fsn 230 midterm Questions With Complete Solutions

Factors that control the growth of microorganisms correct answer: 1. intrinsic parameters 2. extrinsic parameters intrinsic parameters correct answer: internal parts of food that can affect growth of microbes; (existing as an essential part) of the plant or animal tissue: -pH of food, moisture content, oxidation-reduction porteintail (O/R: Eh), nutrient content, antimicrobial constituents, biological structures intrinsic parameters: pH correct answer: -most microbes grow best at pH values around 7.0 (6.6-7.5); neutral pH range; mold,bacteria easily on most of our foods -some exceptions....most fruits have lower pH than vegetables SO molds tend to spoil vegetables -usually meat from a fatigued animal spoils faster than meat from a rested animal; consequence of the pH attained upon completion of right mortis (muscular stiffness following death) -rested animals convert the usual 1% glycogen to lactic acid which drops the pH of the meat from about 7.4 to about 5.6 (BIG) intrinsic paramenters: moisture content correct answer: -main component of most foods is water -water in foods can be in two forms: free water and bound water -microbes grow and live in water -the free water is what microbes grow in -water activity (Aw): water requirements of MOs is expressed as water activity (Aw) in the environment -Aw of most fresh foods is above .99 -by lowering the Aw we can control microbial growth -drying can help preserve food from microbial spoilage by lowering the Aw methods to lower the Aw correct answer: -salting -adding sugar -using additives or ingredients as humectants (additives: lubricants) -lose flavor when dehydrating foods intermediate moisture foods (IMF) correct answer: -foods that are intermediate moisture range but have a prolong shelf life -these foods contain humectants -humectants: chemical compounds that absorb water and lower the Aw: glycerol, sorbitol, other sugars, propylene glycerol, etc Intrinsic parameters O/R potential correct answer: -oxidation/reduction potential -the tendency to yield electrons (become oxidized) -to capture electrons (becomes reduced) -O/r or Eh is measured in mini volts (mV) -the greater the degree to which a substance oxidizes the more highly positive the Eh value and the greater the degree to which a substance reduces the more highly negative the Eh value O/r potential correct answer: -microorganisms display varying degrees if sensitivity to the O/R potential of their growth medium -some bacteria require reduced conditions for growth: