Elevated concentrations of oxygen on the stability of live mussel stored refrigerated

The stability of bivalve molluscs was studied in live mussels (Mytilus galloprovincialis) packaged under modified atmospheres. Studies of physical, chemical, microbiological and sensory parameters have detailed these changes in the live packaged mussels. The highest survival was achieved at high oxygen concentrations, i.e. 75%, in the absence of carbon dioxide. The improved storage conditions promote shelf life in 80% of the packaged mussels, reaching a storage life of 6 days when held at 2–3 °C, whereas control molluscs packaged in air did not exceed 3–4 days when stored under the same conditions. Sensory analysis of cooked products from live mussels packaged under 75% oxygen:25% nitrogen were optimum throughout the period of storage. Secondly, the results for the most effective treatment were compared with those for an approximate 75–80% oxygen mixture achieved by applying partial vacuum to the packaging machine. This option employed only oxygen and decreased packaging time, which reduced mussel packaging stress by avoiding elevated vacuum conditions. It provided operational and economic advantage to commercial mussel packaging.     

pH spatial distribution model during ripening of Camembert cheese

During ripening of Camembert cheese, a soft cheese, the pH values continually change, which impacts the growth of Listeria monocytogenes. In this study, a pH distribution model suitable for the ripening phase of Camembert cheese was developed and verified. An experimental trend-based statistical model for pH using normalized time and normalized pH as variables was developed to determine the evolution of pH. The pH model showed good agreement with the mean pH measured values, i.e., the pH model was able to capture the magnitudes and trends sufficiently. The R² values for top surface, center, inner-outer side surface, and bottom surface regions’ mean measured and pH model-predicted values were 0.97, 0.95, 0.99, and 0.99, respectively.     

Protein isolation from blue mussels (Mytilus edulis) using an acid and alkaline solubilisation technique—process characteristics and functionality of the isolates

BACKGROUND: The pH shift method was developed to isolate proteins from low‐value raw materials by solubilisation at high or low pH followed by precipitation. In this paper the application of the pH shift method on isolated mussel (Mytilus edulis) meat and whole mussels is reported. RESULTS: Highest protein solubilisation was achieved at pH values of 2.6 and 12. The optimum precipitation pH values were established as around 5.8 following acid solubilisation and 5.2 following alkaline solubilisation. Protein recoveries were 430 and 580 g kg^?1 with the acid and alkaline processes respectively. Using whole crushed mussels, the corresponding recoveries were 310 and 480 g kg^?1. Process modifications to further improve protein recovery resulted in only a marginal increase. Lipid oxidation was not induced during pH shift processing, but heavy proteolysis occurred during the acid process version. Proteolysis could not be prevented by porcine plasma protein. Alkali‐produced proteins performed better in all functionality tests compared with acid‐produced proteins. The acid process removed slightly more lipids, recovered relatively more cysteine, methionine and lysine and resulted in whiter isolates. CONCLUSION: The pH shift method can be successfully used to extract functional proteins from mussels and add value to blue mussels unsuitable for human consumption (with or without shells). Copyright © 2012 Society of Chemical Industry     

Design of an Optimum Computer Vision‐Based Automatic Abalone (Haliotis discus hannai) Grading Algorithm

An automatic abalone grading algorithm that estimates abalone weights on the basis of computer vision using 2D images is developed and tested. The algorithm overcomes the problems experienced by conventional abalone grading methods that utilize manual sorting and mechanical automatic grading. To design an optimal algorithm, a regression formula and R² value were investigated by performing a regression analysis for each of total length, body width, thickness, view area, and actual volume against abalone weights. The R² value between the actual volume and abalone weight was 0.999, showing a relatively high correlation. As a result, to easily estimate the actual volumes of abalones based on computer vision, the volumes were calculated under the assumption that abalone shapes are half‐oblate ellipsoids, and a regression formula was derived to estimate the volumes of abalones through linear regression analysis between the calculated and actual volumes. The final automatic abalone grading algorithm is designed using the abalone volume estimation regression formula derived from test results, and the actual volumes and abalone weights regression formula. In the range of abalones weighting from 16.51 to 128.01 g, the results of evaluation of the performance of algorithm via cross‐validation indicate root mean square and worst‐case prediction errors of are 2.8 and ±8 g, respectively.     

Utilisation of front face fluorescence spectroscopy as a tool for the prediction of some chemical parameters and the melting point of semi-hard and hard cheeses: a preliminary study

The objective of this preliminary study was to evaluate the usefulness of front face fluorescence spectroscopy to predict some chemical parameters [pH, fat, dry matter (DM), fat in DM, total nitrogen (TN) and water soluble nitrogen (WSN)] and cheese meltability of semi-hard and hard cheeses. Dynamic testing rheology was used to determine the melting point of cheeses corresponding to the temperature at which loss tangent (tan δ) = 1. Tryptophan and vitamin A fluorescence spectra were, also, recorded on cheese samples at 20 °C. The partial least squares (PLS) regression with the leave one-out cross-validation technique was used to build up calibration models. Excellent predictions were obtained from the tryptophan and vitamin A models for fat (R ² = 0.99 and 0.97, respectively), DM (R ² = 0.94 and 0.96, respectively), fat in DM (R ² = 0.92 and 0.99, respectively), TN (R ² = 0.91 and 0.91, respectively). Excellent predictions were also obtained for WSN (R ² = 0.96) and melting point (R ² = 0.97) from vitamin A spectra, while only good predictions for these two parameters (R ² = 0.90 and R ² = 0.87, respectively) were obtained from tryptophan spectra. The results for pH were good (R ² = 0.82) and approximate (R ² = 0.76) with tryptophan and vitamin A, respectively.     

Application of Mid-infrared Spectroscopy for the Measurement of Several Quality Parameters of Alcoholic Beverages, Wine and Raki

Mid-infrared (IR) spectroscopy, which is a rapid and relatively small amount of waste producing technique, was used to predict several quality parameters of two types of alcoholic beverages, wine and raki. Mid-infrared spectra of red, rose and white wines and a traditional aniseed alcoholic beverage, raki were collected and relations were established between measured chemical parameters (pH, brix, total phenol content, anthocyanin content, titratable acidity, sugar content, electrical conductivity and some colour parameters) of these beverages and their infrared spectra using chemometric techniques. Partial least square regression provided excellent prediction of total phenol (R ²?=?0.97) and anthocyanin contents (R ²?=?0.98) of wine samples and a good prediction of pH (R ²?=?0.9), brix (R ²?=?0.92) and colour intensity (R ²?=?0.93) values were obtained. Brix, total phenol and sugar content of raki samples were also estimated very successfully (R ²?=?0.99) for raki and good prediction was obtained with pH value. Mid-IR spectroscopy in combination with chemometrics could be a promising technique for determination of several quality parameters of alcoholic beverages simultaneously and rapidly.     

Lipophilic toxin profiles detected in farmed and benthic mussels populations from the most relevant production zones in Southern Chile

Lipophilic toxins associated with diarrhoeic toxins were found in Mytilus chilensis (Blue mussels) and Aulacomya ater (Ribbed mussels). These shellfish samples were collected from Chiloe Island, Southern Chile. The samples were tested by liquid chromatography–tandem mass spectrometry (LC-MS/MS). After the analysis, four toxins were found: DTX-1, DTX-3, YTX and PTX. All toxins were identified by comparing their HPLC retention times with those of analytical standards and confirmed by LC-MS/MS. Dinophysistoxin-1 (DTX-1) and dinophysistoxin-3 (DTX-3) toxins were the major components within the mussel extracts. Nevertheless, the percentages of these toxins differed depending on the area they were collected from and/or the sampling date. The levels detected in Butacheuques Island for okadaic acid (OA) was 267?±?3.5?µg OA?eq?kg^?1 (p?<?0.05) and for DTX-3 was 183.4?±?7.5?µg?kg^?1 in ribbed mussels. Pectenotoxin (PTX) and yessotoxin (YTX) were the toxins detected in minor proportions in the toxic profile of the bivalves. The maximum concentration of YTX detected in ribbed mussels was 85.2?±?2.8?µg?kg^?1 in Mechuque Island, whereas the PTX-2 level in ribbed mussels was 82.0?±?2.4?µg?kg^?1 in Cailin Island. Analogues of YTX and PTX-2 were not detected in any of the analysed mussels, which did not support the supposed presence of isomers of toxins as a result of the enzymatic metabolism of bivalves. This study found evidence proving co-occurrence of lipophilic toxins – like PTX and YTX – with diarrhoeic toxin in samples collected in Southern Chile, which is, to date, the more complex mix of lipophilic toxins ever found in mussels samples from Southern Chile.     

Technical note: Rapid field test for the quantification of vitamin E, β-carotene,and vitamin A in whole blood and plasma of dairy cattle

Fast and easy tests for quantifying fat-soluble vitamins such as vitamin E and vitamin A, as well as β-carotene, in whole blood without a need to preprocess blood samples could facilitate assessment of the vitamin status of dairy cattle. The objective of this study was to validate a field-portable fluorometer/spectrophotometer assay for the rapid quantification of these vitamins in whole blood and plasma of dairy cows and calves. We measured the concentrations of vitamin E and β-carotene in whole blood and plasma from 28 dairy cows and 11 calves using the iCheck test (BioAnalyt GmbH, Teltow, Germany) and compared the results with the current analytical standard (HPLC) in 2 independent laboratories, one at the University of Potsdam (Germany) and at one at DSM Nutritional Products Ltd. (Kaiseraugst, Switzerland). For vitamin A, the HPLC measurements were done only in the laboratory in Germany. The whole-blood concentrations of vitamin E as determined by iCheck (blood-hematocrit-corrected) ranged from 1.82 to 4.99 mg/L in dairy cows and 0.34 to 3.40 mg/L in calves. These findings were moderately correlated (R² = 0.66) with the values assessed by HPLC in dairy cattle (cows + calves). When calves were excluded, the correlation was higher (R² = 0.961). The β-carotene and vitamin A values obtained by the reference method HPLC were highly correlated with the iCheck methods in whole blood (R² = 0.99 and 0.88, respectively). In plasma, we observed strong correlations between the concentrations assessed by iCheck and those of HPLC for vitamin E (R² = 0.97), β-carotene (R² = 0.98), and vitamin A (R² = 0.92) in dairy cattle (cows + calves). For vitamin E, β-carotene, and vitamin A, we compared the relationship between the differences obtained by the iCheck assay and the HPLC measurements, as well as the magnitude of measurements, using Bland–Altman plots to test for systematic bias. For all 3 vitamins, the differences values were not outside the 95% acceptability limits; we found no systematic error between the 2 methods for all 3 analytes.     

Incidence of persistent contaminants through blue mussels biomonitoring from Flekkefjord fjord and their relevance to food safety

ABSTRACT

Dredging activities can lead to the re-suspension of contaminated sediments, resulting in a potential hazard for the whole ecosystem and also for human health. Six-month active biomonitoring was performed in order to monitor the trends of different classes of both legacy (organochlorine – OCPs – and organophosphate (OPs) compounds and polychlorinated biphenyls – PCBs) and emerging (polybromodiphenyl ethers – PBDE – and per- and polyfluoroalkyl substances – PFASs) organohalogen compounds, as well as polycyclic aromatic hydrocarbons (PAHs), in blue mussel (Mytilus edulis spp.) specimens transplanted at different depths in the Flekkefjord fjord. Such biomonitoring was performed to evaluate the efficacy of sediment restoration activities and to check for the potential environmental risk for the biota and food safety for human seafood. Negligible contamination by OCPs, OPs, PBDEs and PFASs was noted in mussels over the 6-month biomonitoring, while a notable increase in the concentrations of PCBs and PAHs occurred in mussels transplanted at 15 m depth in three sampling sites within the fjord, as a consequence of an undersea landslide which occurred during restoration activities. Levels of PCBs and PAHs suggested a potential risk for mussel predators and also for the human health, as they exceeded the limit set by the European Commission for the consumption of bivalve molluscs. These results confirm the reliability of active biomonitoring to flank dredging activities aimed at ecosystem restoration in order to monitor the trend of contaminants and to estimate the potential risk for the aquatic communities and human health.     

Comparison of in vitro degradation of temperate forages using the gas production and filter bag techniques

BACKGROUND: Two of the most promising in vitro techniques for dynamic forage evaluation are the gas production (GP) and filter bag (FB) techniques. To improve our understanding of how these techniques describe the dynamic degradation of forages, 20 temperate forage samples were analysed by each method at different time points during a 96 h incubation period. The results of the recordings were fitted to a biphasic Michaelis–Menten model describing the degradation of rapidly and slowly degrading forage fractions. RESULTS: GP and disappearance from the FB measurements were correlated at all time points from 6 to 96 h (R² = 0.27–0.74), except at the 24 h incubation point. When GP was transformed into organic matter degradation (OMD), there was an even stronger correlation (R² = 0.54–0.75) between the techniques at all intervals. Comparison of the parameters from the Michaelis–Menten model resulted in correlations (R² = 0.83) between the sizes of the estimated forage fractions, but not between parameter determining the rates of their degradation. CONCLUSIONS: Both the GP and FB techniques have the potential to estimate the degradation of individual feed fractions in forages. Further studies in which the in vitro parameters are evaluated against livestock data, are needed to confirm the findings of this study, however. Copyright © 2007 Society of Chemical Industry     

HYDRATION KINETICS OF LUPIN (LUPINUS ALBUS) SEEDS

The hydration kinetics of lupin (Lupinus albus) seeds was studied by soaking in water at temperatures of 20, 30, 40 and 50C (±1C) in constant‐temperature water bath for 9 to 12 h. The weight gain due to the hydration process was determined in terms of moisture content (% dry basis). Water absorption rate was high at the early stage of hydration (20–60 min depending on temperature) followed by a decreased rate and finally approaching equilibrium condition. Peleg's equation adequately described the hydration characteristics of lupin seeds under the experimental condition (R² = 0.96 to 0.99). The Peleg rate constant k₁ decreased from 2.537 to 0.241 min/%, while Peleg capacity constant k₂ increased from 0.0036 to 0.0070/% significantly (P < 0.05) with an increase in temperature from 20 to 50C, demonstrating that the water absorption rate increased and water absorption capacity decreased with increase in temperature. The temperature dependence of k₁ and k₂ was described by Arrhenius type equation with R² values of 0.98 and 0.97, respectively, and activation energy of 60.44 kJ/mol. The agreement between experimental and estimated values of the hydration data (R² = 0.97 to 0.99) confirmed that Peleg's equation could be used to describe the hydration characteristics of lupin seeds under the experimental conditions considered.     

Matrix effect on paralytic shellfish toxins quantification and toxicity estimation in mussels exposed to Gymnodinium catenatum

Paralytic shellfish toxins were quantified in whole tissues of the mussel Mytilus galloprovincialis exposed to blooms of the dinoflagellate Gymnodinium catenatum in Portuguese coastal waters. A validated liquid chromatography method with fluorescence detection, involving pre-chromatographic oxidation was used to quantify carbamoyl, N-sulfocarbamoyl and decarbamoyl toxins. In order to test for any matrix effect in the quantification of those toxins, concentrations obtained from solvent and matrix matched calibration curves were compared. A suppression of the fluorescence signal was observed in mussel extract or fraction in comparison to solvent for the compounds dcGTX2?+?3, GTX2?+?3 and GTX1?+?4, while an enhancement was found for C1?+?2, dcSTX, STX, B1, dcNEO and NEO. These results showed that a matrix effect varies among compounds. The difference of concentrations between solvent and matrix matched calibration curves for C1?+?2 (median?=?421?ng?g^?1) exceeded largely the values for the other quantified compounds (0.09–58?ng?g^?1). Those differences were converted into toxicity differences, using Oshima toxicity equivalence factors. The compounds C1?+?2 and dcNEO were the major contributors to the differences of total toxicity in the mussel samples. The differences of total toxicity were calculated in ten mussel samples collected during a 10-week blooming period in Portuguese coastal lagoon. Values varied between 53 and 218?µg STX equivalents kg^?1. The positive differences mean that the estimated toxicity using solvent calibration curves exceed the values taking into account the matrix. For the toxicity interval 200–800?µg STX equivalents kg^?1 an increase was found between 44 and 28%.     

Hyperspectral imaging for the investigation of quality deterioration in sliced mushrooms (Agaricus bisporus) during storage

In this study, the potential application of hyperspectral imaging (HSI) for quality prediction of white mushroom slices during storage at 4 °C and 15 °C was investigated. Mushroom slice quality was measured in terms of moisture content, colour (CIE Lightness, L* and yellowness, b*) and texture (hardness, H and chewiness, Ch). Hyperspectral images were obtained using a pushbroom line-scanning HSI instrument, operating in the wavelength range of 400–1,000 nm with spectroscopic resolution of 5 nm. Multiple linear regression (MLR) and Principal Component Regression (PCR) models were developed to investigate the relationship between reflectance and the various quality parameters measured. 20 optimal wavelengths for quality prediction were selected after performing an exhaustive search for the best subsets of predictor variables on a calibration set of 84 samples. PCR applied to the set of optimal wavelengths gave the best performance as compared to MLR and PCR on the entire wavelength range. When applied to an independent validation set of samples, PCR models developed on the calibration set were capable of predicting moisture content with RMSEP of 0.74% w.b. and R ² of 0.75, L* with RMSEP of 0.47 and R ² of 0.95, b* with RMSEP of 0.66 and R ² of 0.75, H with RMSEP of 0.49 N and R ² of 0.77 and Ch with RMSEP of 0.27 N and R ² of 0.72. Virtual images showing the distribution of moisture content on the mushroom surface were generated from the estimated PCR model. Results from this study could be used for the development of a non-destructive monitoring system for prediction of sliced mushroom quality.     

Assessing beef carcass tissue weights using computed tomography spirals of primal cuts

More than 800 beef primal cuts from 44 Aberdeen Angus and Limousin-cross steers carcasses were scanned using spiral computed tomography (CT) and dissected. Thresholds for the segmentation of fat, muscle and bone in the CT spirals were estimated with the objective of assessing the weight of these tissues in the primal cuts and in the entire carcasses. Thresholds were estimated using half of the dataset (DBE) and then validated in the other half (DBV). Automatic image analysis procedures were used to assess tissue weights. The R² of the regression between primal tissue weight by dissection and CT were high in both datasets for fat (DBE, 0.89; DBV, 0.92), muscle (DBE, 0.99; DBV, 0.99) and bone (DBE, 0.95; DBV, 0.97). The estimation of total carcass tissue weights were also very accurate for the three tissues (R² values of 0.95 to 0.96), indicating that CT scanning may deliver very accurate information on beef carcass composition faster and with lower cost than physical dissection and without damaging or depreciating the primal joints.     

Determination of aflatoxin risk components for in-shell Brazil nuts

A study was conducted on the risk from aflatoxins associated with the kernels and shells of Brazil nuts. Samples were collected from processing plants in Amazonia, Brazil. A total of 54 test samples (40?kg) were taken from 13 in-shell Brazil nut lots ready for market. Each in-shell sample was shelled and the kernels and shells were sorted in five fractions: good kernels, rotten kernels, good shells with kernel residue, good shells without kernel residue, and rotten shells, and analysed for aflatoxins. The kernel?:?shell ratio mass (w/w) was 50.2/49.8%. The Brazil nut shell was found to be contaminated with aflatoxin. Rotten nuts were found to be a high-risk fraction for aflatoxin in in-shell Brazil nut lots. Rotten nuts contributed only 4.2% of the sample mass (kg), but contributed 76.6% of the total aflatoxin mass (µg) in the in-shell test sample. The highest correlations were found between the aflatoxin concentration in in-shell Brazil nuts samples and the aflatoxin concentration in all defective fractions (R ^2?=?0.97). The aflatoxin mass of all defective fractions (R ^2?=?0.90) as well as that of the rotten nut (R ^2?=?0.88) were also strongly correlated with the aflatoxin concentration of the in-shell test samples. Process factors of 0.17, 0.16 and 0.24 were respectively calculated to estimate the aflatoxin concentration in the good kernels (edible) and good nuts by measuring the aflatoxin concentration in the in-shell test sample and in all kernels, respectively.     

Shrinkage and quality characteristics of whole fruit of Chinese jujube (Zizyphus jujuba Miller) in microwave drying

Drying characteristics of whole fruit Chinese jujube was studied as distinct from fruit slices. Shrinkage, density, vitamin C, colour and rehydration of Chinese jujube were measured in microwave drying at power level of 1.2, 1.67 and 2.5 W/g (dry base, db). Unlike fruit slices or lumps where, no matter at the beginning or at the end of drying, shrinkage volume typically equals the volume of removed water, ratio of the shrinkage volume to the volume of removed water of Chinese jujube could range from 2 to 2.6 at the beginning of drying, and at the end of drying, it could be 1.15 for higher microwave level (2.5 W/g, db), whereas, for lower power level (1.2 W/g, db), it was about 1. Unlike shrinkage curves in hot air drying that could be described with a three‐segment linear model, shrinkage curves in microwave drying could be well described with a cubic polynomial (R² > 0.99). When compared with the low power level (1.2 W/g, db), higher microwave power level(2.5 W/g, db) increased by 87.9% of the retention of vitamin C, 14.6% of the density and 8.7% of the extent of browning, decreased by 12.9% of the soluble solids content.     

Evaluation of in-line absorption photometry to predict consistency of concentrated tomato products

This study evaluated the correlation between optical density as measured by absorption photometry, water-insoluble solids (WIS) and consistency as measured by the Bostwick consistometer for a variety of concentrated tomato products. Linear regression analysis indicated a linear correlation (R²=0.97) between optical density and WIS content in diluted tomato paste, a linear correlation (R²⩾0.92) between optical density and consistency in various commercial tomato products and a linear correlation (R²=0.93) between optical density and consistency during commercial production of tomato puree made from ripe tomatoes. The optical density appeared to be unaffected by product temperature and flow rate. Potential limitations of in-line absorption photometry to monitor and control tomato product consistency are briefly discussed.     

Mathematical models of pretreatment processes to utilize purple-fleshed potato (<Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.) peels for anthocyanin extraction

The effect of particle size on the extraction rate of anthocyanin from Solanum tuberosum L. (purple-fleshed potato) peels (PFPPs) using the stagnant single-stage batch extraction system was investigated. Core pretreatment processes such as drying and grinding were quantitatively evaluated using mathematical models. The drying behavior of PFPP was successfully described using thin layer models (Page model and Midilli-Kucuk model). The effective diffusion coefficient of drying temperature at 40°C was determined to be 1.67x10^?12 m²/s. The grinding time to obtain particles of a specific size was accurately estimated using the grinding kinetic model (R ²=0.97). The extraction rate of anthocyanin increased as the particle size decreased; however, when the particle size was 0.15mm, the anthocyanin content decreased. Our study demonstrated that the grinding kinetic model is useful to estimate the grinding time to produce an optimum particle size for anthocyanin extraction from PFPP.     

Geographical and annual variation in lipophilic shellfish toxins from oysters and mussels along the south coast of Korea

To better understand critical aspects of diarrhetic shellfish poisoning (DSP) occurrence in a chief producing region of bivalves in Korea, the geographical and annual variation of DSP toxins and other lipophilic toxins in mussels (Mytilus galloprovincialis) and oysters (Crassostrea gigas) were investigated by liquid chromatography-tandem mass spectrometry in an area on the south coast of Korea from 2007 to 2009. The total lipophilic shellfish toxin (LST) levels in bivalves showed geographical and annual variations. LSTs were detected mostly in the hepatopancreas of mussels from Jinhae Bay throughout the entire year, except in November and December of 2007, but were almost undetectable in all samples during the entire year in 2009. The peak DSP toxin (okadaic acid plus dinophysistoxin 1) levels in the hepatopancreas of mussels from Jinhae Bay and the Tongyeong region were 945.3 and 37.6 ng/g, respectively. The DSP toxin content was about 10 times higher in mussels than in oysters collected from the same region. The major toxins in bivalves were okadaic acid and dinophysistoxin 1; however, pectenotoxin 2 or yessotoxin was occasionally detected as a major component. The results of a quantitative analysis of phytoplankton showed that Dinophysis acuminata was the most probable source of the LSTs, with the exception of yessotoxin. When the highest DSP toxin level was measured (945.3 ng/g in the hepatopancreas of mussels from Jinhae Bay), the toxin concentration in whole mussel tissue was calculated to be 114.0 ng/g. The calculated highest DSP toxin level in whole oyster tissue from both regions was 15.0 ng/g. The calculated maximum toxicities in whole mussel and oyster tissues were lower than the regulatory limit (160 to 200 ng/g) in Korea, the European Union, and the United States. Korean oysters (242 samples) and mussels (214 samples) were thus deemed safe for consumption. But because such variation was detected in a relatively small area of the coast, it is possible that at some locations or during a specific period LST levels could exceed the standard and a few consumers could be at risk of experiencing DSP.     

Formation of Resistant Starch in Corn Starch and Estimation of its Content from Physicochemical Properties

The effect of autoclaving temperatures (100‐120°C) on yields of enzyme‐resistant starch (RS) from normal corn starch and the physicochemical properties of autoclaved‐cooled starches were studied. The RS content increased linearly with increasing autoclaving temperature (R² = 0.993) and the number of autoclaving‐cooling cycles at an autoclaving temperature of 120°C. The effect of the number of autoclaving‐cooling cycles was more pronounced than that of temperature. The swollen starch weight measured at 60°C slightly increased as the RS content increased, and then drastically decreased with the continous increase of the RS content (R² = ‐0.969). As the RS content increased, all parameters of Rapid Visco Analyser (RVA) viscosity except breakdown decreased. Log RVA peak viscosity showed a negative correlation with the RS content (R² = ‐0.986). The enthalpy in the differential scanning calorimetry (DSC) endotherm corresponding to the transitions of RS linearly increased as the RS content increased (R² = 0.988). The RS content of the heat‐treated starch estimated from the relationship between RS content and swollen starch weight at 60°C, log RVA peak viscosity or DSC enthalpy was in good agreement with that determined with the standard method.