The texture of low calorie grape juice jelly

 In this work the production of grape juice jellies with a low methoxyl pectin was studied. Availability of this kind of jelly will increase the range of dietetic products and is a promising alternative use for grapes surplus to the needs of the enological industry. The formulation of the jellies was optimized by response surface methodology (RSM), using as independent variables total sugar content (20 – 50°Brix), low methoxyl pectin content (0.5 – 1.5%) and processing temperature (55 – 90°C) at five levels. The dependent variable was the overall balance (B), a response obtained from sensory analysis. B was chosen from a series of sensory attributes evaluated by a test panel and the data treated by principal component analysis (PCA). The resulting polynomial equation (R ² = 0.92) showed the maximum value for B to occur for a jelly produced with 38°Brix of total sugar, 1.2% of low methoxyl pectin and a processing temperature of 69°C. The sensory-optimized jelly was objectively characterized for texture and dynamic rheological behaviour. Received: 2 October 1996 / Revised version: 7 January 1997     

DEHA-plasticized PVC for retail packaging of fresh meat

 A selection of frequently consumed meat products were packed in two commercial types of plasticized PVC film with declared plasticizer compositions of 11 and 21% di-(ethylhexyl)adipate (DEHA), respectively. The meat products were analysed for DEHA after packaging and storage until their “use by” date. Pretreatment of the meat, including cutting, chopping, cooking and packaging, was performed according to normal practice in a Danish supermarket. All samples contained DEHA. In general the investigation showed that a high fat content in or at the surface of the meat and/or a high storage temperature and/or repeated repackaging with new film during treatment gave rise to the greatest amount of DEHA migration from the film into the meat. No significant differences in DEHA migration could be seen when comparing the two films, although they were quite different in terms of plasticizer composition. The DEHA concentration at the “use by” date in fresh lean trimmings and slices of pork leg was 1 – 2 mg/kg, whereas neck and strip loin with some fat at the surface contained about 5 – 10 mg/kg. More fatty types of meat such as minced beef and pork with 18 – 20% fat, packaged once in plasticized PVC, contained around 20 mg DEHA/kg. When previously packaged loin was cut into steaks or chops, repackaged, minced and repackaged again, the DEHA concentration doubled to around 40 mg/kg. Finally if meatballs were then produced from the said mince, repackaged and stored at 65°C for 24 h, the DEHA concentration reached 100 mg/kg. Based on the evaluations of DEHA given by the EU Scientific Committee for Food, the National Food Agency considers concentrations of DEHA in foods higher than 18 mg/kg to be unacceptable. Received: 24 June 1997     

Optimization of stepwise blanching of frozen-thawed potato tissues (cv. Monalisa)

 Response surface methodology was used to compare the effect of temperature and time of the first step of blanching on compression, shear, tension and stress-relaxation parameters of frozen-thawed potato tissues. A central, composite rotatable design was used to study the effects of variation in levels of temperature (52.93–67.07  °C) and time (15.86–44.14 min) on rheological parameters. Blanching temperature was the most important factor affecting the mechanical properties tested. The models fitted for the apparent modulus of elasticity in compression, maximum tension force, and relaxed force in the first cycle (F _r1); all had R ²>0.85 (P≤0.01) and were used for doing predictions. Optimum conditions were with in the ranges of temperature (60–65  °C) and time (25–35 min) used for each factor. In the experimental verification of the models at 65  °C during 30 min, the lowest percentage residual between experimental and predicted values was obtained for F _r1 (0.644), which was therefore the most appropiate parameter for detecting the firming effect that the pectinesterase activity produced on frozen potato tissues as a consequence of stepwise blanching under these conditions. Received: 3 February 1999 / Revised version: 12 April 1999     

DEHA-plasticized PVC for retail packaging of fresh meat

 A selection of frequently consumed meat products were packed in two commercial types of plasticized PVC film with declared plasticizer compositions of 11 and 21% di-(ethylhexyl)adipate (DEHA), respectively. The meat products were analysed for DEHA after packaging and storage until their “use by” date. Pretreatment of the meat, including cutting, chopping, cooking and packaging, was performed according to normal practice in a Danish supermarket. All samples contained DEHA. In general the investigation showed that a high fat content in or at the surface of the meat and/or a high storage temperature and/or repeated repackaging with new film during treatment gave rise to the greatest amount of DEHA migration from the film into the meat. No significant differences in DEHA migration could be seen when comparing the two films, although they were quite different in terms of plasticizer composition. The DEHA concentration at the “use by” date in fresh lean trimmings and slices of pork leg was 1 – 2 mg/kg, whereas neck and strip loin with some fat at the surface contained about 5 – 10 mg/kg. More fatty types of meat such as minced beef and pork with 18 – 20% fat, packaged once in plasticized PVC, contained around 20 mg DEHA/kg. When previously packaged loin was cut into steaks or chops, repackaged, minced and repackaged again, the DEHA concentration doubled to around 40 mg/kg. Finally if meatballs were then produced from the said mince, repackaged and stored at 65°C for 24 h, the DEHA concentration reached 100 mg/kg. Based on the evaluations of DEHA given by the EU Scientific Committee for Food, the National Food Agency considers concentrations of DEHA in foods higher than 18 mg/kg to be unacceptable. Received: 24 June 1997     

Walnut, microbial transglutaminase and chilling storage time effects on salt-free beef batter characteristics

Response surface methodology (RSM) was used to assess the effect of walnut content (W), microbial transglutaminase/sodium caseinate (MTG/C) content and storage time (ST) at 3 °C on water- and fat-binding properties, texture profile analysis and dynamic rheological characteristics of salt-free beef batters. Walnut addition favoured the binding properties and elastic modulus (G′) of raw meat batters (20 °C); however, increasing amounts of walnut caused G′ to decrease at 70 °C. MTG/C had no effect on binding properties, but it did cause increases in the hardness of cooked meat batters and in the rheological properties of both raw and cooked samples. The products formulated with MTG/C and stored for up to 11 days at 3 °C presented good gel-forming ability; however, binding properties were poor, so that other ingredients like walnut were needed to improve the binding properties of the products.     

Optimization analysis by capillary electrophoresis of thiamine in meat: comparison with high perfomance liquid chromatography

 A new capillary electrophoresis (CE) method for the analysis of thiamine in meat is proposed. Samples were submitted to acidic and enzymatic hydrolysis and the extracts were purified using ethanol and an ion exchange column. The thiamine content was determined by CE using 100 mM sodium tetraborate, 50 mM sodium phosphate (pH 7.6), 50 mM sodium dodecyl sulphate and 10% isopropyl alcohol as a separation buffer solution. The analysis was carried out at 15 kV and 50  °C in a 70 cm effective length× 75 μm i.d. fused-silica capillary using on-column UV detection at 254 nm and 7 s injection time (27 nl injection volume). The results obtained by CE for thiamine contents in meat were compared to those obtained by HPLC using an ion-pair reverse phase column with post-column derivatization and fluorescence detection. Received: 24 August 1998 / Revised version: 21 January 1999     

Identification of biomarkers of meat tenderisation and its use for early classification of Asturian beef into fast and late tenderising meat

BACKGROUND: The objective of this work was to study the post‐mortem evolution of potential biomarkers (µ‐calpain activity and proteolytic profile) of meat tenderisation in bovine longissimus dorsi (LD) muscle from several biotypes coming from two beef breeds (‘Asturiana de los Valles’ and ‘Asturiana de la Montaña’) and showing different levels of muscular hypertrophy (mh/mh, mh/+, + /+). RESULTS: LD samples were taken at 2, 12, 24 and 48 h and 3, 7, 14 and 21 days post‐mortem. The presence of muscular hypertrophy produced a faster rate of pH decline, faster exhaustion of µ‐calpain activity and earlier occurrence of proteolytic changes. Changes in the electrophoretic pattern of some peptides from sarcoplasmic (glyceraldehyde‐3‐phosphate dehydrogenase) and myofibrillar (troponin T and troponin I) muscle extracts within the first 24 h significantly correlated with meat toughness and allowed accurate discrimination of meat products into two groups: (1) fast tenderising meat, coming from mh‐biotypes, and (2) late tenderising meat, from normal (+/+) biotypes. CONCLUSION: Early monitoring (within 24 h after slaughter) of selected biomarkers in LD muscle allowed accurate prediction of ultimate meat toughness and could be used in the meat industry as a tool for early classification of beef into fast and late tenderising meat. Copyright © 2012 Society of Chemical Industry     

Changes of the volatile fraction of cooked chicken meat during chill storing: results obtained by the electronic nose in comparison to GC-MS and GC olfactometry

 In the present study the changes of the volatile fraction of heat-treated chicken meat in the course of chill storage were observed by using different techniques. It was the aim of the study to compare the results obtained by the new technique of the electronic nose to those gained by GC-MS and GC olfactometry (using comparative aroma extract dilution analysis). Chill storage at 4  °C of cooked chicken meat showed large increases in concentration as well as in flavour dilution factors of typical lipid oxidation products such as saturated and unsaturated aldehydes as well as alkylated furans, especially within the first 24 h. These results were confirmed by cluster analysis of selected lipid oxidation products. Analysing the chicken meat with an electronic nose showed results which are highly correlated with those obtained by commonly used and well-known gas chromatographic techniques.     

Decomposition of sinigrin by methanol/ammonia/water treatment in model systems and mustard (Brassica nigra L.) seed meal

 Sinigrin (allylglucosinolate) was stored at 20  °C, 40  °C, and 60  °C in solutions containing 10% ammonia in 95% methanol (CH₃OH/NH₃/H₂O). The individual samples were analyzed for their contents of sinigrin, its decomposition product allyl isothiocyanate (AITC) and other reaction products. The major reaction products were allyl thiourea, methyl ester of N-allyl thiocarbamoyl acid and allyl cyanide. A newly identified decomposition product of sinigrin was ethylcyanide. Defatted Brassica nigra seed meal was treated by the CH₃OH/NH₃/H₂O mixture to simulate the procedure used for rape and mustard seed meal detoxification. suspensions of the meal in the above mixture of solvents were heated at 20  °C, 40  °C and 60  °C, respectively. The major reaction products were the same as those arising from sinigrin. Minor products identified were 4-hydroxybenzyl isothiocyanate formed from sinalbin and 2-hydroxy-butenyl cyanide which arises from progoitrin. In all cases, AITC was very rapidly decomposed. Mechanisms explaining sinigrin decomposition are presented and discussed. Received: 3 May 1999     

软包装即食小龙虾关键工艺对质地的影响

为探究关键工艺对小龙虾产品品质的影响,以小龙虾为原料,通过质构分析、低场核磁共振与感官评价等方法,研究保水剂（1%、1.5%无磷保水剂和1.2%碳酸氢钠+4%海藻糖）、干燥条件（温度:70、80、90 ℃;时间:0.5、1、1.5、2 h）及杀菌条件（100、115、121 ℃;15 min）对其水分、质构特性及感官评分的影响,优化软包装即食小龙虾加工工艺并探究水分与质地的关系。结果表明,保水剂（1.2%碳酸氢钠＋4%海藻糖）添加增加了虾肉中的不易流动水和自由水含量,并显著提高虾肉的持水性,降低虾肉硬度（P < 0.05）,且随干燥温度的升高和时间的延长,虾肉水分含量显著减少（P<0.05）,硬度和咀嚼性增加;而过高的杀菌温度破坏虾肉内部纤维结构,导致虾肉咀嚼性差。结果表明虾肉制品的水分含量显著影响其产品品质,同时确定了即食小龙虾加工工艺最佳条件,即添加保水剂（1.2%碳酸氢钠+4%海藻糖）,70 ℃下干燥1 h,115 ℃杀菌15 min时虾肉感官品质较佳,吡嗪类化合物增加,具有炸虾特有的风味。研究结果能为软包装即食小龙虾加工产品品质的提升及产业化提供理论参考。     

The extraction of yellow gentian root (Gentiana lutea L .)

 Several solvents have been investigated for the preparation of bitter compounds of gentian roots (Gentiana lutea L.) for food applications. The highest concentrations of the bitter compounds, amarogentin and gentiopicroside, were obtained with ethanol : water 55 : 45 (v/v), propylene glycol: water 30 : 70 (v/v) and ethanol: propylene glycol: water 20 : 20 : 60 (v/v/v). Enzyme treatment prior to solvent extraction gave a greater extract yield (3.5%) but the amarogentin and gentiopicroside concentrations remained the same. The volatile fraction was affected by the solvent used through the formation of esters of organic acids from the plant. Received: 22 January 1997 / Revised version: 18 March 1997     

Principal component analysis to study the effect of temperature fluctuations during storage of frozen potato

 The effects of temperature fluctuation ranges, number of fluctuations carried out, and packaging during frozen storage on the texture of potato tissue in terms of compression, shear, and tension rheological parameters were assessed through data generated according to a factorial design using principal component analysis (PCA). Five ranges of fluctuation (–24  °C to –18  °C, –18  °C to –12  °C, –12  °C to –6  °C, –24  °C to –12  °C and –18  °C to –6  °C) applied 2, 4, 8, 16, 24, and up to 32 times on unpacked and pre-packed frozen potatoes, were considered. The controls were unpacked and prepacked frozen tissues thawed immediately without undergoing any fluctuation. In addition, several geometrical, technological, and chemical parameters were determined. PCA showed that maximum shear force, F_s was the best rheological parameter for differentiation of the structural damage and softening occurring in the tissue at each treatment, which was closely related to its duration, TT _d . PCA did not permit complete discrimination between the five fluctuation ranges, but it clearly separated samples subjected to –18  °C/–6   °C from those subjected to –24  °C/–18  °C. Frozen samples undergoing up to four fluctuations formed a separate cluster from those undergoing a higher number. Analysis also clearly separated unpacked from pre-packed samples in response to slower freezing rates reached in the latter. Received: 17 December 1999     

Microbiological and physico-chemical characterisation of deep spoilage in Spanish dry-cured hams and characterisation of isolated Enterobacteriaceae with regard to salt and temperature tolerance

 The microbiological and physico-chemical characteristics of dry-cured Spanish "serrano" hams with deep spoilage were compared to unspoiled hams, and the evolution of similar characteristics was studied during the early curing stages of previously refrigerated or frozen hams. The results suggest a relationship between deep spoilage and the presence of Enterobacteriaceae, caused by insufficient NaCl concentrations during curing. Strains of Serratia liquefaciens, Enterobacter cloacae and Proteus vulgaris, which comprised the most frequently isolated species of enterobacteria from spoiled hams, were therefore characterised in a model system in order to examine their ability to grow in different NaCl concentrations at different temperatures. Strains isolated from normal hams during early curing stages and from the production environment were included for comparison. The results showed that all strains were able to grow in 7% NaCl at 5  °C, and that strains isolated from spoiled hams did not differ from those isolated from normal hams and from the environment. The NaCl tolerance of strains isolated from spoiled hams was closely linked to incubation temperature, and a reduction in temperature from 5  °C to 2  °C reduced the tolerance significantly. Received: 23 December 1998     

Properties of refrigerated ground beef treated with potassium lactate and sodium diacetate

BACKGROUND: Ground meat is product that perishes easily and therefore various preservatives are applied to prolong its shelf life. The aim of this study was to investigate the effect of potassium lactate and sodium diacetate (Protec K‐DI preparation) on general proteolytic activity, protein degradation, texture, colour and water‐holding capacity of vacuum‐packaged ground beef. RESULTS: The activity of endogenous proteolytic enzymes, and hence the rate of protein hydrolysis changed significantly (P < 0.05) during refrigerated storage. The proteolysis was more intensive in the meat with the preservative than in a control sample. According to the results of SDS‐PAGE, the level of myosin in ground beef decreased with increasing storage time, whereas the preservative did not have a significant effect (P > 0.05) on these changes. However, its impact was the most significant in the case of tropomyosin and troponin T content, as well as changes of 30 kDa protein content. The preservative as well as the increase in storage time influenced an increase in content of polypeptides, peptides and some amino acids in the samples, and had an inhibiting effect on unfavourable changes in ground beef hardness. The preservative addition allowed the meat to maintain desired meat colour, and the main pigment during refrigerated storage was oxymyoglobin (MbO₂). CONCLUSION: Results showed that the Protec K‐DI preparation can be useful in minced meat production as a good stabiliser of colour and texture despite the increase observed in proteolytic activity after the preservative addition. Copyright © 2007 Society of Chemical Industry     

Aggregation of minced hake during frozen storage

 Aggregation in minced hake muscle (Merluccius merluccius) during storage at –20  °C was studied in conditions where there is progressive deterioration of functionality and texture as measured by apparent viscosity and shear resistance. Natural actomyosin was extracted with 0.6 M NaCl over a period of 49 weeks. Insoluble residue was extracted successively with 2% sodium dodecyl sulphate (SDS) and 2% SDS plus 5% β-mercaptoethanol (ME) solutions. SDS–polyacrylamide gel electrophoresis was performed on the extracted fractions. The results showed a 75% decrease in 0.6 M NaCl extractability by the end of the storage period. Initially the remaining precipitate was all extracted in 2% SDS and although the amount extracted in this solution increased as storage time progressed, its proportion decreased, accounting for as little as 40–50% of the protein aggregate by the end of storage. The proteins most involved in formation of the aggregate not extracted in 0.6 M NaCl were myosin and actin. Neither of these proteins was fully recovered in the fractions extracted with 0.6 M NaCl, 2% SDS, or 2% SDS plus 5% ME, and therefore it was inferred that they were forming part of the aggregates, bound by covalent bonds. Received: 17 November 1998     

Applicability of lactic acid and nisin to improve the microbiological quality of cold-smoked rainbow trout

 The effect of lactic acid and nisin whey permeate on the microbiological and sensory quality of cold-smoked rainbow trout was studied. Lactic acid and whey permeate were mixed with salt solution and injected into fish fillets in concentrations of up to 2.5 g/kg lactic acid, 30 g/kg whey permeate and 20 g/kg sodium chloride. After smoking at 28  °C for 6 h the fillets were sliced, vacuum packed and stored at 3  °C. The aerobic and anaerobic/facultative anaerobic counts were measured after 1, 8, 15, 22 and 29 days of storage. The influence of the treatment on the sensory characteristics was analysed after 8 and 22 days by sensory profiling. A triangle test was used in order to ascertain at which stage the sensory quality of the samples changed during storage. Bacterial counts of smoked fish stored for 29 days were lowest in those samples containing a combination of lactic acid, sodium chloride and nisin whey permeate. Lactic acid alone did not affect the odour or flavour characteristics of the fish but did affect their texture as determined by sensory evaluation making it less elastic when stored at +3  °C for 8 days. A combination of lactic acid and nisin whey permeate enhanced the characteristic fishy flavour of the product. Differences between treatments in elasticity and fishy flavour were not detected after 22 days of storage. According to the triangle test, the samples from all treatments remained unchanged over the first 15 days. Received: 23 March 1998 / Revised version: 19 June 1998     

Freeze- and bake-stable glazing for confectionery products characterized by differential scanning calorimetry

 A freeze- and bake-stable glazing for pastry has been developed based on an optimization procedure in which starches and carrageenans as thickening agents were combined with sugar alcohols and sodium tripolyphosphate. Instrumental gloss measurement on test biscuits showed that glazing consisting of 3% ι-carrageenan and 15% sorbitol (w/w) had maximal gloss. This was confirmed on pastry products. In contrast to glazing based on mannitol, no crystallization problems were encountered for this glazing, for which differential scanning calorimetry showed that some water freezes at –3  °C followed by freezing of supercooled encapsulated water at –20  °C and by a glass transition at –61  °C. During normal frozen storage of preglazed, nonbaked pastry, the glazing is thus in a nonstable rubbery state with a limited resistance to water migration and ice crystal formation, which can be substantially improved by storage at temperatures below –61  °C. Received: 1 March 1999 / Revised version: 19 April 1999     

Application of multivariate statistical methods to extend the authenticity control of flavour constituents of apple juice

 The distribution of 15 aroma constituents, including the (R)- and (S)-enantiomers of ethyl 2-methylbutanoate, in 30 commercially available and laboratory prepared apple juices was evaluated by multivariate statistical methods. Principal component analysis and cluster analysis revealed ethyl 3-methylbutanoate, 3-methylbutyl acetate and (R)-ethyl 2-methylbutanoate as key components for the differentiation of apple juices. In freshly pressed and some commercial juices ethyl 3-methylbutanoate and 3-methylbutyl acetate were not present, and the (S):(R) ratio of ethyl 2-methylbutanoate was found to be >99 : 1%. Another group of commercial products was separated in which the amounts of ethyl 3-methylbutanoate and 3-methylbutyl acetate exceeded 1 μg/l and 180 μg/l, respectively, and in which the (S):(R) ratio of ethyl 2-methylbutanoate was <97 : 3%. The statistical data confirmed the high selectivity of apple fruit tissue in biosynthesizing 2-methylbutyl and 2-methylbutanoate esters, and could also be used to extend the results of enantio-multidimensional gas chromatography and other authenticity analyses. Received: 20 April 1998 / Revised version: 23 June 1998     

A lab-on-a-chip-based multiplex platform to detect potential fraud of introducing pig,dog, cat,rat and monkey meat into the food chain

Food forgery has posed considerable risk to public health, religious rituals, personal budget and wildlife. Pig, dog, cat, rat and monkey meat are restricted in most religions, but their sporadic adulteration are rampant. Market controllers need a low-cost but reliable technique to track and trace suspected species in the food chain. Considering the need, here we documented a lab-on-a-chip-based multiplex polymerase chain reaction (PCR) assay for the authentication of five non-halal meat species in foods. Using species-specific primers, 172, 163, 141, 129 and 108-bp sites of mitochondrial ND5, ATPase 6 and cytochrome b genes were amplified to detect cat, dog, pig, monkey and rat species under complex matrices. Species-specificity was authenticated against 20 different species with the potential to be used in food. The targets were stable under extreme sterilisation (121°C at 45 psi for 2.5 h) which severely degrades DNA. The assay was optimised under the backgrounds of various commercial meat products and validated for the analysis of meatballs, burgers and frankfurters, which are popular fast food items across the globe. The assay was tested to detect 0.1% suspected meats under commercial backgrounds of marketed foods. Instead of simplex PCR which detects only one species at a time, such a multiplex platform can reduce cost by at least fivefolds by detecting five different species in a single assay platform.     

A time temperature integrator for particulated foods: thermal process evaluation

 A time temperature integrator (TTI) was developed by immobilizing Bacillus stearothermophilus spores in a cylindrical particle consisting of an alginate-starch-mushroom purée. The particle showed homogeneous spore distribution, and when heated over a temperature range of 121 – 130° C negligible spore leakage was observed after the thermal process. The experimental data on spore survivor levels obtained for each temperature-time combination were compared with theoretical predictions using a mathematical model. The results showed a good correlation between the experimental and theoretical data. All these results provide evidence that this artificial particle could be a very reliable TTI for monitoring the thermal impact on micro-organisms during validating sterilization processes in continuous aseptic systems. Received: 25 February 1997