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Microbiological analyses of commercial sprout seeds indicated aerobic plate counts (APC) and confirmed coliforms ranging from 11 × 103/g, respectively. Fecal coliforms were detected in the range from 7.3 to 11 × 102/g; Listeria or Salmonella were not detected. Seeds, pregerminated in potable water (16-18 h, 20-22°C), contained an APC ca. 1 logarithm higher than the corresponding dry seeds. Increased levels of confirmed and fecal coliforms were also detected as a result of soaking. The APC of retail sprouts ranged from 3.6 × 103 to 3.7 × 109/g. All samples contained confirmed and fecal coliforms. Coagulase positive staphylococci were detected in ca. 24% of samples analyzed.

Germination and outgrowth of Bacillus subtilis spores was investigated using laboratory media containing butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tertiary butylhydroquinone (TBHQ) and propyl gallate (PG). Although all antioxidants inhibited or retarded germination initiation and outgrowth, only BHA and TBHQ were effective at relatively low concentrations (150 and 100 ppm, respectively). Furthermore, BHA and TBHQ (150 ppm) were also shown to reduce spore growth by approximately 1 and 4 log10 within 72 and 6 h, respectively. The difference in the number of survivors between thermally (10 min at 80°C) and BHA (150 ppm)-treated germinated spores indicated that the antioxidant was effective against only a certain portion of the total heat-sensitive spore population. Sporostasis caused by BHA appeared reversible by the addition of Tween 80.

The effects of diet type (corn- vs. wheat-based) and multicarbohydrase addition on growth performance, digesta pH and viscosity, intestinal populations of Clostridium perfringens and lactic acid bacteria, and gut lesion score (from 0 to 4, where 0 = no gross lesions, 4 = severe extensive necrosis) of broiler chickens during oral challenge with C. perfringens (none or 10(8) cfu/bird on d 13) were studied in a 39-d experiment. A total of 1,216 male Ross-308 chickens was assigned to 8 dietary treatments in a randomized complete block design providing 8 replicate pens per treatment. Diets were formulated to meet the NRC protein requirement but were suboptimal in energy level. When compared with birds fed corn-based diets, chickens fed wheat-based diets had inferior (P < 0.01) final BW (2.49 vs. 2.59 kg) and feed conversion ratio (FCR; 1.83 vs. 1.78). Pathogen challenge significantly (P < 0.05) impaired growth performance and increased C. perfringens numbers and average lesion score. Increased (P < 0.01) C. perfringens counts (2.4 vs. 1.5 log(10) cfu/g of digesta) and intestinal lesion score (0.9 vs. 0.4) were observed for challenged birds fed wheat-based diets. No difference in digesta pH and lactic acid bacteria numbers were found among the treatments. Enzyme addition to both the corn- and wheat-based diets increased bird final BW (2.57 vs. 2.51 kg; P < 0.01), decreased overall FCR (1.78 vs. 1.83; P < 0.01), and, in those consuming wheat-based diets, reduced digesta viscosity (from 4.1 to 2.7 mPa.s; P < 0.01). Enzyme supplementation assisted the challenged birds in maintaining their optimal growth performance by improving (P < 0.05) average daily gain (59.5 vs. 56.9 g) in those consuming corn-based diets and FCR (1.83 vs. 1.90) in those consuming wheat-based diets to values similar to those observed in control birds (59.7 g/d and 1.84, respectively). In conclusion, enzyme addition improved growth performance and mitigated the negative effects of C. perfringens challenge.

Commercially sterile garlic, sage, black pepper, cinnamon and clove were investigated as heat sensitizing agents towards Bacillus subtilis spores. Heat treatment at 80°C for 10 min of all spice-spore mixtures (0.9 g spice/0.1 g spores) in distilled water (9 mL) reduced initial counts (106/mL) by approximately 0.5–1.0 logarithms, with the exception of garlic which showed no effect. The clove-spore mixture exhibited the greatest reduction in survivor counts. Dry spice-spore mixtures conditioned for 24-96 h in relative humidities (RH) from 64 to 98% and at temperatures from 25 to 35°C, prior to heat treatment, exhibited additional reduction in survivors. The clove-spore mixture exhibited the greatest decrease in heat-treated survivors (approximately 4 logarithms) after conditioning at 96% RH and 35°C for 96 h. Relative humidity conditioning of cinnamon-spore mixtures, regardless of treatment regime, did not reduce the number of heat-treated survivors. Increasing the temperature and/or RH of conditioning for the remaining spice-spore mixtures generally increased heat sensitization. Aw-equilibrated spice-spore mixtures which were not heat-treated (controls) showed no reductions in viability. Moisture sorption by the spices during conditioning only partially influenced their heat sensitizing effects.

The effect of incorporating trisodium phosphate (TSP) in pea starch (PS) and acidified sodium chlorite (ASC) in calcium alginate upon the antimicrobial activity of TSP and ASC was studied against a 3-strain cocktail of Salmonella inoculated on chicken skin. The influence of polymer coating concentration on skin pH, coating-skin adhesion, and coating absorption upon antimicrobial performance were investigated. Aqueous solutions of 0.5 to 4.8% (wt/vol) PS were prepared with 10% (wt/vol) TSP (PS + TSP coating), and alginate + ASC coatings contained 1% (wt/vol) calcium chloride in 1,200 ppm of ASC mixed with an aqueous solution of 0.5, 1.0, or 1.5% (wt/vol) sodium alginate. Coating drops (10 microL) were placed on chicken skin thighs, and the angle formed by the tangent of the liquid surface at the skin interface (contact angle) was measured using a digital camera to assess coating-skin adhesion. Excised skins were mounted in a ring holder, and 5 mL of the coatings was applied to the skin. Weight changes in the skins that were related to coating absorptiveness were recorded. The TSP dissolved in 3.5% PS and ASC in 1% alginate reduced Salmonella by 1.6 log cfu/g and 1.4 log cfu/g, respectively, within 24 h. These reductions were significantly greater than those caused by TSP or ASC alone in water for up to 120 h. In coatings, TSP and ASC caused significant elevation or reduction of skin surface pH for up to 120 h, respectively. The TSP destabilized PS with 88% of the coating having dripped from the skin 1 h later. Coatings with 0.5% PS were absorbed quickly by the skin and had high skin adhesion, whereas those with >3.5% PS had low skin adhesion and slow absorption. Alginate coatings with or without ASC were stable, and about 50% of the coating weight was retained at 120 h. The latter coatings appeared to have low absorptiveness because the skin gained approximately 1.0% of its weight within 60 min following application. These findings indicate that effects of the agents in coatings on skin pH, the extent of coating adhesion, and absorption may contribute to overall antimicrobial behaviors.

Increasing the growth performance of broiler chickens by supplementing their diets with exogenous enzymes can also contribute to positive changes in gut health. In this respect the growth of various bacteria normally associated with the gastrointestinal tract of poultry was assessed in vitro using a medium containing arabinoxylan, β-glucan, guar gum and raffinose and their corresponding enzymes. Overall, enzymes releasing the largest amounts of free sugars yielded the largest increase in bacterial numbers. Accordingly, β-glucan and raffinose treated with their respective enzymes promoted the largest number of bacterial types, reaching a minimum of 1.0 log10 population within 6 h at 40 °C. A broiler chicken growth trial was also conducted using wheat-, barley- and corn-based diets with and without enzyme and probiotic addition. Escherichia coli, coliforms, enterococci and aerobic and anaerobic sporeformers were monitored for growth in both the caecum and ileum. Enzyme supplementation reduced E. coli levels in the caecum of broilers fed wheat- or corn-based diets. A further reduction in E. coli numbers was observed in broilers fed the same diets supplemented with a combination of enzyme and probiotic. Enzyme supplementation had much less of an effect on microbial populations in the ileum. Inclusion of probiotics reduced E. coli levels in the caecum and ileum but only in broilers fed wheat- and corn-based diets. Anaerobic spore levels in the ileum increased in all diets containing probiotic. Overall, inclusion of enzymes or probiotics exhibited mixed effects on gut bacteria, depending on the nature of the carbohydrate source and enzyme. Copyright © 2007 Society of Chemical Industry

Harvesting of Brazil nuts not only helps to preserve the Amazon rainforest but also provides income to individuals who would otherwise have little means of making a livelihood. Recently, the European Community has tightened the quality requirements for Brazil nuts, particularly with regard to aflatoxin levels and microbiological contamination. The objectives of this research were to gain a better understanding of the origin of aflatoxins on Brazil nuts and to microbiologically evaluate some of the operations involved in processing. In this regard, five Brazil nut pods were aseptically picked from trees located in each of three concessions of the Peruvian Amazon rainforest (Madre de Dios province). The exteriors of the pods and the nuts were examined for yeast and molds, including Aspergillus flavus and Aspergillus parasiticus, and for bacteria, including Salmonella and Escherichia coli. Brazil nuts obtained from various commercial process operations located in Peru were similarly evaluated. Exteriors of all Brazil nut pods did not contain A. parasiticus, and only pods from one concession yielded A. flavus isolates. All isolates tested were aflatoxigenic (630 to 915 ppb total aflatoxin). Coliforms, E. coli, and salmonellae were not recovered from any of the pods. Whole, in-shell nuts obtained after opening the pods yielded no A. flavus or A. parasiticus. Aflatoxins were not detected (detection limit 1.75 ppb) in any of the nuts. Whole, in-shell and shelled nuts from various process operations were all positive for A. flavus but negative for E. coli and salmonellae. Soaking of whole, in-shell nuts before cracking or shelling increased coliform numbers, whereas levels of A. flavus decreased. In order to gain a better understanding of the sanitary performance of the unit process operations, additional evaluations should be conducted on product lots processed on different days. Also, the microbiology of product processed from common lots should be followed through the various unit operations and compared.

The effect of an initial cold shock treatment (2 h at 10C), following an abrupt downshift in temperature from 37 to 10C, on the subsequent growth and survival of Escherichia coli strains O157:H7 and MY20 (Biotype 1) in acidified Trypticase soy broth (TSB) and fruit juices (orange, apple) was investigated. Overall, no difference in growth at 37C was observed between each cold shocked and noncold shocked E. coli strain when cultured in TSB adjusted with either acetic acid (pH 6.0)or malic, citric and tartaric acid (each adjusted to: pH 4.5, 5.0, 5.5, 6.0). However, significant (P ± 0.05) differences in survival were observed between cold shocked and noncold shocked populations in TSB acidified with acetic acid (pH 5.0) or citric, malic and tartaric acid (pH 4.0). For strain MY20, survivor levels for cold shocked cells in TSB acidified with acetic acid citric, malic and tartaric acid at 8C were significantly (P ± 0.05) higher than in noncold shocked populations. Also, at 37C survival levels for cold shocked cells were significantly (P ± 0.05) higher than noncold shocked cells in TSB acidified with either malic or tartaric acid (pH 4.0). For the O157:H7 strain, survivor levels were higher (P ± 0.05) for cold shocked cells when maintained in TSB at 37C regardless of acid type. At 8C, cold shock treatment only increased (P ± 0.05) the survival of the O157:H7 strain in TSB adjusted with acetic acid (pH 6.0). Acid cross protection induced by cold shocking, as evidenced by enhanced survival, was not apparent for either E. coil strain in apple (pH 3.5) or orange juice (pH 3.8) maintained at 8C.

Omega-3 enriched eggs are currently produced by hens fed a flax diet. Since omega-3 polyunsaturated fatty acids are prone to oxidation, the addition of vitamin E is supplemented into the hen's diet as an antioxidant. Typically these eggs contain about 2 and 4 times more omega-3 fatty acids and vitamin E, respectively compared to regular eggs. Since table eggs have a long history of association with foodborne salmonellosis, it was of interest to compare the growth and/or survival of several bacterial pathogens in omega-3 and regular eggs. In this respect nalidixic-resistant Escherichia coli and Salmonella Typhimurium were inoculated into regular and omega-3 hen's egg products (whole eggs, albumen, yolk) and incubated at 22, 8 and -20C. Time-course studies indicated that by 72 h both Salmonella and E. coli levels increased by 7 logs at 22C in both types of whole egg. At 8C population levels for these bacteria both increased by approximately 3 logs at 6 weeks. In regular and omega-3 yolks, salmonellae maintained at 22 and 8C for 48 h and 6 weeks increased by approximately 6 and 1.5 logs, respectively. E. coli levels were higher in egg yolk compared to Salmonella at both temperatures. Regardless of the yolk source, however, no significant (P>0.05) differences in population levels were observed. Survival patterns of E. coli at -20C were not significantly (P>0.05) different between whole egg sources. This trend was also observed in the yolks. For Salmonella no significant (P>0.05) differences in survival were observed between yolk preparations maintained at -20C. Increasing the level of α-tocopherol from c. 63 to 240 ppm in regular egg yolk, resulted in no significant (P>0.05) differences in the growth of Salmonella at 22C. In addition, when the bacterium was heated in regular egg yolk amended with vitamin E at 56.5C, no significant (P>0.05) difference was observed in resistance regardless of α-tocopherol (55- 713 ppm) or total tochopherol (92-1238 ppm) level. Cette etude compare la croissance et/ou la survie de bacteries pathogenes dans des oeufs ordinaires et des oeufs enrichis en omega-3. Des souches de Escherichia coli et Salmonella typhimurium sont inoculees a des oeufs entiers, des blancs, et des jaunes d'oeufs, et incubees a 22, 8 et -20°C. Les resultats montrent que la croissance et la survie des 2 bacteries testees dans les oeufs ordinaires et enrichis sont similaires. Une exception possible est observee dans la survie de Salmonella a -20°C dans l'oeuf entier qui est plus importante dans les oeufs ordinaires.

The survival of Escherichia coli O157:H7 strains in both frozen foods and trypticase soy broth (TSB) was investigated following cold shocking at 10 degrees C for 1.5 h. Using both trypticase soy agar (TSA) and violet red bile agar (VRBA) as recovery media, it was demonstrated that survival levels between cold shocked (CS) and non-cold shocked (NS) E. coli in ground beef or pork were not significantly different (P < or = 0.05). In contrast, cold shocking E. coli in either milk, whole egg or sausage resulted in a significant(P < or = 0.05) enhancement in survival. For milk, survival levels of CS E. coli, by 28 days of frozen storage, were 1.89 and 1.66 log10 cfu/ml higher on TSA and VRBA, respectively, when compared to NS cells. In egg these values were 0.64 and 1.31, while in sausage, values of 0.74 and 1.19 were obtained. In TSB (pH 7) survival of CS E. coli for some strains was about 3 log10 cfu/ml higher when compared to NS cells. Acidification of TSB (pH 5), however, appeared to negate the protective effects of the cold shock treatment. In milk, increasing the differential between the growth and cold shock temperatures resulted in higher numbers of survivors. In this regard the growth-cold shock temperature protocol giving optimum protection was 37-10 degrees C. In contrast, growth of E. coli at 20 degrees C followed by cold shocking at 10 degrees C did not result in any significant freeze protection. In addition, increased protection due to cold shocking was correlated with the appearance of a novel protein appearing at pI 4.8 following isoelectric focusing analysis, thus demonstrating an alteration of protein synthesis.

The effects of diluting concentrated pesticide products with water containing Escherichia coli O157:H7 (human, bovine and ground meat strains), Salmonella typhimurium, Salmonella enteritidis, Shigella sonnei, Shigella flexneri and Listeria monocytogenes were investigated. Individual cultures were inoculated at about 10(2) colony-forming units (cfu) ml(-1) into the following commercial pesticide products--Roundup, Poast & Merge, Gramoxone, Afolan, 2,4-D amine, Dithane M45, Benlate, Bravo 500, Ridomil 240EC, Thiram 75WP, Sevin XLR+, Lorsban 4E, Diazinon 500, Ambush 500EC and Lagon 480E--following dilution with sterile tap water to recommended spray application concentrations (pesticide solution). Following incubation at 22 degrees C for 1 h, survivor levels for all three E coli O157:H7 strains in pesticide solutions of Roundup, Poast & Merge, Gramoxone, Dithane M45, Ridomil 240EC and Lagon 480E were lower (P less than or equal to 0.05) compared to their survival in water. In several pesticide solutions (Afolan, Bravo 500, Lorsban 4E and Ambush 500EC), survivor levels were no different (P greater than or equal to 0.05) from the control after 1 h; however, by 24 h, population levels of all strains in these four pesticide solutions were higher (P less than or equal to 0.05) than those observed at 1 h. Overall, similar survivor or growth patterns were observed with the remaining bacteria, with the exception of S flexneri. For this bacterium, survival or growth was poor, especially in Bravo 500, which consistently supported substantial growth of the other micro-organisms. Time course growth studies over 96 h at 22 degrees C were conducted with Salmonella, Shigella, Listeria and E coli O157:H7 in solutions of Afolan, Bravo 500, Lorsban 4E and Ambush 500EC. Overall, a 100 to 1060-fold increase in population was usually obtained in these pesticide solutions by 96 h. Changes in either the initial inoculum level of E coli O157:H7 from about 10(2) to 10(4) cfu ml(-1) or temperature (from 20-22 to 31 degrees C) and concentration (from 0.5 to 1.5 times the recommended spray concentration) were shown to affect its growth in the pesticide solutions. The findings of this study indicate that some pesticide products, when diluted using contaminated water, may have the potential to promote growth of pathogens which could increase the risk of more widespread contamination of standing crops, including fruits.

Spores ofPenicillium roquefortiwere produced using potato dextrose agar which was solute agjusted using either NaCl, sucrose, or glycerol to water activity (aw) levels of: 0·99 (control), 0·97, 0.·90 and 0·88. All spore crops, regardless of the sporulation awon which they were produced, exhibited near total germination within 24 h at 22°C in sterile water. However, when spores were initially heated either in water (42°C, 2 h or 55°C, 10 min) or in air (60°C, 20 min) and then germinated, levels were observed to decrease particularly for spores produced on 0·88 awadjusted media. Germination levels were also observed to decrease with time when harvested spores were initially suspended in sterile distilled water (0 to 24 h, 2°C) and then heated. Control spores (0·99 aw) showed no effects. Heat studies of spores suspended in water were used to calculate thermal decimal reduction times (D). Control spores and spores produced at 0·88 awwith glycerol, exhibitedD55°Cvalues of 10·3and 2·3 min, respectively. Specific effects attributable to the nature of the solute appeared to influenceDvalues; however, no clear trend was observed. The results of this study indicated that spores that were produced at reduced awbecame heat-sensitized perhaps owing to injury and/or damage incurred during sporogenesis.

Morphological changes and associated growth kinetics were correlated to ochratoxin A (OA) production byAspergillus alutaceus(parent). Two strains (hypo and hyper), isolated following gamma radiation of the parent, which differed in their ability to synthesize OA relative to the parent, were investigated. The impact of l -glutamic acid (0.5 g/100 ml), a known stimulus for production, was also investigated with regards to fungal morphology. Results indicated significant differences between strains in regard to their hyphal growth unit length (G). The hypo and hyper strains exhibited the highest (184 μm) and lowest (125 μm) G, respectively. Addition of l -glutamic acid reduced both the G values and the mean tip extension rate for all fungi; the specific growth rate, however, remained unchanged. Levels of OA were highest (177 μg/mL) when produced by the hyper strain especially in media containing l -glutamic acid. An opposite effect was observed with the hypo strain. Growth rate patterns in terms of leading hyphae and lateral branches at the colony margins appeared highest for the parent at 7 and 14 days. Inclusion of l -glutamic acid into the growth medium resulted in increased growth rates for both the parent and strains by day 14. At this time maximum growth was achieved by the hyper strain.

The recovery of Escherichia coli ATCC 11775 following irradiation in phosphate buffer at 0C was assessed using a two-stage incubation protocol. In the first stage survivors were recovered on basal yeast extract agar (BYEA) plates and incubated at 18C (18C-resuscitation) for specified time intervals (0 to 48 h). In the second stage, the incubation temperature was increased to 37C and the survivors were incubated for an additional 24 h to promote colony development. Controls consisted of survivors which were directly incubated at 37C on BYEA for time intervals equivalent to the total times used in the two-stage incubation protocol. The ratio of colony-forming units obtained with and without (control) the 18C-resuscitation protocol was used to calculate recovery factors (RF). Depending on the applied dose, RFs ranged from ca. 2.5 (0.44 kGy) to 15-18 (0.76 kGy) following an optimal resuscitation time of 24-28 h. Irreparable damage, incurred by incubating survivors directly at 37C (37C-damage) for 10 min prior to their recovery using the two-stage protocol, was minimal regardless. of dose; however, extending 37C-damage to 60 min decreased RFs by ca. two-thirds. RFs for cells increased from 1.6 to 375 following irradiation at 0.25 and 0.53 kGy, respectively. In ground beef, RFs for cells treated at the highest dose (1.50 kGy) increased by ca. 100-fold following 18C-resuscitation. In contrast, the 18C-resuscitation protocol exhibited minimal effects when E. coli was irradiated in trypticase soy broth. Survivor levels for E. coli following either gamma or electron beam irradiation appeared similar ; however, both appeared higher following the 18C-resuscitation protocol.

The microbial decontamination of chicken feed, obtained from a commercial pellet mill, was evaluated using a direct-fired steam conditioner (DFSC ; APC System®). The standard plate count of the feeds before (mash) and after (pellets) conditioning ranged from 65 x 10 4 to 83 x 10 5 colony forming units (CFU) g -1 and from 91 x 10 1 to 92 x 10 3 CFU g -1 , respectively. The incidence of Escherichia coli, Salmonella and Listeria in the feeds before conditioning was 61.7, 8.3 and 27.1%, respectively. Following conditioning these levels were reduced to 1.7, 1.7 and 0%, respectively. Species of Listeria and Salmonella identified included L. monocytogenes, L. innocua and S. agona, S. ohio, S. heidelberg, S. senftenberg, S. tallahasse and S. braenderup, respectively. Compared with a conventional, indirect-fired boiler-generated-steam conditioner (IFSC) the direct-fired steam conditioner proved superior in regards to pathogen decontamination ; no E. coli, Salmonella or Listeria were recovered from mash lots positive for these microorganisms. However, with the IFSC system, both E. coli and L monocytogenes were recovered at levels of 11.1 and 5.6%, respectively.

The influence of excreta from the red flour beetle, Tribolium castaneum (Herbst), on the growth of Aspergillus alutaceus (formerly A. ochraceus Wilhelm NRRL 3174) and ochratoxin A (OA) production in sterile wheat was investigated. When sterile excreta (3–6%) was added to wheat, OA production by A. alutaceus during the first 2 weeks of growth was significantly ( P > 0.05) reduced. A similar trend was observed with fungal growth. The addition of equivalent levels of uric acid (76.8 or 153.5 mg/g wheat) to sterile wheat resulted in no significant ( P > 0.05) effect on OA production although fungal growth appeared slightly enhanced. In non-sterile wheat, the addition of sterile excreta (5%) significantly ( P > 0.05) reduced OA production compared to the control. The presence of excreta in a grain bulk may favor fungal competition thereby inhibiting OA production.

Canadian regulations require that chicken carcasses with visible post-evisceration internal contamination be removed from the process line. Such carcasses are condemned after unaffected parts are salvaged by hot-boning. The present study was performed in order to provide data in regards to the microbiological safety of reprocessed broiler carcasses. Contaminated carcasses were reprocessed manually off-line and in a vent-down position by an immediate 5-sec inside/outside (I/O) spray wash followed by vacuuming and 1 15-sec I/O spray wash. Average colony forming units (log10/mL) for inspection-passed and reprocessed carcasses included: standard plate count (SPC), 3.99 and 3.55; coliforms, 3.49 and 3.07; Escherichia coli, 3.34 and 2.96; and Staphylococcus, 2.42 and 1.53; respectively. The detection frequencies for Salmonella and Campylobacter were 4 and 5% and 84 and 74%, respectively.

The survival of Escherichia coli and Staphylococcus aureus during the production of khoa, a heat concentrated Indian milk-based product, was investigated. Heat processing of milk containing from 3.6 to 6.5% fat at either 63 or 73 C eliminated all E. coli. Under similar processing conditions, S. aureus was recovered, but only when heated in milk at 63 C containing 6.5% fat. Potassium sorbate (3000 ppm) appeared more effective in inhibiting the growth of selected yeast and molds in khoa at 7 C, compared to ascorbic acid (3000 ppm). Reducing the water activity (a(w)) of khoa from 0.97 to 0.93 did not appear to enhance the preservative effect. The reduction of E. coli or S. aureus in khoa during prolonged storage at 6-7 C, was less than one log cycle, regardless of a(w) or preservative type. Survival of S. aureus in khoa appeared to be enhanced with a decrease in a(w). The potential for pathogens to survive in khoa during processing should be taken into consideration when formulating heating protocols.

Phytosterols play a major role in functional foods. Their ability to reduce serum cholesterol in humans has been widely proven and they are now being added to various dairy based products. The present study investigated the potential antimicrobial activity of phytosterols in milk and their effect on yogurt starter cultures. A commercial phytosterol (0.26% to 1.8%, w/v) preparation (CPP) consisting of ss-sitosterol, campesterol, sitostanol, and campestanol had no effect on the standard plate count (SPC) and psychrotroph population in pasteurized milk stored at 4 degrees C. In addition, a challenge study employing Pseudomonas spp. in milk at 4 to 7 degrees C confirmed that the CPP was not antimicrobial. However, the addition of a dispersible CPP consisting of 0.72% phytosterol containing 0.02% to 0.03% sodium stearoyl lactylate (SSL) did appear to affect the SPC and psychrotrophic bacteria in refrigerated milk. The dispersible preparations did not, however, inhibit the growth of Pseudomonas. An investigation into the antimicrobial activity of SSL revealed that it alone had no effect on the SPC in milk. The CPP had no effect on growth and acid development by Lactobacillus bulgaricus and Streptococcus thermophilus during yogurt production at 33 degrees C and storage at 4 degrees C for 30 d. This is seen as a beneficial feature since growth and acid development by these organisms are crucial for yogurt quality. Saccaromyces cerevisiae and Aspergillus ochraceous added to yogurt as typical contaminants also were not inhibited. While the CCP was somewhat antimicrobial when formulated with dispersing agents, it otherwise had no antimicrobial activity.

The irradiation sensitivity of fungal spores to either gamma or electron beam irradiation was evaluated in distilled water. The D10 (the dose required to reduce the initial population by 90%) gamma values ranged from 0.236 to 0.416 kGy and from 0.209 to 0.319 kGy for Penicillium and Aspergillus species, respectively. The D10 electron beam values ranged from 0.194 to 0.341 and from 0.198 to 0.243 kGy for Penicillium and Aspergillus species, respectively. Of the aspergilli species evaluated, only half exhibited significantly (P < 0.05) greater sensitivity to the electron beam treatment compared to gamma irradiation. Four of the six penicillia species evaluated also exhibited significantly (P < 0.05) higher sensitivities to electron beam treatment.

Cheddar cheese slices, surface-inoculated with either Penicillium cyclopium or Aspergillus ochraceus spores, were vacuum packaged and irradiated using an electron beam accelerator. Following treatment at .21 and .52 kGy, the shelf-life of cheese containing P. cyclopium was extended by 3 and 5.5 d, respectively, in comparison with inoculated, untreated samples. Under similar treatment and storage conditions, cheese containing A. ochraceus exhibited average shelf-life extensions of 42.5 and 52.2 d, respectively. Increasing the postirradiation storage temperature to 15°C reduced the shelf-life of cheese, especially with samples containing A. ochraceus . The lowest dose required to inactivate ca. 50 to 60 spores/cm 2 of either A. ochraceus or P . cyclopium on the surface of cheese was ca. .42 and .95 kGy, respectively. Irradiation survival curves of A. ochraceus and P. cyclopium spores in cheese yielded average values (the dose required to reduce initial population by 90%) of .21 and .42 kGy, respectively.

Eugenol, the major essential oil of clove, in sublethal concentrations (0.02-0.03%, v/v) inhibited the production of alpha-amylase, protease, and subtilisin by Bacillus subtilis in laboratory media. Microscopic observations revealed that at these eugenol concentrations, B. subtilis cells appeared swollen and distorted and/or appeared as very long and thin filaments (> 100 μm). Of 20 amino acids investigated, only L-glutamic or L-aspartic acid (>5.0 mg/ml) prevented such morphogenic distortions when added to eugenol-containing media before inoculation. Addition of these amino acids also resulted in an increase in biomass and protease production. In contrast, the addition of serine (> 1.0 mg/ml) enhanced filamentous growth but reduced the production of protease and subtilisin.

A first report of an active and stable polyphenol oxidase system in tubers of Jerusalem artichoke (Helianthus tuberosus L.) is presented. The crude enzyme, extracted in 0.1M phosphate buffer, pH 6.5, showed optimum activity using dihydroxyphenol substrates. In this respect, chlorogenic acid followed by catechol showed the best reactivity. The enzyme exhibited an optimum pH of 6.0 using 0.01M catechol as a substrate. The specific activity of the enzyme was approximately 13 and 3 times the level found in potatoes and sugar beets, respectively. Thermal inactivation data indicated an apparent activation energy of 54 KJ/mole. Over 84% of the total soluble enzyme was located in the tuber peels.

Spores of Bacillus subtilis stored under different concentrations of clove infusion were microscopically observed to undergo germination. These spores, however, did not outgrow when subcultured on nutrient agar. Spores which remained refractile during storage in clove infusion at 37°C outgrew when transferred to nutrient agar. Clove ash was determined to contain substances which allowed complete germination or darkening of spores in distilled water. Eugenol, an essential oil found in cloves was determined to be sporostatic at concentrations of 0.05 - 0.06% (v/v). Several closely related compounds; isoeugenol, gingerol and zingerone also showed sporostatsis at levels of 0.05 - 0.6, 0.90 - 1.00, and 0.80 - 0.90% (v/v) respectively.

Bacillus subtilis spores produced on trypticase soy and nutrient agar, containing either 0·12% w v clove powder or 0·02% v v eugenol, were evaluated for germination and heat resistance. Spores produced in the presence of these compounds exhibited both a decrease in their rate and extent of germination when compared to control spores, regardless of the temperature (25–48°C) or pH (6·0–8·0) employed. When nutrient broth was replaced with trypticase soy broth as the germination medium, all treatment spores showed enhanced germination; the overall extent of germination, however, remained repressed. Washing the treatment spores with Tween 80 did not appreciably alter their rate of germination. All treatment spores contained lower levels of dipicolinic acid when compared to the control (7·9–8·7 and 9·8%, respectively). Heat resistance (D90°C) was highest with spores produced on nutrient agar-clove (6·5 min) followed by nutrient agar-eugenol (6·0 min) and trypticase soy agar-clove (5·0 min). Spores produced on trypticase soy agar-eugenol and nutrient agar exhibited the same heat resistance (4·5 min).

Phenolase from tubers of Jerusalem artichoke was fractionated by metal chelate affinity chromatography using copper conjugated to iminodiacetic acid Sepharose 6B. Four fractions obtained after chromatography showed various specific activities, with an increase in activity of 160-fold for the first unbound enzymatic fraction, and 18-fold for a fraction eluted with glycine buffer. Electrophoresis of phenolase fractions in gradient polyacrylamide gel resulted in a pattern consisting of three major groups of bands differing in relative mobilities.

A bacteriocin-like agent, thermocin, produced by the rough variant (Rh) of Bacillus stearothermophilus var. calidolactis was shown to inhibit acid production in Delvotest® P ampoules. The minimum concentration of thermocin resulting in a positive test was 0.9 arbitrary units(Au) per mL. Thermocin concentrations of 0.8-0.6 and 0.5 Au/mL resulted in doubtful and negative results, respectively. Preincubation of the ampoules for one hour at 63°C slightly decreased the sensitivity of the Delvotest® to thermocin. It is suggested that assay tests yielding false positive results should be analyzed for the presence of Rh (thermocinogenic) variants, as a possible source for these type of results.

The antioxidant activity of ten spices commonly used in the formulation of a fermented meat sausage (Pastourma) were evaluated using a hemoglobin peroxidation procedure involving safflower oil in a water emulsion (10%). Clove followed by rose petals and allspice exhibited the highest antioxidant index when used in a dry form. In an aqueous-based microbiological broth, cloves again showed the highest antioxidant index followed by black pepper, ginger and rose petals. Generally anti-oxidant indices were higher in emulsions containing dry spice than in an aqueous based microbiological broth.