheless, NaOCl (0–10 ppm) had no impact on a* and b* values. During frozen storage at −18 °C for 10 weeks, fresh squid, pink squid samples without and with treatments with 3% NaCl solution containing 0.5% H₂O₂ had no changes in a* and b* values during frozen storage. Nevertheless, thiobarbituric acid reactive substances value, disulphide bond content, thaw drip and shear force were more pronounced in treated pink squid, compared with pink squid without treatment (control) and fresh squid, respectively, during the extended storage (p < 0.05). Higher denaturation and aggregation of muscle proteins during frozen storage were observed in treated pink squid than that without treatment and fresh squid, respectively. Therefore, pink squid treated with oxidising agent was prone to protein aggregation and denaturation during the extended frozen storage, though it could lower the pink colour. Therefore, fresh squid without treatment using oxidising agent is recommended for production of frozen squid with negligible loss in quality during extended storage.