Intermediate Moisture Foods Research Articles

A survey of the physico-chemical and microbiological quality of different pastırma types: a dry-cured meat product

Pastırma, a traditional Turkish dry-cured meat product, is categorized as an intermediate-moisture food. It is produced from whole muscle and/or muscles obtained from certain parts of beef and buffalo carcasses. This is the first study dealing with some physico-chemical (fatty acid composition, moisture, ash, total fat, residual nitrite, pH and colour) and microbiological properties of sırt, şekerpare, bohça and kuşgömü pastırma types. Significant differences were determined among the pastırma types in moisture (P < 0.01), ash (P < 0.01), salt (P < 0.01), total fat (P < 0.01), residual nitrite amounts (P < 0.05), stearic acid (P < 0.05), L* (P < 0.01) and a* (P < 0.05) values, total aerobic mesophylic bacteria (P < 0.01), lactic acid bacteria (P < 0.01) and Micrococcus/Staphylococcus (P < 0.01) counts. No difference (P < 0.05) was observed in average pH and b* value and fatty acid composition among the pastırma types except for stearic acid. However, the salt amount in all samples was above the maximum acceptable limit. Pseudomonas counts in 48.39% of pastırma samples and Enterobacteriaceae counts in 4.84% of pastırma samples were > 2.00 log colony-forming units per gram (CFU g−1).

Mechanisms of Repair of Low Water Activity and pH-Injured Z ygosaccharomyces rouxii YSa40 in Glycerol and Sucrose/CPB Liquid Holding System

This study demonstrated injury of a 2-day-old stressed Zygosaccharomyces rouxii YSa40 (Xerotolerant yeast) cells in 0.64 water activity (aw)/pH 3.5 glycerol (GLY)/CPB stress system. The effects of metabolic inhibitors on repair of the low aw injury were also investigated by resuscitating the low aw injured cells over a time period of 24 h in a suitably designed 0.87 aw/pH 3.5 GLY and sucrose (SUC)/citrate phosphate buffer (CPB) liquid holding (LH) system. On use of appropriate inhibitory concentrations of metabolic inhibitors, repair processes in low aw-injured populations involved cell membrane and cell wall synthesis, protein and DNA synthesis and adenosine triphosphate (ATP) from glycolysis, but without oxidative phosphorylation. During 24 h of LH period, ATP was vital to maintain the cell viability of the surviving population on 0.94 aw/pH 3.5 sugars/basal medium agar (lactic acid); while allowing its injured population to repair at low aw injury in the LH system. This oxidative phosphorylation pathway can provide insight into various mechanisms of repair in low aw-injured yeast cells. Practical Applications Results generated in this study are expected to benefit food industries where problems related to recovery of injured microbes are involved, especially in Intermediate Moisture Food products.

Assessment of the physical, mechanical, and moisture-retention properties of pullulan-based ternary co-blended films

Multi-component substances made through direct blending or blending with co-drying can form films on the surfaces of intermediate moisture foods (IMFs), which help retain moisture and protect food texture and flavor. An IMF film system based on pullulan, with glycerol serving as the plasticizer, was studied using alginate and four different types of polysaccharides (propyleneglycol alginate, pectin, carrageenan, and aloe polysaccharide) as the blend-modified substances. The physical, mechanical, color, transparency, and moisture-retention properties of the co-blended films with the polysaccharides were assessed. A new formula was established for the average moisture retention property, water barrier, tensile strength, elongation at break, and oxygen barrier property of the ternary co-blended films using the Design Expert software. The new model established for moisture content measurement used an indirect method of film formation on food surfaces by humectants, which should expedite model validation and allow a better comprehension of moisture transfer through edible films.

Influence of Chemical Preservatives on Survival and Growth of Z ygosaccharomyces Rouxii YSa40 in Glycerol-Based Pineapple Model Systems and Intermediate Moisture Pineapple Products

This study investigates the growth and survival of Zygosaccharomyces rouxii (a xerotolerant yeast) in the glycerol-based intermediate moisture food (IMF) pineapple model systems (0.87 aw/pH 4.1 GLY/CPB/BM and 0.87 aw/pH 4.5 GLY/CPB/BM) containing various levels of chemical preservatives (sodium benzoate, potassium metabisulphite and potassium sorbate) used singly or in combination. Comparing the two different levels used singly, the three preservatives were more effective in inhibiting yeast growth at a higher 0.1% (w/w) than at a lower 0.01% (w/w) level of the preservative, with potassium metabisulphite showing most inhibitory effect at 0.1% (w/w) level. When the combinations of two to three preservatives at 0.01% (w/w) level were evaluated, a synergistic growth inhibitory effect was achieved. Combination of three preservatives was more effective compared to a combination of any of the two preservatives. At different pH values, preservatives used singly or in combination were shown to be more effective in inhibiting growth at lower pH value of 4.1 than at a higher pH value of 4.5. Taste evaluation of six formulated acidified 0.87 aw/pH 3.7 glycerol-based IMF pineapple products showed all formulations to be acceptable. However, microbial challenge studies showed that of all the six taste-acceptable glycerol-based IMF pineapple products, only the product that contained 0.1 % (w/w) potassium metabisulphite was shelf-stable up to 6 months of storage at 30C and may be commercially viable. Practical Applications The results of this study will benefit the food industry wherein preservation of intermediate moisture pineapple-based products or other intermediate moisture products is required to overcome contamination problems, especially from xerotolerant yeasts.

Strategies to increase the stability of intermediate moisture foods towards Zygosaccharomyces rouxii: The effect of temperature, ethanol, pH and water activity, with or without the influence of organic acids

Intermediate moisture foods (IMF) are in general microbiologically stable products. However, due to health concerns consumer demands are increasingly forcing producers to lower the fat, sugar and preservatives content, which impede the stability of the IMF products. One of the strategies to counteract these problems is the storage of IMF products at lower temperatures.Thorough knowledge on growth/no growth boundaries of Zygosaccharomyces rouxii in IMF products, also at different storage temperatures is an important tool for ensuring microbiologically stability. In this study, growth/no growth models for Z. rouxii, developed by Vermeulen et al. (2012) were further extended by incorporating the factor temperature. Three different data sets were build: (i) without organic acids, (ii) with acetic acid (10,000 ppm on product basis) and (iii) with sorbic acid (1500 ppm on product basis). For each of these data sets three different growth/no growth models were developed after 30, 60 and 90 days.The results show that the influence of temperature is only significant in the lower temperature range (8–15 °C). Also, the effect of pH is negligible (pH 5.0–6.2) unless organic acids are present. More specific, acetic acid had only an additive effect to ethanol and aw at low pH, whereas sorbic acid had also an additive effect at the higher pH values. For incubation periods longer than 30 days the growth/no growth boundary remained stable but enlarged gradually between day 60 and 90, except for the lower temperature range (<12 °C) where the boundary shifts to more stringent environmental conditions.

Effect of the Local Microenvironment on Survival and Thermal Inactivation of Salmonella in Low- and Intermediate-Moisture Multi-Ingredient Foods

Multi-ingredient foods having low- or intermediate-moisture characteristics may pose a special challenge to process design and validation. Ingredients of these foods can create local microenvironments that may have a distinct impact on pathogen survival and processing requirements. In this study, two model systems, each consisting of 80% commercial peanut butter (P) and 20% nonfat dry milk powder (M), were formulated to be identical in composition, but different in the source of the Salmonella contamination as originating in either the ingredient P or M. Immediately after inoculation, Salmonella showed a 2.0-log reduction when M was the contaminated ingredient compared with a 0.6-log reduction when P was the contaminated ingredient. This pattern of survival was consistent with the single-ingredient control containing only M (2.5-log reduction) or only P (0.7-log reduction), suggesting that the immediate proximity of cells is determined by the contaminated ingredient in the model system. After 5 weeks of storage, the survival rates of Salmonella in the two systems remained different, i.e. a 4- and 2-log reduction resulted in the system with M or P as the contaminated ingredient, respectively. Furthermore, thermal inactivation efficacies also differed significantly between the two systems. Fourier transform infrared spectroscopy demonstrated the nonhomogeneous distribution of water, lipid, and protein, indicating that varied local microenvironments were present and likely affected the behavior of the pathogen. The impact of the microenvironment on inactivation and survival of Salmonella was further confirmed in a butter cookie formulation in which Salmonella was inoculated via four different ingredients. This study shows that the local microenvironment in low- and intermediate-moisture foods affects Salmonella survival and thermal inactivation. The ingredient source of the contamination should be taken into account for process design and validation to ensure the safety of the product.

Delivery of probiotic bacteria in long life ambient stable foods using a powdered food ingredient

Purpose – The authors aim to report a novel encapsulation technology for probiotic bacteria, through which L. casei CRL431 cells have been successfully delivered in shelf stable dry and intermediate moisture foods. Design/methodology/approach – Manufacturing of the probiotic ingredient involved a proprietary technique using combination of controlled fermentation of the L. casei CRL431 cells, encapsulation in a food grade matrix and drying under controlled parameters. Findings – The developed ingredient was stored at 25°C for a period of 12 months. The loss in cell viability was 1.9 log cfu g-1 after 12 months and maintained at 8.3 log cfu g-1. In vitro gastric juice and bile salts incubation revealed that the probiotic cells were better protected within the encapsulated than in the free form. The survival of the encapsulated cells was 5.0 and 2.1 log cycles higher than free cells in gastric juice and bile salt solution respectively. Fortification of probiotic bacteria did not have any negative impact on the sensory qualities of the foods mentioned above. Research limitations/implications – The developed technology is only applicable for fortifying dried or intermediate moisture foods with beneficial probiotic bacteria. The water activity of the products needs to be ranged from 0.2 to 0.5. A higher moisture contained food will lead to bacterial proliferations, product spoilage and loss in storage viability of the fortified probiotic cells. Practical implications – A general guideline issued by FAO/WHO states that any good effect of probiotic bacteria on human health can be obtained only if consumed at a level of 10^7 to 10^8 viable cells per day. Delivery of such a concentration of live probiotic cells is particularly challenging in the case of long shelf life foods. As shown in the results, the authors' probiotic powder is able to deliver over 100 million live cells per gram after 12 months of ambient storage. Even the foods fortified with this powder are able to deliver over 1 million cells per gram after six months of ambient storage. Social implications – The developed technology rightly identified the gap for fortifying probiotic bacteria into foods stored under ambient conditions which is a real hindrance to reach out to consumers particularly in the developing countries where refrigerated supply chain and storage are not yet established in an efficient way. It is believed that millions of people in developing countries with a tropical climate would be benefited with the goodness of probiotic bacteria using the help of this technology. Originality/value – The research work presented here is completely original and in-house research output of the Riddet Institute, Massey University, New Zealand. A successful commercialization of this new novel technology is deemed to be of very high value to any institution.

Storage Stability of a Commercial Hen Egg Yolk Powder in Dry and Intermediate-Moisture Food Matrices

Quality loss in intermediate-moisture foods (IMF) such as high-protein nutrition bars (HPNB) in the form of hardening, nonenzymatic browning, and free amino group loss is a general concern for the manufacturers. To measure the extent of quality loss over time in terms of these negative attributes, through changing the ratio by weight between two commercial spray-dried hen egg powders, egg white (DEW) and egg yolk (DEY), the storage stability of 10 IMF systems (water activity (aw) ∼ 0.6) containing 5% glycerol, 10% shortening, 35% protein, and 50% sweetener (either maltitol or 50% high-fructose corn syrup/50% corn syrup (HFCS/CS)) were studied. Additionally, the storage stability of the DEY powder itself was investigated. Overall, during storage at different temperatures (23, 35, and 45 °C), the storage stability of DEY in dry and IMF matrices was mainly controlled by the coaction of three chemical reactions (disulfide bond interaction, Maillard reaction, and lipid oxidation). The results showed that by replacing 25% of DEW in an IMF model system with DEY, the rate of bar hardening was significantly lower than that of the models with only DEW at all temperatures due to the softening effect of the fat in DEY. Furthermore, the use of maltitol instead of HFCS/CS in all bar systems not only resulted in decreased hardness but also drastically decreased the change in the total color difference (ΔE*). Interestingly, there was no significant loss of free amino groups in the maltitol systems at any DEW/DEY ratio.

Storage Stability of Food Protein Hydrolysates—A Review

In recent years, mainly due to the specific health benefits associated with (1) the discovery of bioactive peptides in protein hydrolysates, (2) the reduction of protein allergenicity by protein hydrolysis, and (3) the improved protein digestibility and absorption of protein hydrolysates, the utilization of protein hydrolysates in functional foods and beverages has significantly increased. Although the specific health benefits from different hydrolysates are somewhat proven, the delivery and/or stability of these benefits is debatable during distribution, storage, and consumption. In this review, we discuss (1) the quality changes in different food protein hydrolysates during storage; (2) the resulting changes in the structure and texture of three food matrices, i.e., low moisture foods (LMF, aw < 0.6), intermediate moisture foods (IMF, 0.6 ≤ aw < 0.85), and high moisture foods (HMF, aw ≥ 0.85); and (3) the potential solutions to improve storage stability of food protein hydrolysates. In addition, we note there is a great need for evaluation of biofunction availability of bioactive peptides in food protein hydrolysates during storage.

Storage stability of hen egg white powders in three protein/water dough model systems

In recent years, due to the specific health benefits associated with bioactive peptides and the reduction of protein allergenicity by enzymatic hydrolysis, the utilisation of protein hydrolysates in the intermediate-moisture food (IMF) market, such as high protein nutrition bars (HPNB), has significantly increased. Currently, no reported study is related to the storage stability of dried hen egg white (DEW) and its hydrolysates (HEW) in an IMF matrix. Therefore, three DEW/HEW dough model systems (100%HEW+0%DEW, 75%HEW+25%DEW and 50%HEW+50%DEW) were established using two commercial spray-dried egg white powders to study the effect of temperature and fraction of HEW on these IMF models (water activity (aw): ∼0.8). During storage at three different temperatures (23, 35 and 45°C) for 70days, the selected physicochemical properties of the dough systems were compared. Overall, kinetic analysis showed an apparent zero-order model fit for the change in the colour (L∗), fluorescence intensity (FI) and hardness, as a function of time, for different dough model systems. As expected, the L∗, FI and hardness increased as a function of time mainly due to the Maillard reaction. The amount of free amino groups decreased, with an increase in rate of loss, as temperature increased in the 100%HEW+0%DEW model. When DEW was substituted for some HEW, the regeneration of the free amino groups after loss was observed as a function of time. Furthermore, when the percentage of HEW was decreased, the incidence of mouldy samples occurred sooner, which indicates that HEW has some antimicrobial ability, especially in the 100%HEW+0%DEW system where mould growth did not occur.

Effect of Fructose and Glucose on Glycation of β-Lactoglobulin in an Intermediate-Moisture Food Model System: Analysis by Liquid Chromatography–Mass Spectrometry (LC–MS) and Data-Independent Acquisition LC–MS (LC–MSE)

To evaluate the effect of glucose and fructose on the glycation of β-lactoglobulin (β-Lg) in intermediate-moisture food (IMF), model systems consisting of β-Lg, glucose/fructose/sorbitol, glycerol, and water were established. All systems were stored at 25 and 35 °C for 2 months. The progress of the Maillard reaction and the mass change of β-Lg were investigated by the browning assay and gel electrophoresis, respectively. Meanwhile, liquid chromatography-mass spectrometry (LC-MS) and data-independent acquisition LC-MS (LC-MS(E)) were used to monitor the glycation extent and the glycated sites of β-Lg. The results indicated that glucose had a higher reaction activity of glycation than fructose, but both sugars had similar preference on the glycation site for β-Lg. The ranking order from high to low for the 9 detected glycated sites was L 1, K 91 > K 47 > K 70, K 77, K 83, K 100 > K 75 > K 135 for both sugars.

Moisture-Induced Quality Changes of Hen Egg White Proteins in a Protein/Water Model System

In recent years, the intermediate-moisture foods (IMF), such as nutrition and energy bars, are a rapidly growing segment of the global food market. However, due to moisture-induced protein aggregation, commercial high protein nutrition bars generally become harder over time, thus losing product acceptability. In this study, the objectives were to investigate the moisture-induced protein aggregation in a hen egg white proteins/water dough model system (water activity (a(w)): 0.95) and to evaluate its molecular mechanisms and controlling factors. During storage at three different temperatures (23, 35, and 45 °C) for 70 days, four selected physicochemical changes of the dough system were analyzed: the a(w), the color (L* value), the fluorescent Maillard compounds (fluorescence intensity (FI) value), and the remaining free amino groups. Overall, the physicochemical changes of egg white proteins in the dough system are closely related to the glass transition temperature (T(g)). The effect of moisture content on both the L* and FI values occurred as a function of storage time at 45 °C due to the Maillard reaction. The change of the remaining free amino groups at different temperatures was derived from the coaction of both the Maillard reaction and enzymatic hydrolysis from molds. Additionally, through analyzing the buffer-soluble egg white proteins using gel electrophoresis, our results showed that moisture-induced aggregates were produced by two chemical reactions during storage: the disulfide interaction and the Maillard reaction. Furthermore, the effect of two processes during manufacturing, desugarization and dry-heat pasteurization, on the physicochemical changes of the egg white proteins was elucidated. In order to prevent or reduce moisture-induced protein aggregation during product storage and distribution, two potential solutions were also discussed.

Screening of different stress factors and development of growth/no growth models for Zygosaccharomyces rouxii in modified Sabouraud medium, mimicking intermediate moisture foods (IMF)

The microbial stability of intermediate moisture foods (IMF) is linked with the possible growth of osmophilic yeast and xerophilic moulds. As most of these products have a long shelf life the assessment of the microbial stability is often an important hurdle in product innovation.In this study a screening of several Zygosaccharomyces rouxii strains towards individual stress factors was performed and growth/no growth models were developed, incorporating aw, pH, acetic acid and ethanol concentrations. These stress factors are important for sweet IMF such as chocolate fillings, ganache, marzipan, etc. A comparison was made between a logistic regression model with and without the incorporation of time as an explanatory variable. Next to the model development, a screening of the effect of chemical preservatives (sorbate and benzoate) was performed, in combination with relevant stress factors within the experimental design of the model.The results of the study showed that the influence of the investigated environmental stress factors on the growth/no growth boundary of Z. rouxii is the most significant in the first 30–40 days of incubation. Incorporating time as an explanatory variable in the model had the advantage that the growth/no growth boundary could be predicted at each time between 0 and 60 days of incubation at 22 °C. However, the growth/no growth boundary enlarged significantly leading to a less accurate prediction on the growth probability of Z. rouxii. The developed models can be a useful tool for product developers of sweet IMF. Screening with chemical preservatives revealed that benzoic acid was much less active towards Z. rouxii than sorbic acid or a mixture of both acids.

Sanitation of Selected Ready-to-Eat Intermediate-Moisture Foods of Animal Origin by E-Beam Irradiation

To optimize the sanitation treatment of ready-to-eat (RTE) intermediate-moisture foods (IMF), the behavior of Listeria monocytogenes Scott A (CIP 103575), L. innocua (NTC 11288), Salmonella enterica serovar Typhimurium (CECT 443), and Escherichia coli O157:H7 (CECT 4972) following treatment with electron-beam irradiation has been studied. As food matrixes, three RTE vacuum-packed products (Iberian dry-cured ham, dry beef [cecina], and smoked tuna) were used. Although an irradiation treatment is not necessary when the 10(2) colony-forming units/g microbiological criterion for L. monocytogenes is applied, a treatment of 1.5 kGy must be applied to IMFs to meet the food safety objective in the case of the "zero tolerance" criterion for the three strains. The IMF products presented negligible modifications of color (L*, a*, and b*), sensory (appearance, odor, and flavor), and rheology (hardness, springiness, adhesiveness, cohesiveness, gumminess, chewiness, and breaking strength) parameters at doses lower than 2 kGy. Therefore, the treatment of 1.5 kGy warrants safe IMF with sensory properties similar to those of the genuine products.

고압 균질기를 이용한 가식성 톳 필름 개발

톳으로부터 HPH를 이용해 식품에 적용 가능성이 있는 가식성 필름을 제작할 수 있었다. HPH 처리 압력의 증가는 필름의 강도와 깨짐성을 증가시켰고, 단면이 조밀하고 균일한 필름을 형성시켰다. HPH의 처리 횟수의 증가 또한 필름의 단면을 조밀하게 하였다. 개발된 톳 필름은 보고된 많은 다른 생고분자 필름들에 비해 상대적으로 강도, 깨짐성, 그리고 수분 저항력이 낮아 코팅 또는 롤을 비롯한 필름 형태로 건조 식품 또는 중간 수분 식품에 적용될 수 있는 가능성을 보여주었다. Edible biopolymer films were developed from hijiki (<TEX>$Hizikia$</TEX> <TEX>$fusiforme$</TEX>), using a high-pressure homogenization (HPH). Effects of pressure and pass number of HPH on color, tensile, moisture barrier properties, flavor profiles, and microstructure of hijiki films were investigated. A hydrocolloid of hijiki was processed by HPH at 69, 103, or 152 MPa with 1, 2, or 3 passes. A hijiki-base film was formed by drying a film-forming solution which was prepared by mixing of the HPH-processed suspension with glycerol and Polysorbate 20. Tensile strength and elastic modulus increased with increasing HPH pressure. Uniformity of the films increased as the pressure of HPH with 1 pass increased and the number of pass increased at 152 MPa. Water vapor permeability (<TEX>$2.1-3.3g{\cdot}mm/kPa{\cdot}h{\cdot}m^2$</TEX>) and water solubility (0.4-1.0%), which are relatively low compared to those of many other edible films, show the potential that hijiki-base films are applied to the range of low to intermediate moisture food as wrapping or coating.

MOISTURE ADSORPTION ISOTHERMS AND HEAT OF SORPTION OFAGARICUS BISPORUS

ABSTRACT Moisture adsorption isotherms of Agaricus bisporus were determined at different temperatures (5, 15, 25 and 35C) using a static gravimetric method. Several saturated salt solutions were prepared to obtain different water activities in the range of 0.11–0.93. Freeze-dried A. bisporus was equilibrated with designed saturated salt solutions. For certain water activity, the equilibrium moisture contents of A. bisporus decreased with increasing temperature. Adsorption isotherms of freeze-dried A. bisporus followed type III isotherm, which is typical for polysaccharide products. Nine models were used to fit experimental data by linear regression analysis method to ascertain the best of fit. Comparisons were based on mean relative percent error (E), standard error (SE), coefficient of correlation (R2) and residual plots. Among the models tested, the Halsey model achieved the best fit. Based on Clausius–Clapeyron equation, the net isosteric adsorption heat of A. bisporus decreased from 12.12 to 0.30 kJ/mol when the moisture content increased from 8 to 50 g/100 g dry matter. PRACTICAL APPLICATIONS A. bisporus's shelf life is only 1–3 days at ambient temperature. Drying, especially freeze-drying, is one of the main preservation methods for A. bisporus. Developing moisture sorption isotherms (MSIs) for A. bisporus could provide essential information about optimizing its drying process and storage conditions. In addition, isosteric heat of sorption in dehydrated and intermediate moisture food also plays an important role in modeling of various food processing and storage. Optimization of drying process and storage conditions of dried A. bisporus could be obtained by developing its MSI.

The Effect of Gamma Irradiation on the Nutrional Properties of Sunflower Whole Grain Cookies

Bakery and intermediate moisture food products like breads, dried fruit, cereals, cookies and crackers can benefit from irradiation processing. However, irradiated lipid - rich products must be assayed carefully in terms of safety, nutrition and acceptability. In the integral biscuits, the ready-to-eat industrialized sunflower whole grain cookies, the sources of vitamin E are oils, seeds, nuts and cereal grains and also, the ready- to-eat sunflower whole grains. Vitamin E represents an essential component in human nutrition required for the preservation of lipids in stable form in biological systems and also in foods. The possibility of using gamma irradiation to improve the microbiological and fungal quality of different foods has been studied and is nowadays applied commercially. Usually, macro and micronutrients, essential amino acids, essential fatty acids, minerals, trace elements and most vitamins not suffer significant losses in irradiated food process. In this work, data about on the effects of ionizing radiation on the vitamin E content and nutritional analysis (carbohydrate, proteins, lipids, alimentary fiber, volatile substances and ashes) of sunflower whole grain cookies. These samples were treated with gamma irradiation and their changes evaluated in vitamin E content and physicochemical analysis. Irradiation was performed in a 60Co Gammacell 220 source at doses of 3 kGy. For vitamin E (as σ-tocopherol) determination a method based on colorimetric measurements was used. The physicochemical analysis were performed by standard methods. Irradiation at 3 kGy resulted in no changes in vitamin E content. Also, no significant difference was observed between the biscuits irradiated and non – irradiated for the physicochemical analysis. From the obtained results it is possible to conclude that there is a significant stability of the vitamin E content at assayed γ-irradiation dose. And also there is no considerable difference for physicochemical properties contents of sunflower whole grain cookies.

Effects of sucrose crystallization and moisture migration on the structural changes of a coated intermediate moisture food

The purpose of this study was to investigate whether moisture migration and sugar crystallization play an important role in the changes of IMF matrix structure. The migration of water was monitored with changes of water activity in different physical domains of samples during storage, while the crystallization of sucrose was determined with X-ray powder diffraction (XRD). The formation of both a hard inner-layer and agglomerated particles in the inner matrix was observed during storage. Our results suggested that both moisture loss and sucrose crystallization were mainly responsible for the formation of the crusty intermediate inner layer, and the agglomerated matrix particles were the result of sucrose crystallization.

Evaluation of the efficacy of four weak acids as antifungal preservatives in low-acid intermediate moisture model food systems

The potential efficacy of four weak acids as preservatives in low-acid intermediate moisture foods was assessed using a glycerol based agar medium. The minimum inhibitory concentrations (MIC, % wt./wt.) of each acid was determined at two pH values (pH 5.0, pH 6.0) and two a w values (0.85, 0.90) for five food spoilage fungi, Eurotium herbariorum, Eurotium rubrum, Aspergillus niger, Aspergillus flavus and Penicillium roqueforti. Sorbic acid, a preservative commonly used to control fungal growth in low-acid intermediate moisture foods, was included as a reference. The MIC values of the four acids were lower at pH 5.0 than pH 6.0 at equivalent a w values, and lower at 0.85 a w than 0.90 a w at equivalent pH values. By comparison with the MIC values of sorbic acid, those of caprylic acid and dehydroacetic acid were generally lower, whereas those for caproic acid were generally higher. No general observation could be made in the case of capric acid. The antifungal activities of all five weak acids appeared related not only to the undissociated form, but also the dissociated form, of each acid.

Effects of Polyols on the Stability of Whey Proteins in Intermediate-Moisture Food Model Systems

The objective of this study was to investigate the influence of polyols on the stability of whey proteins in an intermediate-moisture food model system and to elucidate the effect of polyols on the hardening of whey protein-based bars during storage. Four major polyols, glycerol, propylene glycol, maltitol, and sorbitol, were evaluated in model systems, which contained whey protein isolate, polyols, and water. The results showed that glycerol was the most effective polyol in lowering water activity and provided the soft texture of intermediate-moisture foods, followed by sorbitol and maltitol. These three polyols stabilized the native structure of whey proteins, provided a desired texture, and slowed the hardening of the model systems. Propylene glycol should not be used in whey protein-based high-protein intermediate-moisture foods because it caused changes in protein conformation and stability as observed by differential scanning calorimeter and Fourier transform infrared spectroscopy and resulted in aggregation of whey proteins and hardening of the bar texture during storage, causing loss in product quality.